What are some different types of wood sealers? When are they used? How do you use them?
Wood sealers penetrate the wood to keep the finish on top of the wood. Most finishes profit from the use of a sealer because it primes the wood for the finish, ensuring that the stain will be absorbed uniformly. What type of finish you select, will determine what type of sealer you should choose. If you have an oily wood, like a rosewood, make sure you use a sealer. The oil could bleed out, damaging your finish. Here is a list of types of finish and the sealers that work best with that choice.
Polyurethane - Polyurethane is a durable and fast-drying finish. Use a lacquer-based sealer before it.
Lacquer - For a Lacquer finish, use a lacquer sealer. 1 lb.. cut shellac works well. Thinned shellac is a good all-purpose sealer. Use orange shellac for dark woods, and white shellac for light woods.
Shellac - For a Shellac finish, use a shellac sealer. The same rules apply as with the lacquer finish.
Varnish - For regular varnishes the shellac sealer or lacquer sealer will work.
If you are going to finish your wood with an oil, penetrating oil or tung oil, you will not need to use a sealer. The oil will act as a sealer as well. Make sure you apply the sealer evenly, and let it dry well before applying a finish. The sealer will smooth the grain of the wood out, so your finish absorbs evenly. It will also lengthen the life of your wood.
If you are wanting to seal wood outdoors, but not stain it, apply something like Thompson's water seal. You can use anything that will keep the water from pounding on your wood. This will keep your wood protected, so it lasts longer.