^This

As far as glass shattering, the localized heat from NaOH dissolving followed by relatively cold water cooling it (from shaking or stirring) is enough to shatter cheap glassware (especially glassware not made for cooking). I have had the bottoms sheer off of glass wine jugs from heat changes like this, and since then I only use pyrex/borosilicate glass for anything involving heat.

I used to work in a chem lab and had a pyrex volumetric flask almost completely split in half from the heat released by diluting sulfuric acid in water (came VERY close to having 2L of 6M sulfuric acid dump on me). Pic attached, the solution was dripping out of that crack.

If you plan on playing with strong acids and bases regularly, I highly recommend investing in some good beakers and flasks and a hotplate/stirrer to mix them evenly. Lab glass costs about the same as glass from a grocery or hobby store, and could save your life.

On a side note, I have used thick HDPE 2 plastic chemical bottles to dissolve hydroxide. It gets too hot to touch but retains its shape and doesn't melt, so if I'm too lazy to pull out a hotplate I just toss it in there and gently shake and then crack open the lid and let it sit until it cools off.

-Treehouse

That's interesting treehouse! I've never had a problem with overheating solutions in a volumetric flask. But I've always used an ice bath =P

I’ve had bad glass shatter from very little heat. Very bad idea not to use good glassware. Every time I put pure NaOH into my glassware it would attach itself to the glass so I stopped doing it, and now mix in a big 5000 ml HDPE container first and place it in a cold bath to cool. No point working with it when the lye is going crazy hot but its relatively harmless when diluted just remember goggles and gloves.

Using things like mason jars should not be recommended IMO. Magnetic stirrers/ heat plates are great too as they mean you don’t have to pick up the glassware and agitate it yourself. No open flames either.

The more you can keep away from or minimize the time holding and carrying a hot jar of corrosive and flammable liquid all the better.