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until most of the pores are filled. Water-base grain fillers have the advantage of curing very quickly. Another good thing about them is that they are non-flammable and can therefore be ordered in America and shipped to countries such as my homecountry Austria where “grain fillers” or “paste-wood fillers” are difficult or impossible to obtain. Because water-based grain fillers harden very quickly, you should never apply them on too large an area at a time. Use a filler that is darker in color than the wood you want to fill.

Finishing

Applying oil

Oiling the guitar is a simple and quick way of finishing. Some guitarbuilders just oil their guitars and leave them untreated otherwise, which gives the surfaces a very natural look and feel. Oiled surfaces, however, offer only little, if any, protection at all against moisture exchange and are also less durable. On the other hand oil finishes are very easy to repair.

There are different types of oil which you can use: the good old raw linseed oil, boiled linseed oil, or tung oil to name but a few. Tung oil (also called China wood oil) is produced from the tung nut, and five or more coats give only a little more protection than boiled linseed oil. There are also blends of different types such as Danish Oil or teak oil.

Raw linseed oil takes very long to cure and is therefore not suitable; use boiled linseed oil instead, as it contains additives to make it cure more quickly. Boiled linseed oil is easy to apply but cures rather soft. Apply it with a cloth or brush it on, wiping off the excess after half an hour (1). Boiled linseed oil that has been heated flows even better, soaks into the pores more deeply and is therefore a good choice for the first coat: heat a pot of water to about 150 degrees Fahrenheit (65° C), then remove it from the heat source and put the finish container into it. Don't use a brush for applying heated oil, as it ruins the bristles.

Three to four coats give a satin surface, seven or more coats a slight sheen. If you do not want to apply any wax, leave the surface to dry for a few days and then polish it, using a cloth over a block of softwood.

Finishing the body and the neck with Danish Oil (2) saves time, gives good results and can therefore only be recommended. Danish Oil is an oil-varnish blend. It cures to a satin sheen and is much more protective than boiled linseed oil while being just as

easy to apply: two to three coats are totally sufficient; allow each coat to dry for several hours. Instead of buying Danish Oil you can make your own by mixing one part of varnish, one part of boiled linseed oil and one part of mineral spirits. It's always a good idea to pour everything through a paint strainer to remove impurities and undissolved residue.

Polymerized oils can be made from any curing or semi-curing oil by heating them to approximately 500 degrees Fahrenheit (250 degrees Celsius) in an oxygen-free environment. They cure to a fairly hard and glossy surface. Their short curing time, however, makes them more difficult and time-consuming to apply. The fact that they are quite expensive is less of a problem considering the small surfaces of a guitar. Polymerized oils are applied very thinly and each coat should be allowed to dry a sufficiently long time. During these periods of drying a thin film can and, in fact, should form on the surface. Polymerized oil is, for instance, used for oiling gun stocks. As such it is available from hunting stores.

Applying wax

A thin coat of wax can, but does not necessarily have to, be applied after the wood has been oiled. Applying such a coat results in better protection and a satin surface that feels very smooth. Regular rewaxing will be required, especially around the neck. Fortunately, this is not a difficult job at all, and it ought to be part of the routine maintenance and care of your instrument anyway. Pure beeswax or any commercially available paste wax are suitable for use on guitars.

Lightly wet the oiled surface with lacquer thinner or mineral spirits. Then dip a folded-up piece of 0000 steel wool or a synthetic alternative such as 3M's ScotchBrite (4) into paste wax and rub it evenly onto the surface, pressing only lightly to avoid rubbing open the thin, hardened topcoat of oil. By roughening up the surface with steel wool the surface is made larger so that the wax coat bonds to it better.

After applying the wax use a clean cloth to polish the surface to a flat sheen. If too much wax has been applied, the surface will become sticky and everything but a waferthin layer will have to be polished off. If a surface has become dull, remove the wax with mineral spirits and then

Always dry oily rags out-of-doors: when wet they can self-ignite!

