Glossary of Finishing Terms

I've been compiling this glossary for some time now, and I hope I've got most of the finishing jargon that a typical woodworker is likely to encounter listed here. This listing is restricted just to finishing terminology, but it includes commonly encountered chemicals, dyes, plant extracts, finishing tools, types of finishes, application techniques, defects, and other terminology that is often specific to finishing wood, and is often not found in any normal dictionary.

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Accelerator: A catalyst or activator added to a finish or applied prior to finishing, used to speed the drying or curing of the finish.
Acetone CH₃COCH₃: A solvent, soluble in water or alcohol, acetone cleans & removes epoxy resins (uncured), polyester, ink, adhesives, & contact cement. Dissolves or softens many plastics. Chief ingredient in nail polish remover.

Acetone, Toluene, & Methylene Chloride (ATM): A paint and varnish stripper. Less expensive than straight methylene chloride, nearly as effective, but still produces toxic fumes, and is flammable.

Acetone, Toluene, & Methanol: Commonly labeled as "refinisher", dissolves shellac and lacquer quickly.

Activator: See Accelerator.

Adhesion: The ability of one material to cling to another; in finishing, the bond between separate coats of finish. Poor adhesion between coats of finish results in peeling and flaking of the overlying finish. The only cure is normally to strip and refinish. Adhesion between coats of finish is improved by deglossing, or scuff-sanding between coats, to provide a better mechanical grip. The usual test for adequate adhesion between coats of finish is to use the tip of a X-acto knife to make parallel cuts through the finish in a 2" by 2" grid pattern with roughly 1/4" spacing between scored lines. Clear packing tape is then pressed down onto this surface and burnished with something like the edge of a credit card. When the tape is peeled off, the amount of finish flaking off indicates the degree of adhesion between the coats. Some flaking is acceptable, but more than about 15% indicates an adhesion problem. One common fix would be to apply a shellac-based sealer between coats, and be sure to degloss between coats as well. See also Degloss.

Alizarin: A synthetic dye or the active coloring agent of madder root. Produces "Turkish Red", crimson, orange, yellow, and brown, depending on the mordant.

Alkanet Root: An ancient organic dye from the borage family. Used in French polishing, produces gray tones with alum, a range of reds with linseed oil.

Alkyd Resin: One of the most common resins used in paint and varnish, alkyd resin offers similar protection to other resins but has greater clarity and less tendency to yellow over time.

Alligatoring: See Crazing.

Alum (Aluminum Sulfate) Al₂(SO₄)₃: A chemical mordant. Comes as white mineral salts, non-toxic. Produces purplish and dark crimson tones.

Aluminum Oxide (AlO) Al₂O₃: The abrasive most commonly found on power sanding equipment, designated on the back of sandpaper as "AlO". Aluminum oxide is friable, meaning its crystals fracture as they wear out, producing new sharp cutting surfaces. This allows the sandpaper to continue cutting aggressively much longer than other abrasives. Some pre-finished flooring has aluminum oxide added to the finish to increase its abrasion resistance. Such flooring will also take a bite out of your carbide-tipped saw blades, so don't cut pre-finished flooring with your best blades.

Ammonia / Ammonium Hydroxide NH₄ (aq): Usually in a 28% aqueous solution, highly toxic, used in fuming. Produces dark violet browns with logwood dye, light yellow browns with brazilwood dye, reacts with the tannin present in some species to darken or "age" the wood. Anhydrous ammonia is highly dangerous, so avoid it. Household ammonia is not concentrated enough to have any lasting effect.

Aniline Dye: Powdered, water-soluble dye, produces penetrating, transparent colors, brilliant, compatible with any finish, usually non-toxic, will raise grain. Aniline dyes can be used to tint water based finishes. When applied directly to the wood, they tend to bleed into water based topcoats. This can produce problems by highlighting drips, sags, and lap marks; but if carefully used, it can also have the effect of evening out the color absorption in highly figured woods. Bleeding can be prevented by applying a dewaxed shellac sealer over the dye. Aniline dyes also come in alcohol soluble form (see Spirit Stain).

Annato: A natural dye made from the seeds of a Central American Tree. Produces oranges and golds with dichromate, tin, or alum, oak brown with lye.

Asphaltum: A petroleum distillate dye made by dissolving roofing tar in mineral spirits. One of the professional finisher's "trade secret" colors.

Badger, Badger Bristle: A soft, resilient bristle favored for oil varnishes and lacquer.
Banding: Linear patterns of overspray caused by not overlapping adjacent passes with a finish sprayer sufficiently.
Belt Sander: A power sander that uses a loop of abrasive driven between two rollers. Belt sanders are very aggressive, and are mostly used for stock removal. Due to the linear sanding motion, belt sanders leave a prominent scratch pattern of parallel lines.
Binder: Any resin used to bind particles of pigment to each other and to the wood. Used in paints and stains. The same resins used for varnish can also be used as binders, but drying oil, shellac, and even red wine vinegar (the sugars are the binder) have been used.
Blotching: The tendency for stain or dye to color wood unevenly. Cherry and pine are two woods that commonly blotch when stained. Blotching can be caused by irregular grain, by resins in the wood, or by a combination of the two. In irregular grain, the cellular structure of the wood deviates from a straight growth pattern, therefore there will be some amount of end grain exposed on the wood's surface. This end grain absorbs much more stain or dye than the surrounding areas, becoming much darker. Resins in the wood, particularly in gum deposits found in cherry and pine, are dissolved by the solvents in oil base stains, partially sealing the surrounding wood. This prevents the stain or dye from penetrating and adhering to the surface. Blotching can be prevented by partially sealing the wood with a stain controller or ½ lb. cut dewaxed shellac, and by treating exposed end grain with wood size.
Blushing: A whitish discoloration, usually in lacquer, caused by the finish absorbing water. In cool or humid weather, the cooling effect caused by the rapid evaporation of solvents from the lacquer will cause moisture to condense on the surface, causing the lacquer to blush. This can be prevented by adding a retarder to the lacquer to slow the evaporation of the solvent. A similar condition to blushing is caused by leaving moisture in contact with a finish. This is remedied by carefully buffing the surface with a cloth moistened with the appropriate solvent (evaporative finishes), or by treating with a commercial ring remover (some reactive finishes).
Bristle: The brush material of a finishing brush. When used alone, the term usually refers to China bristle. See also Badger, Camel, China Bristle, Chisel Cut, Fitch, Flagged Bristles, Flat Cut, Nylon, Oval Cut, Ox Hair, Polyester, Sable, Squirrel Hair, Taklon, Tapered Bristles, Tipped Bristles.
Brush Marks: Parallel marks in the finish left by a brush. A properly thinned finish will 'flow out' as it cures, giving a surface free of brush marks.

Burn In, Burn-In: 1) Burn In. To melt purpose-made shellac sticks into small gouges in finished surfaces using a burn in knife. The sticks come clear and in a wide array of colors to match most finished surfaces. Fresco colors mixed with shellac may then be painted on to simulate wood grain.; 2) Burn-in. The degree to which a coat of finish dissolves the previous coat. In evaporative finishes, burn-in is 100%. Waterborne finishes have a burn-in of 10-20%. Reactive finishes have a burn-in of 0%.

