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The Finish Magic or Myth
By Paul McGill

I have heard many things in my career about finishes. I always try to understand why the subject of finishes strikes such passion in so many instrument lovers. I have also tried to maintain perspective about what is important and what beliefs just don't seem to matter. The problem is that there is more to it than just sound. It would be nice if there were no trade-offs to consider. However, when it comes to the finish, it must be considered that its primary purpose is to protect a fragile object that should always be handled with care.

Some years ago I saw a PBS television show on violins. Isaac Stern was pontificating in glowing terms about the Stradivarius violin he plays and giving most of the credit for the sound he loves to the finish of the instrument. He said that the finish recipe was lost and that this great secret was gone forever. I would never argue a point of sound with a player. However, I think the instrument making community has a very good idea about what the old varnishes ingredients were.

Let's start with the earliest finishes. Many centuries ago man kind discovered fermentation, the means by which to make alcohol. Further experimentation revealed ways to purify alcohol and make it usable for finishing work. Resins dissolved into alcohol could then be applied to different surfaces to create a film which could act as a barrier to elements which could harm the surfaces. Alcohol is a very quickly evaporating solvent. For this reason, the solution, otherwise know as a spirit solution or a spirit varnish, is not easy to apply. The resins dry too quickly for the surface to flow out and become flat and smooth. A special technique is required to apply these resins for a high gloss effect. This technique is called French polishing.

I often am asked the question, "what is French polish made of ?". French polish is not an "OF" it's a "HOW". Many resins will dissolve in alcohol including: Shell Lac, Sandarac, Elemi, Pontaniac, Damar, Mastic, as well as too many others to list. All of these materials are naturally occurring. After world exploration found and returned these materials to Europe many centuries ago, different formulations were blended to discover the most durable finishes that could be devised.

French polish is the "How" developed to help these fast drying resins flow out and become flat and glossy. The technique is simple but requires great skill and patience to perfect. A tampon is created by wadding a piece of cotton or wool inside a piece of woven material such as linen. Wool makes a good material to start the process because it does not retain moisture as well and more finish will pass through it on a stroke of the hand leaving a greater film on the surface. As the finish builds, small amounts of mineral oil are used to lubricate the surface so the rubbing tampon does not stick to the film. The continued action of the mildly saturated tampon moving across the film allows the resins to flow out and become completely flat if done with sufficient skill. The process gets very difficult to perfect when working in corners, and places like along the edge of fretboard, above the top, and heel of a guitar.

The finished product has to be treated very delicately because of the permeability of the film. It has low resistance to moisture and can break down in seconds if exposed to alcohol-- not a good idea to get a beer around one of these jobs. Even with the extra maintenance, many players prefer French polished guitars because there is less finish on the instruments. This is because the final surface is the result of build-up of the surface, rather than abrasively polishing it, which removes some of a heavier film, as done in most manufacturing situations. It would be more dangerous to grind away or abrasively polish a finish applied by French polishing, because it's desired to be a thin application and it is easy to abrasively polish through to the wood.

French polishing is a very fine art. It has great uses in restoration of instruments since it can be applied over surfaces that otherwise show finish build-up. Because it dries so quickly it can fill in most unevenness' of a surface, such as nicks or dings. Most old violins have a lot of resins worked into the original film using this technique. I have never tried this, but I heard a story about a restorationist who quick dried his finish by burning out the alcohol with a match. Apparently it flames off in one quick blue flame. I have never had the nerve to try this. Has anyone tried this? I would love to know what the out come was.

I usually try to dissuade a guitarist from French polish finishes. The application can take as much as 30 hours of laborious rubbing, and when I am done the guitar is doomed to having the finish marred or stained so constant repair is required. Most of the time the client will give up and ask that I refinish the guitar with a more durable material. I have invariably found that the sound is unchanged by this transformation. If the client can hear the difference and really wants it though, I do it. Perhaps my ears are not as good as theirs. Or perhaps my practicality out weighs my sense of romance after days of rubbing and sore fingers and shoulders.