Applying Danish Oil

First and second coat: apply plenty of oil with a cloth, wipe off the excess after about 10 minutes and then allow to dry for several hours or overnight.

Third coat: apply the oil and sand the wood while still wet (from the oil) with 320-grit paper; wipe off any excess oil after 10 minutes and leave to dry for 24 hours.

How to best apply tung oil and other polymerized oils

First coat: pour some oil into a container and dip a cloth in it; apply the oil thinly and allow to cure for at least 24 hours.

Second and third coat: proceed as with first coat: wipe on the oil and leave each coat to cure for at least 24 hours.

Fourth coat: only pressing lightly, smooth the surface in long, even movements, using 220-grit paper and removing the dust very carefully with a cloth; apply the fourth coat of oil very thinly: the wood can absorb less now; leave to dry for more than 24 hours.

Fifth coat: only pressing lightly, smooth the surface with 320-grit paper to an even, flat sheen; use 0000 steel wool for areas that are difficult to get to; remove any dust very carefully; apply the fifth coat very thinly with a lint-free cloth and leave to dry again for more than 24 hours.

Sixth (final) coat: apply the oil very thinly and evenly with a lint-free cloth, starting by wiping in circles and finishing with long zig-zag movements; after about two weeks' time raise the sheen of the surface to a high-gloss finish by first smoothing it lightly with 600-grit wet/dry paper and water before wiping it off and polishing it with white polishing paste, applying the paste with a pad.

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French polishing

French polishing is the quite workintensive technique of applying shellac with a cloth pad. This very old finishing method gives particularly good results on mahogany, but also on other types of wood. In French polishing shellac is applied by moving the pad in sequences of circles and figure eights, using a bit of oil as a lubricant. French polishing has a reputation of being very difficult - apparently only experts are capable of doing it. I don't agree. The first time I tried French polishing I was very pleasantly surprised by the results I achieved and watching the gloss slowly develop was a very satisfying experience indeed. To me French polishing is a great and extremely rewarding technique - so why not give it a try? Besides, shellac is not affected by hand sweat and can withstand temperatures of up to about 80 degrees Celsius (176 degrees Fahrenheit). It is, however, quite easily damaged by alcohol. Surfaces thus damaged are fairly straightforward to repair, though. Avoid using alcohol-based stains under a shellac topcoat as this will cause the stain to be dissolved by the alcohol contained in the shellac mixture, which will lead to patches forming on the surface.

If you are interested in a video demonstration of french polishing, I can recommend the video by Jeff Jewitt. Details can be found in the literature section.

Shellac

Shellac is a natural resin secreted by insects in India onto tree branches. Workers collect the branches of these trees and scrape off the raw shellac before melting and straining it to remove any impurities contained in it. Shortly before becoming solid one part of the substance is worked into a thin sheet; both hands and feet are used for this (if you have ever made filo pastry at home, you can probably picture how this is done - although this doesn't mean I use my feet to make filo pastry!). After it has become solid the shellac is broken up into small, thin flakes and then shipped around the world. While it still is an important product today, shellac was once used for French polishing on almost all acoustic guitars before nitrocellulose lacquer was invented. The fact that shellac was replaced entirely by lacquer for guitar-finishing purposesdoesn't mean that it has any other drawbacks than its time-consuming application. It is, in fact, a rather good choice for finishing an electric guitar as it is a quite tough finish. Shellac can be brushed or sprayed on. If you spray it, remember to take the usual safety precautions.

Dissolve the thin shellac flakes (1) by simply pouring them into alcohol and shaking the solution repeatedly before leaving the flakes to dissolve overnight. Always prepare only the amount that is needed for a particular job as it will not keep very long. A simple test to show whether old shellac can still be used or not is to leave a small drop of the solution to cure overnight; if it doesn't cure but remains gummy, pour it away. Different shellacalcohol mixtures are commonly used: a mixture of a 1/4 pound of shellac flakes dissolved in 1 pint of alcohol is called a “2-cut” solution; the same solution can be produced by simply putting the shellac flakes into a glass container and filling it up with alcohol to twice the height of the flakes.

