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Why is the erlynmeyer style flask the automatic go to for yeast starters? I know people use other containers besides flasks, and some flasks dont have flat bottoms but is there something special about the shape or angle of the sides? Just thought this was a good question to throw out there and see what comes back!

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I'm sure there are many positives, but one negative is that the conical shape means a smaller surface area for gas exchange, making it less than ideal here. –  mdma May 5 '13 at 5:37
    
It's a good question, but very easy to answer en.wikipedia.org/wiki/Erlenmeyer_flask –  paul May 6 '13 at 21:17
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So you can pretend you're Walter White! –  Dan May 21 '13 at 10:57
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3 Answers

up vote 11 down vote accepted

Speaking from experience as a molecular biologist. Erlynmeyer flasks are nice for a couple of reasons. The main alternative being a standard beaker which is essentially the same size at the top and the bottom. First off the neck size makes it easy to hold in the hand. Second a smaller opening reduces the chance of getting airborne material into the flask. Third try swirling around some liquid in a normal beaker and then an erlynmeyer flask, the narrow neck on the flask keeps the liquid inside the vessel better than a beaker. Fourth, when doing biological cultures you want to keep the media aerated and the wide bottom of the flask allows you to keep a high surface area with which to introduce air. Finally, the narrow neck allows us to use smaller stoppers which reduce the chance of contamination.

Altogether these reasons are why we use erlynmeyer flasks in the lab.

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I agree, but to get a large surface area, you'll need a much larger flask than the size of the starter. E.g. for a 2l starter, a 2l flask gives a small surface area, although this probably is a not a concern when stirring. –  mdma May 5 '13 at 20:58
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You are absolutely right. The bigger the better for surface area. We often use shakers instead of stir plates for cultures. The beauty of the erlynmeyer flask is that they don't spill easily when the liquid inside is vigorously mixed. Try the same thing with a beaker and you would have one major mess. –  Chris Plaisier May 6 '13 at 20:09
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The main reason that I know of is that Erlynmeyer flasks are normally pyrex, or made from a substance which means you can heat it on the stove so you can reduce the risk of getting unsanitary conditions in your starter.

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a downvote and no comment doesn't help anyone. –  mdma May 6 '13 at 21:11
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No. The main reason you use an Erlenmeyer flask over other lab glassware is it's shape, not the material - easy to stop, easy to swirl, stable so it won't tip and spill. You can get all kinds of lab glassware made from borosilicate glass. This type of glass is resistant to thermal shock, so you can rapidly heat and cool it. Pyrex is just a brand, and they make a lot of glass that is not borosilicate. –  paul May 6 '13 at 21:13
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Thanks for the clarification, I've never seen a non-flask shaped brosilicate or other thermal shock proof glass vessel aside from pots. –  DougEdey May 6 '13 at 23:09
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@DougEdey - I agree. While in a lab there are many vessels that are heat proof, I don't think there are so many for the homebrewer that can be obtained easily. –  mdma May 7 '13 at 13:48
    
@DougEdey: I'll bet you have -- Pyrex measuring cups. They may not be laboratory-grade, but they're certainly thermal-shock resistant. –  TMN Jun 3 '13 at 16:15
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While starters ideally don't make use of an airlock to promote maximum O2 exchange, some people prefer to use an airlock to counter wild yeasts and other contaminants. The narrow neck on the conical flask makes using a stopper and an airlock much more practical.

Alternatives to rubber stoppers are foam stoppers which permit gas exchange. Again, these would be impractical for use in a beaker or other wide-mouthed vessel, but work well in a conical flask.

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