French Polish – Shellac, Alcohol, Oils & Technique

French polish or French polishing refers to the art of using what is known as a pad, rubber or muñeca constructed usually of cotton cloth wrapped around some type of core material to apply a finish to a wood surface by rubbing. So the term French polishing is actually referring to the physical act and technique of applying the finish, rather than to the type of finish itself.

The most traditional French polished wood surface is different from what we typically do on guitars today. According to my teacher Eugene Clark, the original craftsmen doing French polishing on furniture would simply fill the pores of the wood and leave only a slight coating of shellac on the surface of the wood.

Today, professional French polishers will usually build the finish on top of the surface more, in order to give it a high-gloss look and to increase durability. However, even with a slightly heavier build, a French polish finish is usually far thinner than any synthetic type of sprayed or brushed finish, which is one reason it lets the voice of the guitar and the sound of the woods come through so clearly when the guitar is played.

The technique of French polishing with shellac resin was refined in France during the 18th century. It was considered the highest-quality wood finish for fine furniture and musical instruments such as pianos and guitars. With the introduction of faster and cheaper nitrocellulose spray technology starting around the 1930s, many factories abandoned the technique. Even though a shellac French polish finish is more labor-intensive and more delicate, it is considered a superior finish for guitars to this day. After years of testing different guitar finishes, it is still my preferred method of finishing my handmade guitars.

There are three main ingredients commonly used to make a shellac varnish for French polishing guitars: shellac resin, alcohol, and oil. In the sections below, we will be looking at each component and the properties and functions they serve in the French polishing system of application and the varnish formulation itself.

To apply this finish using the French Polishing technique you will also need a couple bottles I prefer a 4oz Boston round with a nice cap like these HERE, as well as some material to use for an application pad (usually cotton, linen or cheesecloth)

If you have read my book on guitar making, or if you are a member of the Luthier’s EDGE Online Guitar School, you may already know that just understanding the step-by-step directions isn’t enough—I want to know WHY. I need to understand how things work, and I am betting you’re like me in that regard if you’re reading this right now. So we’ll be talking about what materials are commonly used, of course, but, more importantly, we’ll be looking at why and what purpose each ingredient serves to make a better-looking and sounding finish for our guitars.

The sticklac can also be purified by hand by initially being roughly filtered into what we know as seedlac (see image below). As you might guess by the name, the seedlac form resembles tiny seeds of resin. There is still a good amount of wood chips and bugs in it at this stage, but it is usable for French polishing after being dissolved and filtered.

Button lac is my personal favorite type of shellac to use because it is in a very raw and untampered state. But most importantly, because it was heated more, it forms a tougher, more impact-resistant coating due to the resulting polymerization that occurs from the heating process.

Today, most commonly the shellac flakes are commercially produced in factories using various methods for dissolving and filtering, some of which compromise the gloss, durability and purity of the final flake shellac. Therefore, I try not to use any commercially produced shellac flakes, if possible.

The stunning and unique colors of different shellacs for French polish are a result of several factors. One of the contributing factors in producing the many beautiful shades of shellac is the season in which the shellac was harvested. For example, summer shellac, known as Bysakhi, will be a very dark and intense color, while the winter harvest, called Kusmi, will be more caramel-colored and much lighter.

It is very sad to me that with the great variety of shellacs available, I rarely see people using the darker shades. I feel that for the guitar maker, it is essential to use the darker colors of shellac. Using at least some color will unify the instrument and help it to look like a complete object, rather than a bunch of parts put together.

It is not that hard to use darker colors, once you get your technique mastered to the point that you are applying a very even coat of finish on the guitar. However, some guidelines should be followed to ensure that your guitar will look as beautiful as possible with a darker-colored shellac finish.

Now that we have talked a bit about the shellac resin and what it is, we can talk about the other main component of our French polish finish: alcohol. There are several different types of alcohol that can be used for formulating French polish with shellac, and each type of alcohol will produce subtly different results in the French polish finish. Many people choose the type of alcohol they use for French polishing based on which one is the cheapest, but what they don’t realize is that to do so might be compromising the look of their finish (and introducing possible health concerns). Let me explain why…

 Many denatured alcohols, also known as methylated spirits, usually contain methanol or wood alcohol, which can cause blindness and other health problems. Again, we aren’t drinking it, but exposure in working with even small amounts can add up over time.

