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Author: Subject: Graffiti Removal
VIOLiN
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[*] posted on 16-4-2017 at 17:04
Graffiti Removal


Hello everyone. Unfortunately, one of our walls was graffitied. It is on a concrete block wall. I have tried many things. I've given 2 different types of graffiti removers a go. (Usually phosphoric acid, right?). I have also tried using some of my dichloromethane. Nothing seems to be working! I have even used a wire brush and have pressure washed! So frustrating. Do any of you have any ideas to remove it? Keep in mind strong acids like H2SO4 wouldn't work because it would etch/react with the concrete.
Thank you!
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argyrium
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[*] posted on 16-4-2017 at 19:22


You have not given many details that might help with the type of offense.

Is the concrete surface "raw" or painted? If raw, this may be complicated. Is the graffiti spray paint or a marker? What colour(s)?

Often modern spray paints can be dealt with using MS/DCM or other with surfactants and water (+ elbow grease).

I despise "taggers"..

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VIOLiN
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[*] posted on 16-4-2017 at 19:41


The concrete is raw, unfortunately... In addition to this, we cannot paint over it. The graffiti is black spray paint. I'll give the DCM and surfactant mix a go. Thank you so much for your help.
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Sulaiman
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[*] posted on 16-4-2017 at 23:52


HCl / muriatic acid together with abrasion will remove the top layer of concrete, taking the paint with it.

as always, first test on an area not normally visible.




CAUTION : Hobby Chemist, not Professional or even Amateur
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Melgar
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[*] posted on 17-4-2017 at 00:53


Three replies and no mention of toluene or xylene? Considering that's the solvent used in spray paint, if the paint is a cheap brand (which it usually is; graphitti kids aren't generally a wealthy bunch) then those solvents will dissolve it.

[Edited on 4/17/17 by Melgar]
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argyrium
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[*] posted on 17-4-2017 at 14:53


Actually, one generally does not want to "dissolve" the paint, as this often will cause the pigments to migrate further into other areas before being removed. One wants to cause the paint film to swell and become dispersed into a soap/detergent mixture and then removed w/ water. The use of aromatics, esters, and alcohols may aid in the break-up of the films but best kept at lower levels in a mix to prevent the redistribution of the paint. Addition of a thickener (Klucel, Pemulen, Carpool, xanthin gum, or similar) will help hold the solvents in place and increase contact time.

If thickeners are unavailable, you might try making a poultice from fumed silica of similar.

I'd stay away from acids for the reason alluded to above, but the inclusion of an ionic base would probably be OK or advantageous.

Raw stone/concrete can be difficult to treat.

Please, let us know what happens.

[Edited on 18-4-2017 by argyrium]
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