A marble tile line in a pool was etched from the waterline down, which led to Eric researching the composition and geology of marble and other natural stones. Come to find out, most of them are indeed calcium based, and susceptible to acidic damage.
[00:00] - Intro
[01:00] - What is natural stone?
[02:42] - Calcite is a dense form of calcium carbonate
[06:24] - Aggressive water seeks calcium, even in natural stone
[08:04] - Other natural stones that contain calcium
[11:22] - Closing
188. Water Chemistry vs. Natural Stone
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Eric Knight: I had a phone call yesterday from one of our sponsors at Watershape U and he was talking about a chemistry question that I had not heard before. Normally when people call me with chemistry questions, I've heard the question a lot and I have a canned answer. And anyway, I didn't, I never actually thought about this before. It never even crossed my radar. And so this was not a planned episode, but it was just fascinating. Because I did some research, which is something I do. And I learned a lot about Natural Stone. So I want to share that with you and I think it might be valuable to you. So this is episode 188 of The Rule Your Pool podcast.
And we're going to talk about water chemistry versus natural stone. Let's go.
[00:01:00] What is natural stone?
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Eric Knight: All right. When we think of natural stones, we're talking about stone that is quarried and mined out of the earth and then cut into a shape and installed, right? It's just how the earth made it. It's natural. You know? When you have synthetic stones, I think of like my countertop at my old home that I renovated was quartz.
Now quartz itself is a natural stone, but a quartz countertop is actually synthetically made. They kind of like compress it, I think, and so you can get any pattern you want. It's a little more resilient to a lot of things except heat because of whatever resins they use to, to make the countertop. I mean, it worked great as long as you don't put like a really hot pan on it. But the price difference, at least at the time this was I guess right after COVID, so I, it's probably more expensive now. But the price difference between a natural stone like granite or marble was substantial. Like quartz was less money in my case. And I don't know if that's the case where you are, but it was a lot less money and it was a lot more budget friendly for me and I liked the way it looked. So I went with quartz.
But I've always, in the back of my mind thought of like. If I was to rank like the fancy, fancy kind of natural stones for a countertop in a house, marble's probably at the top. But I also know that you're supposed to seal marble, and you know, if you pour, if you spill red wine on it, like it dribbles down a wine glass, you could have a red ring that gets absorbed if you don't have it sealed.
Consult your manufacturer. I am no stone expert, so let's get that right out of the way. Um, I've just done some research. I've never installed stone. I am not a expert on how it can be sealed or what products to use or what, just, you know, talk to them. But I think of like marble, I think of travertine, I think of granite, those kind of things.
[00:02:42] Calcite is a dense form of calcium carbonate
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Eric Knight: So I did some research here because what the phone call was about was a marble tile line. And right off the bat, I have not really heard of that before. And I think of tile, like glass tile with epoxy adhesive, um, I think a porcelain or ceramic tile, like the typical pool tile that we're used to. But you can actually do it with natural stone as well.
Now what I have seen, and I just assumed it was tile, is I have seen natural stone on vanishing edges because you can get bigger, you know, uh bigger pieces, and it's easier to keep a straight line over a distance, like a vanishing edge. But, um, for the purposes of this episode, this was a marble tile line. And he was calling me because right at the water line and down this marble was getting destroyed. It was becoming very rough. It was like visibly losing material. I was like, man, I, I always thought marble was super hard, super dense. I wonder what marble's made of?
So I looked into it. What do you think marble's made of? Well, it's actually something called metamorphic calcite. Hmm. Calcite, very similar to the crystals that come out of the walls, like plaster walls when the water is too cold and the LSI is low, and you get these crystals that grow. Like in the cold climates like the Midwest and the Northeast. Those are calcite. Well, it's technically calcium carbonate, just like scale or calcium flakes and salt water pools or uh, plaster dust. It's all calcium carbonate. Yeah, that's true.
But calcite is structured a little bit differently. It's kind of the difference between a diamond and a lump of coal. They're both pure carbon, but the way that the bonds are arranged, it's a lot more dense. Another similar example I learned from this show called Forged in Fire, where they make knives, forged steel is where you impact it repeatedly and it kind of realigns the bonds. It makes it a lot stronger. As opposed to cast iron where you just pour molten iron into a mold and let it dry. Or let it cool. That's not nearly as strong as forged. And it's all about aligning the molecular bonds. Watch the show, you'll understand.
So calcite is a much more dense and resilient form of calcium carbonate, but it still is calcium carbonate. So if you have aggressive water, it can go after that. Now, I'm sure there are some sealants and things like that can that can help, but I just didn't know that. I did not realize that marble was a metamorphic form of calcium carbonate. Hmm.
So I, I got some research here. So marble is a metamorphic rock formed when limestone is subjected to high heat and a lot of pressure. Uh, I added a lot, so high heat and pressure over millions of years. So it's recrystallized carbonate minerals. And then you compare that to travertine because they're both made from limestone, but travertine is not metamorphic, it's actually sedimentary rock that is formed by the precipitation of carbonate minerals from solution in ground and surface waters that percolate through the ground. And then, you know, over time they become that same way. So marble has just been under a lot more pressure. Similar again to a diamond versus a lump of coal.
And obviously if it's calcium carbonate, acid can destroy it. And I was thinking about this like, it makes perfect sense now that I say that because I remember my mom was adamant like you, if you're going to use vinegar, it has to be cleaned up immediately and you put baking soda on it. I never really thought about why, but if you have a marble countertop, it's going to etch the countertop because vinegar is acidic. The things you learn. Um, so things from my childhood kind of come up, you know?
