Question from a Student: For high traffic areas, does it make any sense in spraying a protective lacquer finish, after applying the Linseed and Tung Oil finish. It seems that would be the best of both worlds.
Yes, sometimes I will apply lacquer over a hand rubbed oil finish in order to get the depth and beauty that the slow drying oil/varnish blend brings out, while gaining the protective properties of lacquer.
I proceed in the usual manner of sanding the wood to 320, then applying the General Finishes Seal a Cell as the first coat. I want to emphasize that you need to really rub hard and get all of the extra finish off of the surface so that it dries in the wood, not on the wood.
I let the first coat dry overnight in my heated drying room at 75 degrees.
Woodworkers who have a garage shop can create a small or large drying room by using some 2 x 4’s to frame in the area they need and then staple 4 mil plastic sheeting to the wood frame. Sealing the edges with duct tape will help trap the heat inside.
I use an electric oil filled heater to keep my room warm at 75 degrees. They only cost about $50.00 and run a couple of dollars per day to use.
The next day, I rub the surface hard with 0000 steel wool. I prefer the Liberon brand which is more consistent without oil in the steel wool fibers.
After blowing the dust off with compressed air, I apply a coat of General Finishes Arm-R-Seal which has urethane in it. This finish dries faster and if the resins start to set up on the surface, then I apply a little more oil which will dissolve the sticky residue allowing me to wipe and buff the surface clean and dry. Once again, I must emphasize the need to rub hard enough to remove all of the finish from the surface so it appears to be dry. In reality, there is still enough finish there that has soaked into the fibers of the wood to create a soft sheen.
This coat needs to dry for a minimum of 3 days, preferably a week. After this, I will pad on a thin coat of shellac. I have had success mixing my own, or simply using the Zinsser Bulls eye 100% wax free Universal sanding sealer.
The shellac will bond to any finish and any finish will bond to the wax free shellac so it is the perfect intermediate coat to make incompatible finishes compatible.
After the shellac has dried overnight, then I will proceed to the lacquer finish.
The primer for Lacquer is sanding sealer. Sanding sealer has stearates in it to soften it and make it sand easier.
Sanding sealer should never be applied in thick coats. One or two coats thinned with lacquer thinner is all you need. The sealer helps the lacquer bond better to the surface.
I prefer to use a vinyl sanding sealer which is more water resistant then regular sanding sealer. Two thins coats should be enough followed by very light sanding with 320 grit paper.
You need to to apply the lacquer within a certain time window to get a good bond to the sealer, so make sure you read the directions on the can for best results. I would say as a general rule, apply the lacquer after the vinyl sanding sealer has set for about two hours.
I build all of my coats of lacquer with gloss lacquer which will give you maximum clarity as well as maximum hardness.
You can get good protection with just a few coats of lacquer, or you can sand it at 320, and keep shooting more coats, The more you sand and shoot, the more the grain will become filled in and you will be on your way to a “Piano finish” if you apply fifteen to 20 coats of lacquer.
The so called piano finish refers to a “glass like” surface. This means shooting no more then 3 coats per day and light sanding in between coats to help fill the pores as well as scuffing the surface so that the solvents can evaporate faster.
Eventually you will have a smooth finish that will need to harden for two weeks to a month before wet sanding and rubbing out to a mirror reflection.
Lacquer finishes will shrink as they cure, so be advised to test your coats by seeing if you can dent the finish with your fingernail. If you can, then wait until you can’t dent the surface with light pressure before going on to the next coat.
Chemists are constantly changing their formulas so I always recommend doing your test samples on small pieces of wood (I make sample boards 4 inches wide by 12 inches long x 1/4 inch thick). I highly recommend writing your notes on the back and dating each coat that you apply. Be as scientific as possible to help ensure the best results.