Shellac is a natural resin produced by an insect that lives in Thailand and some regions of India, which uses it to cling to the bark of trees.
Once harvested, after an initial purification process, it is presented in thin, very crumbly flakes, of an amber color.
The main features
It is easy to find in any fine arts shop and is generally sold in 1 kg bags, but it is usually also possible to buy them in fractions of 100 grams.
The key characteristics of shellac are its extraordinary durability and brilliance.
It is no coincidence that it was already used in the 1800s for the finishing of fine furniture, in particular by the French from whom the application and polishing technique was also copied, using a pad; in the past it was mainly used in casting for the production of decorations or small accessories.
Today it is mainly used in restoration and in violin making; in the furniture, even of value, it has been almost entirely replaced by synthetic paints.
Its application takes time and a lot of patience, but the final results are excellent, long-lasting and give the wood a lively and pleasantly soft appearance.
Since it is non-toxic, it is also sometimes used in the pharmaceutical industry for the production of pill coatings or in the agri-food sector as a fruit and vegetable polisher.
The preparation in alcohol solution
The most used solvent to dissolve it is ethyl alcohol, which I personally recommend with a concentration of at least 94 degrees, which is not the common alcohol found in the supermarket and that we often have at home.
The dilution process is very simple: what I report to you does not constitute an absolute rule and it is easy that there are very different opinions and techniques, however it is the result of consolidated experience and notions acquired by expert professionals.
The application of shellac generally takes place in 3 stages: drafting, roughing and polishing. For each of these phases it is advisable to prepare shellac with different dilutions.
The different dilutions
We will start with a 20% dilution, understood as the bottle volume / weight ratio of shellac, or in a 1 liter bottle (better than transparent plastic to preserve the escape of flammable alcohol in case of breakage) we will pour 200 grams of shellac and we will fill the bottle with alcohol to the end.
The shellac will immediately begin to melt with a consequent decrease in volume, but no more alcohol must be added. Let it rest for at least one night and, the following day, shake the contents well and filter everything into a new bottle using a funnel with a common women’s stocking type tights inside.
Our shellac is ready to be used.
Obviously, smaller quantities can also be used, as long as the volume / weight ratio is respected.
For example, for a half liter bottle, we will use 100 grams of shellac to obtain a 20% dilution.
On the basis of what is written above we will also prepare a 10% dilution (so in the case of a 1 liter bottle use 100 grams of shellac and a lot of alcohol until it is filled) and a 5% dilution (50 grams of shellac for the one liter bottle ).
Eventually, useful if we need small quantities, we can also lengthen the already prepared 20% solution to obtain intermediate dilutions: if we pour the 20% solution up to half of it into a half liter bottle and fill the rest of alcohol we will get ready immediately a 10% dilution and so on.
I also use a 2.5% dilution for the final polish.
The polishing pad
There are ready-made pad, but I do not recommend buying them because of their cost.
It is better to be able to adapt them according to the surface we want to trea: the size of the pad in fact must be adequate to the size of the piece that must receive the finish.
The outer layer of a pad is made of a square-sized cotton cloth. The interior, or core, is made up of cotton which forms the absorbent material, wrapped in a woolen cloth that will release small amounts of paint.
Soak the cotton and with the woolen cloth we form a small ball, wrap everything in the cotton cloth, making sure there are no wrinkles on the pad support surface, squeeze it a little to flatten it and our pad is ready.
The application of shellac: brush or swab
For small surfaces we can directly use the 20% solution.
This dilution is also useful if you want to apply with a brush instead of a pad.
Application by brush is certainly simpler but the best results are obtained with the pad so it is good to learn how to use this technique instead.
For medium-large surfaces it is preferable to start from a 10% dilution as this will be more easily workable.
The basic concept for applying shellac is simple: when it is spread, the amount of alcohol contained in it will evaporate (even quickly) while the remaining resin, i.e. pure shellac, will consolidate to form the surface layer.
The intermediate dilutions serve to momentarily revive the shellac to be able to smooth it, thus making the surface homogeneous and shiny.
The cycles of application of the pad
With the pad sufficiently soaked we begin to spread the shellac evenly over the entire surface, without regular movements, as long as you are careful to cover the whole area, paying attention to edges or corners.
The pad will be slid by alternating different movements; the only care to have is not to start the movement or to end it at a point on the surface but to simulate the take-off or landing of an airplane, placing the pad when we start and lifting it when we finish.
This will prevent the formation of annoying imperfections similar to orange peel, called burns.
This phase is called roughing and involves the first smoothing of the shellac layer. When the pad is discharged, a slight crunching sound will begin to be heard.
We can repeat this phase if we wish to have more consistency.
Now we can change the core (cotton plus woolen cloth) and repeat the steps mentioned above using the 5% dilution: the greater presence of alcohol will soften the shellac layer already deposited and then the polishing phase will begin.
When the pad is empty we will feel a slight resistance and we can help by applying a drop of Vaseline oil directly on the pad which, contrary to what many believe, is absolutely compatible with shellac since it is a fatty part like the quantity of wax it contains.
The small presence of oil will immediately make the surface very bright but this is an apparent brilliance due to the oil itself and not to the homogeneity of the shellac.
We insist with at least two coats of 5% dilution and then move on to either 2.5%, if we have prepared it, or by adding a few drops of alcohol on the same pad and insist repeatedly with the usual movements of the pad.
The friction of the pad generates heat and the alcohol evaporates quickly. We continue until we reach the degree of brilliance we want to achieve.
Conclusions and considerations
The pad can be reused sometimes, just place it in an airtight glass jar with a little alcohol inside, which will saturate the air inside so that the pad does not dry out.
The end result is a very smooth and shiny surface, but it takes a lot of patience.
Pad polishing is my favorite technique for applying shellac as it undoubtedly guarantees the best result.
Although it takes time and patience, it is a technique that also relaxes me a lot.
Find out more: Natural Wood Coatings on my workshop