Exploding Erlenmeyers

[pornstache]

I generally keep 4 or so 2000ml flasks in rotation. Until now I've never had an issue with them breaking, but in the span of the past week two died on me. One exploded on the stove shortly after firing it up (What a mess!) and the other cracked in a similar fashion just now. Luckily I was able to get that one off before catastrophe.

Is this normal? Do the constant rapid heating and cooling take their toll?

Unfortunately I'm not sure how old the two flask are but suspect they're not among the newest in my collection...

[seanhagerty]

If you have good quality flasks, this shouldnt be happening unless you have some damage to the glass. A pre existing flaw (like a scratch or crack or chip in the glass) will build up the stresses, and adding additional stresses like heating could cause them to break.

Sounds like you should inspect your remaining flasks for chips or cracks or scratches. Also, setting the flask directly on the burner is bad. It seems i heard something about using a coat hanger thats bent into the shape of an "S" that is set down on the burner to keep the flask from direct contact with the burner, and it reduces the stresses also.

Good luck

Sean

[Bugeater]

The first thing to do is to make sure these are flasks designed for direct heating. Pyrex brand or borosilicate flasks are up to the task.

Next look at how you are heating them. If you are putting them directly onto an electric stove element, you will definitely have problems. The coils will heat in bands across the bottom instead of spreading the heat evenly across the bottom like a gas flame will do. These bands will create a drastic temperature differential between the glass in direct contact and the glass immediately adjacent to it.

If you are using gas, there is either a problem with the glass (not the proper type or having minute cracks) or you are chilling it too fast. Too fast would be something along the lines of moving the flask directly from the flame and sticking it into a salted ice slurry which would have a temperature well below freezing.

You can get away with using the flask on an electric stove if you take precautions to keep the glass from direct contact with the stove element. This is easy to do. Just bend a piece of unpainted coat hanger (or similar size bare copper wire) into a "Z" or "M" shape about the same total size as the bottom of the flask. Set this wire trivet onto the element and put the flask on top of that. This will allow the heat to spread out before it contacts the glass and will more evenly heat it.

I take another approach altogether. I have a pressure cooker that I use to pressure can my starter wort (all grain) in quart jars. Now when I need a starter all I need to do is sanitize the flask, open a jar or two of wort, and add the wort and yeast to the flask. The flask never goes anywhere near a stove.

Sorry about the loss of the flasks. I hope this will help you figure out the problem.

Wayne

[pornstache]

They're good (were good) flasks, mostly from morebeer.
I think rapid chilling plus the occasional hard bump against my ceramic kitchen sink may be the culprits. I've been thinking about the pressure cooker/canned wort method for a while, looks like I just found the motivation.

Thanks for your feedback!

[Stewbacca]

Not to hijack but it is on the same topic.... has anyone had any problems heating flasks on glass cooktops? Does the ceramic/glass spread the heat more evenly than a standard coil electric heating element?

[Charlie]

As a newbie tech I was told that Pyrex glassware would eventually shatter from uneven heating. The type of heating I'm talking about is putting a beaker or erlenmeyer on a hot plate and boiling something in it. The determining factor seems to be the quality of the glassware and the number of duty cycles it has been through. And yup, it's happened to me: You don't have a real mess until you have glass everywhere and 2L of 80% phenol all over the counter.

Autoclaving and oven heating are unlikely to be a problem because of the even heating, but anytime one end is hot and the other end is room temp you have a potential problem.

Charlie