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Jettowski
New Contributor II

Blue copper sulfate stain

I made a huge mistake and cleaned white shell stone with copper sulfate crystals mixed with water to eliminate mold growth. The end result was that it stained the shell stone blue! I should have known to try a small area first, but no. I have tried 30% vinegar, 100% acetone, muriatic acid, and baking soda. I have pressure washed. Nothing.  I am going to try oxalic acid and lastly hydrochloric acid. My very last choice will be to use a power sander. 

I was wondering if anyone knows of a chemical agent that will counteract/remove the blue copper sulfate staining in porous stone. 

Thank you

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3 Replies
Jettowski
New Contributor II

Re: Blue copper sulfate stain

I found the answer at U.S. General Services Administration website. I used a poultice made of 1-part liquid ammonia, 1-part ammonia chloride powder, 4 parts diatomaceous earth, covered with trash bags, left for 24-hours, and blue is gone. Some places required two applications. Much cheaper than some commercial products on the market.

Forestylan
New Contributor

Re: Blue copper sulfate stain


@Jettowski wrote:

I made a huge mistake and cleaned white shell stone with copper sulfate crystals mixed with water to eliminate mold growth. The end result was that it stained the shell stone blue! I should have known to try a small s9 area first, but no. I have tried 30% vinegar, 100% acetone, muriatic acid, and baking soda. I have pressure washed. Nothing.  I am going to try oxalic acid and lastly hydrochloric acid. My very last choice will be to use a power sander. 

I was wondering if anyone knows of a chemical agent that will counteract/remove the blue copper sulfate staining in porous stone. 

Thank you


How did you discover that the copper sulfate crystals stained the shell stone blue? Were there any warning signs during the cleaning process?

 

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Jettowski
New Contributor II

Re: Blue copper sulfate stain

I mopped the stone with copper sulfate crystals and water, then went back to rinse off with a water hose. The blue didn’t rinse off. The stain was immediate. 

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