Australia's Science Forum

Hey everyone

I have a Food Tech teacher wanting to show the kids what effect washing hands has by scraping fingernails before & after.. you know the drill!

I have found some great info on here about taping up the petri dishes & putting them into the incubator at around 30oC (or no more than) but how long do I leave them in the incubator? Until they grow to your satisfaction?

Cheers Kel

Yeah pretty much. You should get some results in two or three days. The longer the more growth of the nasties.

Our food tech teacher did this last week but with washed and unwashed hands, a clean chopping board swab and a kitchen sink swab. Here in the NT nothing is to be incubated above 27 degrees in schools according to out safety manual. We had growth after one night and you could see a difference , but the teacher wanted more so it got left for three days. There were no extra colonies they just got marginally bigger.

I panicked a bit when she called to aske me if they could open the plates after telling her three times befor making them up for her, absolutly not!!! Should have known when she sent the innoculted plates back unsealed it was going to be an issue. Eh! week three and im a little over it already.