Anyone who's tried to return something with a receipt pulled from a wallet a few months later knows the frustration — the paper's still there, but the print has faded to nearly nothing. This isn't a defective printer; it's how thermal paper is designed to work.
How thermal printing actually works
Thermal receipt paper is coated with a chemical that darkens when heated by the print head — no ink involved. That same chemical reaction that creates the print continues to react slowly to heat, light, and humidity over time, which is exactly what causes the gradual fading.
What speeds up fading
Direct sunlight, heat (a car dashboard, a wallet in a hot pocket), and contact with certain plastics or other receipts can all accelerate fading — a receipt left in a hot car can become unreadable within weeks rather than months.
The practical fix: don't rely on the paper long-term
For anything you might need later — a warranty claim, a business expense, a larger purchase — photograph or scan the receipt soon after getting it, rather than assuming the paper copy will still be legible when you need it.
For businesses issuing receipts
If customers regularly need receipts for warranty or expense purposes, offering an emailed PDF alongside the printed thermal slip solves the fading problem entirely — the digital copy doesn't degrade the way thermal paper does.
Storage matters if you're keeping originals
If a receipt needs to be kept as a physical original for some reason, store it away from direct light and heat, and don't stack it directly against another thermal receipt — some can react with each other and fade faster in contact.