Erlenmeyer Flask on Electric Stove

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BillyBroas

BillyBroas

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I have a borosilicate flask coming in the mail and am wondering if it is ok to heat it directly on my electric stove coil. I've read that some people use trivets made from metal hangers as a heat diffuser. This seems like a good idea, but is anybody successful heating it directly? Thanks!
 
You risk cracking the flask if you place it directly on the burner coils. You may get away with it indefinitely, but sooner or later it will likely crack and when it does you will be out one flask and you will have a big mess to clean up. It's simply to make a wire trivet from a coat hanger or other heavy gauge steel wire. I use a burner grate that I salvaged from an old gas stove. It works perfectly for this. I turn the grate upside down on the electric coils and place the flask on the grate. I use another grate when cooling the flask in the sink. This allows the cooling water to flow freely around and also under the flask for faster cooling. You can usually get the gas burner grates for free if you scrounge around a little. An appliance repair shop might also have some lying around out back.
 
Thanks Catt I'll start looking around for a burner grate. That's a smart idea too to use a grate in the sink to let the water flow beneath it.
 
I've heard of people putting a cast iron pan on the coil then the flask into that. The cast iron helps to diffuse the heat.

A flask should be fine directly on a gas stove or a ceramic top.
 
BillyBroas said:
Thanks Catt I'll start looking around for a burner grate. That's a smart idea too to use a grate in the sink to let the water flow beneath it.
Click to expand...

A wash cloth in the sink work well for that. Also helps to protect the sink some.
 
I just don't understand. Why would a direct flame on a boro. flask be ok, but heat from an electric element pose a problem? I'm really not being snarky. I want to know what's going on here because I've always used my flask on my electric stove, and I want to know if I've been putting myself (well, my kitchen stove) at risk this whole time, and the reason why that is.

I understand going from hot to cold quickly and vice versa is not good. The glass will expand/contract, etc. I'm talking about putting some room temperature water and DME in the flask, putting it on the electric stove, and bringing the heat on it up to a boil slowly. Why is this a problem?
 
Munsoned said:
I just don't understand. Why would a direct flame on a boro. flask be ok, but heat from an electric element pose a problem? I'm really not being snarky. I want to know what's going on here because I've always used my flask on my electric stove, and I want to know if I've been putting myself (well, my kitchen stove) at risk this whole time, and the reason why that is.

I understand going from hot to cold quickly and vice versa is not good. The glass will expand/contract, etc. I'm talking about putting some room temperature water and DME in the flask, putting it on the electric stove, and bringing the heat on it up to a boil slowly. Why is this a problem?
Click to expand...

The problem is an electric coil is very hot and direct heat on a single spot of the glss compared to a NG gas flame. A ceramic/glass stove top also provides a more gentle and even heat by acting as a heat spreader from the direct electric coil.
 
ibbones said:
How about if you put the flask in a pot with about one inch of water and boil the water? Would that work?
Click to expand...

I think the boiling water under the flask will cause it to bounce around which may or may not cause a problem. It would be much easier to simply cut a piece of wire from a coat hanger and bend it into a star shaped pattern to make a trivet. Nothing fancy is required, you just want to prevent the flask from contacting the electric burner coils directly.
 
ibbones said:
How about if you put the flask in a pot with about one inch of water and boil the water? Would that work?
Click to expand...

I would think that the water would get in the way. The boiling water would stay at 212° (boiling point of pure H2O). The wort has dissolved sugars in it, so it would boil at a higher temp. So the water would always be trying to cool the wort to 212°.

Disclaimer: The wort may boil with enough contact with the bottom of the pan, but the water would still be a hinderance to faster boiling.
 
Regardless of the burner type, it's probably a good idea to have a pan/pot underneath the flask. Not so much as a heat spreader, but as safety net in case the unthinkable were to occur.
 
