As its name suggests,a thermal printer is one that prints on paper using not ink, but selective heat sequences. Often used for restaurant and retail receipts, you can tell a thermal printer apart from a non-thermal variety because the former prints extremely fast–almost instantly, in fact. In order to be used for such printing in the first place, thermal paper is designed to be extremely heat-sensitive, so if you expose a thermal receipt to a heat source, it may turn completely black. It may still be possible, however, for you to see the receipt again.
Make a digital image of your receipt using a digital camera or, better, a scanner. Photograph the image using your camera or lay it flat on your scanner’s bed and press the “Scan” button. Save the file on your computer as a .JPG image.
Open your file in a photo editing program, be it a for-purchase one like “Adobe Photoshop” or your computer’s default, “Paint.” Right-click your file (hold down “Ctrl” while you click if you use a Mac) and select the name of your photo editing program from the “Open With” sub-menu.
Invert the colors in your image to attempt harvesting your receipt information. If you’re using either the Microsoft or Apple variant of a basic “Paint” program, drop-down the “Image” menu and click “Invert Colors.” If your receipt is salvageable, its original information will show in black on the now-white image.
Print your inverted color image and store it in a safe place. Although a document printed on standard paper won’t be as sensitive to heat as a thermal receipt, you must still take care not to damage it.