Erlenmeyer flask on induction cooktop

I'd like to use my Erlenmeyer flask on my induction cooktop but the induction cooktop will only work with magnetic metals.

I've contemplated using a cast iron skillet and putting the flask on that, but I'm scared that the extremely hot cast iron skillet will end up breaking the glass. I know the flask is "heat proof" but that's only gotta be to a certain degree.

Any ideas?

NAte

You'll be fine. Flasks are made to be used directly on top of bunsen burners and your skillet won't get that hot. Adding a little water to the pan will help spread the heat out even more and avoid getting any hot spots that could lead to damaging the flask. I would also recommend not turning the stove all the way up for the same reason, use a moderate heat setting, just enough to get it up to a boil.

Put it in a sauce pan with some water in it and bring the whole thing up to temperature together, essentially making a double boiler...

Erlenmeyers are made of borosilicate glass and extremely resistant to temperature change. My concern would be how you are planning on distributing the heat throughout the flask -- stir bar?

None of these posts address the real issue that causes flasks to fail on the burner... super-heated hot-spots (due to lack of surface area in contact with the flask). This is precisely the reason they are apt to break on electric burners and placing sitting on an intermediate metal is likely to cause the exact same issue unless you ensure that the surface area is sufficient and/or the heating is uniform and moderate enough to prevent extreme hot-spotting. A heavy duty cast iron pan may be enough, but I would certainly not presume any metal or conductor between them is enough on its own.

Randar said:

None of these posts address the real issue

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Issue was addressed. You'll have to put in frypan with water. As stated above.

BTW, I wish I had an induction cooktop. Very cool. Have you seen the "zoneless" induction cooktops?

I'm wondering why you'd try to put an Erlenmeyer flask on the cooktop to begin with If this is to make your starter wort, I think it's best to start with a regular pot....so that you can adequately stir the malt extract to dissolve everything. Since the flask can stand high temp differentials, you can still use a funnel to direct that wort into the flask....and it still shall be sanitary. You can then chill the wort in the flask however you see fit (whether putting it in the freezer or an icebath).

davesrose said:

I'm wondering why you'd try to put an Erlenmeyer flask on the cooktop to begin with .

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Simplicity. It is very east to just boil in the flask, chill, pitch some yeast, cover with foil and throw on the stir plate.

I'll try throwing it in a large pot that also has water in it and give that a shot. The more I think about this I think it might be ok with a cast iron pan for the flask, but heating that empty cast iron pan for such a long time might be bad for the induction top.

gnatp2 said:

Simplicity. It is very east to just boil in the flask, chill, pitch some yeast, cover with foil and throw on the stir plate.

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I've been making my starter worts with pots, then transfering to whatever vessels, for quite a while now. Believe me, especially if we're talking hot wort here, it's not inconvenient at all.....especially when you compare what you have to do with an actual brew. The only difference is that you have to rinse the pot once you're done with it...that's only 10 seconds more and less then a penny of extra water.

passedpawn said:

Issue was addressed. You'll have to put in frypan with water. As stated above.

BTW, I wish I had an induction cooktop. Very cool. Have you seen the "zoneless" induction cooktops?

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Yes, I have seen them. very cool. I love mine. So easy to clean up. My only beef was having to buy all new cookware. But overall it is awesome (besides this flask issue!)

gnatp2 said:

I'll try throwing it in a large pot that also has water in it and give that a shot. The more I think about this I think it might be ok with a cast iron pan for the flask, but heating that empty cast iron pan for such a long time might be bad for the induction top.

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Ok, i tried putting it in pot of water, but it took FOREVER for the water in the flask to boil and it wasn't boiling very well. Unless someone has a better idea, i think i'm just gunna have to boil in a separate pot and then transfer although I'd rather try to keep it a little bit simpler. I know it isn't complicated but i try to simplify my brewing process wherever possible.

davesrose said:

I'm wondering why you'd try to put an Erlenmeyer flask on the cooktop to begin with If this is to make your starter wort, I think it's best to start with a regular pot....so that you can adequately stir the malt extract to dissolve everything. Since the flask can stand high temp differentials, you can still use a funnel to direct that wort into the flask....and it still shall be sanitary. You can then chill the wort in the flask however you see fit (whether putting it in the freezer or an icebath).

