what is the difference between a porcelian sealer and a granite sealer?

Answer 1

Porcelain is not porous, so if you are sealing tile you would only seal the grout. Where as un-polished granite is porous you would seal the tile and grout in one application.

Answer 2

I've never heard of a porcelain sealer other than the brand name product called Porcelain Sealer which is used to seal granite and other porous stones.
By definition porcelain is not very absorbent, it should absorb less than 1/2 percent of its weight in water in order to be called porcelain, otherwise it's ceramic. You should never need to seal porcelain.

Stone on the other hand is very porous and absorbent and therefore needs to be sealed. If you're working with granite or another natural stone look for a product which says it should be used to seal natural stone. If someone is telling you you need to seal porcelain tile there must be some very specific use or reason why you need to seal it.

Answer 3

It's the bonding agent.