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Unread 01-13-2022, 03:57 PM   #16
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Let's forget about grout sealing for a minute.

It's nice in theory that there's nothing wrong with "moisture" penetrating the grout, but one problem is that it's not really water - it's an organic soup of water, soap, skin cells, conditioners, etc. So as this gunk gets into the porous mortar, it can collect and mold can grow if it stays damp.

So you're assuming a nice shower scenario where the shower fully dries between uses. Some showers are like that, plenty are not.

As for sealers making the look worse, it's really impossible to be worse than totally wet and dark over here, and totally and light over there. They improve the aesthetics in any shower I've ever used them. If you're getting splotchy results, then something else is wrong.
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Unread 01-13-2022, 06:41 PM   #17
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Careful with the assumptions about my making assumptions, Jeff.

How do you suppose we were able to have quite successful tile showers for all the decades before the advent of today's penetrating sealers?

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Unread 01-14-2022, 06:09 AM   #18
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Jeff said, " it's an organic soup of water, soap, skin cells, conditioners, etc. So as this gunk gets into the porous mortar, it can collect and mold can grow if it stays damp."

Makes sense to me but after tearing out many showers that are 30-70 years old, I'm just not seeing a pattern of it. I'm not saying it doesn't happen but very few over the years that I've seen. Maybe I'm just lucky.

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Unread 01-14-2022, 07:29 AM   #19
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OK well cx is just lawyering me now - his points are the valid ones, mine are the invalid ones, I get it.

I already rewrote my initial comment. Of course you don't have to seal grout. What I was trying to say was that grout that claims "no sealing required" is trying to imply that some other competing grouts do require sealing, but they have a special formulation that is "presealed", or "has sealer in it", or something to that effect. With regard to water absorption, it simply isn't true in my experience. Maybe with regard to stain resistance, or mold inhibiting compounds, it might be.

Now of course there are many tile jobs with grout that has never been sealed that do fine. There are lots of jobs that do fine over many years as well, such as tile installed directly over plywood on floors, etc. Lots of things can work, even if they are not ideal.

Personally I find the water darkening of grout to be unacceptably ugly and many of my customers do as well. If that is not an aesthetic concern of yours, then don't worry about it.

cx says "none of [the sealers] prevents all moisture from penetrating the joints. All of them do, on the other hand, tend to retard moisture vapor leaving the joints, slowing the evaporation of water that has entered the joints."

Well you can't have it both ways. You can't have a sealer that allows all the water in, then magically starts disallowing water vapor to leave. The less it allows water to leave, the less water it would have allowed in in the first place. Regardless of what you mean technically by preventing "all moisture" from penetrating, it's pretty clear that if you've put a good sealer on grout, you can see just by looking that the grout no longer gets dark from water absorption. Does "any" moisture get in? Well, if you see a dark spot, that basically means you missed it, or it needs more sealer there. Will some water molecules still get in that don't noticeably darken the grout? Possibly.

cx also says you can get ugly results with sealers as well. In my experience, it's like everything else - a quality sealer, applied correctly, over a quality grout that was also applied correctly, and you should never get any inconsistency issues. At least I've never seen it on a job I've done. Use crappy products or crappy application, and yeah you can get bad looking results. Just like you can get bad looking results from the grout itself without sealer too, as we have seen many times in photos on this forum

In a tile job, yes we build the system so that if water gets in it can drain. But this also works better in showers that tend to get less use and can dry out between uses. Not all showers get used this way, and some stay virtually wet. But the indisputable fact is that all else being equal, we'd prefer the water never penetrated the grout to begin with. This "soup" containing skin oils and cells and organic hair products etc. might not ever cause any problem. I doubt anyone thinks it's an ideal situation though. I know I've taken apart showers that weren't sloped correctly and had a stinky, smelly mess of water in there (under the tiles). So we know that stuff is bad. While a properly drained shower is much less likely to have that kind of problem, is there anyone that thinks any good can come from this stuff penetrating the grout and mortar system? You would certainly prefer it didn't, and undeniably one advantage that solid surface shower pans have over tiled floors is that nothing can penetrate.

If you don't want to seal your grout, don't seal it. But again my original point was simply this - grouts that claim "doesn't need sealing" are misleading in my opinion. Cementitious grouts that is. I think the quality premixed grouts actually don't need sealing because they actually keep water from penetrating in the first place, mostly if not completely, because they don't have the porosity that mortar has. Not all people like them, but that is one advantage of them IMO.
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