I have been working on a pipe with an acrylic stem for the last week or so. Last night I was finish sanding by hand to 500 grit. When I went out to my garage this morning the stem was covered in tiny spiderweb-like cracks. I know for a fact they weren't there last night and it was never dropped. Anybody have any idea what might have happened? The only thing I can think of is that I wiped the whole thing with denatured alcohol and maybe the evaporation had something to do with it but I have done that with all my other pipes so I am kind of at a loss as to what happened.

Yes, that will do it. Denatured alcohol, depending on what it was denatured with, can have some very adverse effects on acrylic and polyester resins. Acetone and lacquer thinner will also have that effect, only much more pronounced.

Thanks Kurt. A couple of related questions: Should I avoid using the DA on vulcanite/ebonite as well, and what do you use to clean dust off the pipe, DA on the stummel and water on the stem?

To clean off dust, I use my hand or a shop towel. Sometimes the t-shirt I'm wearing. Okay, most of the time.

It really doesn't need to be any more complicated than that.

T-shirt. I haven't found any adverse effects using methyl alcohol, otherwise known as methyl hydrate (except blindness etc if you drink it).

Ditto

I use a microfiber cloth that has been pre-treated with a mixture of acetone and blood from a small group of elite Danish pipe makers from Finland. I find this cleans the dust off more effectively, and it exfoliates my skin nicely too.

That, or I use the T-shirt I'm wearing.

Good stuff to know.

+1 on the fancy cotton t-shirt buffer.

I suspect that denatured alcohol and other solvents could play a big part in the criticisms that acryllic stems become brittle with age.