I have heard of people folding aluminum foil a few times then placing that under the flask. Both for electric and ceramic/glass tops. I haven't done it, but that made good sense to me.
 
Boerderij_Kabouter said:
I have heard of people folding aluminum foil a few times then placing that under the flask. Both for electric and ceramic/glass tops. I haven't done it, but that made good sense to me.
Click to expand...
I might try that. I have the ceramic glass top stove and my SWMBO would kick my a$$ is she saw me put a piece of wire on it.
 
ibbones said:
I might try that. I have the ceramic glass top stove and my SWMBO would kick my a$$ is she saw me put a piece of wire on it.
Click to expand...

If you have a ceramic stovetop there is no point in using aluminum foil. Might I refer you to a ceramic top heat/stir plate. If a ceramic hot plate works in the lab, your ceramic stovetop should work at home. :D

You don't need an heat spreader on a ceramic stove, the heat is already being diffused by the ceramic. If the flask breaks due to some unforseen complication (not heatshock) then a small pan would be useful in saving your stovetop from a few hundred mL's of soon to be burnt wort. ;)
 
I have a glass ceramic top stove and this is something I have been wondering about and really appreciate the input of everyone. In the past I have not had any problems but was waiting for something bad to happen. So, this is a nice relief.

However, I have read that you can take the flask directly from the stove to an ice bath. I've been too scared to do this. Has anyone had problems?
 
PorterIV said:
I have a glass ceramic top stove and this is something I have been wondering about and really appreciate the input of everyone. In the past I have not had any problems but was waiting for something bad to happen. So, this is a nice relief.

However, I have read that you can take the flask directly from the stove to an ice bath. I've been too scared to do this. Has anyone had problems?
Click to expand...

I just tried this today. I did take the flask off the burner and put it on a cool area of the stove for a minute. From there I put the flask in cold water in the sink on top of a small cooling rack and let it sit for about a minute before adding ice to the water. So far, so good!

Also, I have a small wire heat spreader that came with my Yama Vac Pot. This is very similar to modifying a wire hanger and putting it on the stove. (I've done that, BTW, and the hanger had a coating that burnt off onto the stove and was a really a biatch to clean off). I used the wire piece under the flask just in case. Although from what I read in this thread I don't think this is required on a ceramic smooth top electric stove, I guess it put me at ease so I am going to continue to use this as a precaution.

When I was listening to the Brew Strong episode on Starters the other day I picked up a great tip. Instead of adding DME directly to the flask, they recommended turning the heat off, dumping the almost boiled water from the flask into a metal bowl and using a metal whisk to stir in the DME and yeast nutrient if you're using it. I used a heat mitt when handling the flask as to not burn the hell out of my hand. After that you can use a funnel to pour the mixed solution back into the flask. I added some firmcap-s to the flask and this worked beautifully!
 
I know the question has already been answered pretty thoroughly, but I wanted to mention that the cast iron pan method is what I use for cooking down sugar syrups and candies. This is the same application.
 
I use a $20 dollar hot plate from walmart that has a cast heating element on top and it has worked fine so far. I have avoided using my glass cooktop stove and any bare element. For $20 you should be safe going this route.
 
Borosilicate is lab glass. It is used under brutal conditions in the lab under direct flam and quenching cold. I have used my Erlenmyers just fine on my electric stove followed by ice baths in the sink with no worries. I wouldn't worry about it, adding a cast iron skillet will just slow down the process.
 
Shooter said:
Just to update my previous claim of putting the flask in a pot of boiling water. This worked fine when I was using a smaller 1 liter flask. I tried it in a bigger flask last night, what a pain!
Click to expand...

Kinda funny, but after my opening post and all the great tips, I ended up making the starter in a pot and then transferred it to the flask after it cooled. Why? It was MUCH easier to stir in the pot.
 
I ended up pouring mine out of the flask and into a pot as well. At least when I got up this morning it had formed a krausen and was happily bubbling away on the stir plate.

