Why Do Receipts Turn Black?

Have you ever noticed that receipts tend to turn black over time? It’s a common occurrence that has left many people wondering about the cause behind this phenomenon. The answer lies in the type of paper used for receipts and the chemicals involved in printing.

Receipts are typically made using thermal paper, which is coated with a chemical called bisphenol A (BPA). This coating allows for the printing of text and images when heat is applied, hence the name “thermal paper.” However, over time, this chemical reacts with elements like oxygen and light, resulting in the characteristic blackening of the paper.

The reaction between BPA and oxygen causes the paper to slowly oxidize, leading to the darkening of the print. Additionally, exposure to light speeds up this process, which is why receipts stored in wallets or exposed to sunlight tend to turn black faster. The high temperature and humidity levels in certain environments can also accelerate the oxidation process.

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Furthermore, the paper’s reaction to heat causes it to darken. When thermal printers generate a receipt, they use heat to activate the BPA coating, which creates the printed content. However, excessive heat, such as exposure to direct sunlight or contact with hot surfaces, can cause the paper to turn black more quickly.

The blackening of receipts has led to concerns about the potential health risks associated with BPA exposure. Some studies suggest that BPA may have adverse effects on human health, including hormone disruption. As a result, many countries have introduced regulations to limit the use of BPA in thermal paper, but it is still widely used.


1. Can I prevent my receipts from turning black?
Unfortunately, the blackening of receipts is inevitable due to the chemical reaction between BPA and oxygen. However, proper storage in cool, dark places can slow down the process.

2. Are blackened receipts still valid for returns?
Yes, despite their appearance, blackened receipts are still valid for returns and warranty claims. Retailers can scan them or manually input the necessary information.

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3. Can exposure to BPA from receipts be harmful?
The exposure to BPA from receipts is minimal and unlikely to cause immediate harm. However, it is advisable to limit direct contact, especially for individuals who are pregnant or have existing health concerns.

4. Are digital receipts a better alternative?
Digital receipts eliminate the use of thermal paper and the associated BPA exposure. They offer a more sustainable and convenient option, reducing paper waste.

5. How long does it take for a receipt to turn black?
The time it takes for a receipt to turn black varies depending on factors such as storage conditions, exposure to light, temperature, and humidity. Generally, it can take a few weeks to several months.

6. Can I recycle blackened receipts?
Yes, blackened receipts can be recycled. However, it’s always best to check with your local recycling facility for specific guidelines.

7. Is there a way to remove the blackening from receipts?
Unfortunately, there is no reliable method to remove the blackening from receipts. The chemical reaction is irreversible, and any attempts to remove it may damage the paper further.

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