A total of at least 4-6 coats will give the best finish & depth. The more coats, the better the finish.
For chairs, benches, chests and other such pieces, 1 to 2 coats should do the trick. Any wooden pieces that will be used outdoors or under a covered porch should only have "spar varnish" or "boat varnish" applied. Never more than 3 coats.
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.
You should use at least 2-3 layers of polyurethane on your wood floor. Depending on the type of polyurethane you decide to use, two coats may be sufficient. However, if you are using a water-based polyester, 4 coats are recommended to get the overall finished look.
Applying too much varnish in one layer or letting it pool up leads to cloudy, discolored spots such as in the image below. This phenomenon is more noticeable with matte varnishes than it is with gloss varnishes but should be avoided regardless of the varnish you are using.
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.
A varnish brush applies the film at the right thickness. After your first coat of paint is dry to the touch, it's safe to recoat typically three to four hours. A good rule of thumb is to wait at least three hours to recoat, if it's water- based.
As a general rule, polyurethane can take as long as 30 days to completely and correctly cure. It would be best to give yourself a full 3- days before using your wood floors following a polyurethane treatment for the best possible outcomes.
Two coats of finish are suggested for most interior projects. When sealing floors, you should apply three coats. However, do not apply more than two coats in one day. 220 grit sandpaper should be used between coats to remove any air bubbles, but avoid using steel wool.
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.
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.
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.
Next layer applied too soon
When a new coat of varnish is applied to a surface that appears dry and is not fully dry, different minute sections of the surface interacts, and expands, differently to the solvents in the new varnish. Sand down, and depending on your visual requirement, repaint.
Applying the varnish coat
Ensure that the surface is clean, smooth, and free from dust. Use a high-quality brush to apply the varnish in thin, even coats, and always follow the manufacturer's instructions for drying times between coats. Sand lightly between coats to ensure a smooth finish.
Four layers are suggested for water based polyurethane and 2-3 coats for oil based polyurethane. Wait for at least 8 hours before reapplying oil based polyurethane and 2 hours for water based polyurethane.
The following are average CURE times based on recommended temperature and humidity: 21 days for water-based products. 30 days for oil-based products. You can use a piece lightly after about 7 days but be cautious - the finish will still be curing for another 2 or 3 weeks.
Make sure to sand the polyurethane between coats.
Sand the wood
This will help the varnish stick and will give you a smooth finish. If you removed the previous coat with sandpaper, you don't need to do this step.
How many coats of varnish should I apply? You can apply as many subsequent coats of wood varnish as you need, but an additional two or three coats is the standard. Remember to tip-off and gently sand between each coat.
In either case, it is better to apply two or three thin coats with sufficient drying time in between, rather than one thick coat of varnish.
To fix this: Allow the finish to dry completely. Lightly sand the cloudy areas with fine-grit sandpaper. Reapply a thin coat of polyurethane, ensuring proper drying conditions.
A: Usually when varnish remains persistently sticky it's the result of application in a humid or cold environment.
Gloss oil-based varnish, polyurethane and Danish oil can last 10 or 20 years, though satin finishes and stains may fail sooner as pigments and flattening agents disable the driers. Water-based coatings and paints can also be viable longer than three years. Shellac, though, can go bad in under a year.