Allow the varnish or lacquer to dry for one day, then level-sand with 400-grit sandpaper to remove bumps and imperfections. This gives you a smooth substrate for the finish coats.
Sand. After the first “sealer” coat has dried, sand it smooth using very fine sandpaper. Not doing this is probably the single most common cause of finishes not feeling smooth after all coats have been applied. The most important thing you can do to achieve smooth results is to sand the first coat smooth.
To get a glossy finish for wood, start by sanding the surface smoothly, then apply a grain filler before lacquer or varnish. For professional-looking results, finalize the work by wet-sanding it with ultra-fine sandpaper and buffing it to create a polished look and feel.
If blotches appear, gradually add varnish to the homemade mix or apply additional coats of conditioner until it blocks the blotch. Don't exceed one part varnish to two parts mineral spirits. Lightly sand the wash-coated surface using the same grit you used on the unfinished wood.
Usually when varnish makes a surface rough, it's either that it's picked up dust during the drying process, or it was being brushed/wiped too long after application.
Remember to let the varnish dry between coats, and to sand and wipe the varnish clean before applying more varnish. Always work along the grain when applying and sanding the varnish. When you get to the last coat, do not sand it. You can continue working with 320-grit sandpaper, or move up to 400-grit.
Blotchy stain often occurs because wood unevenly absorbs stain, causing some areas to be darker than others. Blotchy stain is more likely to happen on soft woods such as pine. Stain rarely turns out blotchy on hard wood like oak.
Hold the brush at a right angle to the work surface, and lightly brush just the tip of the brush over the whole varnished surface. Once again, work in the direction of the wood grain. Apply two thin coats of varnish, then sand and apply another. Most projects will need several coats of varnish.
The streaking you are describing seems to be the result of the finish being applied too thin. But you don't want to go quite as thick as a brushed-on coat.
The way to get the smoothest and best-feeling finish is to “rub out” the last coat using sandpaper and abrasive compounds. Methods of doing this are written about often. It's a mechanical procedure that doesn't differ all that much from sanding the wood.
Rub a generous – but not excessive – coat of oil across the wood. Mineral, rubbing or even vegetable oil work well. Sprinkle FFFF-grade pumice over the oil in a fine layer. Gently and evenly rub across the wood with a felt block, working a small area but using long strokes rather than short bursts.
Brush on a coat of varnish; hold the brush at a right angle 10° to the surface; and, working in the direction of the grain, lightly skim the varnish with the bristle tips to help level it.
No, you don't need to sand the final coat of polyurethane. The only time you should sand the final coat of polyurethane is if you haven't gotten a smooth finish. Different problems can occur when you apply polyurethane, such as dust nibs, bubbles, and streaks.
You really can use just about anything to apply varnish and other finishes to a surface, even a rag or the flat part of your hand. It's what you do after the varnish has dried that makes the difference in the end. The concept of "finishing the finish" is what is important to keep in mind.
The only effective way to lighten the color of wood after it has been stripped of all surface coatings is to use a wood bleach. Sanding does help to lighten wood in many cases, but this only applies to surface soil or grime, and even then only if the discoloration has not penetrated very deeply.
Sand lightly with 240-grit sandpaper between coats, then let the last coat dry for at least 24 hours. This is standard practice with any wood finishing job, and is nothing out of the ordinary. That said, sanding bare wood beforehand to create a smooth foundation is key.
Just dip the brush in and let it drain. You can also pad it on. Finally, for a fine finish you will need to wet sand with 600 grit and water with a drop of dishwasher detergent. Allow at least a week for the finish to cure.
Yes. Minwax Polyurethane should be sanded between coats. Sand with 320 grit sandpaper to get rid of any fine particles of dust that have settled on it while it was still wet. Sanding in this case not only allows for a smoother finish but can also help abrade the surface and increase inter-coat adhesion.