The amazing wood finishing technique of French Polishing
If you’ve ever admired the incredibly beautiful finish on an ancient piece of wooden furniture or a wooden instrument like a guitar or violin, you’re probably looking at wood that has been French Polished.
French polishing is a wood finishing process that produces a high-gloss, deep-coloured surface by applying multiple thin layers of shellac dissolved in denatured alcohol with a rubbing pad.
French polishes are made by dissolving flaked shellac in methylated spirit. The shellac used can range in colour from dazzling clear to dark brown.
Special Pale French Polish is de-waxed Shellac that works well on both light and dark woods.
While you may appreciate the excellent looks, you should also admire the hard work that went into the quality finish, as this process demands a significant amount of time and experience before you can consistently get high quality results.
Some of the most exquisite pieces of wood furniture you’ll ever see were most likely French polished, with hundreds of layers applied by hand.
Despite the fact that it has been present since the 1600s, French polish has fallen out of favour because to its labour-intensive procedure.
Shellac, which is made from a material excreted by the lac bug, an Asian insect, is acceptable for any type of wood, but hardwoods with closed grains, such as maple, spruce, and cedar, are significantly easier to obtain the glossy, faultless French polish finish.
If you’re using it on an open-grain wood like walnut, mahogany, or rosewood, you’ll have to fill the grain with pumice powder, which adds another step to an already lengthy process.
Lac refers to the resinous secretion of the lac bug (Laccifer lacca), which is parasitic on particular trees in Asia, especially India and Thailand. Because of the commercial worth of the completed product, shellac, this insect secretion is farmed and polished.
Shellac is derived from shell-lac, which is the name for refined lac in flake form, but it has come to mean all refined lac, whether dry or suspended in an alcohol-based solvent.
Raw seed lac and ethyl alcohol are the two main constituents of shellac. In fact, most companies want shellac to be as pure as possible, so contaminants from the beetle, the cocoon, and natural waxes are eliminated. The Shellac end product is often dry or flaked, and it is re-moisturized with an alcohol solvent, most commonly denatured alcohol.
Shellac is cleared by dissolving it in sodium carbonate, centrifuging it to remove insoluble solutions, and then bleaching it with sodium hypochlorite. Shellac is now mostly used as a wood sealer and finishing. It has the benefit of being soluble in ethyl or denatured alcohol, which is a non-hazardous solvent. Shellac dries quickly because of the alcohol solvents it contains; these coatings on wood dry in about 40-50 minutes, compared to hours for oil finishes.
Shellac also does not fade or oxidise in the sun. Shellac, on the other hand, has a limited shelf life and may not dry properly if stored past the manufacturer’s recommended shelf life. This shelf life could be as little as six months or as long as three years, depending on the manufacturer’s additives.
To make your own French polish
To prepare the shellac you will need shellac flakes, high grade denatured alcohol, some clean rags or old stockings to use as a filter and a couple of glass containers.
One of the containers is for the mixing and the other is for filtering. I’ve read that metal jars cannot be used. After you’ve gathered all of your items and calculated the amount of alcohol and shellac flakes you’ll need, you can begin the mixing procedure. You’ll notice that the sizes of the flakes in your shellac flakes packet vary.
Grinding shellac flakes into finer powder before dumping them into the alcohol is a helpful tip for getting the shellac to dissolve completely in the alcohol. You can then throw the flakes into the alcohol after they’ve been ground. Close the container and thoroughly shake the contents. Allow the mixture to settle for a day or two to ensure that all of the flakes are completely dissolved in the alcohol. Place the container in a hot water bath on cold days to speed up the dissolving process.
This should never be done with DIRECT HEAT. When the mixture is ready to be filtered, transfer it to a new container. Cover the new container with your rag or stocking material. Make sure the cloth is large enough to not fall into the jar during the pouring operation. Carefully pour the mixture into the new container. At this stage, you should be able to see any flakes or dust that has remained on the fabric. After filtration, the shellac is transparent and ready to use. A new batch of shellac can be used for three months.
You can’t keep the shellac for more than three months because its quality deteriorates with time and exposure to the weather. Producing your own shellac has the advantage of not having the harsh chemical odour that store-bought shellac has, as well as being much easier to apply during French polishing. Taking the time to make your own shellac is well worth the effort because the end result is significantly superior. To learn more about dissolving and mixing shellac flakes, refer to https://www.shellac.net/media/pound_cut_chart.pdf
French Polishing Materials List
Sandpaper in grits varying from 400 to 1,200, A tack cloth/tack rag (This is a lint-free, gauze-like material coated with a sticky substance that is used to remove dust and debris), Shellac, High Grade Denatured alcohol (190 proof), Technical grade FFFF ultra fine pumice powder (use inside cloth pouch), Pure extra virgin olive oil or pure mineral oil, Wool or surgical gauze, Pure cotton fabrics, clean old shirts or rags & some plastic squeeze bottles that can dispense in droplets (fine tips).
