Slippery Rock Gazette

Bob Murrell 

M3 Technologies

Photos by Bob Murrell

I have written many articles regarding certain products to avoid around marble, limestone, onyx, terrazzo, and other calcium-based materials – but it bears repeating. Acids are one of marble’s  biggest enemies. Of course, strong alkalines, such as highly ammoniated window cleaners (like Windex) or oven cleaners, can also be damaging. And as expected, these blemishes must be honed and re-polished to remove.

Even certain granites can be harmed by chemicals. I have seen etching where a tomato was left on a black granite countertop for an extended period which resulted in a bleached effect. It also bears repeating that Black granite is not a true granite. It is more than likely a basalt, anorthosite, gabbro, or similar igneous material. In any case, these stones can be subject to attack by certain chemicals, though they are not normally as sensitive as calcium-based materials are. About the only thing you can do in this type situation is to re-blacken the stone, either with a dye or resin-type product. Heck, I’ve even seen magic marker and shoe polish used. (BTW, if this DIY fix makes you roll your eyes, there actually are black stone waxes available for professionals.) Whatever it takes, ya know?     

Acids and alkalines can sometimes draw out the natural oils in certain stones like slate and other similar materials. This would leave them very dry and chalky looking. This can normally be rectified with the use of color enhancers or topical acrylic sealers.   

Bug sprays can actually be acidic in solution. Re-polishing areas that were sprayed or over sprayed with pesticides may sometimes be necessary. This is something to be aware of, especially in the insect-active month; I have seen this problem several times this year.

Above, left: Etching and discoloration resulting from spillage of an acidic bowl cleaner. Apparently, the maintenance worker was careless when moving  between a men’s and women’s commercial restroom.  Above, right: After grinding and repolishing, this Tennessee marble floor is once again looking spectacular.

Let’s go over some of the “Don’ts” to start, so you can hopefully avoid many of these issues in the first place. 

First and foremost, always tell your clients to never use products that are not specifically made for use on natural stone. You would think that this would be a fairly easy rule to follow. Unfortunately, this is probably one of the biggest causes for acid etching and alkaline burns on natural stone surfaces. 

Never tell anyone to use vinegar (a much touted “natural” cleaner), abrasive powders, or for that matter, any product that is not manufactured specifically for use on natural stone.

There is also a problem with many homeowner-targeted topical coatings, which are being misapplied to natural stone surfaces. Mop and glow, Rejuvenate, and other similarly labeled products should not normally be used on marble, granite and most all natural stone. 

Restoration contractors have to remove these bothersome coatings first, before they can restore the surface to its natural and intended beauty. This ends up costing the client more, as additional steps are required.

Masking and protecting adjacent stone surfaces prior to spraying insecticides is essential for protecting your client’s expensive investment.

I am not usually a fan of topical coatings, but there are certain applications where a sacrificial surface is necessary. Concrete and terrazzo guards are used sparingly to help protect these surfaces from acidic spills and heavy traffic wear. Make sure if you are going to apply a topical coating on any stone or masonry surface to follow the directions implicitly. Normally, multiple thin applications are better than overly thick ones. If you are applying an acrylic, urethane, or epoxy and you leave application marks, dust, bubbles, or any other imperfections in the coating, some times you are basically stuck with the less-than-professional results. What’s worse, many of these topical products can only be efficiently removed by grinding. 

If you have a slate or textured stone, grinding is not applicable. You should be aware that methylene chloride (used for stripping)  is basically no longer available, at least at most big box and hardware stores. I’m not trying to scare you, just make you aware of the potential problematic issues with the use of these types of products.  

Now, let’s take a look at some “dos”. Maybe we can alleviate some potential issues by prescribing proper maintenance procedures.    

Always try to both educate and provide your clients with the correct products to use on their installation. When certain non stone-friendly products must be used, all necessary precautions should be used to protect the stone, by masking the stone with plastic and either painter’s tape or polyvinyl (water proof) tape. 

You will be masking off all adjacent areas anyway when doing any kind of restoration work on the stone. 

So when the need arises for certain products that may be in question, like a toilet bowl cleaner (which is normally an acidic product), use a chemical formula like Majestic Toilet Bowl Cleaner, which is non-acidic. Use either Majestic No-Rinse Neutral Cleaner or Majestic Stone Plus for routine cleaning of all natural stone surfaces. Both of these products are pH neutral and great for all surfaces that are safe for water (even on mirrors). Every client, both residential and commercial, should be left with some of Majestic No-Rinse Neutral Cleaner or the Stone Plus.  

Above, left and right: before and after restoration shows how improper use of simple household cleaning products and spillage can etch and damage a marble counter. Fortunately, this antique Black marble was honed and repolished back to its former glory – but not without a lot of time and effort.

All restoration professionals should not only recommend the use of correct maintenance products, but also the use of cutting boards and coasters. This will help prevent scratching, etching, and water spots (mineral deposits). 

If your client needs to spray insecticides or use strong window cleaners, please make sure that they use protective masking products. Tarps, tape where necessary, and to generally be careful when using these products around natural stone surfaces will help. All spills and any overspray should be wiped up as soon as possible.   

Being cognizant of what happens to certain marbles and other natural stones when they are exposed to acids or alkalines is step one. This will help most to understand what happens to their stone when exposed to these extreme pH levels. Of course, this doesn’t mean they will never have incidents, but hopefully this will help them enjoy their stone surfaces more, and minimize your “could’ve been prevented” return trips. 

As always, I recommend submitting a test area to confirm the results and the procedure prior to starting a stone or hard surface restoration or maintenance project. Remember to use your smartphone or camera to take plenty of before and after pics! Also, the best way to help ensure success is by partnering with a good distributor that knows the business. They can help with technical support, product purchase decisions, logistics, and other pertinent project information.

Bob Murrell has worked in the natural stone industry for over 40 years and is well known for his expertise in natural stone, tile and decorative concrete restoration and maintenance. He helped develop some of the main products and processes which revolutionized the industry, and is currently the Director of Operations for M3 Technologies.