Help with Limestone and Slate Restoration

etinul · 10-23-2007, 09:22 PM

Hello. I am an Architect who loves specifying natural stone on projects and used it extensively in renovating my NYC (Queens) home. I thought I knew how to maintain stone....but after 3 years I realize my maintenance efforts are seemingly useless.

I have two bathrooms. One has a Grey limestone (honed). It's name is Platinum from Stone Source. The other bathroom has green slate with natural cleft finish. I sealed both been with Lithofin PSI impregnator. My problems are as follows:

Platinum Limestone: the shower walls consist of a combination of 5/8" mosaic limestone and 3/8" thick limestone tile. The mosaic is fogging and seems to be decomposing at the base of the wall. The limestone tile, which frames the mosaic, is also presenting problems. The 4" portion, where the tile meets the top of the bathtub, is forming white spots which appear to be pitting the surface of the tile. All this began appearing about 3 to 4 months after the installation, which is approximately 3 years old. See attached pictures 1 and 2.

Green Slate: The problem here is the shower floor, which is made up of 8"x8" tiles (natural cleft). The floor tiles, again after a couple of months, began forming a whitish layer at the perimeter of each tile, like a 1" picture frame. This then began spreading, like a virus, to cover almost the entire tile at some locations. The chrome drain is also almost entirely encrusted by this white stuff, which seems to require scraping to clean. See attached picture. I gruelingly cleaned the tiles a couple of times in the past two years with Lithofin's heavy duty stone cleaner, which removed a good amount of the white stuff, and then resealed the shower floor. It looked ok for a while. The problem keeps coming back and now is in worse condition than ever.

I am really concerned about the limestone pitting, since the tile I used is no longer available. However, both are equally unsightly.

Steve Patrick · 10-23-2007, 09:49 PM

Hi etinul,
What type of bathroom cleaning products have you been using?

etinul · 10-23-2007, 11:56 PM

Hi Steve, my name is Nick. I use Lithofin's daily stone cleaner. Although the stone is definetly not cleaned daily, more like bi-weekly.

cheesedog · 10-24-2007, 02:22 AM

it may be that the slate wasnt sealed enough, or properly. it looks like its just soaking in through the grout and into the tile. that stuff will take several coats

etinul · 10-24-2007, 07:49 PM

interesting cheesedog. I didn't think consider that. However, I did throw a couple of coats of sealer on the tiles. Wether I did it properlt, I don't know.

Steve Patrick · 10-24-2007, 09:21 PM

Hi Nick,
How's the water conditioning there? A lot of chlorine, hard water? This might be interacting with a cleaner or as Cheesedog is referring to maybe the sealer. Looking closely at the shower floor it does look like an application of some sort that has gone awry. The build up around the metal drain looks like a calcium deposit.

etinul · 10-24-2007, 09:42 PM

From what I understand NYC water is somewhat hard; howver, I do not get white buildup on the shower head, which from what I understand happens with hard water. I think your right about the buildup at the drain, you need a chisel to get it off. It's rock hard.

Fred Hueston · 10-24-2007, 10:58 PM

This is a classic case of efflorescence, the pitting and spalling is the result of soluble salts depositing in the pores of the stone.

There a number of reasons for this as follows:

The salts can come from the setting mortar, the grout joints and/or the water.

At this point there is not a lot that can be done but there is lots that can be done to prevent this from happen if it is replaced.

I write specs for stone and tile all over the US. I would be glad to help if you decieded to replace.

Steve Patrick · 10-24-2007, 11:31 PM

Hiya Fred,
So the soluble salts would would be rinsing towards the drain causing the build up.Makes sense.

etinul · 10-25-2007, 01:19 AM

I appreciate the feedback from all of you. Thank you. I am somewhat dissapointed to hear that there is not much that can be done to reverse the effects conflicting my stone. As a last resort I do not mind replacing the slate tile floor in the shower; however, the limestone is irreplacable. It's not available anymore. Apparently the quarry shut down.

If anyone out there has any ideas.....