Problem Solving Forum

| More

March 27 - April 2, 2016

I need to remove coatings from masonry on a historic-preservation project. What are my options for doing so without damaging the mortar joints?

Selected Answers

From Brian Gingras of Finishing Trades Institute of the International Union of Painters and Allied Trades on April 14, 2016:
While I agree with most of the advice provided by the others on this thread, I wanted to float this out there as a suggestion. Over the past several years the Canadian Parliament buildings in Ottawa, Ontario, Canada have been undergoing restoration work which included cleaning of the exterior stonework. I know of a company that was contracted to clean the stonework and used lasers (ablation) to clean the stonework without damaging the stone or the mortar. These buildings are also Heritage sites so they had to ensure there would be no damage to the substrate. Ablation is capable of not only cleaning but also  removing coatings. I think you may want to explore this as an option as I think this may be the way of the future. YouTube has many other videos on using laser ablation, but I wanted to include this specific link regarding the Parliament buildings work.

From Warren Brand of Chicago Corrosion Group on April 13, 2016:
Really interesting thread. Learn something new daily.

From Joe Miller of NextGen Green Building Products, Inc. dba on April 12, 2016:
Yes, soda blasting is the most sensitive abrasive blast method I know about. Dentists use the same process and materials to clean teeth without damaging gums or enamel when used properly. I have used it to remove printing from aluminum cans without damaging the aluminum just to see if it would work. I held the cans in my hands, no gloves. Hope this helps. International Historic Preservation members have reported using it on really sensitive works of art as well.

From Owen Landsverk of Wisconsin Dept. of Administratio on April 12, 2016:
I agree with Tom that it's very likely that chemical removers will saturate the mortar joint to some extent. Another issue to consider is the finish on the brick and how it will react to different cleaning methods. You might be worrying too much about the mortar joints. They are the sacrificial part of the wall assembly and can be re-pointed with matching mortar. I would recommend selecting an area of the wall to perform a mock-up, both for material selection and training the worker in the best approach. Use high image photography to examine the surface of the brick to measure results. Also, for historic buildings, I highly advise reviewing the National Park Service Historic Preservation Briefs 1 & 2-

From trevor neale of TF Warren Group on April 11, 2016:
The type of coating should provide some guidance for a start,  along with testing for  the presence of lead. Latex, being thermoplastic, could be stripped with water under pressure. Alkyds or epoxies present a different scenario, but as Tom has said, please do a small test area first, especially if the operator has not attempted this type of project previously. Sponge blasting offers a variety of abrasives from gentle to aggressive; the abrasive can be  recycled; and it is dust-free. Finally, take your time if it's truly a historic structure.

From Tom Schwerdt of TxDOT on April 8, 2016:
Warren: likely so. Chemical removers will saturate into the mortar to at least some degree, at the very least contaminating them (to a historian  anyway) and quite possibly degrading or weakening them. How damaging a method is also depends hugely on the workers and how they approach the job.

From Warren Brand of Chicago Corrosion Group on April 7, 2016:
Hey Tom:  less damaging than paint remover?

From Tom Schwerdt of TxDOT on April 6, 2016:
Pelletized dry ice blasting is likely to be less damaging than any of the suggestions offered so far. Historic mortar can be quite soft. Whatever approach you try, be sure to TEST in a SMALL, INCONSPICUOUS AREA before committing to the method.

From Warren Brand of Chicago Corrosion Group on April 5, 2016:
It will depend on how hard the paint is. You might want to consider water jetting with aggregate and/or environmentally friendly paint remover. It depends on how hard the paint is and your budget. Paint remover is the best alternative for not damaging the mortar, but it will have the lowest production rate.

From Chuck Benesch of Precision Coatings on March 29, 2016:
Soda blasting or sponge blasting will work.

Please sign in to submit your answer this question    

Tagged categories: Historic Preservation; Masonry; Masonry coatings; Mortars; Paint and coatings removal

Current PSF Question | Submit a PSF Question | Full PSF Archive


HoldTight Solutions Inc.

Axxiom Manufacturing


Western Technology Inc.

KTA-Tator, Inc. - Corporate Office

Abrasives Inc.

Sauereisen, Inc.


Technology Publishing Co., 1501 Reedsdale Street, Suite 2008, Pittsburgh, PA 15233

TEL 1-412-431-8300  • FAX  1-412-431-5428  •  EMAIL

The Technology Publishing Network

PaintSquare the Journal of Protective Coatings & Linings Paint BidTracker

EXPLORE:      JPCL   |   PaintSquare News   |   Interact   |   Buying Guides   |   Webinars   |   Resources   |   Classifieds
REGISTER AND SUBSCRIBE:      Free PaintSquare Registration   |   Subscribe to JPCL   |   Subscribe to PaintSquare News
MORE:      About   |   Privacy Policy   |   Terms & Conditions   |   Support   |   Site Map   |   Search   |   Contact Us