While shellac is not usually the finish paint choice, it is often thought of as the best paint primer available. It has properties that oil and water based paints can't match, and provides a more dependable seal than most other primers are able to provide.
Shellac seals the material. For new construction, the sealant qualities are likely to be less noticeable, but in a remodeled home, it is able to seal in stains as well as odors. Water stains won't rise to the surface of the new paint the way it does with other primers because shellac has a neutral base that won't loosen stains, simply seal over them.
Shellac Binds to Most Surfaces
Shellac makes a perfect paint for homes with heavy smokers. Many paints have a difficult time sticking to walls that have been heavily coated with nicotine. Shellac sticks readily to nicotine covered walls, prevents the stains from soaking through, and eliminates the caked on odors of tobacco smoke.
Shellac Combats Smoke Damage
Homes that have suffered a fire seems to have a pervasive burnt smell, even in rooms where the fire itself never reached. With oil and water based paints, the smell of smoke may linger long after the walls have been painted over. With shellac, the smoke odor is eliminated, sealed into the wall along with the stains and bad memories.
Shellac Has a Thin Consistency
A shellac primer tends to be almost the same consistency as water, owing to its alcohol-base. It is important to keep this in mind, especially if you will be using a sprayer, as the tip must be kept very small to avoid over-application of the shellac, resulting in runs in the paint and uneven coverage.
Shellac Dries Quickly
Because it has an alcohol base, shellac dries very quickly. A primer coat of shellac is ready to receive the first coat of paint in only about 45 minutes, where other primers may require 2-3 hours of drying time in even optimum conditions. Alcohol evaporates much quicker than other substances, and that allows shellac to dry 2 or 3 times faster than other primers. Heavily stained spots may not dry completely for a long period, but aside from these rare spots, the primer dries in nearly record time.
Shellac Makes a Great Undercoating
Shellac is not generally used as a finish paint, but it is widely appreciated as the undercoating to which ordinary paints are applied. It has the ability to stick to most materials, as well as water and chemical stains, and is equally accepting of the paints that are applied to it.
Always Allow Complete Drying Between Applications
Note that occasionally paint will leave a damp looking shiny spot when it is applied to shellac primer. This is actually a slow drying spot caused by the shellac covering a stain or imperfection that doesn't absorb the shellac properly. Most experts agree that if left to cure for a few days, the spot will get smaller and then vanish entirely. Never apply additional paint to a shellac primed surface until at least 48 hours has passed to avoid removing already applied paint that has not fully bonded to the wall yet.