Use the same sanded grout, mixed the same way, throughout. No admix. There's no need for it. TEC XT is one of the most highly modified grouts around. Not only is there not a need for any admix, but it may actually react with the polymers already in the grout. So I guess the short answer is "OMG dont' do that"! :-)

I'm going to give you a little hint that not even very many installers know. Everyone thinks that the solvent based sealers are the cat's meow, and as sealers, they are. They last alot longer, and will do their job alot better. BUT--- as a grout release, not a one of them will stand up to a water based sealer. Years ago, when I lived in south Florida, I did alot of Saltillo (terra cotta) tile. As I'd set it, I'd spray it down with Aquamix's water based sealer. As much of a nightmare as most people think it is to grout terra cotta, using that stuff as a grout release, it was like grouting glazed tile. A couple of years later, I was up here doing a Saltillo floor for my last employer, and they gave me Porous Plus-- supposedly the absolute best sealer for that purpose. I went thru twice the sealer, at almost TEN TIMES THE PRICE PER GALLON, and it STILL didn't do as good a job. I would submit that you'd get the same results with limestone, no matter HOW coarse the texture. Check it out. Water based sealer isn't that much-- only about 20.00 a gallon-- pick up a gallon (and DON'T let them talk you into using ANY kind of solvent based sealer-- not Porous Plus, Not Bullet proof, NONE of them), and seal a piece of tile. Let it dry overnight, and then smear it with grout. Let it sit for about 20 minutes, and try and clean it. I have a pretty good feeling it'll put all your fears to rest.

Well fooey. I checked out the Laticrete site, and I can't find any of their thinsets within a hundred mile radius of here. The big box places only carry their grouts. Also, instead of buying from hakatai directly this time (the first time I used them I purchased from them online), I am going with a local tile place where I purchased the argilla a few years ago. Although an avid net shopper, I have to give some of the local guys credit. They have been super helpful, and now carry the hakatai also. In fact, I was shocked that they're selling me only 7 sheets rather than forcing a whole box on me, and its almost $5 cheaper per sheet from them! Since they carry a lot of underlayment materials, I'm going to ask what they carry and would recommend for both the large travertine and mesh-backed glass. Any other thinset product you could recommend that I might be able to find around here? Looks like I might not be able to avoid an admix after all. I'm not so sure why I'm afraid of it, other than I just feel like keeping it simple will be better for an amateur like me.

I've never done a steam shower in a tub setting. Commercial all-in-one units are available, so it's not that it's uncommon or impossible, but some considerations: You need a rock-solid vapor barrier on the walls and ceiling, and it'll need to be sealed to the tub's flange with a caulk/sealant. Now for steam showers all I've ever used for the past 10 years is Kerdi membrane. It prevents moisture from penetrating deep into the walls. Although you can put Kerdi over drywall, for a steam shower I'd use a cement board like Durock or Wonderboard. Cement board the walls and ceiling, and Kerdi the walls and ceiling. So, from the studs "in" I'd have cement backer board, then Kerdi (sealed to the tub's flange), then thinset and tile. Latex-modified thinset, no mastic. You don't want steam penetrating past the tub/tile and into your walls, so where your plumbing penetrates the walls seal the Kerdi to the shower head arm. Seal the Kerdi behind the valve assembly. Where you tub drain open/close valve is n the tub wall, you'll want to fashion a piece of Kerdi to seal that as well. Getting in and out of the tub? Your door will need a seal on it to keep the steam within the tub enclosure. The steam generator outlet is usually set down low on a wall, sometimes under a bench. The reason is that steam rises, and the outlet gets hot, so placing it under a bench is a good place to hide it. You don't have that option with a tub, so you'll want to place the steam outlet where it doesn't become a burn center. A plus is you can have the steam generator right below the tub, accessible via a panel in the tub apron. Just some quick considerations off the top of my head, I'm sure others will have point-counterpoints to follow. Mongo