A short jaunt to Lowe’s yesterday to get stuff to make shelves turned into an all day adventure, but I have to say I enjoyed myself. (And made it out of Lowe’s with only one new power tool, a cheapo Black & Decker finishing sander.) I am just using pine boards for the shelves, although I tried to sand them down at least somewhat—getting the ends to shed the crags and ridges from being sawed ended up being too much trouble—but I wanted to put a coat of some sort of sealant on them since at least one set of these shelves will be in the bathroom. (And the other will be used in the kitchen, so you can be sure it’ll get at least a few splashes of mysterious kitchen goo.)
I ended up getting a can of polyurethane, which wasn’t what I had originally grabbed. The first stuff had a two-hour cure; the polyurethane suggests six to twelve. So while it was curing outside, passing insects and leaves drawn irresistibly to the sticky surface, it ended up getting rained on. No big whoop in the end—it had set up enough to repel water, although I’m going to have to re-sand the backside where it soaked up some newspaper ink.
Anyway, my question is this: From my cursory reading of the can, it appears polyurethane can cause rags to burst into flame. This is disturbing. I had to throw away my first brush when it hardened, as I didn’t have any mineral spirits around to clean it with. How much of a practical danger is this? Is it only when the polyurethane is still liquid? The Cabot web site doesn’t have much information about it at all.
My hopes for a smooth, shiny surface are pretty much gone, and with it comes a bit of relief. Now I just want to make sure that my cheap pine boards are somewhat moisture resistant while not setting my apartment on fire while I try to figure out how to dispose of my supplies responsibly. I’m not going to do it, but I kind of get why people just pour paint down the bathtub drain. It’s a really easy consideration.
Once the poly is dry, the fire risk drops to nil.
Paint store said to leave empty buckets open to dry, then toss them in the trash. Advice may vary, depending on local disposal regs.
Ultra fine sanding and tack cloth between coats will build you a terrific shine. Do consider a quality brush. Or perhaps a disposable foam brush. Poly’s put on floors with a strange sheep’s wool mop head thingy, fyi. And for touchups, get a can of spray polyurethane.
Here’s a thread with some info on spontaneous combustion:
http://www.woodworkforums.ubeaut.com.au/archive/index.php/t-7707.html
Basically, rapid evaporation creates heat. Poly (and lots of other things) is flammable. Crumpled up piles of rags (or even single crumpled rags) don’t let that heat dissipate, and it can build up to the point of combustion.
If you let the rag dry out in a flat state, in a well-ventilated area (which you probably want to do anyway just because of the stink), you’re probably fine.
Oops, reading further in that thread, it’s not the evaporation that causes the heat, it’s the rapid oxidation. 6 posts down “Marc” has some great info.
Like tim said, spread ‘em out to dry and you’re fine. Then you can toss them in the regular trash. Since I’m most often doing projects in the evening, I usually let mine sit overnight and throw them in the garbage the next morning.
Cut the poly 1:1 with denatured alcohol. It goes on smoother, dries quicker, and is generally easier to deal with.
The down side is that you are actually only putting on half the poly with each coat. So you’ll have to sand it with some 320 and hit it with a tack cloth and do it all over again.
The good news is that it dries in about an hour and you won’t have the issues with puddles, ridges, and insects because it isn’t as thick as straight poly and dries super fast.
You can also save money on brushes since you can apply it with shop towels (either cloth or lint free paper - like the blue ones).
good luck!
poly is wonderful - after it dries - very light 00 steel wool to take the shine away and bubbles if you put it on poorly, then recoat. Do it until you are happy - then the last coat will be your last coat. There is Gloss, semi-gloss and flat - your choice
Anytime there is a problem - steel wool 00 - and even if it’s a spot - hit it and it will blend
poly is wonderful
One I’ve been thinking about doing is a bar covered in bottle caps from various beers, the rough plan is to pour down a thick layer and then set the caps into it, from there, keep adding layers or one thick layer if I can do it with no bugs, leaves, or bubbles. Anyone have any ideas on how to pull this off? think the best thing to do is a test run with a small area, table top size.
any ideas on how to pull this off would be great
not to mention I need to drink more bottle beer, ever since I got the kegerator the number of caps has slowed way down
james poly dries from the outside to the inside - you are going to have to divide let’s say a full 1/4 inch (the thickness of a bottle cap - maybe) into about (to be mathmatical) about 8 to 16 coats - don’t worry about bubbles if you do - buy a pistol and you’ll solve your problem quicker