What exactly are stains? Why do they stay on something seemingly forever? Are they remnants of the liquid that was spilled still on the clothing?

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So I was at work today and noticed a coffee stain on the carpet. The boss said it was from 10 years ago. It had me thinking. Are there still particles and remnants of that coffee from 10 years ago? If so, why? What makes it stain?

In: Chemistry

A stain often occurs when a liquid absorbs into a surface or something rubs off onto another surface.

The carpet will have been “cleaned” from vacuuming however it won’t have been “deep cleaned” (which is why the stain is still there) as the carpet has not been washed with water and cleaning chemicals.

Also some stains are more stubborn than others. Surface stains like grass marks on denim will wash out easily whereas if you get grease on your clothes and wash with detergent it likely won’t remove the stain. However if you add washing up liquid to the stain and then wash as normal the stain should come out because the washing up liquid is designed to clean grease.

Some stains can be removed with a little water and soap. Some require specific chemicals to target the problem.