Author Topic: Directly heating Erlenmeyer flasks  (Read 2594 times)

Offline Jarhno

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Directly heating Erlenmeyer flasks
« on: September 27, 2013, 11:41:02 AM »
Hey Homebrewers, I've got a question for ya'.

I'm wondering how safe it is to boil the wort in my Erlenmeyer flasks (for a starter). I know the glass has a low coefficient for expansion like Pyrex, but I see a lot of mixed advice online and in person.

Some websites advise against directly heating it at all, and some do. When I asked a brewer/employee at a LHBS he advised me to not use an electric coil stove because it creates cold gaps between the metal coils in the glass, and said heating on a gas stove or electric induction stove would be just fine. Before I heard that, I had actually heated on an electric coil stove and didn't notice any problems. Since looking into this matter I have heated my flask on a gas stove and haven't noticed any problem signs, either. (So I've only boiled wort directly in the flask twice).

I figured I'd ask the brightest minds in the brewing community for guidance, so thanks for your time everyone.
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Offline yso191

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Re: Directly heating Erlenmeyer flasks
« Reply #1 on: September 27, 2013, 11:53:55 AM »
I have a glass cooktop on my stove and boil every yeast starter on it.  No issues.
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Offline BrewArk

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Re: Directly heating Erlenmeyer flasks
« Reply #2 on: September 27, 2013, 11:54:58 AM »
I've boiled a 2L on a gas stove (quick boil-over too). 

I think I'd be hesitant on an electric, for the reason you outlined.  My mother used to place a wire ring on the element and put her pyrex on top of that.  She never had a problem, but that's all the guarantee I can give you.

In the lab we use hotplate/stirrers regularly.  They have ceramic tops.
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Offline theDarkSide

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Re: Directly heating Erlenmeyer flasks
« Reply #3 on: September 27, 2013, 11:57:40 AM »
I have a glass cooktop on my stove and boil every yeast starter on it.  No issues.

Same here.  I only stopped because I find it easier to stir up the clumps and prevent boilovers in a pot and then pour through a sanitized funnel into the erlenmeyer flask than boiling in the flask itself, even with Fermcap-S.
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Offline smkranz

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Re: Directly heating Erlenmeyer flasks
« Reply #4 on: September 27, 2013, 12:01:22 PM »
I have a 2L flask which I have boiled wort starters in, on an electric stove, several dozens of times with no problems.
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Offline Jarhno

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Re: Directly heating Erlenmeyer flasks
« Reply #5 on: September 27, 2013, 12:03:46 PM »
Well, all right! This has relieved some of my apprehensions, for sure.

Though I still would enjoy hearing more opinions and experiences!
You can't be a real country unless you have a beer and an airline - it helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer.  - Frank Zappa

Offline denny

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Re: Directly heating Erlenmeyer flasks
« Reply #6 on: September 27, 2013, 01:25:05 PM »
I treid it a couple times and finally decide that for me it was easier to boil in a pot and xfer after boiling.
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Offline riverrat

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Re: Directly heating Erlenmeyer flasks
« Reply #7 on: September 27, 2013, 02:35:21 PM »
A friend had one crack after multiple uses on an electric stove.  After that, continued to use the electric stove, but did not use full power any more.  No more problems yet. 

Still, be prepared to deal with boiling liquid in cracked/broken glass if you choose to boil in it.  No kids/pets in the area.  Have a means of grabbing the hot flask and moving it to a safe location (a large pot, sink, etc.).  And probably want to wear some decent footwear.
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Offline narvin

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Re: Directly heating Erlenmeyer flasks
« Reply #8 on: September 27, 2013, 05:05:35 PM »
I've been using the same flask for at least 5 years on a gas stove with no issues.
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Offline duboman

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Re: Directly heating Erlenmeyer flasks
« Reply #9 on: September 27, 2013, 06:25:04 PM »
I have been using mine on a gas stove with no issues for many years and once boiled goes right into a cold water bath to chill-no issues but I have friends that used electric coils and it cracked:(
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Offline phunhog

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Re: Directly heating Erlenmeyer flasks
« Reply #10 on: September 27, 2013, 06:54:59 PM »
I have a ceramic cooktop with no issues...other than a bad boil over (twice) :o  If you are really concerned with using your electric stove maybe do a double boiler.  Fill a bigger pot with water and put the flask inside of it? Obviously will take a little longer but it will work nicely.

Offline klickitat jim

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Re: Directly heating Erlenmeyer flasks
« Reply #11 on: September 27, 2013, 09:05:58 PM »
Tried once and it shattered. Won't try again. Coils...

Online Thirsty_Monk

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Re: Directly heating Erlenmeyer flasks
« Reply #12 on: September 28, 2013, 11:55:15 AM »
Never insert cold stir bar to boiling wort in Erlingmeyer flask.

Personal experience.
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Offline joe_feist

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Re: Directly heating Erlenmeyer flasks
« Reply #13 on: September 29, 2013, 12:46:00 PM »
I boil in my flask on a gas stove sometimes. No problems. It's typically easier for me to boil in a pot and transfer.
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Offline mtnrockhopper

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Re: Directly heating Erlenmeyer flasks
« Reply #14 on: September 29, 2013, 01:07:10 PM »
I think there are some cheaply manufactured "Pyrex" flasks out there, but most and especially older ones are fine.
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