Wrong Glue

There's a reason I never use polyurethane glue (popularized by the brand Gorilla Glue, but sold under many names). Oh, it's tough stuff, that's for sure, and lots of people love it because it'll bond all kinds of dissimilar, hard-to-bond materials. Unfortunately, it also swells as it cures.

Recently I bought some new adhesive from Liquid Nails called "Perfect Glue." It does not say anywhere on the tube what sort of glue it is; from the look of it, I thought it was an ordinary general-purpose cement such as Duco, which shrinks as it dries, and that's desirable because it keeps joints tight.

Unfortunately, it turned out to be polyurethane. I made that distressing discovery when I noticed that the abutment at the right end of the truss bridge was no longer fitting snugly against the retaining wall the way it was when I'd originally assembled it.

I'm not quite sure what to do about this. As I said, polyurethane glue is seriously strong, so there's no popping the abutment off and re-attaching it. Maybe I'll just fill the cracks with vines. But in truth, that's a cheap cover-up trick.

For the time being, until I come up with a corrective measure, it'll serve as a reminder for two things: first, never use an untested adhesive on an in-your-face bonding job such as this. And second, never use polyurethane glue. It swells.

Postscript: The remainder of the so-called "Perfect Glue" was deposited in the trash.

Off-topic: Knee surgery has been moved from the 31st to the 10th, so while I'm relieved to be getting it over with sooner, I'm now in a mad scramble to prepare for it. So, if the posts stop early next week and don't resume for a while, you'll know why.

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