Varnishes are another early creation of man. I believe that the Chinese had developed them many centuries ago and created art forms like lacquerware around them. The formulation of some of these creations were truly kept secret and are not well known. The basic ingredients of early instruments varnishes however, are clearly; turpentine, oil and a variety of other substances added to enhance flexibility and durability. The resin in the finish is created by allowing the turpentine to polymerize. When allowed to evaporate, turpentine will polymerize into a thick resinous goo. If then spread out it will dry into a brittle film which requires some plasticizer to add flexibility to the film. Stradivarius used this approach to making varnish for his violins. The real question is what plasticizers were used. The reason why the formulas for these old finishes can't be fully identified is that most plasticizers are not stable substances. They can leach out of the film and evaporate over long periods of time. It is hard to identify something that has disappeared. Many use wax as a plasticizer along with oil. There are thousands of substances that can be placed in a poly-turpine varnish for durability and flexibility. The biggest draw back to this finish is that the drying time is incredibly slow. Its advantage is that it flows very well when applied with a brush. After application the finish will self-level better than most finishes and so requires less work to level.

Finishes of the poly-turpine type are not very practical for guitar making for several reasons. The violin and guitar are very different instruments which work in different ways. The guitar being plucked or strummed has far less energy to work with than a violin. The violin is constantly driven by the energy of the player who drags a bow across its strings. The constant transmission of energy is what concerns the viol family instrument maker. Many components of the design of the viol instrument dampen the over tones of the strings so as to element the cacophonous collision of overtones generated by the constant force of the player exciting the strings. The soft, plasticized poly-turpine varnish helps dampen excessive brightness and helps the instrument generate a more balanced sound.

French polishing is not only used to restore finishes, it is also used in combination with varnishes of all types to lend its special appearance over them. When alcohol is applied to an old varnish it eats into its surface, and the new resins, contained in the alcohol, are absorbed into the original film. I wonder if Mr. Stern knows that every time he has his instrument in for routine finish maintenance that the consistency of the varnish actually changes. Over years of servicing the original finish absorbs different French polish resins which work down into the original finish.

There is a great deal of romance about finishes, as well as other aspects of the sound of musical instruments. Many people believe that they hear great differences in the finish applied to their instruments and in some cases it is very true. Peoples' romance about instruments should never go unappreciated because on occasion great knowledge does come from their affinity. However, romance about instruments can also deceive. I have one resonator client who believes that my resonator cones sound better during the first few days after installation and he constantly wanted new ones because he said they sounded better. I decided to make a study of his belief and took a cone which had been in service for many months in another guitar and installed it in his guitar without telling him of its history. He left very happy as usual and called a few days later to say the cone had gone through its deterioration from when it was first installed. He was taken aback when I told him of my test. However, this same client has offered up some valuable insights into my designs which I now use. He still believes there is a difference in new cones, but he accepts the reality of his impression, and I don't have to replace cones for him all the time.

A lot of discussion about the relative advantages of early and more modern finishing practices occurs in the instrument community. Given that early finishes generally were derived from natural sources, they tended to be a little fragile, especially when exposed to any type of solvent. Some materials were more stable than others and, in well designed proportions, could be very effective. Still, a lot of resources were required to be able to formulate these coatings as well as to apply them. So as productivity in industry increased, so did the demand for tough, fast-drying coatings which where easier to apply and, once applied, did not require the space necessary to sit around and harden for long periods of time.

By the mid-19th century varnish manufacturing had developed, and a bugeoning knowledge about chemistry was being applied to oils and resins. These finishes found their way onto instruments such as guitars and pianos and were generally very durable and aesthetically pleasing. Using a variety of oils, ranging from plant sources to petroleum, processes of heating materials to specific temperatures and emulsifying resins, manufacturers created the beginning of the synthetic materials which we find very often in finishes on instruments today. I always have found the finishes of this period very desirable. Turn-of-the-century instruments often have some kind of varnish from this period protecting them, and usually they have held up very well. Some instruments from this period have a varnish which has ultra-violet ray protection that has kept the rosewood dark and apparently unaffected by sunlight. The chemists of this era must have had great knowledge and insight to accomplish this so early on in the development of coatings. Next time you see an instrument from this period, pay special attention to the finish. They usually look better than guitars made in the last fifty years.

The 20th century brought in a new era of finishing technologies. As uses for petroleum were explored, the manufacture of more powerful solvents created an environment in which materials previously impossible to dissolve could now be processed into more chemically resistant coatings. By the 1920's the lacquer age had begun.

