French Polish is a traditional finishing technique used by luthiers and woodworkers. Often times people find this technique intimidating because the preparation and process is usually more time consuming than other finishing techniques.
Fear not! This instructables will show you the basics of french polish. With a little bit of practice and patience, you can do it too.
Step 1: Preparing the shellac
Step 2: Wood surface preparation
Step 3: Make the finishing pad
Step 4: French Polish
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Preparing the Shellac
Before we do the actual polishing, I would like to talk about the finish. The finish itself is a alcohol based finish called 'Shellac'. Shellac is a resin formed from lac bugs in south east Asia. The resin is processed and sold as dry flakes(see picture). There are many different shades of shellac flakes available online. The color varies from gold amber to deep brown caramel. I bought my shellac flakes through this company.
To make the finish ready for french polish, you'll need:
2. Denatured Alcohol
3. A couple of glass containers - one for mixture, and another for filtering.(I use mason jars in this case).
DO NOT USE METAL jars.
4. old t-shirt cloth or stockings (Used as a filter)
'Pound Cut' is the unit that describe the weight that shellac flakes is 'cut' into the alcohol.
Generally '2 pound cut' shellac is a good place to start because it is not too thin or thick to apply. 1 pound cut is used as final finishing when you only need another thin coat to finish the piece. 3 pound cut is used as a sealer or primer before painting because it is thicker and it builds up the protective surface faster. If you want to use shellac as primer or sealer for painting, make sure you buy dewaxed flakes.
To find out the formula for different pound cuts, click here.
Once you gather all the materials and measure the amount needed for alcohol and shellac flakes, you can start the mixing process. *Notice that when you receive your shellac flakes, the sizes of flakes varies in the package. One good tip that helps the shellac dissolve in alcohol thoroughly is to grind shellac flakes into finer powder before you dump it into the alcohol.
After the flakes are grind, you can then dump the flakes into the alcohol. Close the container and shake the mixture thoroughly. In order to have the best mixture result, I let the mixture sit for a day or two so that all flakes are dissolved in alcohol completely.
During cold days, place the container in a hot water bath will help the dissolving process. DO NOT USE DIRECT HEAT for this.
When the mixture is ready for filtering, grab another container. Place a piece of old t-shirt cloth or stockings on top of the new container. Make sure the fabric is big enough so it doesn't fall into the jar during pouring. Carefully pour the mixture into the new container. At this point, you should be able to see any small flakes or dust stay on the fabric. After filtering, the shellac is clear and ready for use!
A new batch of shellac can be used for 3 months. I wouldn't keep the shellac for over 3 months because the quality of shellac changes due to environment changes.
--What if you don't want to make your own shellac? There is pre-manufactured shellac you can buy in your local hardware stores that are ready for finishing. However, the store-bought shellac is usually a lot thicker than 2 pound cut shellac. It needs to be diluted with alcohol before using it. Also, manufactures usually put other chemicals into the mixtures so the shellac last longer.
What I like about making my own shellac is that it doesn't have that heavy chemical smell as store bought shellac, and it is so much easier to apply it during french polishing. Thus, taking time to make your own shellac definitely pays off because the end result is much better.
Step 2: Wood Surface Preparation
For any woodworking project, surface preparation is always important if you want a good finish result. French polish works in a way that the finish gradually builds up over numerous sessions, so any dents or scratches is much more evident on french polish surface.
The process of surface preparation depends on what the wood is for, and the sheen of finish you're going for. Generally if it is a furniture project, I would sand from low grit to high grit, 'pre-raise' the grain with a damp cloth. Then do another sanding before applying shellac. For open grain wood such as walnut, oak, or ash, sand to 400 grit before french polishing. For closed grain wood such as maple, I would sand it to 600 grit. These number of grits is enough for semi-gloss finish. If you're going for a high gloss finish, sand the piece to 600 or 800 grit. It is important to examine the piece in between different grit to make sure no heavy marks are left from previous sanding.
