An international network of/for intelligent organisms
I am trying to do an experiment about the extracellular slime trails and external memory of physarum polycephalum. For that I am using 1-2% agar in petri dishes but some of the newly made ones are just a couple of days old and they have already evaporated. It starts with the agarose gel getting wrinkly and then water vapor gets to the lid of the petri. The slime that I was experimenting on has dried out because the gel had completely evaporatud under it. Went from a 4-5 mm layer to 0 mm in thickness. What could be causing such quick evaporization, some of my other ones don't dry that easily? I used more agar in this newer batch and I have left the lid open for an extended period because the images could not be taken with the fog on the lids.
I replied via email but so others can see. Agar dries out fast, to deal with it you can enclose the whole setup ( camera included ) in a humidity chamber - which can just be a cardboard frame lined with plastic bag and a pad of wet cloth/paper under the samples.
You can also leave the lid on your dishes, as long as you don't get too much temperature fluctuation a couple of 1mm holes drilled around the edge of the lid will keep in moisture but allow enough air exchange to stop fogging.
I made my agar thicker - 1cm and put pieces of it in a tray with 0.5cm water ( which you will have to top up daily ), a square of paper or cellophane on the top of each piece might give you a cleaner background if you're filming for analysis.