Brazilwood: A popular dye from several species of South American redwood trees. Produces vibrant reds, browns, and purples, depending on the mordant.

Bronze Wool: Similar to steel wool but made of bronze. Used in refinishing to strip old finishes. Steel wool sheds fibers, which may stick in the wood and rust later, forming a stain. Bronze has a reduced tendency to oxidize, so it causes fewer problems for the refinisher.

Build: Directly related to the solids content of the finish, build refers to the thickness of finish left on a surface after it has cured. A higher build means that the finish will produce a thicker film in fewer coats.

Butcher Block Oil: Simply mineral oil (paraffin oil). Completely non-toxic, used on cutting boards and such. Nondrying, so it needs regular reapplication to keep the wood's surface protected.

Camel Hair: A very soft bristle from the tails of European squirrels, not from camels. Used for lettering and detail work.

Carnauba Wax: A natural wax derived from the leaves of the carnauba palm of South America. Carnauba is the hardest of the natural waxes, and can be found in pure blocks or mixed with other waxes in paste wax.

Catalyst: A chemical that speeds up the reaction of other chemicals without being consumed by the reaction.

Catalyzed Lacquer: A two part formula that is mixed and than sprayed onto the wood. Harder, tougher, and more resistant to moisture and chemicals than regular lacquer. Some professionals use catalyzed lacquer on kitchen cabinets and for industrial furniture that must withstand exposure to chemicals and abrasion. See also Crosslinked Finish.

Cellulose Acetate Butyrate (CAB) Lacquer: A much less flammable form of lacquer than nitrocellulose, used on aircraft. See also Lacquer.

Chatoyance: A property of reflecting light, most visible on light colored softwoods, mahogany, satinwood, and semi-precious stones like tiger-eye quartz. (The term apparently derives from a French lapidary term for tiger's-eye quartz.) Chatoyance is what gives figured wood its three-dimensional effect, and is a quick test to differentiate between wood veneer and the higher quality printed vinyl laminate.

Chemical Dye: See Chemical Mordant.

Chemical Mordant

A chemical used to "fix" the color of a natural dye or to color wood on its own via a chemical reaction with extractives in the heartwood.
***Chemical Safety Note:***
Always wear gloves designed to resist the chemical(s) being handled, and wear safety goggles designed for protection from spattered chemicals (these have covered vents). Chemical mordants should always be mixed in clean, non-porous containers. Never mix two chemicals without prior knowledge of any potential reactions between them. When mixing chemicals with water, always add the chemical to the water, never the other way around. It is strongly recommended to do further research into the nature of a particular mordant prior to using or handling it.

China Bristle: Bristle from Chinese hogs. Inexpensive, springy, and naturally flagged tips. Popular for disposable brushes, as well as higher quality brushes.

China Brush: A brush with China bristle.

Chip Brush: A disposable, poor quality brush with China bristle, useful for applying stains and glue. So named (so I hear) because it is also the type of brush used by machinists to sweep metal chips off of a workpiece without risking getting cut or caught in the machinery in the process.

Chisel Cut: A brush with a square end but beveled top and bottom edges. The most common type used in wood finishing. The chisel shape is better suited to cutting in edges then a square cut.

Clearcoat: See Topcoat

Coalescing Finish: A new term used to classify waterborne finishes. They do not cure purely by evaporation, nor do they cure mostly by oxidation like reactive finishes; they coalesce. See also evaporative finish, reactive finish.

Cochineal: A natural dye made from dried tropical insects. Produces many shades of red mixed when with alum.

Conditioner: See Stain Controller.

Conversion Gun: A type of HVLP spray gun that is powered by an air compressor; so called because it converts a low volume of highly compressed air into a high volume at lower pressure.

Conversion Varnish: See Catalyzed Lacquer.

Copal Resin: Hard, brittle natural resin derived from modern or fossilized tree sap. Used commonly in varnishes until the introduction of synthetic resins.

Copper Sulfate (Blue Vitriol) CuSO₄: A chemical mordant. Comes as blue crystals, highly toxic, used for preserving wood. Produces dark gray and olive tones with logwood dye.

Crackling: Imitating crackled paint by applying a water-based or latex paint over wood size. See also Craquelure, Crazing.

Craquelure (Crazing): The fine pattern of cracking found on old varnish finishes, also called crazing. The cracks are produced as the wood moves with changes in moisture content after the varnish has lost much of its original resilience.

Crazing, Alligatoring: A pattern of cracks or lines on a newly finished surface, resembles cracked mud on a dry lakebed. Can be caused by re-coating some finishes too soon, or by applying incompatible finishing products without sealing first, such as a waterborne finish over end grain treated with wood size or lacquer over a soft oil-based finish.

Crosslinked Finish: Any finish that polymerizes, forming larger molecules as it cures on the wood. Includes all reactive, catalyzed, and conversion finishes. Since they cure by a polymerization reaction, croslinked finishes do not dissolve easily, and they are the best option for finishes that must withstand chemicals or heat. A side effect of curing by polymerization is that coats of finish do not burn in to previous coats, so scuff sanding between coats is necessary to allow good adhesion between coats.

Cure: The process by which a finish hardens. For evaporative finishes, this is the final stage of evaporation of the solvent. For reactive finishes, the curing process occurs after the main solvents have evaporated, as the finish is polymerizing. A finish is said to be at a "soft cure" when it is dry and safe to be handled, but not fully hardened yet. The finish reaches a "hard cure" or "full cure" when the curing process is completed.

Cutch: A natural dye extracted of the heartwood of the Asian acacia tree. Produces various lightfast shades of brown, from beige to chocolate.

Cutting In: When painting, the technique of using a brush to outline the edge of an area of color first. A good technique will give a straight edge without the need to mask. When pre-finishing, cutting in can be used in lieu of masking around joints, if care is taken to avoid drips and spills getting on the joints.

Danish Oil: Basically, Danish Oil is one part oil, one part varnish resin, and one part mineral spirits. Manufacturers may add other additives such as stain pigments, flatting agents, and so on to alter the properties and look of the finish. Danish oil combines the best features of oils and varnishes: it is fairly durable, penetrates the wood well, and can be applied with a rag.

Dark Rings: Dark colored stains in the wood, caused by a reaction with tannin in the wood. Dark rings can be removed with oxalic acid.

Denatured Alcohol: Ethyl alcohol made unfit for drinking by the addition of other compounds such as methyl alcohol, used to thin shellac, also used as a cleaning agent on glass, metals, and rubber. Dissolves shellac.

Degloss, De-gloss: To remove the gloss, or shine, before coating with a finish or paint, to improve the adhesion between separate coats. Deglossing can be done with fine sandpaper (320 to 400 grit), steel wool (#0000), non-woven abrasive pads (maroon or gray), or, for paint preparation, with a liquid cleaner / deglosser such as TSP (trisodium phosphate).

Dewaxed Shellac: Shellac that has had its natural waxes removed, useful as a sealer under almost any finish. Some shellac comes dewaxed from the manufacturer; it will be specifically stated right on the can. Dewaxed shellac can also be made by letting a blonde or orange shellac sit until the wax settles to the bottom and separating the clear liquid.

Di-Basic Ester (DBE): A paint and varnish remover. Takes up to twelve hours, and is less effective on shellac and lacquer, but is the safest available.

