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BabuFrik
Logs, wood chips & sawdust

Registered: 01/28/20 
Posts: 26
Loc: Kijimi
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Re: How to prevent condensation in agar plates [Re: bathingAPE]
#26553353 - 03/23/20 03:51 PM (3 years, 10 months ago) |
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This is something I deal with in my lab all the time. If you use a pre-heated hot water bath to bring your temperature down to around 50-60°C right after it comes out of the pressure cooker, you can walk the solution down to a low temperature that is cool enough to hold in your hand and add temperature-sensitive antibiotics to it if that is something you do.
Reducing or outright preventing condensation on your plates is a cumulative effort but the steps involved are simple enough to follow for professionals and amateurs alike. Combine the lower solution temperature you get from the hot water bath with stacking your plates, a low RH in the room you are working in, and keeping the surrounding temperature the same throughout the polymerization process to help to reduce it. Lastly, if you have a flow hood or Bunsen burner and are confident in your equipment and method, you can crack the lids as the agar polymerizes to help release some of that local humidity caused by the cooling process.
I pour 20-40 plates about every two weeks or so in my lab and this method is very reliable. The only plates that see any condensation are those that sit on the top of the stacks and I can get rid of that by either cracking them in the hood for a little while, or by putting a 300 mL Erlenmeyer flask filled with hot water on the top. Please feel free to ask me if you have questions about this because I used to do this stuff as an amateur grower before I became a graduate student in a research laboratory and I am able to replicate the same process at home.
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BabuFrik
Logs, wood chips & sawdust

Registered: 01/28/20 
Posts: 26
Loc: Kijimi
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Re: How to prevent condensation in agar plates [Re: seagu]
#26554999 - 03/24/20 11:58 AM (3 years, 9 months ago) |
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Quote:
seagu said: so letting poured plates sit for a few minutes open in front of the flow hood after they gel up? Will this also get rid of the condensation from being stored in the fridge?
Let me make sure to double down on saying that this is a cumulative effort. There is no single solution unless you are lucky enough to have inadvertently accounted for some of the other variables. Pouring a cooler solution closer to its polymerization point, a working area with low RH, consistent temperature conditions throughout the process, and stacking plates as you pour should combine to solve most of the problem even into refrigeration. There might be a little fogging but that should abate normally. Heavy droplets do not usually form unless there is operator error, and that usually involves solution temperatures that are too hot or mixes that are too wet.
During the hot months when RH is in the 80s and climate control is not buffering it well, I pour a smaller number of plates unstacked and leave the lids cracked as they polymerize. The science behind this involves eliminating the local humidity in the dish released by the warm agar that would otherwise condense due to the higher humidity. When the lids are on there is only a small amount of air to buffer that extra moisture so it condenses, but leaving the lids cracked as the agar polymerizes allows the moist air to escape into the larger volume of air in the hood.
I have also poured and stacked as usual, then cracked the lids afterwards to try and evaporate the condensation like you are saying. That version takes longer when you have big droplets and the added time can cause the agar to dry out a little. That drying part is bad for me because I need precise concentrations for my research, but it is not a big concern for my gourmet workups since I am not collecting data. I won't recommend this version for pouring plates because the lid has to stay open for longer to get rid of more condensation. I see less condensation overall when I let the agar gel up while the lid is cracked. You can still do this to mitigate moisture that appears from cold storage, just let your plates warm up first to give the agar a chance to reabsorb some of it. If you have a big problem with condensation and you are lazy, you can always use 99% isopropanol to spray the lids and break surface tension of the water, forcing it to evaporate more quickly, but that is major corner cutting that requires some other precautions involving the spray bottle and filling it to be free of particulates.
For clarity, "cracked" means that the lid is partially off but not fully removed, something like 25-50% off. There is a non-zero risk associated with this technique, but if you are not an amateur, take all of these factors into account, and are confident in your equipment and technique, then you should trust in yourself not to be a vector. Everyone should be doing plate exposure testing on their flow hoods anyway to see if organisms are making it through the filter, so trust in the equipment to do its job and help overcome problems like these.
-------------------- If you are interested in trading mycology club tshirts, or want to help me buy one from your club, send a DM my way
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BabuFrik
Logs, wood chips & sawdust

Registered: 01/28/20 
Posts: 26
Loc: Kijimi
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Re: How to prevent condensation in agar plates [Re: Smartattack]
#26558521 - 03/26/20 07:31 AM (3 years, 9 months ago) |
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Quote:
Smartattack said: I just put mine upside down on my table that happens to have a small space heater under it. You are basically running the physics in reverse, the condensate evaporates and re-condensates on the now cooler agar and if left overnight will just be re taken up by the agar. Works for me many times a week. All my top of stack plates condensate so they get this treatment.
This reads like a good technique and the thermodynamics of this are sound. A light warming element underneath the plates should conduct heat into their systems. That gentle heating will support movement of air through the space in the plates' wells as they warm. My PI never passes up a chance to tell us that "heat goes out" of a system. To his credit, the localized humidity should be carried away with the exiting warm air into the cooler surroundings. I bet that this technique is also successful because most of the conduction is traveling through the top of lid and the condensation on it because the plates are upside down. I do something somewhat similar by stacking plates next to a Bunsen burner and rotating them over a time interval to help remove minor fogging around the edges when it is very humid.
This was interesting thank you for sharing your experience! Those top plates are the bane of people everywhere!
-------------------- If you are interested in trading mycology club tshirts, or want to help me buy one from your club, send a DM my way
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