Each of these depressions was about 2 cm diameter and 7 mm deep. We reused these trays may years. We cut ridged flexible sheeting into 8 x 10 pieces and laid it on top of the tray for a cover. That allowed us to stack the trays about 10 trays high. Some days I filled 30 trays.
Most kids do one or two dishes.
Just think how impressed the judge will be if you did lots of work. Go to our Phage Site for more about such experiments. Huff St., Palmyra IN 47164 Please help by sending e-mail containing your ideast.