Some French polishers use isopropyl alcohol to make shellac. However, in my experience and after helping hundreds of my students master the art of French polishing in my Luthier’s EDGE French Polishing course, it doesn’t always dissolve the shellac flakes very well, can produce mixed results in the final shellac finish, and—in my personal opinion—smells really bad too. So isopropyl alcohol is not a type of alcohol I recommend for shellac French polish finishes.

With the health concerns and other details mentioned above in mind, and the fact that it gives me warmer colors, I only use pure ethanol (Everclear 190 proof) for my shellac French polish finishes.

Note: If denatured alcohol is the only alcohol you have available, it is OK to use it and can get great results. Here is what I recommend to help you get the best results possible from the denatured alcohol:

1. Look up the material safety data sheets online to see the ingredients (Google the brand name + “MSDS”) and look for the brands that have the most ethanol and the least methanol in the mix.
2. Try to minimize skin contact and make sure the room you use it in is ventilated to reduce your exposure to the ketones and other synthetic additives present in the denatured alcohol.

You might think I am being a little extreme, but I would rather err on the side of caution and stay healthy and help you stay healthy, too, than the alternative.

The final essential component in the formula for a beautiful and durable French polish finish is oil. French polishers use many different oils, but the most commonly used oil, based on my experience, is olive oil. The second would be mineral oil, followed by walnut oil.

Different oils bring different properties to the finish during the application and the long-term properties of the finish itself. There are two basic types of oils: drying oils and non-drying oils.

Different finishers have personal preferences in using different oil types, so you’ll need to experiment to determine which oils work the best for your technique and applications. For example, I use both walnut and olive oil in different ways throughout the French polishing process for specific purposes aimed at producing the highest-quality, most beautiful and best-sounding finish possible.

The traditional technique of French polishing refers to the way the shellac finish is applied to the guitar or woodworking project. This is most commonly done with a cotton cloth, usually with some type of core material inside. The quality of the finish is entirely dependent on the proper technique being used to apply it. It takes years of practice to master this fully, and when approached correctly, it can be an incredibly enriching experience, as it was for me. Mastering the French polishing technique forces one to develop control, strength and patience.

The following videos are excerpts from my online French Polishing Course: The Art Of French Polishing. To learn more about this course, CLICK HERE.

If you have done much research on French polish with shellac, you may have discovered many different terms used for what I am referring to as the pad. It is sometimes called a rubber, a muneca, or a fad, as well as other terms. I’ll just be referring to it as a pad here in this article. There are also as many ways to make the pad as there are names for it. Probably the most common materials are cotton or linen cloth for the covering, with cheesecloth inside. In the video below, I’ll show you how I was taught to make the pad by Eugene Clark, using cheesecloth. I’ll also be talking about some of the primary and fundamental techniques I use for applying the shellac varnish using the French polishing technique.

The traditional method for pore filling when French polishing a guitar or any woodworking project uses a natural material called pumice. There are many other methods that one can use for pore filling, such as epoxy or different types of synthetic pore filling mediums. I prefer the simplicity and natural qualities of the traditional pumice powder (2f pumice is my favorite for pore filling). I have found that once the technique is mastered, it is very fast and easy to do and always has the perfect color match. Watch the video below for a brief introduction to pore filling with pumice.

Many modern French polishers now use an epoxy pore filler such as Z-poxy. I haven’t tried it myself, but I am told the results are great, and it can be easier for a beginner to get good results.

One of the reasons I love to teach the art of French polishing is that it embodies the heart of the traditional craft of lutherie. Through learning and mastering this technique, the luthier will raise the quality of his or her instruments and the quality of their time in the workshop as they begin to view the work through the unique lens of their newly acquired skill set and sensitivities.

When I learned this ancient art from my teacher, it not only helped me to make my guitars sound noticeably better and look more beautiful, but it also raised my awareness of my body as it pertains to my technique in all the tasks that I perform as I create my guitars. Thus, mastering the art of French polishing involves mastering your body and mind and spills over into every area of your life.

Looking back, I can say that mastering the French polish technique was one of the hardest things I have ever done and one of the most beneficial, enriching and rewarding. The quiet hours I spend each day French polishing are like my meditation and provide some of the richest and most personally satisfying parts of my day.