Distressing: Producing the look of an antique by mimicking the effects of incidental wear and abuse. Techniques used include scuffing through the finish on exposed edges, beating the wood with irregularly shaped objects, crackling paints, and burnishing wear points.

Double Action: Refers to a finishing spray gun or airbrush where the trigger first opens the air valve, then the fluid valve. This allows the airflow around the nozzle to stabilize before the finish is introduced, resulting in more even flow of finish at the beginning and end of a stroke. This is especially important when color is being applied to the wood to create a fade-in or fade-out effect, such as a sunburst effect on a solid body guitar. In these cases, the finishing pass cannot always be started off of the edge of the wood, so even the first instant of finish flow from the gun is important.

Dragon's Blood: A dye made of resin from the fruit of the rattan palm. Produces bright, lightfast reds.

Drips: See Runs, Sags, and Drips.

Dye: There are two common ways to color wood: stains and dyes. Dyes are solutions of chemicals that bond to the wood fibers. Since the coloring takes place on a molecular level, there is no muddying of the wood grain, and often the grain patterns are highlighted by dyes.

Ebonizing: The technique of dying wood black. Favorite dyes for ebonizing include aniline dye and iron acetate, or iron buff.

Epoxy: A tough and extremely durable glue and finish, as much as fifty times thicker than a coat of varnish. A two-part epoxy adhesive or a specially formulated "bartop finish" epoxy may be used in finishing. When combined with fiberglass cloth, epoxy can produce a protective finish which will outlast any other in such strenuous applications as high traffic wood floors, small boat bottoms, etc., however epoxy/fiberglass is difficult to use and very expensive.

Ethyl Alcohol (Grain Alcohol, Ethanol) C₂H₅OH: This is the drinking type of alcohol. Not usually used for finishing as it is taxed as liquor. See denatured alcohol.

Evaporative Finish: Any finish that cures solely by evaporation of a solvent. Includes shellac and lacquer. These finishes are easy to repair, as any new coat will burn-in to the old finish and blend with it. Evaporative finishes are thermoplastic, meaning they soften with heat. See also reactive finish, coalescing finish.

Extender: 1) A solvent base added to a dye or stain to thin it, simultaneously reducing the color intensity and causing the product to cover more area.
2) A Retarder.

Ferrous Sulfate (Copperas) FeSO₄: Chemical mordant available in crystalline form, highly toxic, reacts with tannin in wood. Produces steel gray to bluish tones, ebony-like black with logwood dye or alum.

Filler: See Wood Filler or Grain Filler.

Finish: Any protective coating applied to wood. A finish may be as simple as a coat of paste wax or oil, or as complex as applications of dye, sealer, wood filler, stain, clearcoat, glaze, more clearcoat, and a final rubbing out and waxing.

Fish Eyes, Fisheye: Depressions in a finish caused by application over an incompatible solvent or other substance such as wax, grease, or silicone oil. Preventing fisheyes between coats of finish can be as simple as waiting until a water or oil based finish has completely cured before applying an oil or water based finish over it. In the case of contamination with grease, oil, or wax, use an appropriate solvent such as acetone to clean the surface, then seal it with dewaxed shellac.

Fitch: 1) Fitch Bristle. Comes from American skunks or European weasels. Soft bristle used for detail work or mixed with other bristles.
2) Fitch Brush. Made from fitch, china, or badger. Used for detail work.

Flagged Bristles: Bristles that split ant the end into several smaller fibers. Flagged tips enable a brush to hold more finish.

Flat: See Matte.

Flat Cut: A square ended shape usually only used on brushes for heavy latex paints.

Flattener / Flatting Agent: A finely ground powder added to finishes to break up the surface, causing it to scatter light. The amount of flatting agent added determines the gloss of a finish. Common flatting agents include silica (ground glass) and zinc stearate. Flatting agents have the tendency to obscure the grain of the wood when several coats of clear satin or semigloss finish are applied, and flatteners are also reputed to soften the coating slightly. Therefore, it is recommended that several coats of gloss topcoat be applied, finishing by rubbing out the finish or by applying a coat of whatever gloss is desired.

Flow Out: The tendency of a finish to flow into depressions left by the application process. When brushing, finishes flow out and fill the brush marks. When spraying, finishes flow out to eliminate orange peel texture.

French Polish: Basically a technique for padding on thinned shellac, sometimes mixed with pumice and/or oil, and rubbed on to produce a unique shine, with each coat buffing and rubbing out any imperfections in the previous one.

Fresco Powders (Earth Pigments, Furniture Powders): Powder, may be suspended in any liquid, lightfast, easy to use, opaque. Can be mixed with protective finishes.

Friable: In abrasive compunds, a friable grit breaks down into smaller, but still sharp grains. Non-friable abrasives wear by the rounding of grit particles, so they will tend to burnish the surface more as they dull.

Fustic: A dye extract from the heartwood of the American Mulberry tree. Produces orange yellow on its own, yellows to greenish-yellows with alum.

Garnet (G / Gar) Al₃B₂Si₃O₁₂: Amber colored abrasive often used for the final sanding before applying a stain. Garnet is non-friable (its crystals wear out and become rounded), and dulls relatively quickly, leaving a much less visible scratch pattern on the wood, but burnishing the surface in the process.

Gel Stain: A stain in a thick gel base; easy to use, covers more evenly on difficult to stain woods like pine. Can also be used as a glaze between coats of clear finish or to produce wood grain effects of painted surfaces.

Glaze: A technique for producing special coloring effects by applying stains or tinted finishes between clear topcoats. Used to color extremely difficult to stain woods like pine and cherry without any chance of blotching. Also used to produce antique effects and to hide repairs or light colored sapwood.

Glazing Stain: Liquid suspended in varnish; excellent for figuring, shading, and correcting sap streaks, opaque. Glazing stain is softer than clear varnish, so it needs a protective topcoat.

Gloss: 1) The degree of smoothness of a surface, at the microscopic level, which determines how well it reflects, rather than scatters, light. Flatting agents may be added to finishes to decrease their gloss to the desired level. Degrees of gloss include: flat or matte (1-9%) low sheen (10-25%) satin, or eggshell (26-40%) semi gloss (41-69%) and gloss, high gloss, or full gloss (70% +)
2) A high-gloss finish, with no flatting agents added. High gloss or full gloss is generally considered to refer to a finish that reflects 70% or more of incident light when tested with a gloss meter. Glossy finishes, since they reflect like a sheet of glass, tend to show slight contours and imperfections in a surface more than lower sheen finishes. Also, since they do not scatter light, glossy finishes generally intensify the color of the wood more than lower sheen finishes.

Grain Filler: Grain filler, or pore filler, is essentially a thinned down wood filler. It is used to get a glasy smooth surface on coarse grained woods for a finer, more formal finish. The filler is wiped or brushed onto the surface of coarse grained woods and packed into the pores. Just before it hardens, the excess filler is wiped off at a diagonal to the grain, leaving it only in the pores. After a little sanding, the wood surface is ready to take a glassy smooth finish. Grain fillers require extra work on the part of the finisher, so they are only used on open grained woods like oak and mahogany, and often only on the surfaces that really show like table tops and cabinet fronts. When using a grain filler on wood that is to be dyed and / or stained, use the dye first, seal the wood, apply a filler that will match the final color of the piece, then apply the stain.

