Popular Woodworking 2006-10 № 157, страница 7
store or I can order by mail and wait. Food dyes certainly should be food-safe, and if you have ever spilled food dye on anything you know it's impossible to remove. Do you think that it would work? My next question relates to the UV resistance of spar varnish. How do you know or figure out which one has the most UV inhibitors ? I made some outdoor furniture with western red cedar, then finished it with three coats of Valspar gloss spar varnish for outdoor use. The varnish failed in one year (gray spots appeared that the varnish then flaked off of). Looking at the cans from various manufacturers, I can't find anything in the list of ingredients that I can relate to UV resistance. I also couldn't find anything on the Valspar or Varathane web sites that would help. Joe Weinig Minong, Wisconsin You absolutely can use food dyes in woodworking. Food coloring from the supermarket would solve both your problems: convenience and food safety. It's most likely, in fact, that the "toy safe" dyes you are buying are the same thing. On your question about spar varnish, it's most likely that the reason you can't find any information on the can is that there's nothing to tell. Home-center spar (outdoor) varnishes work well outdoors away from sunlight. But they don't contain enough UV absorber (if they contain any) to make any significant difference in resisting UV light. If the object you are finishing will be exposed to sunlight outdoors, you should use a marine varnish sold at marinas for use on boats. These varnishes are considerably more expensive than the home-center spar varnishes, but they work, at least for a number of years — especially in your northern exposure. You can do an Internet search for a mail-order supplier. A good example is jamestowndistributors.com. Keep in mind, however, that water will also cause the finish to peel if the water can find a way to get underneath the finish. You have to shield the wood from water contact or thoroughly coat all end grain and joints and keep this coating in good condition. — Bob Flexner, contributing editor Can a Water-based Topcoat Work Over an Oil-based Finish? I recently built an altar and an ambo (an elevated platform) for our church expansion using white oak. I finished them with Minwax English Chestnut (an oil stain), and topcoated with five coats of a water-based urethane. In Bob Flexner's article "Understanding Stains," (June 2006) this sentence appears: "Choose an oil stain to apply under any finish except water-based." I'm now wondering what problems I have to look forward to! Scotty Bies McCormick, South Carolina I apologize for not being more specific. There are two difficulties with applying a water-based finish over an oil stain. The water-based finish wrinkles, or it doesn't bond well. Poor bonding leads to peeling. (Think of putting water on oil; they repel each other.) The trick for avoiding these problems is to let the stain cure adequately. What does this mean? It's different for each stain and finish combination because it depends on the formulation of each. It also depends on the temperature conditions, with warmer temperatures leading to faster curing. If your altar and ambo have been knocked a few times and no peeling has resulted, then you are probably OK. But in the future, you should try the combination of oil stain and water-based finish you intend to use on scrap wood and in similar temperature conditions and with the same drying time before committing to the actual project. Many people have had problems using this combination because they didn't allow the stain enough time to dry. — Bob Flexner, contributing editor Let Components Dictate Design I just read your article "Entertaining Designs" (June 2006). It was great to see an article concentrating on designing a cabinet so as to avoid finding flaws at installation time. I was an audio/video installer for eight years and would like to share some of the challenges I encountered from cabinetmakers. As you mentioned, some audio/video components are around 17" wide; I found that they were mostly around 173/4", so your 18" suggestion is right on and coincidently your DVD drawers fit in that opening as well. As televisions get thinner, that doesn't mean that the cabinet should diminish in depth. I have found that most built-in cabinets are going into a niche that is approximately 24" deep. I think as much of that depth should be used as possible. continued on page 15 popularwoodworking.com i 13 |
