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345536345
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Inconsistent agar firmness in slants?
#26452383 - 01/25/20 06:32 PM (4 years, 4 days ago) |
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When making agar for slants I think I'm somehow not fully dissolving the MEA agar fully such that after pouring, PC, and cooling, some are really soft while others are more firm and "normal". Any tricks to get the MEA fully dissolved? Should I be using hot water on the initial mix?
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Growtech
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Re: Inconsistent agar firmness in slants? [Re: 345536345]
#26452389 - 01/25/20 06:37 PM (4 years, 4 days ago) |
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How are you doing it exactly? If you are just tossing ingredients cold into pressure cooker? I've boiled MEA and agar in a pot before to make sure it's mixed up property before pressure cooking. But I decided that was ultimately an unnecessary step. You can mix it up in the microwave just fine (just stay close and watch so it doesn't boil over). Shake it up, microwave it for a bit... shake it again... microwave it some more until it boils (again, don't let it boil over though). Then shake it again when you take it out. Should be good and mixed up and ready for pressure cooker at that point.
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345536345
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Re: Inconsistent agar firmness in slants? [Re: Growtech]
#26452395 - 01/25/20 06:41 PM (4 years, 4 days ago) |
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My last batch I measured out the appropriate amount of powder on a gram scale and then added the appropriate amount of distilled water (also weighed) to it. I used a spoon to stir it up to what seemed like it was dissolved and then poured into individual centrifuge tubes before putting into the PC.
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345536345
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Re: Inconsistent agar firmness in slants? [Re: 345536345]
#26452402 - 01/25/20 06:43 PM (4 years, 4 days ago) |
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So basically I should be heating it up / shaking it at some point to ensure it's fully dissolved? Certainly not a problem to do but just seeing if that's what the normal approach is b/c my current approach isn't working...
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A.k.a
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Re: Inconsistent agar firmness in slants? [Re: 345536345]
#26452415 - 01/25/20 06:54 PM (4 years, 4 days ago) |
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Yeah it’s supposed to be heated before pc. I’m not sure why but it makes a big difference in clarity for me. Like he said above I microwave then swirl and repeat.
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LAGM2020     
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345536345
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Re: Inconsistent agar firmness in slants? [Re: A.k.a]
#26452422 - 01/25/20 06:57 PM (4 years, 4 days ago) |
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Excellent - thanks. I knew I had to be doing something wrong. Thanks folks!
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Sir Pentinite
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Re: Inconsistent agar firmness in slants? [Re: 345536345]
#26452509 - 01/25/20 07:51 PM (4 years, 4 days ago) |
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Agar doesn't dissolve in water until something like 180°F or higher. I would suggest heating it in a saucepan until dissolved and then cooling to roughly 120°F before loading the vials for slants. It doesn't solidify again until the high 100-teens.
-------------------- "I thought to myself 'Boy, I'm sure glad there's nobody here to see this because this is exactly the sort of thing that gets people riled-up and they assume you're dying and that something has to be done. Where if you're alone, you know, you either come through it or you die, but in any case you avoid the fuss.'" - Terrence McKenna
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rido



Registered: 05/13/19
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Re: Inconsistent agar firmness in slants? [Re: 345536345]
#26452543 - 01/25/20 08:09 PM (4 years, 4 days ago) |
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Quote:
345536345 said: My last batch I measured out the appropriate amount of powder on a gram scale and then added the appropriate amount of distilled water (also weighed) to it. I used a spoon to stir it up to what seemed like it was dissolved and then poured into individual centrifuge tubes before putting into the PC.
There's your problem. As others mentioned the agar doesn't dissolve until 180°F. Get it all melted, mix, then pour after it's cooled a bit and PC as usual.
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345536345
Pan parent!



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Re: Inconsistent agar firmness in slants? [Re: rido]
#26452565 - 01/25/20 08:31 PM (4 years, 4 days ago) |
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Makes complete sense. I make and store 500ml pyrex bottles all the time and so I'm familiar with the melt and solidification temps. When it's all in one bottle it doesn't matter b/c the PC is going to do it all for you - just need to swirl a bit when coming out and/or when reheating if you're saving it off.
For some reason though my brain went out the window when doing slants. Thanks!
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