Gravity Feed: A finish sprayer that has a reservoir above the needle tip, so that the finish flows into the gun by the action of gravity. The advantage to a gravity feed is simplicity and low cost, as well as easy and rapid refills of the reservoir. Since the finish is in a container above the user's hand, a gravity feed gun is not as comfortable to use as the other types, and since the reservoir is vented, it can leak if the gun is turned to an unusual angle, such as when finishing an overhead surface. See also Pressure Feed, Siphon Feed.

Hide Glue: A natural adhesive obtained by cooking animal hides and hoofs. Hide glue, being a natural substance, has a limited shelf life when mixed with water, so it is available in a dry pearl form as well as ready-mixed. Hide glue is used in finishing in a thinned down form as a crackling base and as wood size.

Hog Bristle: See China Bristle.

Holiday: A dry spot or bare patch in a coat of finish. Normally caused by a brush or sprayer running dry.

Hot Coat / Hot Coating: The tequnique of applying a coat of finish over another coat that has not fully cured. This is usually done simply to save time, and can also save a sanding step for some finishes. Not all finishes can be hot coated, however, and it often takes a bit of practice to get the technique right, so don't try it out on that blanket chest that's due for delivery tommorrow.

HVLP: High Volume Low Pressure, refers to a type of finish spraying equipment. Advantages of HVLP include greatly reduced overspray, which also means greater economy of finishing materials.

Hydrated Lime (Quicklime, Calcium Oxide) CaO: A natural mordant available as crystals. Toxic. Produces antique limed finish on hardwoods such as cherry and walnut, must be neutralized with vinegar or other dilute acid.

Indigo: A dye extracted from Indian indigo plants. Produces deep blue, yellow-white with lye.

Iron Acetate, Iron Buff: A chemical dye solution made by soaking rusty steel wool in white vinegar for several days. The solution is filtered and immediately applied to wood. Produces silvery grays on its own, jet black on wood treated with tannin.

Isopropyl Alcohol C₃H₈O: Soluble in water, can be used as a cleaner or to dissolve shellac. Rubbing alcohol is usually a 70% aqueous solution of isopropyl alcohol, however the 30% water it contains renders it completely useless for finishing. The 97% isopropyl alcohol solution found in many pharmacies can, however, be added to shellac to act as a retarder.

Japan Color: Fresco colors concentrated in a varnish; excellent for tinting varnishes. Tends to dry slowly unless Japan driers are added.

Japan Drier: A liquid catalyst added to oil finishes to speed the drying process. Old Japan driers contained heavy metals as catalysts and were highly toxic, modern versions are somewhat less hazardous.

Lacquer: In the broader sense, any varnish that dries quickly and produces a hard, shiny finish may be called lacquer. In the strict definition, true lacquers are nitrocellulose or CAB based. These lacquers are resistant to heat, moisture, and abrasion; and have a uniquely crystal clear, glassy shine. Disadvantages include strong fumes, and blushing in humid weather. Blushing can be prevented by adding a retarder to the lacquer to slow the drying process, and can be repaired by applying blush eraser after the fact. See also Nitrocellulose Lacquer, Cellulose Acetate Butyrate Lacquer, Brushing Lacquer.

Lacquer Thinner: Petroleum distillate, avoid breathing its fumes. Thins lacquers, softens plastics, & degreases. Highly flammable. Dissolves shellac & lacquer. Evaporates very quickly.

Linseed Oil: Oil from flax seed. Linseed oil is treated by "boiling" oxygen through it and treating it with catalysts to partially polymerize it, so when it is applied to the wood it will dry after about 24 hours. Essentially, linseed oil becomes so rancid that it hardens into a tough, rubbery plastic in the wood. Since linseed oil cures by an oxidation reaction, it is called a reactive finish and cannot be dissolved back out of the wood. Linseed oil produces heat as it cures, so oily rags must be disposed of carefully to prevent spontaneous ignition. Linseed oil gives minimal protection from moisture and none from wear, as the finish is in the wood rather than on it. Also, linseed oil promotes mildew growth on outdoor wood. Despite these shortcomings, linseed oil is a very popular finish, and has many advantages as described under Oil Finish.

Logwood: A dye extracted from Central American Campeche tree species. Produces lightfast grays, browns, blacks, blues, and purples, depending on the mordant.

Long Oil Varnish: A varnish that uses a higher proportion of oil to resin. Dries more slowly than short oil varnishes and is softer, but is also more flexible and resilient.

Madder Root: A natural dye extracted from the roots of the Eurasian madder plant. Produces reds, blues browns, and yellows, depending on the mordant.

Mastic Resin: Gum from the Mediterranean mastic tree, commonly used as a resin for varnishes until the discovery of economical synthetic resins. Used today in varnishes for restoration work and on oil paintings.

Matte: A degree of gloss, referring to a finish that has little or no shine. See also: Gloss (1).

Methyl Alcohol (Methanol, Wood Alcohol) CH₃OH: A poisonous alcohol, used primarily as a thinner for shellac, which it dissolves. Do not use with oil or latex paints or with varnishes. Soluble in water, hygroscopic (absorbs moisture from the air). Derived by distillation of wood in the absence of air. Denatured alcohol is the most recommended solvent for shellac, as it is much less toxic.

Methyl Ethyl Ketone (MEK) C₄H₈O: Soluble in water and many alcohols, dissolves plastic, typically used in making model airplanes (airplane glue). Avoid breathing vapors.

Methylated Spirit: See Denatured Alcohol.

Methylene Chloride & ATM (Mixture): A paint and varnish remover. Will remove most finishes, less expensive than straight MC, but still nasty stuff to work with.

Methylene Chloride & Methanol (MC) CH₃Cl + CH₃OH: Paint stripper. Will remove almost any finish, but produces toxic fumes. The most common solvent combination used in paint strippers. Produces harmful vapors and will burn skin on contact.

Methylene Chloride & Methanol & Ammonium Hydroxide CH₃Cl + CH₃OH + NH₄ (aq): The strongest and fastest acting of all strippers, use only when other strippers are ineffective. Can stain some hardwoods, and produces toxic (and explosive) fumes. You can be sure that this is some really nasty stuff. Highly caustic, harmful vapors, will burn skin on contact, flammable, smells really bad.

Milk Paint: A paint made from milk and natural colors. Casein from the milk acts as the binder for earth pigments. Used on reproduction and restoration work, and on country style furniture. Milk paint has a washed-out or chalky look when dry, but colors can be made vivid by application of wax or a clear topcoat.

Mineral Oil, Paraffin Oil: Petroleum distillate, another name for paraffin oil. A completely nontoxic, nondrying oil used on items that will come into contact with food. Also used as a lubricant when rubbing out finishes.

Mineral Spirits: Petroleum distillate, paint thinner. Used as a solvent in many oil finishes.

Mordant: See Chemical Mordant.

MSDS: The Material Safety Data Sheet, usually required to be shipped with any shipment of potentially hazardous material, such as a flammable finishing product. Retailers are also generally required to have these on hand for any finishing products they sell. The MSDS is one place to find out important information about a given finishing product, including safety considerations, ingredients such as the resin base of a varnish, the precent solids of a varnish, and so on. Often, a call to the manufacturer can answer all of these questions and more, but sometimes the MSDS might just be faster.