Many guitar makers and players prefer the aesthetics of lacquer. It has a more brittle quality as it ages than most finishes, and many believe in the effect this has on an instrument's sound. The major reason behind the development of lacquer was the speed at which lacquer solvents would flash off (evaporate off) a surface, allowing the solid materials to cure much more rapidly. So rapidly, in fact, that the drying time had to be retarded in order to brush on the finishes as was done with varnishes, so lacquers eventually came to be sprayed on through the air with a pressurized air gun. I read a book recently on the Steinway Company. Though they had considerable resources invested in finishing pianos in varnishes, when lacquer arrived, they began using it, and their output went up immediately. It is for this reason, I believe, that lacquer was so important to instrument manufacturers. Sound quality was probably not a big consideration when compared to the profitability afforded by this fast curing material.

Lacquer is a heavily plasticized material. The solids used in lacquer are generally one part cellulose to two parts plasticizers. Cellulose is acquired from a plant source (cotton or wood) and dissolved in petroleum based solvents. Plasticizers are traditionally oils which add flexibility to the film to keep it from breaking. Cellulose is a very brittle material, and plasticizing it makes for an inherently unstable material because the plasticizers are all unstable substances which deteriorate or leach out after a number of years.

Early lacquers used castor oil or camphor as plasticizers but as time went by the list of materials grew too long to begin to list all the different substances used for this purpose. Some synthetic materials are even used to try and make the films more long lasting. The history of old nitrocellulose film is a good example of the lack of longevity of this kind of materialthis is why there is a film restoration business. Likewise, the problems of finishes cracking and their poor adhesion on guitars can also be traced to this phenomena. Many older instruments have almost nothing but the cellulose left on their surfaces. The film shrinks to about one-third of its original thickness and becomes very brittle, requiring French polishing to improve its appearance and to add some flexibility. Guitarist who love lacquered guitars need to take extra precautions against exposure to extreme cold, otherwise the plasticizers can get brittle and surface shrinkage can cause the finish to crack.

Other finishes sometimes used in guitar making are enamel varnish and acrylic enamel finishes. Enamels are petroleum based varnishes; acrylics can be added to harden the enamel for a more glossy appearance. Many varnishes used at the turn of the century were basically very similar to these finishes except that the earlier materials tended to use more natural oils as resins. The enamel material has a special quality as it dries. Exposure to light and heat cause the molecules to interlock, making a very tough and chemically resistant surface. The phenomena of interlocking molecules, or cross-linking, generated a search for chemicals which would produce the same effect in the film. Remember years ago when car painters would put cars in ovens and bake the finish on? This was a cross-linking process. Obviously guitars and other wood objects couldn't be baked like a car, so now the additives do the cross-linking, and the finishes are exposed to ultraviolet light to speed the action. The additive used to create this effect isocyanate. The additive reacts with hydrocarbons in the varnish, creating a very stable, tough and durable surface. Finishes like these still have plasticizers but are less dependent on them for elasticity.

Many of the enamel finishes have ester resins in them as solids. By polymerizing ester resins and introducing a cross-linking additive, a poly-ester material is created. Polyester finishes are what is used on many instruments to fill the surface before applying a more aesthetic top coat. Polyesters make a heavy indestructible film (it is the same stuff used to make fiber glass). The only way to remove it is to scrape it off. It has been used mainly on inexpensive production instruments to further reduce finishing time. However, they have been finding their way onto more expensive instruments in recent years.

You can see that finishing has many possible avenues which one can pursue. The question raised is what does it do to the sound? Is the finish going to make the guitar louder? Is it going change the character of the tone? Can you put on a blindfold and tell if the finish is French polish or polyester just by the sound that comes from the guitar? Magic or myth, finishing is likely to remain a subject of disagreement as long as guitars are around, However, years of work with all these different materials teaches the maker that the finish is just another part of the fine tuning of the instrument and that proper understanding of the value of each material allows the maker to use each finish to its advantage. One example that comes to mind is the use of acrylic enamel finishes on Rameriez guitars. The finish on these instruments can be quite thickso thick that it becomes part of the tone. To compensate, thinner tops were used, and the result was an aesthetic not seen before. It was very popular sound for a long time. The answer in my opinion to the title of this column is that sometimes finishes are magic and sometimes they are myths. Every body's ears will draw their own conclusions. It can be a fun part of the guitar experience. [an error occurred while processing this directive]