Exothermic Reaction

I poured some bleach on a rag and started scrubbing.

The rag got really hot after 30 seconds.

Just to make sure it wasn’t the friction between the rag and the toilet seat, I took the rag, set it on the counter, and poured bleach on one part of it.

Sure enough, the part I poured bleach on was hot to the touch, unlike the rest of the rag.

The rag was part of a pair of old jeans.

Is there something in jeans that reacts with bleach?

Cotton?

Pretty much everything. Bleach is a strong oxidizer.

More likely the blue dye. The whole point of bleach is to turn colored chemicals into colorless or white chemicals, and when it works, that is a chemical reaction, and it may be exothermic.

when you use bleach to bleach something whiter, you use it in a diluted manner (from the already diluted concentration in the bottle).

there was a fashion, to severely spot fade jeans, with a more concentrated amount of bleach. if someone did this with too concentrated amount and/or for too long then they would have a hole in the fabric where the bleach oxidizes the fibers to death.

Bleach works fast on jeans. I dribbled a bit of fairly strong bleach water on one leg of a pair of jeans, and went inside immediately to wash them, but it left a very prominent streak.

I thought maybe I should do some more on that one leg, washing often between applications, and see if I could start a fashion for one-leg spot-faded jeans. Is anybody with me?