If you go much thicker, the coating gets too rigid and will crack/craze due normal wood movement due temperature and humidity. Varnish blends are based on more flexible 'hard' resins than lacquer, but still recommend 0.005 to 0.006" as max thickness.
The symptom of you applying too much varnish is that it runs. Surprise! When there's too much liquid it flows somewhere. Except it then dries.
Applying more than two coats of matt or satin varnish could mean making your painting look cloudy, but with gloss varnish you can apply up to three coats. If you're using spray varnish, you could stick to two to three layers, or apply anything up to 50 coats if you're after an extra high-gloss effect.
Use a chemical paint stripper or sandpaper to remove varnish from wood. Apply the stripper according to the manufacturer's instructions, then scrape off the softened varnish. Sand the surface to remove any remaining residue and refinish as desired. Explore my Quora Profile for more woodworking advice.
Paint stripping removes old paint or varnish with chemicals. This technique can be fast and efficient. If you're looking for a method with minimal effort, no sanding furniture might be ideal.
If you do decide to go ahead and apply new varnish over the top of old varnish, make sure that the existing varnish is scratch-free and do give the old varnish a light sanding using 120-grit sandpaper and wiping away any dust. This will ensure that the new varnish has something to bond to.
In a nutshell, the technique for applying a wiping varnish goes like this: You wipe on a full, wet coat, let it sit for a few minutes to tack up slightly, and then wipe off the excess. Since you're leaving only a light coat on the surface, the varnish levels out very evenly.
Alcohol interacts with wood surfaces, acting as a solvent when it touches wood. Solvents dissolve wood finishes, including staining and varnishes. It does so by stripping away the top layer of the furniture. This can significantly damage the integrity, aesthetics and value of the piece.
If varnish is too thick, it can sag, or orange peel, and not cure properly. Leave trapped dust specs or bugs in place till the varnish tacks over. You can sand them out between coats.
Sanding Tips: No sanding is needed if you overcoat within 48 hours. Don't sand unless the most recent coat has dried for 24 hours. Use 320 grit to prevent scratches; sandpaper finer than 320 grit will not allow proper adhesion. Remove residue before reapplying.
Limited UV Protection: The UV resistance of varnish is not as effective as modern alternatives like UV-resistant wood stains or protective coatings. Environmental Concerns: Traditional varnishes contain volatile organic compounds (VOCs) and other potentially harmful chemicals.
Never more than 3 coats. First coat should be thinned 50% with mineral spirits for good penetration then two full strength, sanding between coats. When applying wipe on varnishes, double the coats.
A varnish coating will have great difficulty adhering to the substrate (new or previously painted, interior or exterior) if any surface contaminants such as dirt, dust, oil, grease, mould, mildew, algae, salt, or other loose or powdery substance is present on the surface.
While polyurethane is water- or oil-based plastic resin, varnish is older and made from resins, oils, and solvents. Because of the higher ratio of solids, varnish is less susceptible to ultraviolet light damage. This protection makes varnish an excellent choice for projects such as outside decks and exterior furniture.
Paint a liberal amount of paint and varnish stripper over the whole door and leave for 20 plus minutes. Slide a clean-edged scraper under the varnish and it should lift if it's ready to be stripped. Use the scraper in the same direction as the grain of the wood and work over the whole door.
Give the varnish a really good stir before you start. Brush it on in the direction of the wood grain, to get the best finish you'll need 2-3 coats. Make sure you leave 1 hour between each coat. Before the final coat give the wood a quick sand down.
If you are getting a rough finish after several coats of varnish, you may want to wet-sand the surface with 220 grit to level it out. Here I have leveled out the finish prior to the final coat and sanded it to 320 grit. I vacuumed the surface, wiped it down with a ragged wetted with mineral spirits.
Marine Spar Varnish can be recoated in 10-12 hours at the recommended coverage rate. The varnish can be recoated without sanding up to 24 hours. Beyond 24 hours, sanding is required.
A: Usually when varnish remains persistently sticky it's the result of application in a humid or cold environment.
Sanding between coats of varnish is important because it achieves two things: First, it knocks down the “high spots” and second, but more importantly, it provides a tooth for the next coat to adhere to. Otherwise, the subsequent coats can delaminate and lift off in large sheets.
Citristrip is a good alternative to Minwax If you're looking for a less toxic varnish stripper. Aside from Minwax, Citristrip was the best for removing finish. While the manufacturer recommends leaving it to soak in for at least 30 minutes, I noticed the finish bubbling up after only about 12 minutes.
Whatever product you want to use, as a general rule, you will have to completely remove any existing varnish, waxes, oils, wood stains, dust, dirt, grease, uneven areas and sticky stuff before applying a wood varnish.