Finish Line
M M l F i n i s h L i n e www.modernwoodworking.com 24 SEPTEMBER 2009 PROBLEM 1. Orange-peel and texture in the fi nish and/or the fi nish does not spray out well. Solution: As a rule of thumb, water-based fi nishes generally require more atomization energy than do solvent-based coatings to break the material into satisfactory particle size. Large particles will cause texture in the fi nish that may not fl ow out before the coating dries. The use of standard air spray or HVLP spray gun technol-ogy generally results in large particle size with wa-ter-based coatings. We recommend using air-assisted airless technology to apply water-based sealers, prim-ers, paints, and clear coats. Air-assisted airless spray gun technology uses both air and hydraulic pressure to break up the material, resulting in a much fi ner particle size and a beautiful fi nish. PROBLEM 2. The coating is thick with a high viscosity. Solution: Water-based coating viscosity can be drastically affected by temperature and agitation. With some materials, when the tem-perature of the coating drops below 65°F, the viscosity may increase two-fold. Bringing the coating tem-perature up to 72°F will dramatically lower the viscosity and allow the coating to be sprayed normally. Gentle agi-tation of water-based coatings will also benefi t in a lower material viscosity. Be careful not to over-agitate the coat-ing as agitation may cause damage to the coating or en-train unwanted air into the material. PROBLEM 3. Adding water to the material to reduce viscosity causes it to run and sag. Solution: Water has a very high surface ten-sion making it a very effi cient solvent. If water is used to reduce the coating, only about 10 percent of the quantity of water is needed as a reducer compared to what is need to reduce a solvent-based material. For example, if you normally reduce lac-quer thinner 20 percent, water-based materials would re-quire 2-percent added water to achieve the same type of reduction. Rather than using water as a reducer, however, a better choice may be to use a solvent that will be soluble in water-based materials (such as EB Glycol or Butyl Cel-lusolve). Check with your supplier for their recommen-dations. Adding water to your coating for a reducer may result in excessive grain raise, a longer drying time, and may decrease the smoothness of the fi nish when dry. Welcome to the world of green fi nishing. Many large and small shops have taken the leap to convert to wa-ter-based fi nishing in all of their fi nishing processes. The process to convert to water-based fi nishing can be problematic at best. Here are eight of the most com-mon problems and recommendations for solutions. By Phil Stevenson, president of the American Wood Finishing Institute, www.awfi .org Water-based Finishing Problems solutions for