# Best way to clean and seal limestone hearth before use?



## jcims (Nov 19, 2011)

Hi Folks,

Several years ago I purchased two large cut limestone slabs to use as part of my hearth.  I wasn't quite ready to complete the construction, so I burned for two years without it in place.  Now i'm ready, and have the slabs in place, but they have two years of dust and some marking from the cardboard spacers the vendor used in delivery.

So, two things.  First, I need to clean them.  I'm thinking just mild soapy water and maybe a brass brush, but if there are any particular chemicals that do well with limestone, I'm not opposed to that idea.

Second, I want to seal the thing as well as possible.  I didn't really know what I was getting into when I purchased them, and now realize that this material was probably a mistake.  The thought of all those little pores getting packed with ash and sawdust makes me nervous.  I'm almost inclined to pour a heavy epoxy coat on it, or something else that will be impervious to ash/soot/dust and hold up for a few years without requiring a re-do.

Any other suggestions before I go down that one way street?

Here's a quick shot to see what I'm getting into.  It's two slabs, 2.5'x6'x2".







Thanks


----------



## stejus (Nov 19, 2011)

There's a product I used to seal some stone sections for my stone mantle.  It's made by "Tile Guard" and called "Enhance & Seal".  It darkens the rock and seals it.   Best to do a section that isn't visable first to see the results.  

http://www.tile-guard.com/Product-Information/Enhance-and-Seal-Quart


----------



## Milton Findley (Nov 19, 2011)

Looks like it would be a great substrate for a very nice ceramic tile hearth.


----------



## begreen (Nov 19, 2011)

That'll make a beautiful hearth just like it is, but it will need a sealer, I suspect something silicone based. 

These articles should get you started:

http://www.baneclene.com/articles/limestone.html
http://www.drytreat.com/Surfaces/Limestone


----------



## nate379 (Nov 19, 2011)

I used something called that to seal my concrete patio last year.  It was around $150 for a 5 gal pail.



			
				stejus said:
			
		

> There's a product I used to seal some stone sections for my stone mantle.  It's made by "Tile Guard" and called "Enhance & Seal".  It darkens the rock and seals it.   Best to do a section that isn't visible first to see the results.
> 
> http://www.tile-guard.com/Product-Information/Enhance-and-Seal-Quart


----------



## jcims (Nov 21, 2011)

Hi Folks,

Just wanted to thank you for the input.  Trying the Tile Guard product, which seems to have been purchased by DuPont.

We'll see how it goes!

Take care.


----------



## Wade A. (Nov 21, 2011)

jcims....sorry not to have posted this sooner.

I too have a limestone hearth, and I understand how you'd have some initial misgivings. I had those too, but I've come to accept that I might have been overly worried. 

My stone is acid washed, which has a bit more texture.....and more micro pores for soot and ash to lodge. I told myself that I would not seal it the first season, and see how it went. I'm well into the second season, and I'm still on the fence, but I'm thinking I won't seal it.

My first concern is that the heat is going to cook any sealant I put on it, possibly outgassing or yellowing the finish. I plan to coat a stone sample with a couple of different coatings first, put them under the stove, and see what happens. Haven't gotten around to that yet though. If anyone has actually done this to a limestone slab, I'd love to get their opinions on whether they are happy with it, or not.

Initially, you're going to stress over every soot mark you get on it. It is just part of the process of accumulating a patina. Scrub it with mild soap and water if it really bugs you, and that will  even out the dark spots and give a nice burnish to the stone.  It will darken somewhat, but like I said, I don't find that unattractive.  If you ever want to get it back to shiny new, a little phosphoric acid (grout haze remover) will do it toot-sweet. That will also take off that cardboard stain, BTW.

Limestone is most vulnerable to is scrapes and gouges... don't drop a fireplace tool on it and you'll be good.  

My advice? Live with it some, accept it for what it is, and you may decide that sealing is not necessary.


----------



## jcims (Nov 22, 2011)

ploughboy said:
			
		

> jcims....sorry not to have posted this sooner.



Don't think twice!  I'm glad you did.  I haven't applied the sealer as I'm getting it cleaned up and really appreciate the heads up on the phosphoric acid.  I may give that a try, as I've got those 'stripes' 90% removed with a stainless brush and some elbow grease, but there's still a shadow left and the haze remover will likely do the trick.  If they weren't so perfectly straight and clearly 'artificial', I wouldn't think twice about it.

I know exactly what you're saying about being overly worried.  Once the stove is up and running and I get my first ding and scuff out of the way, I don't imagine I'll be too worried about it any more.  I just tend to operate this way, nail biting anxiety gives way to nit witted apathy in short order. 

Thanks again!

Bob


----------



## homebrewz (Nov 22, 2011)

That's a very light looking limestone. Around here it usually comes in darker shades. 

Whatever you do, a little bit will probably go a long way. Limestone is a fairly soft rock. It falls between 3 and 4 on the hardness scale (1-10) depending on what type of limestone it is. Its a carbonate (basic) so it also reacts with acids, which is why various acids are used to etch/clean it. I think some kind of polishing//burnishing would look really nice.


----------



## Wade A. (Nov 22, 2011)

Glad to help Jcims. Too, don't go overboard with the acid.....check what the dilution is and work in smal quantities.  You can actually bleach the stone to the point where you'll have as noticeable a spot as you had with the stain! Your stone does look somewhat lighter than mine, so that might not be too big a concern.

I agree with homebrewz that a polished finish would be more durable and easier to keep clean in general. I opted for the rougher finish because I thought it would look "warmer", and I think it does.


----------