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Another person missing the point.

Boil in flask means you save a pot (and funnel?) to wash, the effort and risk of injury from transferring boiling hot wort, and the effort of sanitizing the flask.

You think it's hard to dissolve the DME in the hot wort? Not so much, in reality. A little swirl and boom... it's in solution.

And the thermal shock is when you are at most risk of breaking the flask. Unless you doled out a hefty sum for the good lab grade ones (more than double the price of the typical homebrew versions), the imperfections and thinner walls will make the flask more susceptible to cracking due to thermal shock. Whether that is due to using on a stove element or pouring hot wort in or dunking into an ice bath... it's all thermal shock (to varying degrees)

These flasks are MADE for use over an open flame. Homebrewers will lug around glass carboys and do all kinds of stupid **** to save 5 bucks here or there but being too afraid to use a flask on an open flame is one of the silliest things I have seen in this community.


To the OP who is worried about it? Use any heavy-walled pot with just a LITTLE water in it (just enough to keep the flask and the pot surface from being super-heated and to create a thin layer to help conduct heat more uniformly.

gnatp2 said:

Ok, i tried putting it in pot of water, but it took FOREVER for the water in the flask to boil and it wasn't boiling very well. Unless someone has a better idea, i think i'm just gunna have to boil in a separate pot and then transfer although I'd rather try to keep it a little bit simpler. I know it isn't complicated but i try to simplify my brewing process wherever possible.

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I thought the whole point for an induction cooktop was that you could get water to boiling very quickly in the proper vessel. I'd say using that proper vessel to get the water boiling, then adding your malt extract....well that seems way more effecient and simpler then getting a glass vessel to work on such a stovetop The savings in time you'd have, you could easily pitch to the flask and clean the pot out....

Randar said:

Another person missing the point.

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And you seem to still not know what an induction cooktop is (as evident in both your posts here)....google is a good feature.

davesrose said:

And you seem to still not know what an induction cooktop is....google is a good feature.

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I certainly do considering I have used them extensively, but thanks chief.

Randar said:

I certainly do considering I have used them extensively, but thanks chief.

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Then what all the BS about open flame???

I think the "BS" is the point that the adiabatic flame temperature of natural gas is around 3540F, way higher than an induction cooktop will achieve.

I don't see any problem with using a flask on top of a skillet on an induction cooktop, except for maybe killing the seasoning on the skillet.

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davesrose said:

Then what all the BS about open flame???

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Replying to your comment about why you don't know why anyone would put it on the cooktop and while pointing out that it's made to be used over an open flame (as noted by jds much hotter than induction or electric)... with proper precaution there is no reason not to do it if you wish to save the steps previously noted. I looked back and noticed I was not very clear about what point(s) I was addressing where.

jds said:

I think the "BS" is the point that the adiabatic flame temperature of natural gas is around 3540F, way higher than an induction cooktop will achieve.

I don't see any problem with using a flask on top of a skillet on an induction cooktop, except for maybe killing the seasoning on the skillet.

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And that 3540F point would be fine for the bunsen burner that scientific equipment is normally equated for. You folks are missing the point that an induction system does not use a direct heating element.....it needs a metalic/magnetic vessel in order to create heat within itself. Boiling water within in it is the most effecient and quickest way to finish off the wort.

davesrose said:

And that 3540F point would be fine for the bunsen burner that scientific equipment is normally equated for. You folks are missing the point that an induction system does not use a direct heating element.....it needs a metalic/magnetic vessel in order to create heat within itself. Boiling water within in it is the most effecient and quickest way to finish off the wort.

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Not missing the point in the least bit. Use the metal skillet/frying pan with a thin layer of water to act as the "heat transfer mechanism". What part of that do you keep refuting?

NOBODY has said anything about putting the flask on the induction cooktop without an intermediate heat transfer medium. Hell, you do the same with an electric cooktop since they are prone to extreme hot-spots.

Randar said:

Not missing the point in the least bit. Use the metal skillet/frying pan with a thin layer of water to act as the "heat transfer mechanism". What part of that do you keep refuting?

