Split my Pyrex Flask

So I was getting ready to make a starter yesterday. Thinking gas would be better for my flask than sitting on the electric burner, I got out my nice butane catering burner. Set it up, fill my flask with warm water, and set it on the burner. Turn it on about halfway, and about thirty seconds later I hear a bad sound. Sure enough, there is a crack running all the way across the bottom of a 2000mL Pyrex flask. It doesn't leak much water, but it's really broken. Anyone else had a similar occurance? I thought these things were pretty resilient to temperature...

They usually are fairly tough, but a small chip or hairline crack could have done it in. Also, is the butane burner a single flame or does it have multiple jets? If it's just a single flame in a small area that could have caused the glass to expand at a much faster pace than the rest of the flask leading to the break.

Matt

I always try to limit the speed of temp change the best I can. That means if the flask starts with cold tap water, it goes on a low flame for 5 minutes, then higher. When I'm going to chill, I leave it alone on the stove for 5 minutes, then under some luke warm water for a minute, then into the icebath. So far so good.

FYI, my flask says "SIMAX" on it so I know for sure it's good borosilicate.

Bobby_M said:

I always try to limit the speed of temp change the best I can. That means if the flask starts with cold tap water, it goes on a low flame for 5 minutes, then higher. When I'm going to chill, I leave it alone on the stove for 5 minutes, then under some luke warm water for a minute, then into the icebath. So far so good.

FYI, my flask says "SIMAX" on it so I know for sure it's good borosilicate.

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Bobby_M; are there other types of "Pyrex style" of manufactures of borosilicates that we should stay away from preventing the above failure? I myself treat my one litre as a thin wine glass that has lasted for over 30 years. I'm looking at 5 litre in the near future.

I find that I have a lot less problems if I make starters in a stainless pot. The advantage is that I can use a high flame on the stainless pot to get to a boil fast and then turn off the heat while adding the DME and yeast nutrient and stir well before resuming the boil and there is nothing to fear. After the pot is back to a boil I pour it into the flask and boil for 15 minutes with the foil on top.
Cool in tap water followed by an ice bath.

it takes a lot longer but I have always used a double boiler for my pyrex flasks, I know it shouldnt be necessary but I feel better about it.

I know everyone loves sexy looking erlenmeyer flasks but I have been using a 1L mason jar In which I heat starter nutrient in the microwave. Granted I don't use a stir plate but this could be used to stir in as well.

k1v1116 said:

it takes a lot longer but I have always used a double boiler for my pyrex flasks, I know it shouldnt be necessary but I feel better about it.

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+1, good safer way to do it. The water does a lot better job at evenly heating it. As stated before, heat on one area could just make the surrounding glass heated and easily crack.

Proof of point- take a bottle- beer, wine, doesn't matter- put in a little oil (sat 1/4'-1/2') and heat a nail until red hot. Drop in the bottle, and after a few seconds run it under cold water. Watch out for glass as the bottom busts out! If done right, you get a nice clean break where the top of the oil was.

BrewBeemer said:

Bobby_M; are there other types of "Pyrex style" of manufactures of borosilicates that we should stay away from preventing the above failure? I myself treat my one litre as a thin wine glass that has lasted for over 30 years. I'm looking at 5 litre in the near future.

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That's a good question. I may be jaded due to the fact that Pyrex the company started making glassware that are NOT borosilicate. Perhaps all labware is the real deal but I want to see it in writing on the flask.

It's a multiple flame source type burner, looks just like your stove. I had it on low with warm tap water in it...it may have had a small crack in it before, but I didn't notice it. I usually make my starters in a pot as well, but for some reason this time I didn't. Oh well, I guess I'm out the money for that one...next time I'll have to get a bigger one

Bobby_M said:

That's a good question. I may be jaded due to the fact that Pyrex the company started making glassware that are NOT borosilicate. Perhaps all labware is the real deal but I want to see it in writing on the flask.

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Interesting news. Do you have something to back that claim up? Pyrex is a registered trademark for 7740 borosilicate glass, and that hasn't changed to my knowledge. If you have something to support that, please share.

Pyrex info

I'm looking for more source info for you because I know I've come upon it before but here's just a quick "care and instructions" excerpt from their website:

"Avoid Sudden Temperature Changes to your Glassware. To avoid the risk of breakage due to a sudden temperature change to your Pyrex glassware, DO NOT add liquid to hot glassware, place hot glassware on a wet or cool surface, or handle hot glassware with a wet towel, wet potholder or other wet cloth. DO NOT place hot glassware directly on a countertop or any metal surface, or in the sink. Allow hot glassware to cool on a cooling rack, dry potholder or dry cloth. Be sure to allow hot glassware to cool as provided above before washing, refrigerating or freezing."

On wiki: Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915. Originally, Pyrex was made from thermal shock resistant borosilicate glass. In 1998, Corning sold its consumer products division which subsequently adopted the name World Kitchen. Pyrex kitchen glassware is now made of tempered soda lime glass. [1]. Pyrex laboratory glassware is still made of borosilicate glass [2].

I suppose I'd trust that a flask would fall under labware so it shouldn't be an issue. I remember shattering my "Pyrex(r)" measuring cup by thinking it was borosilicate.

From Wikipedia

Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915. Originally, Pyrex was made from thermal shock resistant borosilicate glass. In 1998, Corning sold its consumer products division which subsequently adopted the name World Kitchen. Pyrex kitchen glassware is now made of tempered soda lime glass. [1]. Pyrex laboratory glassware is still made of borosilicate glass [2].

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PYREX

So if it is a true Erlenmeyer flask you are probably just fine. (I still think it sucks their kitchenware is no longer borosilicate)

I was told never put these on electric burners ever, gas only. Maybe all that electric over time made a hair line crack?

We use KIMAX in our lab. We can take it from the autoclave to ice water bath and they're pretty solid.