Cracked Erlenmeyer Flask

Just a note of caution for those who boil and chill in Erlenmeyer flasks. You might be well served to do the occasional visual inspection. I just lost mine this weekend.

I have a glass top stove where I boil my starters in the flask (recommended on Morebeer website) then I chill in an ice bath. Pretty standard stuff and I've been using the same 2L flask for 3-4 years brewing twice a month or so.

This weekend we heard a very strange creaking then saw small drops of work leak out the bottom of the flask onto the burner. I immediately slid the flask off the hot burner, but I knew we were stuck. The leak dropped faster and faster, so I tried to pick the flask up...all I did was touch it and the whole bottom broke lose - a perfect circle - oh and hot wort everywhere.

I got the mess cleaned up, and remade a starter in a new vessel.

I'm not sure if 3-4 years of boil/chill finally broke the flask down or maybe it got a hair line crack somehow an I didn't notice. Either way, I will be doing a close inspection of my starter flask (when I buy a new one) from now on.

Oh, it was a borosilicate flask.

I try to temper the change in temps just a bit by letting the flask sit for a minute then gently running a little room temp water over the flask before plunging into cool tap water....

Than, after a minute or so, I add the ice. Just a precaution, really, but if you take a couple extra minutes to ensure you aren't going to go from the heat of the electric/gas/whatever element (the glass is much hotter than the liquid where it comes in contact with the burner) straight to the ice bath, I think you'll be less likely to cause stress fractures or weaknesses over time.

I agree with Randar. Extreme heat cycling will not maximize the life span of your flask.

I actually just lost a flask this weekend as well. It was the first time that I tried heating directly in the flask instead of transferring. I read that heating on an electric stove top was not recommended so I tried using an old backpacking stove for the flame. But while I was messing around with the gas flow, I guess I super-heated it and the whole bottom dropped out. Made quite the mess and I got a pretty good burn from it. Not a good time, let me tell you. I'm sure there's a safety message in all this somewhere...?

BrewBarron said:

...I read that heating on an electric stove top was not recommended...

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I found out after creating my last starter, that I could put my Erlenmeyer directing on the stove, but I have an electric. Why are they not recommended?

blu666z said:

I found out after creating my last starter, that I could put my Erlenmeyer directing on the stove, but I have an electric. Why are they not recommended?

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Because the electric elements tend to superheat very small areas of the flask which will add thermal stress and more opportunity for failure. You want an even heat across the surface area of the flask, so if there isn't a really good flush mating of the flask and the element, you are adding potential risk of failure.

Gas is very hot as well, but it heats evenly as long as you don't crank the hell out of it.

Also, some people report failures even with gas but I tend to think this is due to using cheaper homebrew flasks instead of the lab grade ones or flasks that have undergone a lot of thermal stress/abuse from doing things like the OP apparently did (right from flame to ice bath).

So...if I only have an electric stove, would I be better off using my gas, backpacking stove?

You would be much better off putting your flask in a pan of water and then heating it. Much less thermal shock to the flask and even if it all goes to crap and the flask breaks you will still have the secondary containment of the pan to catch the mess before it gets away from you.

Good idea. Thanks.

Yeah, No, I don't recommend using the backpacking stove. Mine did not evenly distribute the heat and probably was like a laser beam at the center of the flask. Of course it was cranking since I was trying to figure out the gas flow, but nope, don't recommend it.

Couldn't you microwave it instead?

I set a flask right after the boil on a 12" x 12" slab of granite of room temp, within 30 seconds heard a dull pop the bottom broke off clean with a mess.
H had it for six years it must of been 15 years old.

A microwave is a good idea ... probably the best come to think of it.

For open flame, in the chemistry lab where I worked, a 4" X 4" steel wire mesh was used to set the flask upon, above the flame by 3 to 4 inches. This spread out the hot gas flow and provided a large even heat source. The backpack stove only provides a fraction of an inch.

Flasks have a life span. They fatigue with repeated heat cycling. Some are built better by design and some are built on a Monday, so to speak. YMMV.

The same principle would apply to glass carboys. For optimal safety, any glass item should be retired after X amount of time/uses.

blu666z said:

So...if I only have an electric stove, would I be better off using my gas, backpacking stove?

