Popular Woodworking 2009-04 № 175, страница 12

Popular Woodworking 2009-04 № 175, страница 12

The Wood Whisperer

BY MARC SPAGNUOLO

A Sticky Situation

Six common situations where specialty glues serve you well.

A glue for every reason. While woodworkers generally rely on yellow glue (polyvinyl acetate) for most glue jobs in the shop, depending on the task at hand, there might be a better choice available.

t goes without saying that most of our projects would be nothing more than a loose assembly of parts without the holding power of glue. Thankfully, modern adhesives are accessible, usually inexpensive and keep us from having to mill wedged tenons for every-thingwe build. Most woodworkers begin by usinggood old yellow glue (polyvinyl acetate orPVA). It's a great general-purpose glue that serves me well for about 90 percent of my tasks. But there are a number of unique glues that work particularly well for specialized applications.

Working With Veneer

Veneer requires two major things from glue - rigidity and a long open time. Sounds like a job for urea formaldehyde! There are two brands of urea formaldehyde that I use in my work. DAP's Weldwood is a powder that you mix with water and Unibond800 is a liquid resin that is mixed with a powder activator.

Because of its water content, Weldwood is not ideal for veneering. By introducing water into the equation, both the veneer and the substrate swell. Then as the glue cures and the water evaporates, there could be open seams and cracks - that's trouble. However, this same properly is what makes it great for things such as bent lamination, where a little extra moisture helps the laminations flex.

For veneering, Unibond800 is my glue of choice. Of course, if you want to be a traditionalist, you can try hammer veneering with hide glue. 3ut that's a subject for another article.

^pnline EXTRAS

To watch The Wood Whisperer select, mix and use the appropriate glues for veneer, goto:

popularwoodworking.com/apr09

Hurry Up-The Clue is Drying

It's a common scenario. You're gluing up a project and before you can get everything situated, the glue starts to dry. Panic sets in. You pull out your .rusty dead-blow hammer and proceed to beat the daylights out of your latest masterpiece. Now unless you're into distressed furniture, this is bad.

To avoid this situation, it's a good idea to use glue with a lor.ger open time. You should have enough time :o assemble the parts, position your clamps and check to make sure each and every piece is positioned correctly.

Two of my favorite options are slow-set epoxy and just about any urea formaldehyde glue. Both give you up to 30 minutes of open time and that should be enough for just about any project, including those notoriously long bent-lamination clamping sessions.

So what are the downfalls? Epoxy and some varieties of urea formaldehyde can be pricey. And both should be handled carefully as they docontain harmful substances (refer to manufacturers' instructions for details). These safety precautions are really just a minor detail and are well worth the time and effort for the extra open time you get in exchange.

Designed to Fail?

When we build our projects, it's important to think about their future - not necessarily next month or even next year. I'm talking 10 or more years from now. A chair, for example, with constant use, will almost certainly be in need of repair at some point in its lifetime. So it's not a bad idea to use glue that facilitates easy repairs.

One ofthe best (and oldest) glues for this

20 ■ Popular Woodworking April 2009

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