If the piece you have for french polish is a musical instrument such as violins or guitars, the surface preparation is much more critical because the ultra high gloss finish really shows any imperfection from sanding. In between each grit, wipe the surface with damp cloth. This way it allows the wood to 'pre-raise' the grain thoroughly. Repeat sanding and damping, then sand it to 1000 grit.
Step 3: Make the Finishing Pad-pt.1
Last step before french polish is making the finishing pad. You will need old t-shirt cloth for this step.
The finishing pad consists of two part: inner cloth and outer cloth wrap.
Pictures shown here are the steps to make the inner cloth. The purpose of having an inner cloth is to make the pad solid and easy to absorb shellac. The method I use here to fold the inner cloth is from my personal experience. I find this method works best for me. When you fold, make sure the bottom is flat and you don't feel any creases translated through the fabric. If the bottom is not flat and is uneven, it will create an uneven finish surface during french polishing. The shellac will also have a bigger chance to get stuck on the wood if the pad is not folded correctly.
Step 4: Make the Finishing Pad-pt.2
After you make the inner cloth, place it in the center of another fabric.
Grab all four corners towards the center. Gather all fabric into the center, and wrap the inner cloth completely.
Twist the fabric in the center tightly together.
You want to make sure the inner cloth is not wrapped firmly in the center.
Tie a knot after you twist the fabric together.
It needs to be a firm knot so the fabric doesn't slip out during french polish.
Pound the bottom on a flat surface a few times so that the bottom sits firmly flat on the wood surface.
Now you are ready for french polish!
Step 5: 'Charge' the Finishing Pad
Materials you'll need:
-Shellac (In this case I made a batch of 2 lb. cut shellac)
-Lubricant oil (any household oil works well. I use virgin olive oil here)
-A couple of pipettes (For drawing shellac and lubricant oil onto the finishing pad)
-Wood piece (All sanded and ready for finish)
First, you need to 'charge' the finishing pad. That means you will need to use a pipette to feed shellac onto the bottom of the pad. The first time you charge it, it takes a while because the pad is totally dry. Keep charging the shellac until you feel the shellac coming through the bottom and it making the fabric damp. It takes a few times to know the right amount of shellac you should use. A good way to test it is to pound the pad on the back of your hand. It should feel damp but not too wet.
After the shellac is fully charged, put a few drops of oil and rub it out evenly across the entire bottom of the finishing pad. The purpose of lubricant oil is to prevent shellac from sticking onto the wood. A few drops goes a long way. If you put too much oil, it takes longer than it should be to build up the thickness of shellac.
Step 6: French Polish
After you charge the finishing pad and it is ready to be used, you can start the french polishing; finally!
Gently move the finishing pad across the surface with small circular motions or figure 8 motions. Remember that once you start polishing, never stop at mid point. If the shellac is running out, move your finishing pad toward the edge of your wood in circular motion as well.
The first session you do will give you a good sense of how much shellac you should put each time and how much lubricant oil should be used. If the finishing pad gets stuck easily, that means you either charge too much shellac at once or put too little oil to allow the pad moves smoothly. Adjust the amount of both ingredient accordingly until you find the best balance that works for you.
After one session is done, examine your piece under a light and see if there's any scratches or uneven shellac build ups. To fix the unevenness, take a 800 grit wet-and-dry sand paper, sand the surface with soap water. You should be able to see that all the high spots are sanded and eventually the surface is flat.
Make sure to sand between each session in early stages, so the shellac builds up evenly. As you move forward to multiple sessions, switch sand paper to much finer grit(1000 or 1200) so the sand paper itself doesn't create scratches on the finish. Shellac dries really fast comparing to other finish such as lacquer or oil based finish. It usually dries in 5 to 10 minutes after you finish a session, but I like to wait for about 30 minutes before I sand the surface.
If you want to achieve a high gloss finish, a good thickness of shellac finish can take up to 30 sessions or even more.When you're doing the last few sessions, switch to 1 pound cut shellac. There is no need to sand in between at this stage. The purpose of 1 pound cut shellac is to provide the high gloss finish touches rather than building up the thickness.
In this instructables I decided to demonstrate with figured maple because the unique grain pattern really pops after french polish.