The processed resin that was secreted by insects native to Asia, shellac has many uses from watchmaking to nail polish as well as wood-finish.
Shellac is a more than a thousand years old non-toxic wood finish option that can add smoothness to the wood without a plastic-like quality and is a viable natural alternative to synthetic finishes such as polyurethane.
Many different colors are available for an interested buyer, and they can be bought in dry form or premixed with alcohol.
However, with all of its advantages, shellac is not a perfect choice for a coffee or dinner table as it can disintegrate through exposure to heat and alcohol and becomes less water-resistant over time, making it more suitable for surfaces that won’t have such usage.
Shellac dries quickly, allowing many coats to be applied in a single day, and is very easy to repair in case of deterioration. In addition, it is a versatile material and, therefore, can be applied in a variety of ways, from brushing to padding.
But is it possible to apply shellac by spraying?
The answer is yes, it is indeed possible to apply shellac by spraying, but there are some fine points that the wood finisher needs to know to have satisfying results.
Is It Possible To Apply Shellac By Spraying?
Shellac is the dried resin of lac bugs that live in the forests of India and Thailand, which is suitable for usage as a wood finish product.
It is thinned by alcohol, and it can be applied in various ways once the mixture is ready.
It is very much possible to apply shellac by spraying, and the wood finisher can choose between preparing their own mixture or buying a premixture.
The film thickness will take longer to build when spraying compared to brushing, but as shellac is quick to dry, it is possible to apply many coats in a single day.
Shellac is as adaptable as it is natural, and spraying it is a method as viable as brushing or padding. Some certain tips and tricks that are useful to follow when spraying shellac, such as sanding the coat after the first or second application and reinforcing the end product with 0000 steel wool, which will be detailed further in the next section.
Four or five coats of shellac will need to be sprayed to build up a satisfying thickness of the film, and while the result may lack in durability compared to other options such as lacquer, it compensates for this weakness by being very easy to repair.
How to Apply Shellac by Spraying?
Those who are familiar with spraying lacquer may realize that spraying shellac is more challenging; this is because it is a thicker material.
Shellac should be sprayed in thin and even coats, and as was noted before, many coats (four or five) can be applied in a single day as it dries quickly.
A practiced method is sanding the coat after the first spraying using a 220 free cut paper, then putting the rest of the coats on and letting the wood dry overnight. Sanding it the next day (again using a 220 free cut paper) will give a clean and smooth result.
A different yet also practiced way is to spray two light coats, then sand them with 320-400 free-cut paper. After applying two more light coats, the end product can be reinforced with 0000 steel wool.
As alcohol is a polar solvent, directly applying shellac may raise the grain in the wood, so sealing the grain first using an oil-based polyurethane finish is recommended. It should be noted that it takes longer to spray shellac than to brush it as it takes longer to build up thickness.
After the process, the spray gun should be cleaned using a gun wash product.
How to Thin Shellac for Spraying?
Shellac is an evaporative finish, meaning that when applied to a piece of wood, the alcohol in the mixture vaporizes and leaves the flakes of resin behind, which covers the surface as a film. To thin shellac is to mix the flakes with alcohol to make the mixture that will be applied to the wood, and there naturally isn’t one formula that fits all uses.
So what is the proper ratio for the mixture needed in spraying shellac?
Shellac can be bought in premixed spray form, or it can be thinned from flakes, and it is also possible to further thin premixed products. For the process of thinning shellac, knowing the term “cut” is very important, as it signifies the ratio between the alcohol and shellac flakes that are in the mixture.
A pound cut is one pound of shellac flakes in a gallon of alcohol, and it is the cut you need for spraying. The higher pound cut will result in a thicker mixture that dries slowly but builds a film more quickly, while the lower cut will be like water, dry very quickly and build a thin film layer.
A pound-cut is the ratio needed to make the mixture for spraying shellac, but to actually mix a gallon of alcohol with a pound of shellac flakes is not recommended, as the mixture has a shelf life.
This is also important to remember when buying premixed products, and those that are older than a year shouldn’t be bought. In making the smaller mixture, the pound cut ratio should be kept. A cup of alcohol and an ounce of flake is the pound-cut mixture needed for spraying shellac.
The flakes should be weighed and poured into a jar, and the alcohol should be added later. Pulverizing the flakes beforehand (in a food processor) will speed up the process. The mixture should be stirred to prevent the flakes from clumping at the bottom.
Smaller batches will dissolve in a few hours, while larger batches take more than a day, so having the jar somewhere easy to shake a couple of times a day is practical. When the flakes are dissolved completely, the mixture should be strained through a paint strainer or a piece of cheesecloth which will catch impurities.
It is recommended to use regular denatured alcohol for the mixture.
Shellac is a traditional and non-toxic wood finish option that is increasingly popular. It is a material that is used even to cover pills, making it a very healthy alternative to synthetic finishes such as polyurethane.
Certain fine points need to be remembered, but with these kept in mind, shellac is a practical wood finish that has proven its worth for over a thousand years.
As it is adaptable material, shellac can be applied in a variety of ways, and it is possible to apply shellac by spraying. Shellac dries quickly, allowing for many coats to be applied in a single day.
It should be sprayed in thin and even coats four or five times, and the coat should be sanded after the first or second application. Sanding it the next day will provide the wood finisher with a clean result.
Alcohol is a polar solvent, and as the shellac mixture has alcohol as the main ingredient, it can raise the grain in the wood, so sealing this grain with oil-based polyurethane before applying shellac is recommended.
Shellac can be bought in premixed spray form or thinned from flakes. The ratio of shellac flakes to alcohol needed for spraying is a pound cut, meaning a pound of shellac flakes to a gallon of alcohol. As shellac has a shelf life making smaller mixtures is more practical and less wasteful, an ounce of shellac flakes to a cup of denatured alcohol is also the pound cut in smaller form.
The flakes should be poured into the cup and alcohol added on top of it, and the mixture should be stirred a couple of times during the day until the flakes are dissolved. Smaller batches take a few hours to dissolve.
Shellac wood finish becomes less water-resistant over time and can disintegrate if exposed to heat or alcohol, but it is effortless to repair. It might not be a perfect finish for a coffee or dinner table, but it is a proven, practical, and non-toxic option that can be applied with spray.