1. Initially, thermal paper was tested within the microwave. When it was heated nothing occurred. I thought that this might be because there was no moisture inside the microwave, so I therefore decided to wet the paper. This caused water marks to appear.

2. Working as a cashier I knew that receipt paper was heat sensitive. Although it would be hard to attach this to a 6x6 inch square, I decided to try this material. when I heated the paper, spots appeared, but they were not permanent. After soaking the slips in water much of the chemical that caused the change had washed off.

3. I then decided to test receipt paper in which only the back was wetted. This was done by floating the sheet in a water bath. The results of this were both permanent and distinct, but the receipt paper was not large enough.

4. Next, I tried fax paper which was exactly the same as the receipt paper. This worked perfectly, and was what I based the rest of my experiment on.