Here is a thread that you might find helpful for starters.

Here is a link that might be useful: tile

One of the most important comments on the link is about overlays which "look" like tile. Not only is the dot matrix of printing seen, but you can see where they wrapped the tile, clipped paper for rounded trim.. I bought a huge amount, along with trims. All taken back. The overlay was chipping paper on back edges and sides. I couldn't imagine how this would stand up to much of anything.

Out of curiosity I went back to the tile displays and it was amazing how many products were being sold with this process. Now I'm confused as to what porcelain is.

Check and recheck to identify how the tile is made and flaws. Not all is done the same way, but one type of what I experienced could make it's way into a tile project.

Thanks for the info. Knowning what to look for is helpful. I like the look of the polished travertine but haven't seen the polished in a porcelain tile yet. Looking at samples next week