Naphthalene (Naphtha) C₁₀H₈: A petroleum distillate used as a medium-volatility solvent. Removes grease and waxes prior to finishing. Used to thin varnishes. Evaporates more quickly then mineral spirits.

NGR Stain (Non-Grain Raising): Liquid, dissolved in methanol & petroleum distillate solution; does not raise wood grain, lightfast. May be either a dye or a dye / stain combination.

Nitrocellulose (NC) Lacquer: The most common type of lacquer. Nitrocellulose is made from cellulose (often cotton fiber) treated with concentrated sulfuric and nitric acids. Nitrocellulose is highly flammable (even explosive), and should not be used on surfaces that may be exposed to sparks or extreme heat. A more flame-resistant version of lacquer uses cellulose acetate butyrate. See also Lacquer.

N-Methyl 2-Pyrrolidone (NMP): Paint stripper. Takes up to three times as long as methylene chloride to work, and is more expensive, but is safer due to decreased volatility.

NMP & DBE (Combination): Faster at stripping paint than Di-Basic Ester alone, but more expensive and less effective than methylene chloride based strippers.

Non-Woven Abrasive: A spongy abrasive made from plastic with embedded abrasives, contains no metal. Used for scuff sanding between coats of finish, as it does not tend to cut through the finish on high spots or corners.

Nylon: Used as a synthetic bristle for brushing waterborne coatings. Nylon can be flagged and tapered like natural bristles.

Oil: See Oil Finish

Oil & Beeswax: A popular finishing combination made by melting the wax, then stirring in tung oil. Can be buffed to a satiny smooth finish, smells pleasant, and works well on tool handles. Other waxes may also be used for a harder finish.

Oil Dye (Oil Stain): Liquid dissolved in mineral spirits; penetrates open-grained wood, moderately lightfast, transparent, easy to apply & mix colors, bleeds, needs a sealer coat of dewaxed shellac.

Oil Finish / Penetrating Oil: This category includes tung oil, mineral oil, linseed oil, and similar products. Oils actually penetrate into the wood, thus not providing the protective surface layer that other finishes do, but bringing out more of the wood's grain and color than other finishes can. Oils have a relatively low resistance to water and alcohol. Most oils have dryers added to them, while others, like mineral oil, do not dry out. Oil finishes are easily repaired by simply re-coating the scratched surface with more of the same oil. Linseed oil is not suitable for outdoor finishes, as it promotes mildew growth.

Oil & Urethane: A popular mix combining the penetration and grain-enhancing properties of an oil with the durability and surface finish of polyurethane. Also takes longer than regular polyurethane finishes to dry. Usually only comes in a satin gloss, a side effect of the oil.

Orange Peel: A finishing defect characterized by the finish having a texture like the peel of an orange. Usually caused by spraying with the gun's nozzle too close to the surface, or with too much air pressure being supplied to the gun.

Orbital Sander (1/4 Sheet Sander): A final finishing sander. Uses ¼ of a standard sheet of sandpaper which is held on by clips on each side of the sander's pad. Used as the final power sander before switching to sanding with the grain by hand with a sanding block when the wood is to be dyed or stained.

Oval Cut or Oval Chisel Cut: A chisel cut brush with an oval, rather than rectangular cross-section. Holds more finish than a standard chisel cut brush. Popular for shellac, lacquer, and oil varnishes.

Overspray: Errant particles or droplets of finish from a spray gun. Standard (high-pressure) finish sprayers may waste more finish as overspray than actually ends up on the wood. HVLP systems waste far less finish as overspray. Overspray adhering to a finish is often caused by holding the spray gun too far from the wood.

Ox Hair: Silky, durable hair from behind the ears of oxen. Used as a bristle in brushes for sign painting.

Oxalic Acid (COOH)₂: Used to remove dark stains from woods with high tannin content. Obtained as crystals, colorless, odorless, toxic.

Padding: A technique used to apply shellac or lacquer. A ball of cloth is moistened first with the appropriate solvent, then with the finish. It is then wrapped with a couple layers of cloth, care being taken to avoid wrinkles. The pad is then rubbed over the wood surface and recharged with finish as necessary. The advantage of the method is that the finish is applied in hundreds of very thin coats that dry almost instantly. This provides a tough, dust free finish, although it requires more skill and effort on the part of the finisher.

Paraffin Oil: See Mineral Oil.

Paint Thinner: See Mineral Spirits.

Paste Wax: Typically a mix of carnauba, beeswax, and/or other waxes, usually mixed with a solvent to form a paste, hence the name "paste wax". These finishes can produce from a matte to a high gloss finish, although this depends on both the product and the surface to which it is applied. They cannot be topcoated with any other finish, but can be applied over any other finish. Wax finishes on their own do not provide the long term or wear protection of other finishes, and need to be reapplied periodically; however, they do an excellent job of providing a replaceable topcoat for other finishes, increasing their wear and moisture resistance.

Paste Wood Filler: See Grain Filler.

Peeling: Indicates that a layer of finish did not bond well to the underlying material, and is now peeling off. This is usually caused by not de-glossing the underlying coat of finish, or by using incompatible products without an appropriate sealer in between, or by contaminants on the surface such as wax. See also Adhesion, Degloss.

Penetrating Oil: See Oil Finish.

Penetrating Oil Stain: See Oil Dye.

Phenolic Resin: One of the oldest synthetic resins used in varnish. Phenolic is harder than other resins, but tends to yellow more.

Pigment: A pigment is a finely ground powder used to add color to paints and stains. Pigments can be chemicals that do not dissolve in whatever solvent they are used with, or natural mineral and plant materials. See also Stain.

Pickling Stain: A white stain usually applied to medium brown woods for a pickled finish.

Polyester: Used for synthetic bristle brushes, often mixed with nylon.

Polymerizing Finish: See Crosslinked Finish.

Polyurethane: Any varnish formulated with urethane resins, usually an alkyd / urethane base. Available in flat to glossy, extremely durable and highly resistant to water and alcohol. Easy to apply, but difficult to strip off. Can come in oil or water based formulations, and with or without UV inhibitors, to keep colorful woods from fading outdoors. Although they sometimes have decreased wear and water resistance, water based urethanes lack the strong solvent smells of their oil based counterparts, so are good for use in enclosed or less ventilated spaces. Tends to have a "plastic" look.

Potassium Carbonate (Potash) K₂CO₃: Chemical mordant, comes as crystals, mildly toxic. Produces a range of greens with alum and fustic.

Potassium Dichromate K₂Cr₂O₇: Chemical mordant. Crystals, orange in color, extremely toxic, reacts with tannin. Produces deep reds to rich browns, combines well with aniline dyes.

Potassium Permanganate (Violet Potash) KMnO₄: Chemical Mordant available in crystalline form. Mildly toxic, used for ebonizing. Turns wood with high tannin content a purplish brown. Dyes skin brown on contact, won't wash off.

Pound Cut: The standard units for describing the concentration of shellac resin in alcohol solvent. Refers to the number of pounds of shellac resin in one gallon of solution. A three pound cut, the most common cut, means one pound of shellac flakes dissolved in one gallon of alcohol. A more practical means of calculating and measuring pound cut is to use ounces per cup, e.g. two ounces of shellac flakes in one cup of alcohol makes a two pound cut.