I've always shaken my starters to aerate in the past. So, my four year old and two year old were extremely curious about the new stir plate. I swear those kids can be entertained by the oddest things!
 
I too have opted to boil in a pot cool and transfer. I tried direct heat with flask inside a pot and the pot smoked so much that I set off every fire alarm in my house before I could get it boiling. Also tried to direct heat the flask with pot of water and that is just too slow. when I finally got the wort boiling in the flask it boiled up and out of the flask and ended up making a big mess. So no more boiling wort inside a flask for me!
 
Sorry to bring this back from the dead but i have a suggestion...Put your DME in first!! I decided to try to put it in after i got the temp up with a spoon...I wish i hadnt. Of course the sugar stuck to the spoon so I tried tapping it side to side in the flask and it cracked. Boohoo!!

Besides my stupidity it has taken many red hot boils to cool ice baths no problem!
Although I may have weakened the glass or had too much of a temperature differential and this led to the weakened point where the spoon was tapping!
 
CrookedChris said:
Any thoughts on putting it directly on a glass top electric stove?
Click to expand...

Any method that depends on heat transfer between 2 hard surfaces will make it more susceptible to cracking. It's all about super-heating in a localized spot, similar in effect to putting a lot of pressure over a lot of area vs a lot of pressure over a very small area. Cast Iron or the like is probably your best bet.

Electric burner coils are notoriously uneven and even a glass cooktop may exceed the ratings of the borosilicate if the flask is not sitting evenly (although heatplate/stirplate combos are going to exhibit similar to the glass cooktop, so the risk is likely to be greatly reduces vs the el cheapo electric coils.)
 
binaryc0de said:
I too have opted to boil in a pot cool and transfer. I tried direct heat with flask inside a pot and the pot smoked so much that I set off every fire alarm in my house before I could get it boiling. Also tried to direct heat the flask with pot of water and that is just too slow. when I finally got the wort boiling in the flask it boiled up and out of the flask and ended up making a big mess. So no more boiling wort inside a flask for me!
Click to expand...


Any "coated" metal (please oh please don't tell me you used a teflon pan) can superheat like that and give off noxious and in many cases carcinogenic fumes.
 
I add boiling water to my DME & yeast nutrient in the flask and whirl to dissolve. I simmer it on my backpacking stove for 15 minutes. 2 liter flasks cost too much to risk on stove elements or other hard surfaces.

Plunge it (gently) with oven baked foil krinkled on top into a cold water bath for 15 minutes. Pitch yeast and grow it. I use a rubber band to hold foil on and prevent critters (mice, cats, bugs) from finding their way into my starter wort. Whirl frequently and if time permits, settle yeast in refrigerator or cold cellar overnight so I can decant most of the spent wort before pitching. I sanitize with star san and no longer flame edges.

A 1.2 liter starter of XL Wyeast 1056 started pushing air through the airlock of a 1070 IPA this past weekend in under two hours. YMMV
 
In all my chemistry labs in college where we did experiments using borosilicate or pyrex flasks, we frequently brought them directly from flame and boiling to a cold water bath. Some of the chemicals we used boiled at MUCH higher temps than water. If you are boiling wort in a flask, the highest the temp can get is only around 220'F (remember it's mostly water, and sugars will elevate the boiling point slightly). I can't remember a single flask breaking from going directly from very hot to a cold bath.
 
Greetings, CantWinThisGame, and welcome to HBT :mug:

There's a significant difference between heating with flame vs contact with an electric element (the topic) and that's not even considering lab grade glass vs what most of us peons obtain.

imo, putting an e-flask in direct contact with an electric range element never a good idea...

Cheers!
 
day_trippr said:
Greetings, CantWinThisGame, and welcome to HBT :mug:

There's a significant difference between heating with flame vs contact with an electric element (the topic) and that's not even considering lab grade glass vs what most of us peons obtain.

imo, putting an e-flask in direct contact with an electric range element never a good idea...