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Because you and jds refer to the least conductive vessel there is: a cast iron skillet. The cast iron skillet is good for direct heating elements like a gas stovetop or electric (for even heat distribution), but you want the most magnetic for an induction system. You also change your conditions here as you learn more about induction systems, I see...

davesrose said:

Because you and jds refer to the least conductive vessel there is: a cast iron skillet. The cast iron skillet is good for direct heating elements like a gas stovetop or electric (for even heat distribution), but you want the most magnetic for an induction system. You also change your conditions here as you learn more about induction systems, I see...

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So are you saying that you can't use the method of an intermediate heat transfer medium to do the job or are you now just picking nits?

Randar said:

So are you saying that you can't use the method of an intermediate heat transfer medium to do the job or are you now just picking nits?

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Well as far as intermediate heat transfer: the flask would create another heat transfer itself wouldn't it? Again, heating water in the initial vessel is the most effecient....

davesrose said:

Because you and jds refer to the least conductive vessel there is: a cast iron skillet. The cast iron skillet is good for direct heating elements like a gas stovetop or electric (for even heat distribution), but you want the most magnetic for an induction system. You also change your conditions here as you learn more about induction systems, I see...

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Actually, cast iron's conductivity, both thermal and electrical, is quite a bit higher than stainless. That's exactly why cast iron pans work well at distributing heat in cooking. Furthermore, cast iron responds very well to induction cooking (unless you need a pan that heats up or cools off very fast -- Cast iron has a lot of thermal mass). Try something. Take a fridge magnet, and stick it to the bottom of your best stainless cookware. Then, try the same with an old cast iron skillet.

Guess which one the magnet will stick to more strongly? I'll bet a beer on the cast iron.

And neither are used for conductive materials in electrical systems (no matter what stainless composite we're talking about). But that's another discussion. The OP has already said they tried the flask in a pot....they stated it took forever....I provided grounds for why. A flask, especially lab grade, will provide another substantial heat transfer....so it's obvious to me as to why it does take a long time to get water to boil within it, as oposed to the original source.

Man, all I have to say is this: I had a really nice 2000ml flask I bought from northern brewer. I used it a million times on my electric stove with no problems. The second time I used it on a gas stove with medium flame, it cracked all the way around the bottom. Luckily, I was able to save the starter, but man was I pissed! I don't know the science behind why it cracked, all I remember is, how everone kept saying how rugged they were and how they were made for that kind of thing. Now I'm back to using a regular old coffee pot for my starters again . A lesson learned for me.

Chances are the flask wasn't "lab grade". Regular pyrex is soda-lime glass: which doesn't accept quick temperature changes as much as the original pyrex compositon: borosilicate, which is still used in Pyrex's "lab" range of products. "Lab" Pyrex can except focused heat flames way more then soda-lime can.

davesrose said:

Chances are the flask wasn't "lab grade". Regular pyrex is soda-lime glass: which doesn't accept quick temperature changes as much as the original pyrex compositon: borosilicate, which is still used in Pyrex's "lab" range of products. "Lab" Pyrex can except focused heat flames way more then soda-lime can.

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Those bastards! >:-0

There's no way in heck that somebody would try to sell a soda-lime erlenmeyer flask, especially not from Northern Brewer.

rockfish42 said:

There's no way in heck that somebody would try to sell a soda-lime erlenmeyer flask, especially not from Northern Brewer.

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And now that you mention it, let me just say that I wasn't refering to NB as bastards either, they were great as far as customer service. I was just poking fun at whoever manufactured the flask. I suppose I really should be poking fun at myself. Im thinking I had to have done something wrong. Maybe too heavy on the flame, I don't know.

I wonder if you can turn the cast iron skillet upside down and still activate the induction burner... that way you could protect the season on the pot and still have a nice evenly heated surface on which to heat your flask.

I see no issue with using cast iron as a heat transfer surface, I'd just throw a little oil on it afterwards like you should do after you cook with it.

Wow. Everyone so touchy about heat and flasks!! Thanks for the help guys but lets all remember that this is just beer!

davesrose said:

The OP has already said they tried the flask in a pot....they stated it took forever....I provided grounds for why.

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To clarify, the reason it took forever to boil is not due to slow boiling time of an induction top. The reason is that the water in the flask is separated from the water in the pot and the water in the pot (outside the flask) gets to 212F very quickly while water in the flask is only being heated by 212F water. It takes a lot longer to heat this way rather than the water being heated DIRECTLY from the pan. The water in the pot got to 212 in a few minutes while after 15 minutes the flask water was only around 170F.

