58 - Miter Saw Station, страница 11

But if you're building an outdoor project from something like cedar or pressure-treated lumber, you can skip the misting altogether. These materials typically have a higher moisture content. So you don't need to add anything extra.

Assembly Time - At this point, you can assemble the project. And this is where polyurethane glue really shines — you don't have to work as fast as the pit crew at an Indy race. Poly glue provides more working time when it comes to assembling and positioning the parts of a project before you clamp it up.

A yellow glue can set up after only a few minutes. I've actually had the parts of a project "seize" before I could get everything assembled and then positioned correctly.

That's not likely to happen when you use a polyurethane glue. Most poly glues have working times ranging from 20 to 30 minutes. So when you have to assemble a complex project, a poly glue provides more time to get everything right where it needs to be.

Clamping - When it comes to clamping, using poly glue isn't a whole lot different than other glues. Moderate clamping pressure is all that's required. As long as the pressure spreads the glue into a thin layer, you'll end up with a strong, consistent bond.

The thing to remember is that you'll need to leave the assembly clamped up for several hours. So don't get in too big a hurry to pull the clamps off your assembly.

IN THE SHOP

Cleanup - Once the glue has set, the next step is to get the dried glue off. Unlike yellow glue which can be a problem to remove, poly glue breaks down into a fine dust when you sand it. Or you can simply scrape it away or pop it off with a chisel, as shown in Step 4.

As you can see, dealing with cured poly glue on a project isn't a problem. It's a different story if the glue dries on your hands — as I learned the hard way.

I didn't give much thought to cleaning up the first time I used poly glue. Once I was done working, I tried to scrub the glue off with a little soap and water — without success.

The glue stained my hands and fingers a dark brown. And it was a few days before it started to wear off.

To avoid this problem, I find it best to slip on a pair of disposable gloves as soon as I pull the bottle of poly glue from the cabinet. Then whether I'm assembling a project or cleaning up afterwards, ifs a simple matter to toss the gloves in the trash once I'm done.

Safety Note: Some people can be sensitive to polyurethane glue. So besides wearing gloves, it's also a good idea to work in a well-ventilated area or even wear a respirator.

Even though it's almost impossible to clean poly glue off your hands, removing any excess from your tools or workbench is a lot easier. All it takes is a paper towel or cloth soaked in a little acetone or mineral spirits, as shown in the margin photo. (And don't forget the gloves.)

4 Remove Excess. Finally, remove the dried "foam" by scraping (shown above left) or sanding. Removing glue from hard-to-reach areas like a corner (photo at right) is a snap with a sharp chisel — it "pops" right off.

k Polyurethane glue that's stored upright (right) will cure at the top of the container, unlike the "upside-down" bottle shown at left.

Shelf Life & Storage - Another drawback of poly glue is its shelf life. I've kept yellow glue around for over a year and used it without any problem. But poly glues often have a shelf life much shorter than that.

As soon as you open the container, poly glue can start to cure. So it's a good idea to close the container anytime you're not using it And when you put it away, squeeze out any excess air (and moisture) first.

Some manufacturers have even designed their containers to store "upside down," as you can see in the photo above. This way, any glue that does cure will be at the "bottom."

Cost - The thought of throwing out any glue because it's cured in the container is bad enough. But when you consider that polyurethane glue costs two to three times as much as yellow glue, the sticker shock just might make you think twice (or three times) about buying some.

But as I mentioned before, you're only using about one-third as much (and generally, only applying it to one side of the joint). So the actual costs of using it are fairly comparable.

Use It or Lose It? - Despite some of its drawbacks, polyurethane glue has a lot more going for it That doesn't mean I'm going to replace the yellow glue I've used in the past. But it will have to share some of the shelf space in my cabinet with a small bottle of polyurethane glue. &

k Cleaning up uncured poly glue isn't a problem when you use a solvent like mineral spirits (and a pair of disposable gloves).

No. 58

ShopNotes

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