Posted by Bill Martinelli [ 24.93.18.98 ] on December 22, 2003 at 01:05:15:
For those ready to brave a sprayed on finish. Please be careful. You need a mask, ventilation and surroundings that dont start fires.
Some ideas to get you started for spraying a finish. First have all your prep work in order. Then choose a finish that will be correct for your application. This little summery is for lacquer and does not take into account the pros and cons of other types of finish. There are many types of wood finish available today. Varnish, Shellac, Polyurethanes, Water based, Oils, and Waxes to name a few. We are just going to talk about lacquer for now since it sprays on easily. Builds and dries fast, and is easy to work with.
First we have preparation. Remember that a clear wood finish will not mask any flaws in the wood. In fact, a film type finish will accentuate the flaw. A good fit between parts is a must and sanding with the grain using 220 paper helps out. Work your way up to 220 grit in steps. Unless you have some major sanding to do, avoid using 80 grit. Start off with 100 grit, sand again with 150 and then with 220. If you’re using pre-veneered plywood then you should start with 150 grit paper. Random orbit sanders are a great thing but always end your sanding adventure with hand sanding in the direction of the grain using garnet sand paper.
Now that our cabinet is finish ready we can choose a finish brand. Sherwin Williams has local stores in many big cities and carries professional wood working products. SW Low-VOC is a good lacquer. I don’t use the water white lacquers because I prefer the amber, mellow tone you will get in a few months. If you want a finish that will have virtually no yellowing, use water borne Lacquer/Varnish/Polyurethane. For the ultimate in amber and mellow ageing tones, use Varnish. I only use Spar Varnish since it is also waterproof and you will never have water damage from open windows, plants or drinking glass. Minwax Helmsman is adequate choice for Spar Varnish. Mohawk, Crystalac, Pianolac, McFadden and Target are some suppliers for quality wood finishes, to name a few.
I use Hood Finishing products, Magna-Shield lacquer. You can look at their products at http://www.hoodfinishing.com/ . This is a Pre-Catalyzed lacquer that has 40% solids and complete burn in between coats. This makes sanding between coats un-necessary. Though sanding is always necessary with polyurethanes or varnish. For added depth use 75% sheen gloss and rub it down to a satin luster. Use a self sealing lacquer because they sand easily. Your first coat will be a sealer and lock the wood fibers down and “pop” the grain. Even with careful sanding some of the wood fibers will be locked in an upright or out of alignment position. This is why after applying the first coat of a finish you will have some fuzzy texture to your project and it will need smoothing. Sand with 220 grit paper.
The better spray gun you can afford the less headache you will have. Having said that, there are a few HLVP conversion guns on the market for $100 that will suit your needs quite nicely. HLVP is a must. The stuff stinks and you don’t want it bouncing all over. More importantly, finish is not cheap and you don’t need to be spraying it all over hells half acres. When your done, always clean your gun.
Good finish techniques that will give you a durable finish as well as a rich look consist of 5 coats and a little elbow grease. For thinning and air pressure, talk with the material supplier. They know the climate you live in and the best flow charactoristics of the materials they are selling. When your all ready to start here is a little progression you can follow. Very open grain woods may need more coats if the grain is not filled. For a less "plastic" look, less coats may be your choice.
• Spray sealer coat
• Wait 1 hour and sand smooth with 220 production trimite paper
• Spray full wet coat No.2
• Wait 1 hour
• Spray full wet coat No3
• Wait 1 hour
• Spray full wet coat No.4
• Wait 24 hours
• Sand with 220 paper
• Spray full wet coat No. 5
• Wait minimum 3 days. (3 weeks would be fantastic)
• Sand with 400 paper
• Steel wool using 0000 grade steel wool and use a wool oil
• Wash off all excess wool oil with damp cloth a few times
• Paste wax with Johnson’s paste wax. Wipe off when hazy
Now you can sit back and admire your work. I’ll talk more about touch ups and repairs another time. If you hanker for an Oil finish, you’ll have to consult upon Dr. Epstein since he has some cool tricks for Tung oil, Danish oil, French polish and Shellacs.
Bill
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