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General Category => Equipment and Software => Topic started by: Jarhno on September 27, 2013, 11:41:02 AM

Title: Directly heating Erlenmeyer flasks
Post by: Jarhno 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: yso191 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: BrewArk 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: theDarkSide 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: smkranz 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: Jarhno 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!
Title: Re: Directly heating Erlenmeyer flasks
Post by: denny 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: riverrat 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: narvin 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: duboman 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:(
Title: Re: Directly heating Erlenmeyer flasks
Post by: phunhog 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: klickitat jim on September 27, 2013, 09:05:58 PM
Tried once and it shattered. Won't try again. Coils...
Title: Re: Directly heating Erlenmeyer flasks
Post by: Thirsty_Monk on September 28, 2013, 11:55:15 AM
Never insert cold stir bar to boiling wort in Erlingmeyer flask.

Personal experience.
Title: Re: Directly heating Erlenmeyer flasks
Post by: joe_feist 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: Jimmy K 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.
Title: Re: Directly heating Erlenmeyer flasks
Post by: rjharper on September 29, 2013, 03:52:09 PM
To add to the great advice so far, as a former lab chemist, I'd use a Pyrex flask on a gas stove or ceramic top electric, but certainly not on a coil, for the hot spot reasons mentioned. It won't work on an induction top, because that requires cookware with ferromagnetic properties.

All that said though, every time I've tried to use the erlenmeyer directly, I've had awful boil overs!  :o
Title: Re: Directly heating Erlenmeyer flasks
Post by: oldmankaufman on September 30, 2013, 07:20:21 PM
I've been making starters directly in Erlenmeyer flasks for a couple years now. Some on an electric coil stove, but never directly on the coils. Use some sort of diffuser between the coils and the flask to avoid the hot spots. Mine was a doubled up, perforated aluminum thing sold as a "double boiler". Takes forever to get to a boil, but at least you get good control of the heat to limit boil overs. I've switched to a small Coleman propane camp stove that screws directly onto the bottle and have had pretty good success provided the flask is adequately sized. I had a 500 ml crack using this small burner but 1L and 2L flasks have been good to go with the heat output available.

As for the boil overs - It is best to keep your initial volume of wort to about half the total flask volume Then 5-6 drops of a foam control agent per 1L of wort usually keeps the foam inside the flask, even with Wheat DME.  Don't forget the stir bar before you start the boil if you've got a stir plate. As someone else here mentioned, Cold bar+hot glass=unhappy brewer.

Also consider using a "lab thermometer"  (cheap glass type) pushed through a foam stopper and into the wort during the boil and ice bath. It's one slick, sanitary way to make sure you hit your pitching temp.
Title: Re: Directly heating Erlenmeyer flasks
Post by: coastsidemike on October 01, 2013, 08:13:37 PM
Is it necessary to prepare starters with a full boil?  Avoiding the flask boil-over is hard to manage, and realizing I never thought to use a smaller burner.  Seems like sanitation-wise being above 180 is necessary, and thus holding in the 195-200+ degree range should be more that sufficient.
Title: Re: Directly heating Erlenmeyer flasks
Post by: Jimmy K on October 02, 2013, 06:34:17 AM
Is it necessary to prepare starters with a full boil?  Avoiding the flask boil-over is hard to manage, and realizing I never thought to use a smaller burner.  Seems like sanitation-wise being above 180 is necessary, and thus holding in the 195-200+ degree range should be more that sufficient.
The steam from boiling will sanitize the walls and whatever foam/foil cap is on the flask, which is convenient but can be accomplished other ways too. I've been bringing it to boil and then removing from heat and allowing it to cool slowly. I'm sure it stays above 180 for quite a while this way. Steam sanitizes very quickly, so a few seconds should do it.

