Art Todesco wrote:
Does anyone know of a chemical method of
smoothing out the inside of a toilet
trap? I have 3 almost identical toilets
and most suffer from too small opening
through the porcelain. Recently, one
developed the ability to catch toilet paper
and hold it in place. I am guessing the
finish has gotten rough.

More likely accretions of hard water deposits.

Muriatic acid should take care of it.