Materials for French Polishing Classical Guitars
By Orville and Robert Milburn
The tools and materials used in French polishing classical guitars are few and very simple. As a matter of fact, for an investment of a few dollars you can obtain all that is needed to finish a number of instruments. At the end of this article we will list some merchants where dependable materials may be purchased.
Lac is a natural substance that is secreted by the insect "Coccus lacca" often referred to as the lac beetle. This substance is collected from a variety of trees that play host to the insect. The Lac is taken from the tree branches and bark. The harvested lac is cleaned and processed into a variety of different forms including hand processed (shell lac) which is scraped from heated bags of lac.
|Shellac flake on left and ground shellac on right. The shellac flakes were ground using a coffee grinder. Shellac is non-poisonous and is approved for use in food by the FDA.|
The bags of harvested lac are heated over an open fire. As the lac melts, the bags of lac are squeezed with a tourniquet producing enough pressure to force the melted lac to the outside surface of the bag. Much of the lac is processed into thin sheets which are crushed into brittle flakes for preservation and storage. Most of the shellac is used for industrial purposes while some of the shellac is processed into ready-to-use finishing material which can be purchased in most paint or hardware stores. A great deal of the shellac flakes are processed and sold to professional finishers who specialize in beautiful hand rubbed finishes. Over a period of years the term "shell lac" has become known as "shellac." For one of the finest articles and complete description on how shellac is harvested and processed, you may want to obtain a copy of "American Lutherie No. 54, summer 1998." The article was written by Cyndy Burton, who is one of America's finest luthiers and French polishers. The shellac that we will be using is sold in flakes. The flakes are available in at least four types. The type of shellac denotes the color, from light to very dark, usually referred to as "white," "blonde," "orange", and "dark" (or "garnet"). The shellac flakes are then dissolved in alcohol only as needed. The reason for this is that dissolved shellac has a short "shelf- life." When a mixture of shellac and alcohol sets for a long period of time it collects moisture and undergoes a chemical degradation called hydrolysis. It is desirable to mix only what you plan to use in a few months time. Never use pre-mixed, canned shellac from the store for French polishing. Ready-mixed shellac is composed of number of additives designed to extend its shelf life, increase flow, and retard drying time so that it can be applied using a brush. Even though most ready mixed shellacs are of very high quality, the additives that they contain are not suitable for French polishing. Purchase only high quality shellac flakes from a trusted merchant. We will list names and addresses where shellac flakes can be purchased at the end of this article
We will be using a lot of alcohol. The alcohol will be used for dissolving shellac flakes, thinning, pore filling and other French polishing procedures. Good quality hardware store alcohol is all that is necessary. Some people, however, are sensitive to the materials that are added to the alcohol in the denaturing process. Denatured alcohol is ethanol to which has been added a small amount (about 5%) of a poisonous alcohol (usually methanol) Above all, keep denatured alcohol out of reach from children and locked in a safe place. If you are concerned, you may wish to purchase pure alcohol from the liquor store. The only drawback of this approach is that you will pay a lot for the pure ethanol. There is a small concern that some denaturing agents may cause problems with the rate at which the alcohol evaporates. Read the labels on the alcohol you buy and purchase ethanol that has been denatured only with methanol. Again, we will mix only what is required as we work. An open container of alcohol will draw moisture as it evaporates and break down its purity so keep lids or caps on all bottles.
Pumice is used for grain and pore filling and is also used as an abrasive at certain times during French polishing. Pumice is often used as a polishing compound for many other types of finishing and is available in specialty paint stores. We use FFFF grade (F stands for floated. Fine pumice particles stay suspended in solution for a longer period of time and thus have a larger "float" grade) pumice which is very fine. Pore filling and the use of pumice can be a difficult part of French polishing early on. Once learned however, the job will be straightforward and almost effortless.
|These are the main materials used for French-polishing. The containers are chosen to aid in dispensing proper amounts of the various materials.|
Olive oil is used as a lubricant as we French polish. The shellac is applied using only the muneca or folded pad. The muneca must be pressed very firmly against the surface of the wood in order to dispense the shellac properly. This firm pressure also "amalgamates" each microscopic layer of shellac with the previous layer making it possible to "build" a rich and seemingly deep finish- and one that is quite hard. The judicious use of oil allows one to press hard and firmly against the wood without the muneca sticking or dragging. As the shellac is laid on the surface the oil will tend to permeate through the finish and rise to the top. It is therefore important to use only oil that will not get trapped under the shellac and destroy the finish. It is advisable to use only pure 100% virgin olive oil. Other oils such a walnut oil, baby oils (mineral oil), and some paraffin oils can have additives such as antioxidants and perfumes that can create problems with the finish itself. The beginner should use only pure olive oil before he or she experiments with other lubricants
We will be covering some detailing and preparation of the guitar for French polishing as well as the polishing itself. We will include all grades and type of abrasives needed as follows:
The above abrasives should be all that you will need to complete your first French polishing project.
