Hey all,
I was frustrated with all of the water condensation I've been getting with my agar plates.
Since I use a pour method, I've been pouring the agar while still hot into the sterile plates and as they cool they give off a lot of vapor which condenses on the lid of the plate.
While this is mostly an annoyance, the mobile water droplets can act as a vector for contamination to travel within the plate. The moisture can also form an airtight seal of liquid water around the edge of the plate, preventing gas exchange. Not good.
So I started googling around and found a few tips which I wanted to share with you all ...
Prevention
These steps help prevent condensation if you haven't poured your plates yet. Please note that these tips may not be applicable for no-pour methods.
- Let your agar cool to 127-131F (53-55C) before pouring. This will minimize evaporation but means you'll have to act fast once the agar reaches this temp since it will start to solidify at 122F (50C). I like to fill the pressure cooker with water to the height of the agar and can then use an instant read thermometer to check the water temp around the agar jar before removing it ... bearing in mind that the agar will be slightly hotter than the water it's sitting in. A hot water bath or well calibrated hot plate would be very useful to slow the cooling rate of the agar container and keep it in that critical 53-55 C range.
- Stack the plates and put an empty plate on the top for additional insulation. Stacking plates in this way slows the cooling process and encourages condensation on the sides rather than top or bottom of the plate. This has sometimes helped me but seems less reliable.
- Leave the plates partially open until they solidify. Not for the faint of heart! If you're using this method, I would pour extra plates to cover contamination losses, let the plates cool with some sterile cover above them (if using a still air box), and gestate the plates (after cooled and covered) for a few days to see if any contamination is present before inoculating. This should be very effective in reducing condensation but is time consuming and more prone to contamination.
Mitigation
If your plates are already poured and have condensation in them then you can do the following to mitigate the impact of having free flowing water in your plate ...
- Store the plate upside down. This prevents the water from contacting the agar and mycelium. So if there is contamination present it should not be able to use the water movement to spread.
- Temporarily remove the condensation by placing a warm object on the plate for 10-15 min. I like to use a mug of hot coffee. The gentle warmth from the cup will cause the water droplets to evaporate without harming the mycelium. The condensation will unfortunately return but it will provide several minutes of clear viewing, which should be enough time to assess the plate. Please note that this will not work if you're storing your plates upside down.
adadada
Edited by adadada (09/13/16 08:10 AM)
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