There is a difference between sanitation and sterilization. If you want sterilized wort, I'm not sure 180 would do it. But if you'll only use the yeast in a single batch, sterilized wort isn't needed.
Title: Re: Directly heating Erlenmeyer flasks
Post by: narvin on October 02, 2013, 07:26:19 AM
+1 to foam control!  I use a flask because it's one vessel, no mess, and there's nothing to sanitize, but a boil over definitely ruins that.
Title: Re: Directly heating Erlenmeyer flasks
Post by: Stevie on October 07, 2013, 03:25:20 PM
I use an electric stove with a Lodge cast iron skillet as a defuser. Works well. I am still searching for the magic  temperature setting between "taking forever" and "wort on the ceiling"
Title: Re: Directly heating Erlenmeyer flasks
Post by: davidgzach on October 07, 2013, 05:14:42 PM
Glass top stove, 5L Bomex Erlenmeyer and a drop of fermcap.  Heat to boil and directly to ice bath.  Zero problems, many starters.....

Dave
Title: Re: Directly heating Erlenmeyer flasks
Post by: klickitat jim on October 07, 2013, 09:17:05 PM
I'm still a fan of pressure canned starter. Wicked easy. Always waiting for me in the pantry.
Title: Re: Directly heating Erlenmeyer flasks
Post by: morticaixavier on October 08, 2013, 07:24:10 AM
I'm still a fan of pressure canned starter. Wicked easy. Always waiting for me in the pantry.

yup.

I just captured two new strains of saison yeast a couple weeks ago because I had a few jars of wort in the pantry ready to go. easy peasy.
Title: Re: Directly heating Erlenmeyer flasks
Post by: klickitat jim on October 08, 2013, 08:51:21 AM
I have some pils malt laying around that needs to be used, and a weekend coming where I won't have room in the fermentor freezer, so I'm going to mash and can two cases of 1.030 pils
Title: Re: Directly heating Erlenmeyer flasks
Post by: Jeff M on October 20, 2013, 06:17:58 PM
I'm still a fan of pressure canned starter. Wicked easy. Always waiting for me in the pantry.

Can you describe the process?  Every time i make a start i end up boiling over from my flask, then you have to chill etc. it just becomes a horrible process.
Title: Re: Directly heating Erlenmeyer flasks
Post by: klickitat jim on October 20, 2013, 09:42:50 PM
Sure. I put 3 oz of DME in each quart jar. I fill with warm water to an inch from the top. I wipe off the mouth and put a new canning lid on. I shake till there's none stuck to the bottom. I adjust the lid ring to finger tip tight. From there follow your pressure canner instructions. I process mine at 20 psi for 15 min.
 
I usually make this on a non brew day and can up a case or two.

Wort ends up about 1.035 which is great for building buddies. On the day I make my starter I sanitize my flask, stir bar, a funnel, and a chunk of foil. I put the yeast in and a couple quarts of premade wort. Bingo.
Title: Re: Directly heating Erlenmeyer flasks
Post by: morticaixavier on October 21, 2013, 07:30:59 AM
Sure. I put 3 oz of DME in each quart jar. I fill with warm water to an inch from the top. I wipe off the mouth and put a new canning lid on. I shake till there's none stuck to the bottom. I adjust the lid ring to finger tip tight. From there follow your pressure canner instructions. I process mine at 20 psi for 15 min.
 
I usually make this on a non brew day and can up a case or two.

Wort ends up about 1.035 which is great for building buddies. On the day I make my starter I sanitize my flask, stir bar, a funnel, and a chunk of foil. I put the yeast in and a couple quarts of premade wort. Bingo.

I actually do this even when I'm not planning on storing long term, minus the pressure part. I just process in a water bath. If you do it a night or two ahead of time it's perfectly safe to leave it on the counter or pop it in the fridge.

Or mash a couple extra pounds on the next AG brew and run off the last bits into quart jars and pressure can. If you are making a 1.050+ beer you probably don't even have to add any grain, just run an extra gallon of near boiling water through your grain after your last batch (or last runnings)
Title: Re: Directly heating Erlenmeyer flasks
Post by: Jeff M on October 21, 2013, 05:21:16 PM
Awesome sounds pretty neat.  course ive never had to process anything through a water bath, thank god for them internets!