[Goose]

I can opine, with plenty of editorializing, about cleaning graffiti from deeply textured surfaces because this is a daily thing in our practice.

Goose is correct. Blast.  Better yet than sand.....dry ice. It works like a charm, does not harm the substrate, and there is no secondary mess to clean up after. About as environmentally friendly as it gets, and you can rave at the same time.

This has been an evolution, based on lots of experience and conversations with the pros who clean graffiti.

The cheapest solution is to continuously paint over it. But with nicer surfaces like split face or ground face concrete masonry, weathered steel, or stone, this isn't an option. We then turned to anti-graffiti coatings. I hated them. They made the nice surface look waxy and awful, and they are a single use product. They are intended to prevent a strong bond between the paint and substrate, but come right off when cleaned, along with the graffiti. The product needs to be reapplied, but after any time in UV there is no way to make it uniform with surrounding surfaces and it looks even more godawful than after first applied. The clincher was one of our client's maintenance super who previously worked for Caltrans getting graffiti off of highway signs. He said anti-graffiti coatings simply made their job exponentially harder.  Worse than useless. Got it.

Sandblasting is how we prepare substrates to receive new coatings. It removes everything. SSPC-6 is commercial blast cleaning or you can dial it to SSPC-10 for near white blast cleaning. I don't think SSPC goes to 11, but I'll check it out.  We recently completed six miles of seawall with 100 years worth of sacrificial steel for corrosion. The raw steel surface will behave better than a painted one, particularly where buried. But people will tag anything and there are thousands of square feet of accessible canvas. Ultimately we went with dry ice blasting, because it is acceptable in environmentally sensitive areas and wow, does it work.

Thank you very much for this post! It is always great to get the info from somebody who is "in the business" and actually knows. I was unaware that dry-ice blasting actually existed. Not having water and sand as a "residue" is obviously a very big benefit of the process. In both sandblasting and dry-ice blasting appropriate equipment is required to do the job. I would guess that the dry-ice equipment is a bit more complex than for sand but not by anywhere near enough to outweigh its advantages. Your statement "wow does it work" indicates there is no downside in using it. Very cool! (I had to do it:-)

[Goose]

I can opine, with plenty of editorializing, about cleaning graffiti from deeply textured surfaces because this is a daily thing in our practice.

Goose is correct. Blast.  Better yet than sand.....dry ice. It works like a charm, does not harm the substrate, and there is no secondary mess to clean up after. About as environmentally friendly as it gets, and you can rave at the same time.

This has been an evolution, based on lots of experience and conversations with the pros who clean graffiti.

The cheapest solution is to continuously paint over it. But with nicer surfaces like split face or ground face concrete masonry, weathered steel, or stone, this isn't an option. We then turned to anti-graffiti coatings. I hated them. They made the nice surface look waxy and awful, and they are a single use product. They are intended to prevent a strong bond between the paint and substrate, but come right off when cleaned, along with the graffiti. The product needs to be reapplied, but after any time in UV there is no way to make it uniform with surrounding surfaces and it looks even more godawful than after first applied. The clincher was one of our client's maintenance super who previously worked for Caltrans getting graffiti off of highway signs. He said anti-graffiti coatings simply made their job exponentially harder.  Worse than useless. Got it.

Sandblasting is how we prepare substrates to receive new coatings. It removes everything. SSPC-6 is commercial blast cleaning or you can dial it to SSPC-10 for near white blast cleaning. I don't think SSPC goes to 11, but I'll check it out.  We recently completed six miles of seawall with 100 years worth of sacrificial steel for corrosion. The raw steel surface will behave better than a painted one, particularly where buried. But people will tag anything and there are thousands of square feet of accessible canvas. Ultimately we went with dry ice blasting, because it is acceptable in environmentally sensitive areas and wow, does it work.

Thank you very much for this post! It is always great to get the info from somebody who is "in the business" and actually knows. I was unaware that dry-ice blasting actually existed. Not having water and sand as a "residue" is obviously a very big benefit of the process. In both sandblasting and dry-ice blasting appropriate equipment is required to do the job. I would guess that the dry-ice equipment is a bit more complex than for sand but not by anywhere near enough to outweigh its advantages. Your statement "wow does it work" indicates there is no downside in using it. Very cool! (I had to do it:-)