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"How to remove silver-based ("stealth ink") graffiti"



Q. Hi Everyone,

I have been researching this for so long now. We supply a nanotechnology coating which allows 98% of graffiti to be removed with a simple cleaner, however, the 2% we are having a major problem with is a product called "stealth ink". We have done laboratory tests on this "pen", with a result, which I already knew, that the clear solution is a mixture of alcohol, water and silver nitrate. The ink goes on clear, but then begins to stain in UV light. When it is "fresh" it is easily removed, but leave it for an hour or so and it becomes almost impossible to remove. I am hoping, that with what we know in chemistry today, there is a way to remove this stain from the walls. I have the report from the most recent analysis if anyone would like to read it, but they offer no solution apart from "grinding" the surface, repainting and then re coating. Surely there must be a better way. Just so you all know, we have tried, hydrogen peroxide with ammonia (no effect), hydrochloric acid, nitric acid and finally a very fine cutting agent, we call the product here "Brasso", which is used for polishing brass, but with a LOT of elbow grease, it does remove the stain, however, it leaves a shadow and takes a very long time. Surely there is a way to convert the silver back to a salt of some kind and then wipe it off?? I am in desperate need of a solution which works. I look forward to some positive replies.vPlease keep in mind, that the solution to remove this needs to be on a commercial level, where any can apply, wait and wipe. This is on public transport vehicles where the turn around time of cleaning the vehicle is quite short.

Kindest regards,

Hubert Novak
- melbourne victoria australia
^


July 27, 2016

A. You might try photographers hypo (sodium thiosulfate) in water, perhaps with a mild abrasive.

dave wichern
Dave Wichern
Consultant - The Bronx, New York
^


July 31, 2016

A. The purpose of "hypo" in traditional photography is to dissolve unexposed silver halide salts. On its own it has no effect on metallic silver which is what you have when UV acts on silver nitrate.
The process you are looking for is 'silver bleach'. There are a number of options available and since I do not know your exact problem, I suggest that you look at some of the formulations at
http://resources.conservation-us.org/pmgtopics/2001-volume-nine/09_01_Nishimura.html

geoff smith
Geoff Smith
Hampshire, England
^

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