Seal it -- it won't stain. Well, I can't speak for writing on it with a Sharpie, but those other things have probably all been on my counters as well as plenty of chili and chocolate and something that someone left by the sink and left pink marks that I think were from paper or printing ink. I don't have stains. If you seal marble, the issues are mainly about whether you are bothered by etching. If you have read past threads and weren't surprised by the results, you should also know to seal the marble. And that sealing marble is not much more than wiping the sealer on once every year or two.

Oh yeah, 36 hrs of lemon juice would leave quite an etch! IRL, I haven't had anything that has stained my marble, even tomato sauce...I guess the sealer is working. My little etches come and go....I think they "fade" away, but then I get a new one, I don't know...it seems to be a dynamic process. I really don't notice them much...my marble is honed, not sure if that is the difference. Of course, your sample looks honed, too.

Why does the sealant prevent staining, but not etching? Is etching the effect of actual damage or erosion of the surface, or is it something else?

The sample is honed, and I assumed it was sealed but I guess not. I'll call the stone yard to get the scoop. The stains seem a little faded today - I'll take a picture later on.

Etching is a chemical reaction between calcium carbonate in the marble and whatever acid happens to be around. A stain isn't a chemical reaction, it's just the material soaking in to the marble. Eventually the carbon chains in the material break down via oxidation and the stain goes away. There are various basic (as opposed to acidic) poultices that can be used to reverse the stain. The sealer prevents absorbtion, but can't prevent the chemical reaction of acid on calcium carbonate.

I just had Carrara marble countertops put in and I love them! The place I used acid washes the marble before it is given four coats of sealer. They say this is to basically pre etch it. It has been about six weeks and so far no etching. I even had someone spill a big mojito full of lime juice all over the island and nothing. I was surprised to not find much info on acid washing on this forum, but I highly recommend it.

I have never understood how exactly sealers work, so keep that in mind.

Pre-etching or honing disguises later etches somewhat I guess, but etches are places where the marble has been dissolved by acids. I have never understood why that doesn't also remove the sealer - or maybe it does? Are you supposed to keep resealing periodically?

annkathryn, thanks for your reply. Why do stains oxidize over time from marble but not from my white shirt where I got a blueberry stain? :( Will Sharpie ink eventually oxidize? How does the sealant prevent the staining material from soaking into the marble, but can't prevent etching.

bmorepanic, exactly...why doesn't the etching remove the sealer? Let's say it does. Will etched spots now be unprotected from staining?

I think etching does remove the sealer?

annkathryn The sealer prevents absorbtion, but can't prevent the chemical reaction of acid on calcium carbonate.

Absolutely. Just because a place gets etched doesn't mean it will stain later. As an aside most, if not all, samples of marble are not sealed (at least they aren't in my neck of the woods). I have no stains on my counters and we consistently get coffee blobs and other things that stay on the marble for HOURS without notice. No stains. None.

nini804 My little etches come and go....I think they "fade" away, but then I get a new one, I don't know...it seems to be a dynamic process.

I have wondered this as well. We have had our marble in for 18 months. I used to "polish" the marble every other week (or I did the first year, LOL!)and took pics of one etch as an experiment. These pics show the same etch over time. It was the first etch that I ever noticed on our marble so it really stuck out to me at first. I don't even realize that it's there anymore (I haven't looked and probably wouldn't think twice about it anyway).

First etch, circa March 2011:

{{!gwi}}

Same etch, different angle:

{{!gwi}}

Same etch (could there BE another? Probably not, as it looks like WC Fields nose), about 4 months later. It's not as pronounced, is it?:

{{!gwi}}

I have often wondered if the Marble "Polish" actually subtly etches the surface even more after time. I have no idea, yet I just don't worry about it anymore.

Day 3 - I think the blueberry has faded just a little.

This sample isn't sealed, so that explains the dramatic stains.

i love my marble and would install it all over again if given the opprtunity. sealing prevents stains just need to be careful about acids. i use strategically placed cutting boards. have a few small etches but they are limited and due to the honed surface are not visible unless in certain lighting when the angle is right.

I acid-etched the black marble tile that I used for a counter in my kitchen. Even though we refer to a sealer, I've read that the solution used on marble is an impregnator (we're all adults here--no snickering ;]), which fills the pores, blocking stain absorption.

I have a honed carrara slab that's never been treated, as I roll out dough on it. It has etches, but no stains. I've mentioned before that I use a smooth sanding sponge on etches--not so much now that the newness has worn off, but it works well on honed marble.

I should have added this link:

Here is a link that might be useful: sealers/impregnators

Stones stain because they are porous. The staining material gets wicked into the microscopic pores in the material. Stone sealer fills the pores which stops staining. It doesn't cover the surface so it doesn't stop interaction of the stone with acids so etching can still occur.

The etches are normally very shallow - just a change in the top surface so the sealer probably goes deeper in the stone than the material removed by etching so etching doesn't interfere with the sealer working.

I think that the difference between a stain in stone and a stain in your white shirt is that the stain in stone has just soaked into the pores but it hasn't bonded with the molecules in the stone. A poultice can pull it out and absorb it into a different material or, in time, it can evaporate or oxidize out. With the material in the shirt, the stain may bond with the shirt material and dye it more permanently.

cloud-swift, thank you. Your answers make a lot of sense.