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RedRum42
CleanJunkie


Registered: 01/05/15
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Loc: Minneapolis
Last seen: 9 years, 8 months
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Disappearing agar... evaporation?
#21301962 - 02/20/15 01:12 AM (9 years, 10 months ago) |
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I got some pre poured agar petri dishes, noc'd them, and let them sit for about a week. Some small growth within first 3 days, but then it seems to have stopped. And the agar that used to be at least a few cm thick is now paper thin.. What the hell happened? Agar evaporation?
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Straya
Wot?!


Registered: 03/04/12
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Re: Disappearing agar... evaporation? [Re: RedRum42]
#21302149 - 02/20/15 04:05 AM (9 years, 10 months ago) |
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Hmm this happened to me a few months ago with Ps. sub. Following.
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TheMustardTiger


Registered: 08/19/13
Posts: 4,700
Loc: Sunnyvale Trailer Park
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Re: Disappearing agar... evaporation? [Re: Straya]
#21302196 - 02/20/15 04:48 AM (9 years, 10 months ago) |
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Sounds like the water to agar mixture was high. I pour my plates thin on purpose so maybe the vendor you ordered them from did as well. Always post pictures of possible.
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Straya
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Quote:
TheMustardTiger said: Sounds like the water to agar mixture was high. I pour my plates thin on purpose so maybe the vendor you ordered them from did as well. Always post pictures of possible. 
You think too much water in the solution? Would you say it is better to have more Agar than not enough?
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TheMustardTiger


Registered: 08/19/13
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Re: Disappearing agar... evaporation? [Re: Straya]
#21302208 - 02/20/15 04:57 AM (9 years, 10 months ago) |
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Quote:
surf_ride28 said:
Quote:
TheMustardTiger said: Sounds like the water to agar mixture was high. I pour my plates thin on purpose so maybe the vendor you ordered them from did as well. Always post pictures of possible. 
You think too much water in the solution? Would you say it is better to have more Agar than not enough?
I like thin plates because the wedges are easy to handle and I buy commercially prepared nutrient agar which is a little pricey so I like to conserve as much as possible. Nothing wrong with thinly poured agar.
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Straya
Wot?!


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Psilicon
Really Nice Guy


Registered: 08/26/12
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Re: Disappearing agar... evaporation? [Re: Straya]
#21302333 - 02/20/15 06:17 AM (9 years, 10 months ago) |
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Quote:
surf_ride28 said:
Quote:
TheMustardTiger said: Sounds like the water to agar mixture was high. I pour my plates thin on purpose so maybe the vendor you ordered them from did as well. Always post pictures of possible. 
You think too much water in the solution? Would you say it is better to have more Agar than not enough?
I agree with mustard, but if you're asking if it's better to have more agar in an agar solution than to have too little, I'd say that it's equally inconvenient to have 1% as to have 3%, but for different reasons.
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RedRum42
CleanJunkie


Registered: 01/05/15
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Re: Disappearing agar... evaporation? [Re: Psilicon]
#21302449 - 02/20/15 07:08 AM (9 years, 10 months ago) |
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They were pretty thick to begin with and now are paper thin. Will post pics in a minute
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RedRum42
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Registered: 01/05/15
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Loc: Minneapolis
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Re: Disappearing agar... evaporation? [Re: RedRum42]
#21302538 - 02/20/15 07:39 AM (9 years, 10 months ago) |
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after about 8 days.

what they looked like originally
Edited by RedRum42 (02/20/15 07:40 AM)
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Psilicon
Really Nice Guy


Registered: 08/26/12
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Re: Disappearing agar... evaporation? [Re: RedRum42]
#21302567 - 02/20/15 07:52 AM (9 years, 10 months ago) |
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Oh, that just dried out because you don't have the edges wrapped.
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CliftonGK1
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Registered: 03/27/13
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Re: Disappearing agar... evaporation? [Re: Psilicon]
#21302856 - 02/20/15 09:07 AM (9 years, 10 months ago) |
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Get some parafilm, or even just wrap the edges with a tight stretch of plastic wrap or electrical tape. Something to seal the plates and keep the evaporation down.
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Hashish
Knowledge is Power



