Popular Woodworking 2000-06 № 115, страница 60
paint and varnish removers: strongest to weakest STRIPPER TYPE HOW TO IDENTIFY DESCRIPTION POTENTIAL PROBLEMS COMMENTS Lye Methylene chloride/Methanol (MC) Methylene chloride/Acetone, Toluene, Methanol (MC/ATM) Acetone,Toluene, Methanol (ATM) Acetone,Toluene, Methanol (ATM) "Refinisher" Contents list sodium hydroxide or caustic soda.Available as powder or paste.Warns of severe burns if it comes in contact with your skin. Contents list methylene chloride and methanol. Non flammability is usually mentioned. Contents list methylene chloride, methanol, and a combo of acetone, methyl ethyl ketone, toluene, xylene. Contents list some combo of acetone, methyl ethyl ketone, toluene,xylene and methanol Contents list some combination of acetone, MEK, toluene,xylene and methanol N-methyl Contents list n-methyl pyrrolidone (NMP) pyrrolidone and possibly one or two additional ingredients The most effective stripper. The strongest and fastest-acting solvent stripper. The weakest and cheapest methylene-chloride stripper. Almost as effective as MC/ATM but without methylene chloride. Very inefficient as a stripper because no wax is included to slow evaporation. Effective on most finishes, but two or three times slower and more expensive than methyl-ene-chloride strippers. Di-basic esters Contents list "ester" or The slowest of the (DBE) names of solvents ending in "- strippers. ate," which are esters. Damages wood. Darkens many woods and can cause finish problems. Contains wax which must be removed before applying a finish. Contains wax which must be removed before applying a finish. Contains wax which must be removed before applying a finish. Too slow on everything except shellac and lacquer. Trying to rush it. Trying to rush it. Included water may blister veneer and warp thin wood. Very dangerous to use because it causes severe burns to skin and eyes. Keep clean water close by for washing. Fumes are a health hazard.Work outside or in a room with cross ventilation. Fumes are a health hazard.Fumes and liquid solvent are a fire hazard. Fumes are a health hazard.Fumes and liquid solvent are a fire hazard. Fumes are a health hazard. Fumes and liquid solvent are a fire hazard. Fairly safe to use because of slow evaporation rate and non-flammability. Fairly safe to use because of slow evaporation rate and non-flammability. MC/ATM strippers opened the market to two alternative solvent strippers. The more effective of the two is n-methyl pyrrolidone (NMP). It is non-flammable and is thought to be less toxic than MC and ATM. It's not that NMP is safe to work with, but that it evaporates so slowly that the air in a room has time to replace itself several times over before toxic concentrations are reached. Slow evaporation translates into reduced effectiveness (consider that these strippers are usually packaged in plastic containers), but an NMP stripper will remove all but the most stubborn coatings if you give it enough time — overnight in many cases. The reasons NMP strippers haven't caught on better are their expense (about three times that of MC unless other solvents are added to reduce the cost) and the misleading claim listed on most containers that the stripper works in 30 minutes. Claiming too much for a product may get a customer to buy it once, but rarely a second time. Di-Basic Esters (DBE) The first of the alternative strippers to appear on the market is based on several esters, called di-basic esters, combined with 50- to 70-percent water. These esters are very slow-evaporating, and thus weak as strippers. DBE strippers work even slower than NMP strippers, especially on shellac and lacquer, but just as with NMP strippers, manufacturers exaggerate the speed. The problems this has caused, in addition to the damage the included water causes to veneer and wood, has led to the virtual disappearance of this stripper from stores. Lye Though it's rarely used, lye (sodium hydroxide) is both cheaper and more effective than the solvents discussed above. The problem with lye is that it will burn you severely if it gets on your skin, it can cause significant damage to the wood by making it soft and punky, and it may darken the wood and cause finishing problems. You can buy lye in powder form at paint stores and sometimes at supermarkets, and mix it with water, about V4 pound of lye to one gallon of warm water. Pour the lye into the water, not the other way around or it may boil over and burn you, and use a steel container like a coffee can, not aluminum, plastic or glass. The heat that is created by the chemical reaction of the lye and water will heat the container, so don't hold it while mixing. You can also buy lye in powder or paste form packaged with a cloth that you can apply over the lye to aid in the removal of paint or finish. Conclusion For difficult coatings such as paint, polyurethane and catalyzed (two-part) finishes, you should use a strong MC or lye stripper. For weaker shellac, lacquer and oil finishes, any of the strippers will work, given enough time. Next issue, I'll tell you how to use these strippers effectively. PW Bob Flexner is a nationally known finishing expert in Norman, Oklahoma, and the author of "Understanding Wood Finishing." |
