Slippery Rock Gazette

Bob Murrell 

M3 Technologies

Photos by Bob Murrell

Not every project turns out as easy as you had hoped for. Some are pretty straight forward and relatively mundane. However, there are those that you must actually have to think yourself through. And what I mean by that is that sometimes you will have to think on the fly and just make things work, kinda like MacGyver (lol).  

Of course, submitting a test area to confirm the results and the procedure, like I always recommend, is definitely advantageous and will help to minimize unexpected surprises. But smaller projects, time constraints, and yes, dare I say it, a cocky attitude can sometimes get in the way of good protocol.  

Let’s take some nightmare examples just to drive the point home. So when you come upon a floor, say slate, crab orchard, or bluestone, and the floor has a coating of some type. You know, there are many different types of coatings. Some are fairly easy to remove and others, not so much. If the coating is a typical floor finish, then the removal should not be too hard, with exceptions for low lying areas and how much texture the surface has.

Above, left: This dilemma presented as a failed acrylic coating on terra cotta tile installation. The problem was to completely remove the old coating before applying a new coating to achieve the customer’s desired level of shine.   Above, right: On this project we had to remove — by hand,  using razor blades — layers of urethane coatings from a once beautifully polished black marble floor.

Above, left: When a job generates poultice removal waste, it must be disposed of properly according to federal, state and local regulations.   Above, right: Remember to do cleanup on your equipment (like this floor squeegee) after the stripping process. Stripping clogs the channel and reduces pick-up effectiveness.

Because a surface has a texture, coating removal by cutting or grinding with scrapers, diamonds, and other similar methods is not applicable. Therefore, the use of chemical stripping products will be necessary. Of course some mechanical action will also be necessary, like the use of a brush and maybe even a grit-type brush. Sometimes a very open weave black stripping pad can also help.

When we are talking about urethane and epoxy type coatings, they can often be very stubborn and time consuming to remove, as well as requiring exposure to dangerous chemical strippers by personnel. I don’t know how many times I have found that the use of methylene chloride works better than other products. This, however, is really bad stuff, if not handled correctly. That’s why it is getting harder and harder to find as many states are banning its use or at least reducing the availability of the product.

There are newer (safer) soy-based stripper products that do work but are not quite as efficient as the old methylene chloride strippers. There also are, what I call, poultice type strippers or removers, that I have used very successfully on several occasions. 

Of course any of these stripping methods are normally very messy, time consuming, and necessarily a down and dirty physical type of work. This therefore, translates into an increased cost. Being on the floor with a wire brush in your hand (with gloves) and using a chemical stripper is much harder and longer work than polishing with 5X. Surface texture with low areas and of course the grout lines will most always present a stubborn issue. 

Let’s not forget that any of these stripper products must also be disposed of properly, according to state and local laws. Some states are stricter than others regarding this issue but generally speaking, you really don’t want to just pour that stuff down the drain. That would be a definite no-no most anywhere and probably a fineable offense or worse. None of us needs that kind of problem. And another issue is equipment cleanup – don’t forget about that. Just sayin…        

Most likely you will need the above procedure for textured stones that have been sealed with a topical coating of some sort. That is usually where the coatings are found, and sometimes, it is a combination of different coatings that have been applied over the years. However, believe it or not, I do see the occasional polished marble with an improper coating applied on it. This can be especially true of older installations because restoration, and maintenance for that matter, wasn’t quite the same back in the day. When a polished marble became dull, typically a wax might be applied to help restore a little gloss. And sometimes, a harder coating has been applied.

In certain applications, it may pay to grind the coating off, but normally we would want to use the least aggressive method that does the job. If it is a really hard acrylic, urethane or epoxy type coating, sitting on the floor with a razor blade has been required more than a few times. You will probably have to do corners and some detail with this method as well. You don’t really realize how much product there could be until you see it curl up in a pile, while using your blade. Remember to use a good razor blade holder and keep a fresh blade in as much as possible to help efficacy and efficiency.

Of course when you get the coating off of the marble, it is then time to figure out why it was coated and develop a plan to restore it back to its intended beauty. Maybe it was just normal foot traffic wear? Possibly some scratches that whomever decided that a coating would disguise? In any case, you must have the coating properly removed to proceed with the restoration. Both diamonds (certainly resin type) and polishing abrasives do not perform as intended on topical coatings.

Regarding terrazzo and most concrete, there usually aren’t any grout lines or texture on the surface. So most all of the options are available for coatings removal on these surfaces, so it depends on the application and desired appearance. There is, however, stamped concrete that contains both texture and simulated grout lines. Stamped concrete may be integrally colored or dyed so a coating is normally applied to protect this coloring.

Above, left: Serpentine flagstone floor after restoration and color enhancement, with previous coatings removed.   Above, right: Poultice paint stripper being applied to serpentine flagged floor to remove many years of applied coatings. It was allowed to dwell for about 48 hours prior to removal.

The moral of these stories is these coatings can be difficult to remove. In some situations, removal may not be necessary as just cleaning and adding more product may be sufficient. If the current product has indeed failed and must be removed, I recommend doing multiple tests with multiple stripping chemical agents and methods (possibly with a brush) before agreeing to a price. You don’t want to be left holding the bag, especially on a failed project. Also, evaluate whether a coating is necessary going forward. I would definitely recommend against it on most any polished or honed surface and even on textured surfaces, a color enhancer would normally be preferred.  

As always, I recommend submitting a test area to confirm both the results and the procedure prior to starting a stone or hard surface restoration or maintenance project. Also the best way to help ensure success is by partnering with a good distributor, like BBI, that knows the business. They can help with technical support, product purchase decisions, logistics, and other pertinent project information.

I pray you all stay safe and healthy.

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.