How to restore the handwriting of thermal paper rolls

Put the thermal paper rolls whose handwriting has receded into the incubator,control the temperature scale of the incubator.The temperature is usually 75 to 100 degrees.When the thermal paper rolls is heated, the original handwriting is white and the original blank is black,and then the handwriting appears.If the handwriting is not clear, you can use the color difference before and after coloration to input the image into the electronic computer through a high-pixel digital camera or scan directly with a scanner.