Registered: 12/04/14
Posts: 492
Loc: 2 the Moon
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Re: Disappearing agar... evaporation? [Re: CliftonGK1]
#21303085 - 02/20/15 09:53 AM (9 years, 10 months ago) |
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use parafilm or micropore tape. i use glad cling wrap to wrap my plates because cling wrap is permeable. NOT saran wrap, get cling wrap!
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taGyo
Strainiac/AMU



Registered: 10/16/14
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Loc: Journal Land
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Re: Disappearing agar... evaporation? [Re: Hashish]
#21303129 - 02/20/15 10:02 AM (9 years, 10 months ago) |
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Go to walmart.
Buy transpore tape.
Tape the sides on opposite ends. Works like a charm. When you're ready to open the petri just stick something in between the open space on the sides and rip the tape off. Don't bother cleaning the tape, you have a high chance of cracking the petri.
I used to do this before I got parafilm. The lid keeps all contams out, the tape is just to hold it in place.
Transpore isn't as sticky as Scotch or other brands. I did this with Scotch and it failed miserably. Extremely hard to take off.
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Hashish
Knowledge is Power



Registered: 12/04/14
Posts: 492
Loc: 2 the Moon
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Re: Disappearing agar... evaporation? [Re: taGyo]
#21303141 - 02/20/15 10:05 AM (9 years, 10 months ago) |
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i think thats whats hes doing now
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taGyo
Strainiac/AMU



Registered: 10/16/14
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Re: Disappearing agar... evaporation? [Re: Hashish]
#21303161 - 02/20/15 10:08 AM (9 years, 10 months ago) |
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Always worked for me, I see he's using scotch though.
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PsyCLown89
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Registered: 08/18/14
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Re: Disappearing agar... evaporation? [Re: taGyo]
#21304489 - 02/20/15 02:41 PM (9 years, 10 months ago) |
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You are worrying me now, I made some plates 5 days ago and just used some micropore tape on either side of the plate to keep the lid in place.
I have them stored upside down as well (so the agar is on the "top") as apparently that is how you are meant to store petri's - reason being if there is any moisture, it can't pool and drop onto the agar 
Mine look fine still though, don't seem to be drying out like yours.
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bootster


Registered: 02/22/11
Posts: 1,531
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Re: Disappearing agar... evaporation? [Re: PsyCLown89]
#21304644 - 02/20/15 03:13 PM (9 years, 10 months ago) |
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Is agar a liquid or a solid? I would call it a gelatin. So is it evaporation or sublimation? You've got me thinking on this one.
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Psilicon
Really Nice Guy


Registered: 08/26/12
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Re: Disappearing agar... evaporation? [Re: bootster]
#21304693 - 02/20/15 03:22 PM (9 years, 10 months ago) |
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It's a gel, not gelatin. Check the link in my sig.
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bootster


Registered: 02/22/11
Posts: 1,531
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Re: Disappearing agar... evaporation? [Re: Psilicon]
#21304927 - 02/20/15 04:23 PM (9 years, 10 months ago) |
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Quote:
van der griegen said: It's a gel, not gelatin. Check the link in my sig.
Gel/Gelatin
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Psilicon
Really Nice Guy


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Re: Disappearing agar... evaporation? [Re: bootster]
#21304939 - 02/20/15 04:27 PM (9 years, 10 months ago) |
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All I'm seeing there is the wiki for gel, which is a class of substances, but not for gelatin, which is a specific compound in that class, separate and distinct from agar. And anyway, the water held within gels like gelatin and agar is liquid, so it's evaporation. If the water were frozen into a crystalline structure like with ice, it would be sublimation--doubly so because the matrix is shattered by the ice crystals to the point that when it thaws the water will leak out.
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