Recognizing Easy vs Hard-to-Strip Stone Coatings
By Frederick M. Hueston
Anyone who has been in the stone or tile restoration business long enough has run into the dreaded mystery coating. You walk into a job, the floor looks shiny, and the client swears it was “sealed.” But was it sealed, coated, or dipped in something closer to car paint? Knowing the difference between an easily strippable coating like acrylic and the harder stuff like urethanes or epoxies can save you hours of labor and a lot of frustration.
Acrylics: The Easy Ones
Acrylic coatings are the most common. Think janitorial floor finishes used on VCT and applied to stone and tile. They’re water-based, relatively soft, and they strip with standard high-alkaline strippers.
Clues it’s acrylic:
- The finish scratches easily with a fingernail or a coin.
- It will scuff and mark from shoe traffic.
- If you drip a little high-pH stripper on a spot and let it sit, the finish will soften, turn gummy, and wipe away.
- Often reapplied in layers, so you may see uneven buildup around edges and grout lines.
Removal tips:
Use a heavy-duty floor finish stripper with hot water and a floor machine. Black pads or stripping brushes usually take it off. Wet vac the slurry and rinse thoroughly.
Urethanes: The Middle Ground
Urethanes are tougher. They’re often used where the installer wanted a harder “protective” coating. These can be water-based or solvent-based, and either way they don’t respond as quickly to standard strippers.
Clues it’s urethane:
- Much harder than acrylic, but still flexible enough to dent rather than chip.
- Doesn’t soften with a quick hit of alkaline stripper, though long dwell times might break it down.
- Has a glossier, more “plastic” look compared to acrylic.
- Often applied in thinner coats than acrylic, so you don’t see as much edge buildup.
Removal tips:
You’ll usually need a strong solvent-based stripper or a combination of chemical stripper plus aggressive agitation. Sometimes sanding screens or diamond abrasives are required to break the surface before chemicals can penetrate.
Epoxies: The Tanks of the Coating World
Epoxies are the hardest of the bunch and by far the most time-consuming to remove. They’re chemically resistant, thick, and bond strongly to the surface.
Clues it’s epoxy:
- Extremely hard and glassy, can’t scratch it with a coin.
- Alkaline or solvent strippers barely touch it.
- If you try the spot test with stripper, nothing happens even after 20–30 minutes.
- The surface has a rigid, almost permanent feel.
Removal tips:
Forget about traditional strippers. Mechanical removal is usually the only option. Diamond grinding or sanding is often necessary. You may combine that with a methylene chloride-based or other aggressive solvent to soften what’s left, but it’s messy and hazardous. Always use proper PPE and ventilation.
Field Test Strategy
When you’re not sure what you’re dealing with, here’s a simple approach:
- Test spot with alkaline stripper: if it softens quickly, it’s acrylic.
- Test with a solvent-based stripper: if alkaline doesn’t work but solvent starts breaking it down, you’re probably dealing with urethane.
- If nothing works: odds are you’re staring at an epoxy and will need to grind.
Final Thoughts
The key is to never assume all coatings are alike. Acrylics will have you in and out quickly, urethanes make you work harder, and epoxies can turn into full-scale demolition. Always test first, explain the difference to your client, and price the job accordingly. Misidentifying a coating can turn what should have been a profitable project into a money-loser.