Pre-Finishing: Finishing pieces of a large assembly prior to final assembly. Especially helpful on large cabinets, as it involves finishing flat surfaces rather than vertical surfaces and corners. When pre-finishing, it is important to keep finish off joint surfaces, as wood glue will not adhere to finished surfaces.

Pre-stain Conditioner: See Stain Controller.

Pressure Feed: A type of finish sprayer that uses a pressurized reservoir (or pot) to hold the finish, and a tube to deliver it to the spray gun. Since the reservoir is not on the gun, the gun is lighter and more maneuverable than other feed styles, and since the reservoir may be ten feet from the gun, there is no restriction on how big it can be. This means that the finisher could easily fill the gun with five gallons of finish, and be all set for an uninterrupted marathon of finishing. Since the pot is pressurized, thicker, more viscous finishes can be sprayed, since the pressure from the pot will ensure that the finish will flow through the gun. See also Gravity Feed, Siphon Feed.

Primer: A sealer and neutral colored paint applied as the first one or two coats to promote good adhesion and prevent stains from bleeding into a coat of paint.

Pumice: Finely powdered volcanic glass, used by finishers to rub out the final coat of fine finishes to produce a smooth, even gloss. Commonly available in two grades: 2F, which is fairly coarse, and 4F, which is an intermediate grit. Rubbing with pumice is normally followed by a final polishing with rottenstone and wax.

Raise the Grain: The process of wetting the wood and letting it dry, followed by a very light sanding to knock down the raised grain. When sanding is completed, some of the wood's fibers have been only partially separated from the wood, and when the wood gets wet (by water or any finish containing water), these loose fibers stand up and leave the surface feeling rough. Raising the grain removes these loose fibers so a waterborne finish can be applied without raising any additional fibers. It is very important, when sanding the raised grain, not to over sand, which will create more loose fibers to raise the next time the wood is wet.

Random-orbital Sander (ROS): A sander with a round pad attached to a motor by an eccentric bearing. This produces an orbital motion while the pad also spins slowly on the bearing. The idea is to achieve a more aggressive cutting action while leaving an inconspicuous scratch pattern. Random -orbital sanders are an intermediate step between stock removal with a drum or belt sander and finishing with an orbital sander.

Reactive Finish: A crosslinked finish. Reactive finishes cannot be dissolved like evaporative finishes. Since new coats do not burn-in to previous ones, sanding between coats is necessary to allow for good adhesion of the new coat. Rubbing out is trickier with reactive finishes, because if a coat is worn through, a witness line appears at the interface of the two separate coats. See also coalescing finish, evaporative finish.

Refinisher: See 'Acetone, Toluene, & Methanol'.

Resin: The natural or synthetic polymer that forms the hard film of a finish. Resins also act as binders in most stains and paints.

Retarder: A slow solvent or chemical inhibitor added to a finish to increase its drying or curing time.

Rottenstone: A very fine powder, often made from diatomite, used as the final step in rubbing out a finish. Rubbing with rottenstone polishes away the scratches left after the use of pumice, and a final rubbing with rottenstone and wax will produce a very professional looking, if laborious, finish.

Rub Out: To smooth a topcoat by wet sanding or by using pumice and rottenstone with a felt block and mineral oil or wax. Rubbing out removes imperfections in the finish caused by dust settling onto the tacky finish, bugs, bubbles, and brush fibers.

Runs, Sags, and Drips: Flaws in a finish caused by applying too much finish in one coat, causing the finish to flow along the surface, particularly on vertical surfaces. Can be removed by cutting off the drips after the finish has cured, then sanding the finish flat and applying another coat.

Sable: Bristle from minks or weasels; forms a fine, sharp point when wet. Used for the finest detail work.

Sag: See Runs, Sags, and Drips.

Sanding Block: Any block of material used to support sandpaper when sanding. Sanding blocks can be made from cork, felt, wood, Styrofoam, foam rubber, and more. They may be flat or contoured for sanding curved surfaces and moldings. A good sanding block provides a firm base for the sandpaper, but has some "give" to let the sandpaper conform slightly to high spots and corners, prolonging the sanding life of the paper. When sanding to scuff a surface, a soft-faced sanding block is used, such as Styrofoam, soft foam rubber, or soft felt. When sanding to remove high spots and flatten a surface, a harder faced block is used such as hard felt or wood faced with leather or a thin layer of cork.

Sandpaper: A catchall term for any sheet abrasive, but more specifically paper-backed abrasive. Sandpaper is made by coating paper with glue; the first coat is the make coat, then the abrasive is attached with the size coat. Abrasives used include glass (rarely used), emery, silicon carbide, garnet, and aluminum oxide; the latter three are the most commonly used in woodwork.
Abrasives can be applied in open or closed coats. Closed coat means the entire surface of the paper is covered with grit. Open coat, which is used in woodworking, has about 70% of the surface covered, the open spaces between particles of grit providing a place for dust to collect until it can be cleared from under the working sandpaper.
The weight, or thickness of paper used is indicated by letters: 'A' weight paper is thin and flexible, but tears easily on corners. 'C' weight paper is thicker and tougher, but cannot conform to fine details on carvings and moldings. Waterproof paper and glue is used for sandpaper that will be used for wet sanding.
The coarseness of abrasive particles is given by the grit number of the sandpaper. Grits range from about 20, extremely coarse, to about 2000, "super-duper fine". Woodworkers usually use grits from 60 to 320 or 400 on wood and 320 to 600 on finishes.

Sandarac Resin: A brittle resin obtained from the sandarac tree and certain members of the pine family. Used in the production of varnish until the discovery of synthetic resins.

Satin: A degree of gloss. Refers to a finish that has some shine to its surface, but would not be considered shiny. See also: Gloss (1).

Scuff Sanding: Sanding, usually between coats of a reactive finish, for the purpose of scuffing the surface to promote good adhesion between coats. Usually done with fine sandpaper, such as 320 or 400 grit. See also Degloss.

Sealer: Any film-forming finish applied to wood to seal the surface. Often used to seal in oil, stain, or other matter that may contaminate subsequent coats of finish. Sealers are also used to partially seal wood prior to staining in order to even out the color of the stained wood. Sanding sealers are thinned finishes, usually with stearates added to make them softer and easier to sand.

Semi Gloss: A degree of gloss. Refers to a finish that has more shine to its surface than satin, but less than full gloss. See also: Gloss (1).

Shellac: A natural resin derived from a shell secreted by the lac insect of India during a larval stage. Raw shellac contains both a dark reddish dye and wax. Processing removes the dye, and bleaching can yield a crystal clear shellac. It is the oldest of the surface-film forming wood finishes, and is an excellent sealer. It can be applied over any finish except wax, and almost any finish can be applied over dewaxed shellac. Shellac can produce a "wet look" finish relatively quickly, and dewaxed shellac is quite durable indoors. Wax decreases shellac's resistance to moisture and wear, but can increase the build rate of the finish. Shellac has low resistance to heat and alcohol, but good moisture and abrasion resistance.
Shellac can come ready mixed, or in flakes which are mixed with alcohol. The flake form has an indefinite shelf life. One mixed with alcohol, however, shellac begins to react with it, producing esters that will not dry properly and have reduced moisture resistance. To test old shellac to see if it is any good, place a drop onto a glass plate and let it dry for about 15 minutes. After 15 minutes, the shellac should be dry to the touch, not gummy, and flake off of the glass.
Since shellac is a natural resin, it comes in different grades. These are, in order of refinement: Seedlac (raw, unrefined, dark and waxy, unsuitable for finishing), Buttonlac (the lowest grade useful for finishing), Orange, Garnet, Blonde, Super Blonde, and White or Bleached (the most refined grade, also usually dewaxed). Shellac can be dewaxed by allowing the wax to settle to the bottom, then pouring off the clear liquid into a separate container.

