By Hippie3 (Hippie3) on Sunday, April 15, 2001 - 02:53 am: Edit

one from vaults
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"First you need to get a hold of some light malt extract powder and some agar agar. Malt extract can be found at your local wine and beer brewing store, and agar agar can be bought from Fungi Perfecti, among other places. You also need some petri dishes, also available from FP, or you can pour your agar into empty jars instead of plates if you prefer. Next, mix three grams of malt extract and three grams of agar (or, if you bought them pre-mixed, six grams of the mix) with 149 ml of water (you should use 149 ml instead of 150 because you want to account for an extra ml of peroxide that you will be adding later). I measure out my water with an empty syringe, keeping in mind that one cc is the same as one ml. I mix and sterilize this solution in a half pint jar, because the amount of agar solution is right for that size jar and because the size of the jar fits well in the pot that I use for sterilizing it. It works for me, but it is not ideal for pouring and I'm sure a better substitute could be found. Anyway, close up your container of agar and sterilize for 45 minutes. I sterilize mine by letting it sit in boiling water in a covered pot, but you could use a pressure cooker if you wanted to. While it is sterilizing, thoroughly clean your plates if you haven't already done so, and stack them on a tabletop. As soon as is possible without burning yourself, move the jar of molten agar to the tabletop, open the lid, and insert a clean thermometer into the agar. Since hydrogen peroxide decomposes at 140 degrees fahrenheit, you need to let the temperature of the agar drop below that before you add the peroxide. Otherwise it will decompose into water and oxygen and be effectively useless. This is why the peroxide is added after sterilization. I have found that my agar begins to solidify at around 120 degrees fahrenheit, so fill a syringe with peroxide and when the temperature falls to 130 degrees, add one ml to the molten agar and stir it in with the thermometer. Then remove the thermometer and pour your plates, stacking them as you go. I can usually pour nine or ten plates with this amount of agar. If you want to make a larger or smaller amount, simply adjust the amounts of water, agar, malt, and peroxide, keeping all the ratios the same."