[00:06:24] Aggressive water seeks calcium, even in natural stone
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Eric Knight: But again, I look at marble as like this really, really high end finish. And it is. And I would recommend, like if you can put marble on that, it's just beautiful. But what it means is you need to take care of your chemistry. You can't blame the marble company for it falling apart if the water's super aggressive. And in this case, it's a brand new pool and they did a hot start.
For those of you listening that don't know what a hot start is, that's right after a pool is refinished with a, like a cement based finish, like a plaster or a pebble. A lot of people will just put in a bunch of acid because maybe it doesn't look good from the application or the exposure. It's a big problem. So they'll dump in gallons and gallons of acid to intentionally burn the surface. Uh, they're trying to do it evenly to make it look good. And if you do that, what you're doing is you are intentionally dissolving calcium so that the surface looks more uniform. But if you do that with marble in the water, it's going to go after that marble as well. And it did in this case.
It's basically the same chemical reaction that you would have if you were going after calcium carbonate. You're going to dissolve it. And so what happens is calcium carbonate and acid create calcium chloride, water, and carbon dioxide. If you've ever put acid on. Uh, plaster or anything, calcium based. Cement, anything like that, it fizzes. You've seen this before, pool pros. That fizzing is carbon dioxide leaving. And then calcium chloride, you should know, is basically the salt of calcium. And you buy it in bags, 50 pound bags to increase calcium hardness. So it all comes full circle.
[00:08:04] Other natural stones that contain calcium
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Eric Knight: Anyway, I thought it would probably be a good example to look at other rocks that are used, other stones that are used around pools, not just travertine and marble. Any like paver stones that contain limestone. So yeah, I just said travertine and marble, that's for sure. But anything limestone. Flagstone, technically flagstone is a type of cut where it, I'm going to use the term grain. It's. If you fracture a rock and it's a relatively flat rock, the way that the grain is, that's a type of flagstone, so it's really good for paver stones, for instance. But it's not necessarily a type of stone. There's a lot of different types. I know Oklahoma Flagstone has a lot of limestone in it and iron, and I learned that at Jarred's pool.
My former co-host who never calls me anymore. He wouldn't listen to this anyway. But he has a lot of iron coming out of those rocks because it's just part of what's in it. And if you think going back to marble, it's never like pure white. It always has that well marbling in it. We use that term when we're talking about fat in steaks, right?
Well that's because you have other things in the ground. You've got all sorts of stuff like dolomite and all sorts of cool stuff. Irons and metals and minerals. And that's what gives it that beautiful look. It's no different here. So, um, limestone pavers obviously. That's going to be susceptible to LSI aggressive water.
How about, uh, this one? I don't know how to pronounce. I know shell stone and coquina kina, I don't know. Uh, they are derived from marine life. Like shells. Think about that. What do you think those are made of? Well, yeah, they're made of calcium, coral skeletons, shells, clamshells, things like that. It's all calcium based. It's almost entirely calcium based. Very, very susceptible to aggressive water.
Then there's Shenandoah Bluestone, which apparently has some calcium carbonate in it. I didn't know that. I would think it's more like shale or, um, you know, silt and clay and, and uh, silica and things like that. But yeah, I can have some calcium in there. And then you've got sandstone. Now sandstone's interesting, because sandstone is basically, sand is silica based and that's not really susceptible to calcium destruction. But everything binding it together is calcium based. That makes me think of like pre-manufactured synthetic stones. And these stones are great. They perform great. They can be engineered to be a little cooler to the touch, which is very important if you're walking on a deck barefoot. And they're awesome, but you don't want water to puddle up on them and go after that calcium.
And it makes me think like I have been on a lot of backyard projects where the drainage wasn't great. And so that's one of the things we teach in Construction 2111, is how you pitch and slope the deck drains to make sure that you have adequate drainage. Part of the reason for that is to avoid puddling, and if you've ever looked at puddles on a pool deck, especially concrete or any of these types of stones, they're rough.
And it's like what? I never really put it together until I was doing this research of like, oh yeah, rain is super aggressive on the LSI because it's distilled water. There is no calcium in it. Now it's water on the ground. It's trying to reach its natural state. What's it going to do? And it goes after these stones. So you've got to be able to drain that out effectively.
[00:11:22] Closing
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Eric Knight: I don't know, I, I didn't really have a plan going into this, but I just wanted to share like there are, there are so many things you can learn that you've probably taken for granted. I know that's the case with me on this one. I've just taken for granted that natural stone just looked beautiful and I just assumed it could hold up to anything. And if the chemistry is balanced, it's really good at holding up and it'll stand the test of time in most cases. But if you hot start a pool, that's on you. And that marble's not cheap. And, and a super high-end finish can be ruined by a, a habit. You know, a habit. Oh, I don't like the way that the plaster was exposed. Well maybe the conversation needs to be had with the applicator to make sure that the exposure is done right and that is where training comes in. But even if that's the case, a hot start is not the answer. If it's the tile line that marble's destroyed and it's going to have to be replaced, but that is not a warranty claim. That is not a marble failure. Marble is what it is. The chemistry failed on that.
And if you're a service pro listening to this and you have a high-end pool that has, uh, any of these natural stones really. And, and by the way, I love Natural Stone. I would put it on my own pool if I had the chance. And maybe one day I will build a pool and I will put natural stone on it. Because I, I just think it's gorgeous. If I do that, you better believe I'm not hot starting that pool. Not that I would do that anyway, but I definitely wouldn't do it when you have something like this. So just be aware of it. If you have any questions, reach out. It's ruleyourpool@gmail.com. This was a short episode. I just wanted you to be aware of it. Pool pros. Especially those that have these high-end pool finishes. Uh, yeah, episode 188. Thanks for listening.