Shellac Sticks (Burn In Sticks): Shellac mixed with resin and sometimes waxes, sold as solid sticks. The sticks come in many colors from clear or amber to white, black, and many shades of brown. Shellac sticks are "burned in" to small dings and gouges in finished wood. The color of the stick is matched to the base color of the wood, the stick is burned in and leveled with the surrounding surface, then shellac with fresco colors is painted on to mimic wood grain, matching the repair to the surrounding wood. See also Burn In (1).

Short Oil Varnish: A varnish formulated with a lower proportion of oil to resins. Dries fast and is harder than long oil varnish, but is also somewhat brittle.

Single Action: Refers to a finishing spray gun or airbrush where the trigger only operates the fluid valve, and there is a constant flow of air, or to a gun where the trigger simultaneously opens both the air and fluid valves. See also Double Action.

Silicon Carbide (Carborundum) SiC: Abrasive commonly used for fine grits (over 220) and on wet/dry sanding paper. Silicon carbide is extremely hard, suiting it for sanding between coats of finishes, especially hard finishes like lacquer, but also non-friable, so it doesn't cut as long as aluminum oxide.

Silicone Oil: The wood finisher's nemesis, silicone oil is found in automotive waxes and in old formulations of furniture polishes. Silicone oil has the nasty habit of penetrating wood finishes and getting into the wood itself, preventing anything from adhering to the wood, including the finish. The cure for silicone oil contamination is to seal the wood with a couple coats of shellac-based sealer or vinyl sealer, then topcoat with the desired finish.

Siphon Feed: A finish sprayer that has a reservoir just below the fluid needle. Finish is drawn up into the gun by the partial vacuum created in a venturi, as well as by high pressure air that is vented into the cup from elsewhere in the gun. The advantage to a siphon feed is that when a horizontal surface is being sprayed, the gun naturally hangs in the hand at the correct angle for application, and is therefore very comfortable to use. Since the reservoir is not vented to the outside, a siphon feed can also be used at a greater variety of angles than a gravity feed gun. See also Gravity Feed, Pressure Feed.

Size: Any product, but usually a thin paste, applied to a porous surface to fill and seal it, as in preparation for paint or gilding. See also Wood Size.

Sodium Hydroxide (Lye) NaOH: A chemical mordant. White powder or crystals, highly toxic, highly caustic, hygroscopic, so keep it in a tightly closed container. Easily obtained as a drain opener (Red Devil brand), darkens cherry and oak, must be neutralized with vinegar or other dilute acid.

Solvent: Generally, any liquid that dissolves another substance. In finishing, a solvent is a volatile (evaporating) liquid that is used to thin or remove a finishing product or material.

Solvent Finish: See Evaporative Finish.

Spirit Stain: Alcohol soluble powder; penetrating, dries quickly. Does not raise wood grain the way water based dyes do. May be used to tint shellac.

Spirit Varnish: A shellac-based varnish. Shellac is mixed with other resins to create a quick-drying, tough finish.

Squirrel Hair: Bristle from squirrels' tails; used for detail work

Stain: There are two common ways to color wood: stains and dyes. A stain consists of particles of solid pigment suspended in a solvent with a binder, which sticks the particles to the surface. Stains tend to obscure the wood grain since they are opaque particles deposited on the surface. Stains also tend to highlight texture, since, like paint, they build up thicker in depressions in the wood's surface, like pores, sanding scratches, and end grain.

Stain Controller: A product or solvent applied to wood just before applying a stain. The idea is to saturate the surface of the wood with a clear liquid, so when the stain is applied over the wet controller, it will cover evenly without blotching.

Stannous Chloride SnCl₂: A chemical mordant. White crystals, moderately toxic. Produces light red with brazilwood dye, pink with alizarin, combines well with many dyes.

Stearate: Any of several white, powdery, soapy compounds -- especially zinc stearate. Applied to the surface of some sandpapers to prevent finishes from sticking and clogging the paper. Stearates are highly water repellant, so when using them in conjunction with waterborne finishes, extreme caution should be exercised.

Steel Wool: A fibrous steel product used as an abrasive and polishing agent. Used especially for scuff sanding between coats of finish and for scrubbing off varnish when stripping old finishes. Not recommended for use on bare wood, as steel wool sheds fibers into the wood that might rust later on.

Taklon: A trade name for tapered nylon bristles. Often used in artists' brushes.

Tannin, Tannic Acid C₁₄H₁₀O₉: Yellow or brown powder, mildly toxic, extremely bitter taste. Many woods naturally contain tannin, such as oak and mahogany. Sometimes added to wood to boost its tannin content, for the purpose of using a chemical dye which reacts with tannin. Named for its use in tanning leather.

Tapered Bristles: Bristles that taper from thick at their base to thin near the tip. The taper makes the bristle springier.

Thickness Gauge: See Wet Film Thickness Gauge.

Thinner: A solvent used to dilute, or thin, a finish. The term can refer to any number of solvents, but when used alone, it most commonly refers to paint thinner.

Tinted Finish: Any clear finish that has a coloring agent (pigment or dye) added to it, so that it will alter the color of the wood as coats of it are added. Tinting the finish is often done to build up a richly colored finish, or to add a slight amber cast to an otherwise crystal clear waterborne finish.

Tip Off: A technique for smoothing and removing bubbles when brushing varnish. The brush is held nearly vertical to the wood, with just the tips of the bristles touching. It is then pulled at moderate speed in a continuous stroke along the length of the wood surface.

Tipped Bristles: Bristles that are cut to length, leaving blunt tips. Other bristles are shaped as they are set into the handle, leaving tapered or flagged tips on natural bristles. Tipped bristles are usually found on square cut brushes for heavy latex paints.

Topcoat or Clearcoat: The last coat(s) of finish; or any wood finish that does not contain any added dyes or stains. Usually refers to the final clear coats of film-forming finish (see Varnish) applied over stain to protect against scratches.

TSP (Tri-Sodium Phosphate): A cleaning and deglossing agent used to prepare old painted surfaces for application of new paint. Due to environmental restrictions on phosphates, TSP has been largely replaced by TSP substitutes.

Tung Oil: A natural oil derived from the tung tree of China. Tung oil has less tendency to yellow than linseed oil, and does not promote mildew growth outdoors. Tung oil also cures to a somewhat harder film than linseed oil, making it a more popular ingredient in varnishes.

Turbine: A type of fan used to compress air. In finishing, turbines are used to supply air to HVLP spray guns, and may use from one to five stages, with each stage of the turbine providing incrementally greater compression, and thus greater atomizing power for spraying thicker finishes.

Turpentine: Derived from pine trees, used as thinner and cleaner for oil-based paint, varnish, & enamel. Dissolves wax finishes.