The fact that shellac contains wax can be a problem for certain applications. If the solution is, however, left to stand for a sufficiently long time inside a container, the wax will slowly settle to the bottom and it will be possible to pour out the clear, pure shellac. The difference between wax-free and pale, natural shellac is obvious on the wood as well: natural shellac produces a warm, beautiful color tone whereas dewaxed shellac hardly changes the color of the wood.

Because dewaxed shellac has the advantage of bonding very well with almost any type of surface and coating, it is a very good choice for sealer coats. Even oiled or oily surfaces are easy to finish if a coat of dewaxed shellac is applied before.

Synthetic finishing materials

Synthetic finishing materials are made up of a binder, pigments, a solvent and additives. Often additives are mixed in to improve flow-out and to prevent skinning and foaming. Others serve as stabilizers, UV-absorbers, and so on.

Nitrocellulose lacquer contains nitrocellulose as a binder. This type of finish has been very popular over the years for finishing guitars, but as more and more commercial guitar manufacturers have developed a “green conscience”, it is increasingly becoming replaced by water-soluble or other types of less harmful finishes. Nitrocellulose lacquer dries very quickly and can be brushed or sprayed on.

Waterborne finishes can nowadays compete with solventbased ones.

Conversion finishes are particularly durable and mostly used for industrial purposes. They can sometimes consist of two separate components, the finish and the catalyst, which have to be mixed together before use.

One major disadvantage of almost all finishes is the high amount of toxic, flammable synthetic solvents contained in them. Elements such a benzol, toluol, xylol, ester, ether, ketone, acetone, aromatic carbohydrates and others cause health damage. Some types of finish contain a particularly high amount of solvents, like nitrocellulose lacquer with 75 per cent. When working with such highly-flammable finishes care must be taken to ensure that rooms are well ventilated, a respirator mask is worn and explosion-proof equipment is used. These problems do not exist when using water-based finishes. Today goodquality waterborne finishes can compete with and replace the far more toxic solvent-based ones.

Coloring clear finishes

Sometimes a colored transparent finish may be desirable. To color clear finishes add small amounts of aniline pigments. Such powders are available for both water-based and solvent-based finishes. Simply dissolve the powder by stirring it into the finish and then filter it through a cloth to ensure any not fully dissolved parts are removed. A clear finish tinted in this way remains transparent and leaves the wood texture visible. First seal the wood surface with a clear coat, then sand it before applying as many tinted coats as required until you get the desired tone. Finish off by applying several clear coats for protection.

Nitrocellulose lacquer

Although environmentally problematic, nitrocellulose lacquer has long been the first choice in instru- ment-building. This type of finish cures as a result of the evaporation of the solvent. One major advantage of nitrocellulose lacquer is its ability and readiness to completely dissolve even a fully cured coat of lacquer applied underneath and to homogeneously bond with it. This makes it so easy to polish. Blemishes such as orange-peel noticeable after the application of lacquer can easily be corrected by simple respraying of the surface. Nitrocellulose lacquer is almost hassle-free in its application and can be washed off with lacquer thinner at any time in case anything should go wrong. As with other finishes it is advantageous to spray it on in a “normal”- climate environment. Nitrocellulose lacquer gives the wood a warm, pretty color as it ages, imparting a very special tone to the wood. It fills uneven areas and forms an evenly mirroring topcoat, thus making scratches and other wood defects less visible.

Sanding sealers

A sanding sealer can be applied as a basecoat under a finish. The soaplike additives contained in sanding sealers make sanding easier but also weaken adhesion to the finish coats. This is why you should never apply more than one coat of sanding sealer under any finish. Using such easier-to-sand sanding sealers is important in the furniture industry where large surfaces have to be finished and sanded. They are not at all needed on guitars, though; use a thinned finish for the first coat instead.