purplemama Posted June 26, 2012 Share Posted June 26, 2012 I tried for the 3rd and last time to use agar to make petri dishes for bacteria experiments. First I got the kind in a bottle that you just "melt and pour". It never congealed enough to streak anything. Then, twice I have tried the powdered agar that you have to boil. It never congealed correctly either. I never realized it would be so hard. I was a science major in college...I used these things all the time, but I cannot seem to make a petri dish with agar in it. Fortunately, I have found an experiment book that uses Jello and SlimFast for a substrate, and I am moving on. I would still like to know why, if I am following the directions, my agar didn't set!? Quote Link to comment Share on other sites More sharing options...
AnnaM Posted June 26, 2012 Share Posted June 26, 2012 The only thing I can think of is bad agar? I have never had agar that didn't set. I would love to know how your homemade stuff works though! Quote Link to comment Share on other sites More sharing options...
ChrissySC Posted June 26, 2012 Share Posted June 26, 2012 I found this link while browsing ... http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_Agar.shtml Quote Link to comment Share on other sites More sharing options...
purplemama Posted June 26, 2012 Author Share Posted June 26, 2012 The agars I have used are all from different manufacturers and so it can't be just bad agar. I think I must be the problem...But I am following the directions! Quote Link to comment Share on other sites More sharing options...
cmarango Posted June 26, 2012 Share Posted June 26, 2012 Are you letting it cool at room temperature? From my recollections, we would boil the agar, then add about 0.5 inches to a dish, let it cool out on the bench, and then refrigerate. Quote Link to comment Share on other sites More sharing options...
Miss Tick Posted June 26, 2012 Share Posted June 26, 2012 I'm a long time failer at Jell-O, sounds like I should probably avoid agar too! Quote Link to comment Share on other sites More sharing options...
brendag Posted June 26, 2012 Share Posted June 26, 2012 We had the same problem with the agar that came in our Fungus and Bacteria Magic School Bus Science Kit. It was frustrating to me. My dh who is the science guy says that is part of science. The kids just rolled with it. :tongue_smilie: Good luck!! Brenda Quote Link to comment Share on other sites More sharing options...
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