My old carrara vanity top had that. I found that it was from soaps, and it looked oily to me to (mostly underneath the soap dispenser). Unfortunately, I never really got rid of it until I pitched the vanity top. But it was old and already there when I moved it. If it had been sealed originally, I'm sure it would have been a little better off, but, as you know, still not bullet proof or impervious. If you haven't yet used it, then it's gotta be something with the installation.

@avaaustin The process of attaching fiberglass mesh to ceramic/porcelain tile differs from natural stone processing. Mesh on the back of ceramic mosaic usually doesn't have a layer of glue between the mesh "cells". At same time, the main reason of "resin backing" attached to natural stone is to reinforce it and fiberglass mesh is attached using a "glue" that is mostly polyester. It, first, adds an impervious layer to the back of stone and can significantly reduce the evaporation. Secondly, there could be problems with how well the bond is between the mesh and the substrate since dry set or polymer-modified mortars don't adhere to it very well. True porcelain tiles, whether sealed or unsealed, have >0.5% water absorption. At same time, marble is a translucent stone that will still absorb moisture as vapor even after an impregnating sealer is applied. I can't tell you whether Bulletproof sealer will help you in your situation. With properly installed water-in, water-out system and stone with no "resin backing" it is best to avoid any sealer. That's my strong opinion. Sealing the stone but not sealing the grout will not make any difference. Impregnating sealers are all considered permeable but if there is trapped moisture under the stone unsealed grout won't help.

I'd love some advice/opinions on marble chipping, poor seams, and edgework received from a fabricator. We paid big to splurge on marble slabs and chose to hone them since we couldn't find what we wanted already honed. I was told the honing went well. My contractor was organizing the install with our fabricator. When I went to look I was shocked the company even installed the backsplash, which had large chips on both ends. They told me this is acceptable and happens with marble sometimes. They're only willing to work on doing a better job on the seaming/fill. Chip 1 Chip 2 The sink seam on the backsplash was supposed to be centered to the faucet but is offset to the right a bit. Seam at sink I thought the seam on another part of our countertop was going to be straight but they did a French seam which I hear is often done. The design I signed off on had a dotted straight line so I wonder: Should they have told me they were doing the French? In any case, the curve/arc doesn't look that good to me. French seam The 2 seams we have seem too wide to me as well. Am I being unreasonable to have expected no big chips and better, thinner seamwork? The mitered edges have spots where I can get my fingernail between the edges. Edges 1 Edges 2 The island also has a small section that has chipping/unevenness. I don't know when that happened: during honing or during install. I'm told to live with this as well and worried the chipping will get worse as we use and wipe the counters. Island chips Some other spots have what looks like silver fill. Silver fill Finally, someone on the crew dropped something that left stress marks. I was told these things just happen sometimes. Would you just accept that? We haven't even moved back in or used the counters yet. Stress marks

The photo I posted above is a bonding flange drain that was shown in one of Mr. Starykov’s articles on this subject. When I saw the orange membrane, I assumed it was a Kerdi drain. My post should just refer to bonding flange drains in general. Sorry for the confusion. I am a newbie re: shower pan construction. I‘ve just been doing a lot of research recently in order to avoid having my marble discolor due to water retention. I have read several discussion threads where specifically Kerdi drains + issue with water pooling around the drain have been discussed. These included comments by well respected professionals who would be able to identify a Kerdi drain. There is always is the possibility (probability??) that the dams around the Kerdi drains were caused by installation error. Anyone who spends even a little bit of time on Houzz looking at bathroom renovations knows all too well how often these shower pans are not built correctly! I think catbuilder has “nailed it“ in the above post - there may be (i) too much thinset used to set the drain, (ii) a dam that’s been created around the drain (drain wasn’t firmly set into the the thinset?), or (iii) a valley in the deck mud around the drain. Catbuilder clearly has quite a bit of knowledge re: shower construction/proper waterproofing methods. I do have a question for you - is the marble tile that you’re having an issue with the same as the marble installed previously without issues? There have been a lot of discussions about how the particular quality of the marble tile being installed may have some bearing on the rise in marble discoloration issues. There is a lot of marble being sold in the marketplace that is labeled as ”Carrara” but is actually not from Italy. My understanding is that the density/porosity of marble can vary quite a bit between different varieties. It also can vary somewhat in the same variety. If I hold up two of the Italian Carrara tiles I’ve recently purchased for my shower walls to a light source, certain tiles are much more translucent than others even though they were sourced from the same area. This would contribute to the amount of water being retained inside the actual stone. Then again, if you have a dam or birdbath around your drain, your marble tile is going to soak up some water regardless of type! I REALLY want a marble hexagon shower floor - but all of this is making me VERY ANXIOUS. I specifically decided not to purchase the standard Carrara hexagon mosaic tile that I really wanted since white marble tends to have more issues with this - but if my shower pan has any type of water retention issues, I still will wind up with discolored tile.