Lacquer, like no other finish, highlights spectacular grain and builds a durable finish that gives depth and clarity to the wood surface. It can be applied with either spray or brush. Experience will result in an improved finish.
EQUIPMENT OF SPRAYING
Cheap solution – Syphon-type spray gun and a compressor rated at a minimum of 4CFM at 100PSI
More expensive but easier to use – HVLP system
Many turners use, with excellent results commercially available lacquer spay cans to finish small pieces. A wide variety of lacquer products is available on the market. For best results use nitrocellulose spay can lacquer made for electric quitar application.
A well ventilated spray booth is a must as lacquer vapors are very harmful. At all times use a NIOSH-approved respirator mask. Many good manuals are available on the market to give you the basics in spraying
MOISTURE AND BLUSHING
“Blush” is a white cloudy appearance caused by water vapour that condenses under the finish. HVLP spraying equipment eliminates the water and cooling effect of the air stream because the air pressure is low, thus reduces the chances of “blushing”. Knowing the ambient temperature “relative humidity” and the “Dew point temperature” can determine if a specific day is a good one to spray lacquer.
The Rule 65: DO NOT spray if the temperatures is below 65 degrees F or the relative humidity is above 65%
The 20 degree F rule: It is safe to spray lacquer when the Dew point temperature is greater than 20 degrees F lower than the ambient temperature.
Water-borne lacquers are not discussed. Their film has a cloudy bluish tint and are not crystal clear. Nor are Catalyzed lacquers discussed. While excellent products, the catalyzed lacquers are for professional use and require ventilation and personal respiration equipment, beyond a normal woodworking shop.
Commercial cellulose lacquers are not recommended because their film will turn yellow and become brittle with age.
Deft Brushing lacquers are blended with retarding thinners which allows levelling of the surface film. Better than cellulose lacquers , they remain flexible and do not yellow with age but do not give a museum finish. Deft nitrocellulose can also be used in a spray gun but it runs if you are not careful.
Lacquer in spray cans offer an intereating alternative
CAB-Acrylic lacquer is made with cellulose acetate butyrate and acrylic resins. It goes on crystal clear and does not yellow with age. It stays more flexible over time than other lacquers. Make sure to thin appropriately. Thin it to no more than 50/50 with a commercial thinner for application with 30 PSI at the spray gun. Any product labeled "Lacquer Thinner" can be used. Some, like Sherwin-Williams, are "water white" in the can, and it will not turn yellow in our lifetime
Ditzler (PPG) Automotive Lacquer according to Russ is the best he has used. It will not yellow with age, and the film is flexible and will not crack. Sold for use in high pressure spray equipment. Thin 3-to-1 or 4-to-1.
Waterborne lacquers are not true lacquers and have none of the properties of grain enhancement or gloss found in nitrocellulose lacquers. However, manufacturers are rapidly improving these products.
TECHNIQUES FOR A GOOD FINISH
· Wood selection – Avoid coarse grain (oak, ash) - need a lot of fillers to develop an attractive appearance. Avoid woods that are very soft (cedar, redwood), these don’t provide a rigid enough foundation and very oily woods such as cocobolo can cause adhesion problems until you have some experience with lacquer. Adhesion can be enhanced by cleaning the wood with alcohol, to remove some of the oil.
· The moisture content of the wood must be in equilibrium with the relative humidity of the environment, otherwise you can get blushing under the film or cracking of the film as the wood continues to dry.
1. Brush on a heavy sealer coat of either Deft or the same lacquer thinned out that will be used for spraying. Let sit for a few seconds and wipe off with paper towels, changing them often, until the wood surface is smooth and dry.
2. Wait 30 minutes for the lacquer to be absorbed in the wood and brush with 000-steel wool or 600 gran sandpaperi, and proceed with a first coat.
Alternatively, if you want to accent the grain of a wood like maple apply a liberal coat of oil/varnish finish and immediately wipe the surface dry. Wait until the following day, and buff with 0000-steel wool. To avoid any potential for adhesion problems, brush on a coat of a 2-pound cut dewaxed white shellac. It is best to mix your own shellac because any wax in the shellac could cause problems with the lacquer. Sand the shellac lightly with 600-grit or the same grit that used last for finishing the wood.
3. In many instances if you use close grain wood steps 1 and 2 may not be required. In spraying your first coat of lacquer, make sure that you have the appropriate viscosity, Deft acquer should be diluted 4:1 with lacquer thinner. Apply a wet coat on the entire surface, but not so much that the lacquer runs. If you get a run, or a "fisheye," leave it alone for now - it can be sanded back when the lacquer has dried hard. Try to avoid over-spray, but don't be concerned because there will always be some present. It is impossible to totally eliminate it. Some degree of "blush" can also be tolerated, and it may disappear with the addition of more lacquer or after it is buffed. Wait two or three minutes and shoot another wet coat. More coats can be applied in the same manner to obtain greater depth. If the "blushing" doesn't disappear, or gets worse, the weather conditions are wrong, and you didn't read our previous discussion on that subject.
4. Wait a few days for the lacquer to harden and then buff with white diamond and then linen to get a perfect gloss.