Shellac polish
Shellac polish is the surface treatment of wooden surfaces with shellac dissolved in ethanol . A mirror-smooth and high-gloss surface coating is created on the wood by repeatedly applying and polishing the shellac solution.
history
The history of shellac polishing in furniture production begins around the beginning of the 19th century in France . Quickly accepted as the preferred finish for fine furniture , it spreads quickly across the UK and the rest of Europe . It replaced the wax polish used up until then on simple furniture and complex lacquer polishing processes on court furniture. With the development of nitro lacquer in the twenties of the 20th century, the importance of shellac polishing in furniture production quickly declined. Today they are mainly found in the restoration of antique furniture and musical instruments. Manufacturers of some expensive stringed instruments today still prefer shellac polishes to synthetic paints.
technology
Sealing furniture surfaces with a high-gloss shellac polish is not only a time-consuming process, it also requires an experienced polisher. In the first half of the 20th century, the job of foreman was still an apprenticeship with several years of apprenticeship. Shellac polishing is a complicated surface treatment that consists of three different steps: pore filling, layering and polishing.
A mixture of equal parts shellac, ethanol and the finest pumice powder is used to fill pores . This paste is applied to the wood with a strong bristle brush or a coarse ball of linen and worked into the pores, and then removed with a rubber spatula and a cloth soaked in ethanol. This process must be repeated for coarse-pored wood until all pores are largely closed. However, this method is only used when working with wood for the first time. During a restoration, the fine pumice powder, also called stone powder, is incorporated in minimal quantities with the polishing ball under strong pressure. Only when the wood pores and thus the surface are perfectly closed does it begin to shine. A side view, whereby inclined light shows the evenness of the surface, serves as a control for the experienced craftsman.
After sufficient drying, the layer build-up begins by repeatedly polishing the surfaces evenly with a polishing pad that is moistened with dissolved shellac and a tiny amount of polishing oil, which is usually paraffin oil and is used for lubricity. Care is taken to ensure that the polish is applied evenly. Since the shellac has a strong dissolving property due to the dilution with ethanol, this process must be carried out very carefully. Driving over surfaces that have already been polished has to be done with a great deal of dexterity, as previously applied and dried layers of polish can come off at a point that has been driven over too often.These areas are called burned-out polish, which can only be completely rebuilt with great effort . After each application of a layer, the entire surface is given time to dry out, preferably overnight. Shellac only becomes really hard over the years and requires a long drying time between the individual steps. A polishing process consists of centric circular movements or 8-shaped loop movements over the entire surface to be polished, whereby the surfaces should not be run over too often with the polishing ball, as otherwise the so-called burns can occur when the polish is removed. Even a polishing pad that stays in place for only a tenth of a second or even sticks, can destroy all previous work immediately. The addition of tiny amounts of polishing oil, usually less than a drop on a bale, can help prevent such burnout . This layer construction is continued until a perfectly smooth surface is achieved. Long drying times with recurring collapse due to drying of the pore filling, especially with coarse-pored woods and the need to apply the polish again to achieve a mirror-smooth surface, can make such a shellac polish a very time-consuming job. But just the careful work down to a perfectly mirror-smooth layer should complete this work.
The last step after the surface has dried well is the particularly important removal of the polishing oil used for polishing, as this affects the gloss of the surface and causes streaks to appear. A solution of benzoin in ethanol is traditionally used for this final step, known as buffing or buffing . This benzoin tincture can dissolve the polishing oil from the surface and, by sealing it with a very thin layer of this resin, which is harder than shellac, make the finished shellac polish a little more durable.
Recipes
- Shellac polish (2-lb. Cut) : dissolve 60 g of shellac in 250 ml of ethanol.
- Pore filler : dissolve 100 g of shellac in 100 ml of ethanol, then mix with 75–100 g of pumice powder.
Care of shellac polished surfaces
Cleaning should only take place with a dry, non-scratching, at most “slightly damp” soft cloth, so that even minor dirt can be easily removed. Wet cleaning should be avoided. No further maintenance is necessary. Under no circumstances should any other agents be applied to the polish, as oils that give a short-term shine, in the worst case silicone oils, are almost always introduced into the surface, which can seriously damage a polish. A polishing -called quick to-do revision of polish by the furniture polisher with thin shellac polish at intervals of a few years can maintain such a surface perfect, but is usually not necessary.
Important: Never expose shellac polished surfaces to direct sunlight, as the wood can fade and the surface can become brittle with cracking, which can also occur with any other surface treatment.
Web links
- Manufacture of a shellac polish and its use , feinwerkzeuge.de