French Polishing – Basic Procedure
Begin by sanding your project carefully with 400-500 Grit Silicon Carbide Wet & Dry Sandpaper & remove any dust with a tack cloth.
Wipe off the entire project with a cotton cloth that has been gently dampened with water, this will lift any loose wood fibres on the surface.
Allow the project to dry completely before sanding down any fibres with the same sandpaper. Wipe the project down once again with a tack cloth, then once more with a cloth saturated with denatured alcohol.
The alcohol will remove the remaining of the sawdust without discolouring the wood.
To apply the shellac, a pad composed of firmly wadded wool or gauze surrounded by a piece of cotton cloth is required.
Roll a ball of wool or gauze into a tight ball to produce the pad. Make a teardrop shape by folding the four corners of a 150mm square piece of cotton material up to meet at the top.
The pad’s wool or gauze core will serve as a shellac reservoir. When you press the pad on the wood with a moderate amount of shellac in the core, a thin, even layer of shellac will be left on the surface.
Because shellac is fairly sticky, gliding the pad across the wood’s surface can be difficult at times. To combat this issue, apply a few drops of olive oil or mineral oil to the pad’s exterior surface before each use.
If gliding across the surface becomes tough, add a bit more oil to the pad. As the thin layers of shellac dry, pure oil will rise to the surface, but this will not affect the finish.
Contaminants in the oil may hinder it from rising properly, thus it’s critical to use 100 percent pure, neutral oil. To begin applying the French polish finish, squeeze some shellac into the core of the pad with a squeeze bottle. Tap or press the pad against the back of your hand to distribute the shellac evenly throughout the core.
The cotton cloth should not be wet with shellac since you want to apply extremely light, thin coatings of shellac to the wood. In this scenario, little is more. As a lubricant, apply a few drops of olive oil to the pad with another squeeze bottle that has a fine tip.
The initial layer of shellac will be used to seal the wood, so simply wipe the pad across the wood in the direction of the grain. Beginning and stopping at any point on the stock should be avoided if possible, since this will result in an excessive amount of shellac being applied at the starting and stopping points.
Use a ‘plane landing onto a runway’ motion to place the pad against the grain on the wood. Lift the pad off without stopping when you reach the end of the wood. This will keep any ugly blotches or markings at bay. As you apply this sealing coat, you may see that the cotton cover of your pad gathers up minute bits of dust or other fine particles that have been left behind. If this happens, replace the outer cover of your pad with another piece of cotton cloth and a few more drops of oil.
After applying a single, even coat of shellac, wait a few minutes before applying a second coat. Repeat the technique with a third base coat. Remember to apply oil to keep your pad moving smoothly. Allow your pad to dry completely before storing it in an airtight container. Fill any cracks with pumice and smooth the surface as much as possible.
Place a fresh cover on your pad and add roughly 8-12 drops of alcohol to the core when the shellac in the core is nearly gone. To smooth out the liquid, press the pad against the back of your hand, dab very small amounts of pumice onto your project, and massage small amounts of pumice into the wood in small places at a time with random, circular motions.
Work against the grain to avoid sweeping the pumice out of any open pores. Continue until the sealing coat is exceedingly smooth and all pores have been filled. Before applying the French polish, replace the original core pad with a fresh cotton pad cover.
Reload the core with shellac after adding a few drops of oil to the cover. Begin applying extremely thin coats of shellac to the object in random, circular motions with intense yet even pressure on the wood. Because this thin layer of shellac dries quickly, you can apply numerous tiny layers in a single session. When the pad has to be reloaded, just remove it and reload the core with new shellac.
For this first coat of polish, you may need to make hundreds of passes over the wood’s surface. Take a break after you’re happy with the results and wait a few hours for the shellac to fully cure. Keep your pad in an airtight container to save it for the next part of the process. Pour a little quantity of alcohol into the centre of the pad and spirit the surface using the same ‘plane landing on a runway’ strategy you used to apply the sealing coat.
The oil that has surfaced while the shellac has been drying will be removed at this stage. Before applying the next coat, the oil must be removed. Repeat the polishing and spiriting process at least six more times until you are satisfied with the results. Examine the surface from all angles in bright light. If there are any flaws in the finish, sand them out with 1,200 grit sandpaper and a few drops of oil.
Remove the sawdust with a tiny amount of alcohol, then polish and spirit as necessary to remove the fault and balance the finish. Your project should now have a beautiful, blemish-free, mirror-like finish. Now that the French polishing is completed, you may just let the project alone. However, a final glazing procedure will add sparkle.
To add a glaze, thin out a portion of the 2-pound premixed shellac as directed by the manufacturer. Apply a small quantity of shellac to the pad and a few drops of oil to the cover, and then apply the mixture with ‘plane landing on a runway’ strokes.
This thinner layer of shellac will help fill in any imperfections from the previous stage that are still evident. Make sure to pay specific attention to the project’s corners and edges, which are sometimes overlooked. Apply as many layers of this final glazing as necessary to achieve the desired finish.