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.