Cheers!
Click to expand...

There's actually different grades of borosilicate. The type you used in high school chemistry class was likely "academic grade". The kind used in universities, hospitals, research facilities and commercial labs is "scientific" or "laboratory" grade.

Academic grade often has minute flaws and may or may not crack under direct heat or shock cooling. Laboratory grade is essentially without flaws. Academic grade is either manufactured to lower standards or is culled from lab grade rejects.

I've got lab grade 1 liter and 2 liter Erlenmeyer flasks and 1 academic grade 5 liter flask. The 2 l flask was 3x times as expensive as the 5 l. Needless to say, the 5 l never sees any use other than on the stir plate. I did crack a 1 l flask once on an electric coil element while boiling some wort. Huge mess. Even with lab grade gear, I still use a 3 quart sauce pan to boil, plus the borosilicate takes forever to come to a boil in my wife's induction cooktop. :yes:
 
Welcome back to life 10 year old thread.

I was lucky enough to crack a 5L flask on an electric stove top. 3.5L of boiling hot sugary liquid rushing out all over everywhere will make you snatch a child off the floor real fast. Never again.

I think the problem with electric coils is that the coil gets super hot where it contacts the glass, separated by unheated areas, followed again by super hot spots. This uneven heating is the problem. Any flame type heating heats very evenly. Theres no super concentrated area of heat. Putting on a flat cast iron, or other heat conductive surfaces works well as long as the flask sits flatly against contacting the entire surface area.

Working with glass, if it hasn't broke yet, it's just that ... yet
 
That is exactly the problem, and unequal thermal expansion can be catastrophic wrt glass.
It's also why the bottoms fall out of glass carboys...

Cheers!
 
I have a few 5L flasks and boil in a pot and pour in. My mother has made hot water for her tea in an old Pyrex coffee pot. She uses a trivet that was made from a cloths hanger. Never an issue. I’d love to boil and cook in my flash using my electric stove. I made a trivet and did one in my small 2L flask. The mess would be terrible. Guess I need to brave it
 
Take pictures!

I don't get it. Sheer laziness to clean a pot (takes 20 seconds) doesn't explain the propensity for folks to take stove top risks with e-flasks...

Cheers! (Y'all must be single...and not have Spousal Wrath to think about :D)
 
TristanL said:
I just tried this today. I did take the flask off the burner and put it on a cool area of the stove for a minute. From there I put the flask in cold water in the sink on top of a small cooling rack and let it sit for about a minute before adding ice to the water. So far, so good!

Also, I have a small wire heat spreader that came with my Yama Vac Pot. This is very similar to modifying a wire hanger and putting it on the stove. (I've done that, BTW, and the hanger had a coating that burnt off onto the stove and was a really a biatch to clean off). I used the wire piece under the flask just in case. Although from what I read in this thread I don't think this is required on a ceramic smooth top electric stove, I guess it put me at ease so I am going to continue to use this as a precaution.

When I was listening to the Brew Strong episode on Starters the other day I picked up a great tip. Instead of adding DME directly to the flask, they recommended turning the heat off, dumping the almost boiled water from the flask into a metal bowl and using a metal whisk to stir in the DME and yeast nutrient if you're using it. I used a heat mitt when handling the flask as to not burn the hell out of my hand. After that you can use a funnel to pour the mixed solution back into the flask. I added some firmcap-s to the flask and this worked beautifully!
Click to expand...

If you're going to go to that trouble, you might as well do what I do, which is make my starter in a sauce pan and then just use a funnel to pour into the flask when done. I really did not want wort burned onto my glass top stove at my old house and it would be as big a mess or bigger on the gas cooktop at my new place. I figure the flask will fail eventually and it's most likely to happen when heating or chilling. My flask is always in the sink when it gets wort, so if it fails, it'll be an easy cleanup.
 

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