Universal Tinting Colors (UTC's): In wood finishing, a dye, usually in a proprietary alcohol base, that can be mixed with waterborne, oil, varnish, shellac, or lacquer finishes. In painting, a UTC is a pigment in a similar universal base.

Urethane Resin: A synthetic resin used in varnishes, normally in conjunction with alkyd resin. Urethane offers superior protection in all areas compared to other resins, but is lacking in clarity and is harder to repair and rub to a gloss finish.

UV Inhibitors or UV Blockers: Chemicals added to outdoor finishes to prevent Ultraviolet rays from bleaching wood. UV especially tends to bleach the red tones out of colorful exotic woods, like purpleheart or chactekok, leaving them a dull brown. Any finish containing UV inhibitors, including sun tan lotion (seriously!), can prevent this bleaching. Suntan lotion (e.g. Bullfrog) can be applied under oil and oil-compatible finishes to protect brightly colored woods from fading. Since tanning lotions are of an oily consistency, I would not recommend their application under non-oil compatible finishes such as lacquers or waterborne finishes. Another good UV inhibiting undercoat is Armor All Protectant, commonly used on car dashboards and such. This can be sealed with dewaxed shellac if a waterborne topcoat or lacquer is to be applied.

Varnish: Varnish is an ambiguous term, generally referring to any finish that forms a film on the wood's surface, including shellac and lacquer. Usually, it refers to a finish containing a resin and oil mixture that dries by a polymerization reaction upon contact with oxygen from the air. Resins commonly used in modern varnishes include alkyd, urethane, and phenolic. Either linseed or tung oil can be used, and its proportion to the resin determines the character of the final finish. The three formulations used are long, medium, and short oil. These differ in durability and gloss; long oil (spar varnish) is the most durable, but takes the longest time to dry, allowing more dust to settle onto the finish. Short oil varnishes dry faster and produce a glossier finish, which is also hard but relatively brittle.

Varnish Stain: Liquid, oil stain dissolved in varnish; highly transparent, lightfast, non-penetrating, adds filler, color, and gloss in one operation.

Vehicle: See Binder.

Viscosity: The resistance of a liquid to flow. In other words, how "thick" a liquid is. The viscosity of a finish determines how well the finish "flows out" and hides brush marks. Lower viscosity finishes will penetrate the wood more easily and hide brush or rag marks. Higher viscosity finishes are easier to apply in thick coats, especially on vertical surfaces.

Viscosity Cup: A simple device for measuring the viscosity of a finish that is to be sprayed. The styles of these cups varies, with models by Zahn, Ford, and others, but the idea is usually to time how long it takes the finish to drain from the cup through a hole in its bottom.

Volatile Organic Compounds (VOC's): Any carbon based chemical that evaporates from a finish is a VOC. Environmental regulations now limit the VOC content of all finishing products. In order to comply with ever-stricter regulations, manufacturers of finishing products have reduced the amount and type of solvents in some finishes, which has the effect of increasing their viscosity. Furthermore, in order to comply with EPA regulations on VOC content, manufacturers have to print warnings such as "do not thin" on their labels, to keep consumers from exceeding the VOC limit of the finish. This does not mean that thinning will ruin the finish, it just means that for the same amount of film left on the surface of the wood, more VOCs will be released into the atmosphere. Another way manufacturers have reduced the VOC content of finishes is by switching to producing waterborne finishes.

Wash Coat: A coat of very thin sealer, usually 1/2 pound cut dewaxed shellac. Used to partly seal the wood so a stain or dye will cover more evenly.

Water Based / Waterborne Finishes (Acrylic, Lacquer, Polyurethane, etc.): Not truly water based, but actually water borne. These lack the strong solvent smell of their petroleum based solvent counterparts. They contain acrylic and / or other resins suspended in a water base using dispersants (specialized detergents). Since the dispersants are what keeps the resin from separating, waterborne finishes cannot be thinned more than about 10-15%. Waterborne finishes usually appear milky-white in the can, but dry crystal clear and have good resistance to wear and moisture. They add almost no amber hue to the wood, which looks good on light woods, however it may be desirable to tint the finish golden yellow for darker woods. Some waterborne finishes actually contain some yellow dye to mimic the color of oil-based finishes. The way environmental regulations are going, waterborne finishes are the future of wood finishing, and with the improved chemistry of today's finishes, many waterborne finishes are equal to their oil-based counterparts in terms of toughness, weather resistance, and chemical resistance. See also coalescing finish.

Water Based Stain: Liquid, pigment and suspended acrylic in a water base; non-penetrating, lightfast, brilliant, easy to mix colors, non-toxic, non-flammable. Will raise grain.

White Rings: Rings caused by a finish absorbing moisture. Can be removed with either alcohol or commercial ring remover. Some white colored rings are actually caused by heat, and can only be removed by removing the affected finish.

Wiping Stain: Pigment, suspended in oil & mineral spirits; lightfast, will not bleed, non-penetrating, opaque. The most commonly available type of stain, and tends more to cover unevenly, will show lap marks.

Witness Line: The visible interface between two coats of varnish, produced when one coat is oversanded, exposing the next coat. The only cure for witness lines is to re-coat the surface with more varnish.

Wet Film Thickness Gauge: A device for measuring the thickness of a coat of finish that has just been applied. It may be as simple as a comb-edged tool with notches of varying depth on its edges. It is set into the wet finish (in an inconspicuous area or on a test piece), and the deepest notch that is filled with the finish indicates how thick the wet film of finish is. The finisher then consults the manufacturer's data to find out what percentage of the liquid finish is composed of solids, and can then easily calculate how thick the cured finish will be, as the same percentage of the wet film thickness. This information is useful when a finish is to be rubbed out, as well as for quality control in industrial applications. There are also such things as a dry film thickness gauges, but they only work on finishes that have been applied to a metal substrate.

Wet Sanding: Sanding with a liquid lubricant, usually water or mineral oil. The lubricant carries away the swarf, or particles of finish scraped off by the sandpaper, and prevents it from clogging the paper.

Wood Filler: Wood filler is made from a gluelike resin base with some color, usually fresco colors, and silica or some other neutral colored solid matter to increase its bulk. As the solvent evaporates from the filler, it shrinks a little and hardens. Some fillers come as a two part combination; when the parts are mixed, a chemical reaction takes place that causes the filler to harden. This type of filler does not shrink, but usually smells awful until it sets and requires plenty of ventilation.

Wood Size: Usually hide glue thinned to a watery consistency. Used to seal end grain when staining, allowing the stain to take evenly to the wood rather than turning the end grain black.

Xylene C₈H₁₀: A solvent often used in oil based as well as waterborne finishes, such as water based lacquer.

Zinc Stearate Zn(C₁₈H₃₅O₂)₂: A white, soapy feeling, hydrophobic powder, most often used as a lubricant. It is applied to sandpaper to prevent finish from sticking to it and clogging it. It is soluble in certain petroleum distillates, so it is also used in some sanding sealers to make the finish very easy to sand.

References:

Hand Applied Finishes, Jeff Jewitt, Taunton Press, 1997

The New Wood Finishing Book, Michael Dresdner, Taunton Press, 1999

Pocket Ref, Thomas J. Glover, Sequoia Publishing, 1989

Webster's New World College Dictionary, Macmillan, 1997