Will paint remover hurt a porcelain tub? Need to get blue pain past its sell-by date a tub. ...

Need to get blue pain past its sell-by date a tub. Can I use paint remover on porcelain?

yes - but dilute it with a bit of dampen.

Too many potential reasons to not use it. Even more trouble if it does do wreck. I wouldn't use it. I would use just water or a solvent of some sort depending on the type of paint, latex or solvent base paint.