Prior to any finish the wood must be adequately prepared for finishing. This means that we hand plane the surface until it is completely smooth. You can go directly to finish if you like the effect of leaving some fine tool marks on the surfaces of your work. If you want to have a perfectly flat, smooth surface, sand the planed surface with 400-grit sandpaper. Remove the dust with your bench brush, and then with a tack rag. You may wish to vacuum off the wood, but remember to hold the vacuum nozzle off of the surface. Wipe the surface with a clean cotton rag.
Shellac is a classic finish that can be applied with a minimum of difficulty. We choose to mix our own shellac so that we can control the "cut" or the amount of shellac in solvent. A good solvent to dissolve shellac flakes is denatured alcohol (ethanol with methanol added). This is readily available a hardware stores in USA, but not so in Canada. The use of ethanol is a safe process, since this is the same non-toxic alcohol used in liquor. Some manufacturers use isobutanol to retard the drying time of the finish, which improves workability as the shellac mix is applied to the wood. Behkol is a commercial product from the Behlen Company, which contains 95 % anhydrous ethanol, and 5 % isobutanol. Other products used to dissolve shellac that are available in Canada are the Lee Valley Shellac solvent, or methyl hydrate.
Shellac is actually a secretion of the "lac bug" know technically as "Laccifer lacca". These insects live in trees in India and Thailand. They feed off the sap in the twigs, and then secret a cocoon - type shell which is the source of our shellac. Workers shake the tree branches to dislodge the cocoon, thus harvesting raw shellac know as sticklac. In this form it is unrefined, and will include pieces of twigs. The shellac is then refined to remove the debris, and to reduce the natural wax in the lac. Excess wax reduces clarity in the finish, and reduces moisture resistance in the finish.
There are several grades of shellac. Orange shellac is a mid grade with about 4 % wax content. This grade can be used on dark woods, where the orange color does not change the color of the wood. Orange shellac is less refined, and is therefore less expensive than blonde shellac. Blond and Super Blond shellac is highly refined, such that the wax content is down to 1%. The flakes are light yellowish brown in color. The dewaxing and bleaching is achieved by bubbling Chlorine gas through the shellac. This is the desired shellac for most fine furniture applications.
Mix your blonde shellac in a small jar with ethanol. It will take several hours to dissolve the flakes. Determining your desired cut is an empirical process. You simply look at the color of the mixture using window light. We typically use two cuts - one for thin wash coats that is thinner, and a thicker cut for quickly building coats of shellac. The color may be described as looking like "thin apple juice". If you have excess shellac in your mix, you will notice that your pad begins to stick to the wood as you attempt the padding process. If this occurs, simply add more solvent. Note that shellacs have a shelf life of about 6 months, so mix the shellac when you need it. Old shellac develops gummy substances during a process called esterification where organic acids react with the alcohol. The net result is that the mixture will not cure properly.
Application of the shellac is done as a simple padding process. Make a "pillow" out of a clean white cotton rag that is about 12 inches square. Continuously fold in the corners to make a rounded pillow. Apply your shellac mix to the bottom of the pillow, and then gently wipe the pad across the wood, with the direction of the grain. Use a technique of landing like a plane - touch the wood going right to left at about 1/3 of the distance from the right side of the board. Run the pad across and off the left side of the board. On the next pass, start the padding coming from the left side, landing on the wood 1/3 of the distance from the left side of the board, and running right off the right side of the board. Work from the far side of the panel towards yourself, indexing by ½ of the pillow width per pass. The pillow should be moist, but not wet. Recharge the pillow periodically to ensure that you continue to lay down shellac, and that the surface of the pad in moist, but not dripping wet. Excess shellac mix in the pad will cause the previously applied shellac layers to be re-dissolved, which defeats your building process.
After the first coat, allow the panel to dry for 15 minutes. Shellac dries quickly due to the high alcohol content. If the wood feels cool, the shellac is not dry enough to proceed. Apply a second thin coat and allow this to dry 15 minutes to ½ hour. We will eventually build up 7 or more coats, and the drying time will increase as the coats build. Apply a third coat and allow 1 hour for it to fully dry. Cut back the finish now with 0000 steel wool. Cut about a foot of steel wool off of your roll, and fold it twice to make a hand sized pad for burnishing your finish. This process will knock down any raised grain, and flatten the surface. Use Liberon brand cabinetmakers steel wool without petroleum based oil in it - these oils adversely affect your finish. Apply a 4th coat, and allow it to dry 2 hours. Burnish the surface lightly with 0000 steel wool. Wipe off the steel wool debris with your bench brush, and then dust off the surface with a clean cotton rag before the next layer of shellac. Add the 5th, 6th, and 7th layers with 6 hours of drying time or more between them. Burnish the surface with steel wool between each layer, and then again after the 7th and final layer. You will now have a satin sheen that is extremely smooth. If during the steel wool process you feel a gummy surface, you will have to extend your drying time between layers to allow the shellac to fully cure.
A fine wax is sometimes applied on top of shellac. One such wax is Clapham's bees wax. This is a natural bees wax mixed with Carnauba wax to improve luster. Apply a thin coat of wax in a circular motion with a clean cotton rag in the shape of a pillow. Brush out the wax by making linear strokes with the grain - in the same fashion as the padding process for shellac. Burnish the surface with steel wool immediately after applying the wax - this puts a scratch pattern into the wax to achieve a satin finish. Brush off the steel wool debris with your bench brush, and then with a clean cotton rag. Buff the wax with a clean cotton rag. You will have achieved a wonderfully smooth satin finish.
If the surface has minor damage, you may steel wool the surface, wax the surface, burnish with steel wool, and then buff the surface with a clean cotton rag.
Taken from Rosewood Studio