I tried using the "only a small amount of water in the pan" method and that didn't work very well. The small amount of water between the flask and the pan would boil and cause the flask to kinda jump. Maybe I could use even a smaller amout of water (I had used 1millimeter or so) but having to frequently add water to the iron skillet seems like too much of a pain.

So far, no great solution yet!

bovineblitz said:

I wonder if you can turn the cast iron skillet upside down and still activate the induction burner... that way you could protect the season on the pot and still have a nice evenly heated surface on which to heat your flask.

I see no issue with using cast iron as a heat transfer surface, I'd just throw a little oil on it afterwards like you should do after you cook with it.

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That may work, I'm not sure. Unfortunately because of the handle on the skillet, my surface will be a bit wobbly which scared me a bit.

davesrose said:

I've been making my starter worts with pots, then transfering to whatever vessels, for quite a while now. Believe me, especially if we're talking hot wort here, it's not inconvenient at all.....especially when you compare what you have to do with an actual brew. The only difference is that you have to rinse the pot once you're done with it...that's only 10 seconds more and less then a penny of extra water.

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I think most people who boil directly in an E flask have done it this way before. I know you have a hard time accepting that anyone is smart enough to make this decision for themselves have experience with both methods, but why don't you give it a try?

gnatp2 said:

That may work, I'm not sure. Unfortunately because of the handle on the skillet, my surface will be a bit wobbly which scared me a bit.

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Spray a little bit of pam, put down a sheet of aluminum foil, then put the flask on top?

remilard said:

I think most people who boil directly in an E flask have done it this way before. I know you have a hard time accepting that anyone is smart enough to make this decision for themselves have experience with both methods, but why don't you give it a try?

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And it's evident you have a hard time excepting other methods besides boiling water within an Erlenmeyer flask over an open flame. Direct flame under a flask works fine...but is not as effecient with indirect heating. It's not my fault you think offering another suggestion in alternative heating methods is being close minded.

OP - I prefer to leave my flask (5L) in the sink and pour the hot wort into it from a SS pot. I avoid the volcano boil-overs in the flask (no I don't use silicone anti foaming agents) and I don't risk the mess of a broken flask on my cook-top. After it cools for a bit, I can run some cool water along the sides of the flask, then add ice to the sink and water.

fretsforlife said:

Man, all I have to say is this: I had a really nice 2000ml flask I bought from northern brewer. I used it a million times on my electric stove with no problems. The second time I used it on a gas stove with medium flame, it cracked all the way around the bottom. Luckily, I was able to save the starter, but man was I pissed! I don't know the science behind why it cracked, all I remember is, how everone kept saying how rugged they were and how they were made for that kind of thing. Now I'm back to using a regular old coffee pot for my starters again . A lesson learned for me.

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I find it best to start it off on low heat and then ramp it up over the course of a few minutes. This way, thermal shock is greatly minimized. After boiling though, I DO stick it directly into an ice bath in my sink, but at least if it breaks there, it's a really simple cleanup. But I've never run into that issue anyways.

However, there's a reason flasks are heated over an open flame in a lab setting. You really don't want to be putting it on an electric element. In fact, I'd wager that the integrity of the flask was compromised from constant use on the electric burner, and that it just could no longer handle the greater direct heat from a gas stove.

davesrose said:

Chances are the flask wasn't "lab grade". Regular pyrex is soda-lime glass: which doesn't accept quick temperature changes as much as the original pyrex compositon: borosilicate, which is still used in Pyrex's "lab" range of products. "Lab" Pyrex can except focused heat flames way more then soda-lime can.

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This only applies to Pyrex kitchenware. Unless E flasks have suddenly become a part of the Pyrex kitchen lineup (I'll save you some time: it hasn't), I don't think he was actually using a soda lime flask.

emjay said:

This only applies to Pyrex kitchenware.

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As well as some glassware from the Corning Pyrex Vista glassware lineup. Granted, I wasn't certain if any current Pyrex erlenmeyer flasks are soda-lime...but I never saw a borosilicate lab vessel crack with an open flame. Maybe the nature of the glass changed with whatever kitchen use it got...perhaps you're right about the years of use with an electrical range.