Because it builds up over time and with repeated uses, people often think varnish is difficult to remove. The truth is, however, that removing varnish is relatively simple, and you can accomplish this job with ordinary paint remover.
Step 1 - Observe Safety First
Any time you work with varnish or paint thinners, protect your eyes by wearing protective eyewear. Also, the fumes of both substances can be dangerous to people and animals. Always make sure that you remove or apply varnish in an area with exceptional airflow and wear a proper respirator.
Step 2 - Use Paint Thinner
Paint thinner contains chemicals that are able to break down the composition of paint and lacquer finishes. Work it in with slow, circular motions, and then let it sit for as much as 20 or 30 minutes. Once the sealant has softened, wipe it off with a rag or sponge.
Step 3 - Use Sandpaper
You may also remove varnish with medium-grit sandpaper. Be very careful to remove the varnish but not damage the material underneath. Use a super-light grit to go back over the item before you reapply varnish.
Step 4 - Address Thick Applications
If numerous coats of varnish have been applied to the surface, the resulting goo is liable to be thick and difficult to manage. With a putty knife, scrape a majority of the sludge off. Paint thinner turns a hard protective covering to a messy goo in only a few short moments. For extremely thick concentrations of varnish, allow the paint thinner to sit longer, and go back over the same spots until you have completely erased the varnish.
Step 5 - Complete Cleanup
Use 220-grit sandpaper and go over the entire surface, especially areas that were difficult to reach with the paint thinner. Remove all dirt and debris from the surface, or problems may result when you apply fresh varnish.