Calibrating microwave-incubation times for droplet immunostaining: reversible Thermo-Paint as a low cost alternative.

Reversible Thermo-Paint R50 (Manufactured by Thermographic Measurements, Ltd., Burton, UK and imported in The Netherlands by Blanken Controls, Loenen (Vel.)) has a yellow colour that changes to orange when a temperature of 50 degrees C is reached. Microscopical glass slides can be painted with R50. Under the droplet on the painted slide an orange disk will appear at the moment the droplet has reached the temperature of 50 degrees C. This test provides us with information about how much energy per minute is available to be absorbed by that precisely defined "test droplet" using a certain setup of the microwave oven. The obtained data can be used to calibrate incubation times for various microwave ovens. The results explain why, when short cycle times are used, immunostaining is highly reproducible.