At room temperature, the recording layer is transparent. When suddenly heated to 110 C and cooled, however, the crystal structure becomes irregular. This creates gaps in the resin allowing for the penetration of light which reflects back in diffused white. Taking advantage of this characteristic, heat is applied only where the desired symbols or graphics should appear, and they show up as milky-white writing. With a subsequent heat application of 70 - 100 C, the crystals realign, thus closing the gaps.
Transparency is restored and the printing on the card disappears.
When heated, leuko dye combines with the color activator and changes color. This is the process used in normal thermal paper. In order to erase printed letters in a rewritable medium, the color activator needs to be disassociated from the dye. By rearranging the molecular structure of the color activator, Ricoh has succeeded in developing the world's first technique by which the activator crystallizes, removing itself from the leuko dye and thus removing the color. The black-letter display can be rewritten to with ease because the recording material loses color at temperatures slightly below that required to make the color appear.