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Problem statement

Trish wanted something to use her set of microscopes during her elementary school STEM fair for something fun. We used fresh picked flowers for the low power microscopes, but we wanted something the kids could prepare for the high power scopes.


Staining cheek cells is fun, safe, and personal. We play around with many food colorings, and we got lucky with a BLUE dye that stained the cells RED. Weird right? Turns it the dye had a lot of blue no xx in it and a little bit of red #3 in it.


When we tried the red food coloring, nothing happened. Why? The label showed red dye No. 40. We even tried to mix blue and red, but still nothing. It seemed the Red No. 3 (Erythrosine) was the key, so we went shopping. We went to four stores, and FINALLY found a glass bottle of red food coloring with Red No 3 and Red No 40 together, and it worked, but it still took several minutes before the cells become red enough to see easily. It was also concentrated as all get out, being straight from the food coloring bottle, and difficult to dispense just a small amount.


We ended up with the following recipe:

1 oz dropper bottle of distilled water 10 drops of red dye 10 drops of vinegar (a low pH really helped to activate the dye, or does it activate the cells? anyway it made a big difference)

Put a drop of this onto the slide, and rub the toothpick or q-tip inside your check for 20 ups-downs then stir the droplet on the slide for 10 seconds.

Place a coverslip and put it under the microscope -- easy peasy stained live cells!