- 220 grit open-coat dry sandpaper 3M "Gold" 216U
- 320 grit open-coat dry sandpaper 3M "Gold" 216U
- 400 grit wet/dry automotive sandpaper 3M "Imperial 401Q
- 800 grit wet/dry automotive sandpaper 3M "Imperial" 401Q
- 1200 grit wet/dry automotive sandpaper 3M "Imperial" 401Q
- Micro-Mesh "Cushioned abrasive" 3200
- Micro-Mesh "Cushioned abrasive" 3600
|Here are some of the sanding blocks we use in leveling the finish. In the back is a large wooden block with a cork pad. Next to it is a mahogany block with a round edge to smooth the inner surface of the string slots. Also shown are various rubber blocks. Some are made of pink pencil erasers. Note the various sizes and shapes.|
We will be constructing a rubbing pad or "muneca" (Spanish for rag doll) using wool or surgical gauze for the inner pad and an outer covering of a soft 100% cotton cloth such as t-shirt material. The composition of wool or gauze is ideal for retaining the shellac inside the muneca until it is forced out by the pressure of the hand. Be sure that you use only pure wool or clean cotton gauze for the inner pad or the shellac may not dispense properly. Do not use any synthetic or synthetic blends for any of the muneca components. A well-worn t-shirt is ideal for the outer covering and a cut up wool sock is suitable for the inner pad. Have plenty of soft wiping clothes ready as well. You may want to purchase about a yard of t-shirt cloth from a local fabric store or, better yet, procure a couple of well worn t-shirts. This should be more than enough for the first project. Note that any material that comes into contact with the guitar must first be checked for foreign particles, dirt, etc. Even a tiny speck of dirt can cause visible scratches in the newly applied finish. The finish will be extraordinarily fragile until it hardens.
CLEANING AND POLISHING AGENTS
As we stated before, no polishing compounds or polish is used in the actual French polishing process as we lay on the shellac. When we are finished however, we will need to remove excess oil and clean and polish the instrument to rid it of hand prints. For this we use "Meguiar's No. 7 Show Car Glaze". The Meguiar's #7 contains no abrasives so it is safe for repeated use and maintenance of the finish. If a more aggressive cleaning agent is needed, we will use a very fine rubbing compound such as "Meguiar's #9 Swirl Remover". The Meguiar's #9 contains a very fine abrasive and will remove some finish. Use it to remove tiny scratches. It cannot be used for finish maintenance. These are very high quality products which contain no silicone compounds that may damage the finish or the wood itself. They can be purchased from automotive supply/parts store or auto paint specialty stores.
- A 1" wide x 1& 1/4 long x ½ inch thick rubber block for sanding. A perfectly square wood block with cork glued to the bottom will do as a good substitute. Most any paint store will have rubber sanding blocks that can be cut into smaller blocks. You may also use rubber easers from a stationary store for smaller, ready-made sanding blocks. As a matter of fact, we have a variety of easers of many different sizes and shapes for this very purpose. Be sure to glue the cork using epoxy because the oils and solvents may loosen other types of glues.
- Small squeeze bottles for dispensing the shellac and alcohol are important. Small glue bottles can be purchased at many paint and tool stores and are ideal. You will need at least two squeeze bottles
- A small bowl with an air-tight lid is desirable for storing the muneca and other dispensing clothes to keep them from drying out.
- A salt shaker for dispensing pumice.
- A medicine dropper bottle to dispense oil (purchased from a pharmacy).
- One quart of naphtha solvent.
- Guitar neck rest. Many times while French polishing, the guitar needs to be supported at the neck because of the downward pressure exerted on the top.
- SuperGlue and 5-minute epoxy.
- A stop-watch
- A small funnel
- Typing paper
Finally, you will need a place to work. You may want to set aside a small, well-lighted area or use a spare room in your house to work on your project. An even temperature and a dust-free area are desirable for French polishing. Ideally, the area would be in a corner to help reduce drafts that carry dust (air-carried dust is only a concern late in the process) We have assembled about all that we need for our French polishing project, so let's get started . . .