I can attest - when Pyrex shatters because of heat - It is razor sharp!. I put an empty measuring cup on my glass top stove once, and didn't check that the burned had been on. When I lifted it by the handle, it shattered instantly. Fortunately it all stayed on the stovetop, but, each piece behaved differently than I expected. I could not pick up larger pieces; they were both sharp and had a weird, rough texture. Nothing like the squares of safety glass. Even trying to clean the shards up with paper towel was difficult.
If you have a stress point in the glass, there is nothing you can do to stop that train wreck. Think lye, raw soap batter rivers. Do you have enough neutralizing solution?
For that same reason, I never used Erlenmeyer flasks or beakers for soap making, even though I used to have access to them. They are thinner than the pryex measuring cups, and when they break, have a different quality in the shards, but, a nick or stress point is still an accident waiting to happen.
Dude!
. Agree w/ ya'll if your training or giving a demonstration on DIY Soaping it should be the correct method.
