Erlenmeyer flask heating

I just picked up an erlenmeyer flask for yeast starters and was wondering how I can boil water in it on my electric stove. In the description it says it can be put on open flame. Or should I just boil in a sauce pan and pour into the flask? I didn’t want to mix up a batch of star san if I didn’t have to.

I have read that no flasks can be used on an electric stove. Coil burners heat unevenly which stresses the glass. It is just safer and your flask will last longer, even when using gas, by heating and cooling the wort in a kettle.

Don’t mix up a special solution of Star San. Keep a few gallons on hand in jugs.

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I bought Northern Brewer’s yeast starter kit on Tuesday (preparing for the Wee Heavy that’s on sale).

Watch the video next to the picture of their kit… It answers your question. I also do not have a gas stove so I was wondering the same thing.

Good luck.

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For the electric coil stoves it may be possible to have a metal disc on the coils to evenly transfer the heat to the flask. A disc that would not warp would create an even heating surface. Just a thought . Have not heard of it being used but it seems logical.

Maybe something like this.

The erlenmeyer flask is the perfect shape for creating wort volcanoes. This can be used to reduce the risk of boil overs.

That will even out the heat generated by the electric stove, but it won’t do much to even out how the heat gets to the flask because most of the heat transfer is happening due to direct conduction, which requires physical contact and glass flasks aren’t evenly flat on the bottom. Without very good surface contact, you will get big hot spots where it touches the metal, and less heating where it doesn’t. With a gas burner, you are transferring the heat by ionized air flowing over the surface, which is intrinsically more even.

Is that enough to cause a flask made of pyrex (which is designed to withstand stresses caused by big temperature differences) to break? I don’t know, but I’d play it safe and heat the starter wort in a pot.


When I was extract brewing, I got one of these plates in an attempt to reduce scorching. The high heat of the burner I needed to boil the wort was too much for the burner plate and warped it. Once warped, I lost the even heating. I beat the living snot out of it with a hammer in order to level it out so I could use it again. It would just warp on the next batch. It wasn’t this brand but was exactly the same thing. I think I paid $20.00 for mine. I would not recommend it for brewing or making starters.


This is good information. My musings about the plate does not seem like the way to go.

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I know some brewers take it a step further and flame the mouth and neck of the Erlenmeyer flask before pouring the starter into the wort or next size starter. I simply trust the starsan to do its job as I don’t have a Bunsen burner and haven’t tried this with the little butane jobs.

That’s to sanitize the mouth where it there is most likely to be contaminants. Standard lab procedure actually.

Yeah got that(that’s kinda sorta what I do for a living), I’m just curious how many homebrewers actually_do_ that(and how).

I have a sanitized aluminum foil cap on the flask with a few ounces of Star San solution in the flask. The flask is inverted in a tall tub that once held three or four pounds of cottage cheese for stability. Sanitizer drains from the flask into the cap. Seems to have worked without infection, so far.

edit: Cottage cheese bucket was a five pounder.

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My electric stove doesn’t have the newer coil type elements but an almost flat surface. But I ended up boiling in a saucepan and pouring into flask. I had some leftover Star San in a spray bottle I used to sanitize.

I wanted to check the health of my harvested yeast so I made a starter. Followed the wyeast directions 1 quart of water, 100g of dme, 1/2 tsp yeast nutrient. First time making a starter.

Congrats! I love yeast starters! Happy yeast, better beer!

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I don’t, but I’ve been around labs enough to see how real scientists do things. Needed for lab work, kind of going overboard when it comes to brewing.

Yeah, thats kinda what i thought. With 388 billion yeasties getting poured out of the flask, its hard to see how 1 airborne eschericia coli that adhered to the surface could get much traction. Assuming proper sanitary technique up to that point was followed of course.

@mhall2013, if you want to boil in your flask to assist in sanitizing it you can make the starter by adding the water/DME to the flask and bring it to a boil by placing the flask in a pan of water, boiling it all together. This will provide the consistent heat distribution your looking for.

Thanks loopie I’m brewing as we speak. I’m using the yeast starter I made from harvested wyeast 1272 from the previous batch. Brewing the same recipe. I’m a little nervous to use it but I won’t know unless I do. If I dump it I’ll never know.

It looks pretty good to me. I cold crashed it last night to see how much was in suspension. Should I add yeast nutrients to the boil like I did the starter. Wyeast nutrient blend says last 10 min of boil 1/2 tsp. I don’t want to over do it?

I spot sanitize my flask for every starter (using a spray bottle). Heating and chilling directly in the erlenmeyer sounds cool and everything, but unless you are fond of adding silicon to your starter wort (fermcap), boilovers in an erlenmeyer happen way too easily for my tastes.

Why are you nervous? billions of yeast cells in there…you’re all good!