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You can safely heat your flask on an electric stove, but you will need to use a trivet. You can buy a trivet or make one out of heavy wire. I use a wire coat hanger cut and bent into a star shape. Just place the trivet on the burner and the flask on the trivet.

FireDancer said:

The same principle would apply to glass carboys. For optimal safety, any glass item should be retired after X amount of time/uses.

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So tell me, what is "X" amount of time or number of uses? Without knowing that, the rest is useless IMO.

FireDancer said:

The same principle would apply to glass carboys. For optimal safety, any glass item should be retired after X amount of time/uses.

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I've never heard of retiring glassware due to thermal cycling. I used to work in a lab too. The only glassware I've ever seen retired was due to chemical etching, melting or breakage due to thermal or physical shock.

The microwave is kind of a question as to even heating and the potential for spontaneous violent boiling. With very clean and smooth glass there is a potential to superheat the water prior to boiling caused by exceptional surface tension of the water to a perfect surface. As soon as the water gets agitated it can spontaneously boil over and can be violently dangerous. With an Erlenmeyer flask it is even more violent due to the restricted opening. It's not a common occurrence but is a possibility that is increased in a home-brewer's case by using absolutely clean high quality glass that is common to laboratory glassware. I've never personally seen it happen but have read the safety reports of incidents that have.

So tell me, what is "X" amount of time

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I've never heard of retiring glassware

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Yeah, you are both right. Nobody does this for glassware, hence that is why I used "for optimal safety" and I don't know the value for X. X would depend on too many factors for the variation our community of brewers. The idea is still useful without a definite value for X, IMO.

I plan to retire my carboys soon since they are getting to be near 15 years old and a friend broke his of the same vintage (which I gave him). He tipped it on its side on the lawn while cleaning, no injury thank goodness.

You can safely heat your flask on an electric stove, but you will need to use a trivet

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You have reminded me that my parents used this technique for their Kemex coffee maker.

Nazdravy

Look, they are made to be used over an open flame. If you're still worried about using an open flame, you either need to give up the idea of using it that way or use a mesh dissipator such as this:




Are there still inherent risks of potential failure due to thermal stress/fatigue or due to being a klutz and breaking it?

Sure. Which is why you need to take precaution to prevent scalding or injury when working with them or moving them and by trying to do what you can to minimize extreme thermal shock.

I plan to retire my carboys soon since they are getting to be near 15 years old and a friend broke his of the same vintage (which I gave him).
Nazdravy

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I have and used carboys from my grandparents when they did home brewing
back in the 20's thru late 50's, thick as hell plus still trustworthly today.
they are now retired with the crocks and porcelain bottles from a past era.

I certainly could see that happening-flash boiling or whatever the scientific term is, but it wouldn't it also be pretty easy to baby sit it too? And, if you have a microwave that spins (most do these days) shouldn't you get pretty even heating? I may give it a try as I cringe when I put the flask on our gas stove.

Photomask said:

I've never heard of retiring glassware due to thermal cycling. I used to work in a lab too. The only glassware I've ever seen retired was due to chemical etching, melting or breakage due to thermal or physical shock.

The microwave is kind of a question as to even heating and the potential for spontaneous violent boiling. With very clean and smooth glass there is a potential to superheat the water prior to boiling caused by exceptional surface tension of the water to a perfect surface. As soon as the water gets agitated it can spontaneously boil over and can be violently dangerous. With an Erlenmeyer flask it is even more violent due to the restricted opening. It's not a common occurrence but is a possibility that is increased in a home-brewer's case by using absolutely clean high quality glass that is common to laboratory glassware. I've never personally seen it happen but have read the safety reports of incidents that have.

Click to expand...

ranchonodinero said:

I certainly could see that happening-flash boiling or whatever the scientific term is, but it wouldn't it also be pretty easy to baby sit it too? And, if you have a microwave that spins (most do these days) shouldn't you get pretty even heating? I may give it a try as I cringe when I put the flask on our gas stove.

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My 2 liter flask is too tall to fit in my microwave, otherwise I would do it that way. Using the flask on a gas stove burner should not be a problem as the flame is normally spread well. I've been doing it that way for years without any problem at all.