House Cleaning and Stain Removal Forum

[Frusty]

Please help me clean a stain!

It is on a gray 4'x2'x2' granite historical marker. Evidently, the cast aluminum plaque on top has collected water under it which then ran down the front leaving a black stain as it ran. I have only tried several granite cleaners but they can't touch the stain. I've been told numerous chemicals to try on it but haven't, for fear of making matters worse.

I'm sure someone has run across this problem before, but our local chairman of the historical committee doesn't know what to do. Anyone with knowledge, please advise.
thanks, Frusty

[mrscleannw]

Hello Frusty,
Thank you for writing to Mrs. Clean.

If the granite is damaged or has lost its finish, be careful, as some cleansers can actually make it worse. If this is the case and the granite has lost any of its finish, you may have a permanent stain and you should consult a professional.

Always test in an inconspicuous area first and never use acid on your granite as it will damage the finish.

Granite is an igneous rock and composed primarily of four minerals. Depending on the location of the source rock, granite will vary in composition:

• Quartz
• Feldspar
• Mica and some
• Hornblende

Aluminum; like other metals, does oxidize. The difference with aluminum is it will oxidize the same color as the metal. It is difficult to say what exactly is causing the staining as we can’t tell what the underlayment is or the adhesive type.

Elbow grease:
• First you might try mild detergent and a little elbow grease. Rinse, buff then check the results.

Organic stain:
• Make a paste using powdered whiting (this can be purchased from a paint store) or cream of tartar and mix with 20% hydrogen peroxide (hair bleaching grade).
• Make a thick paste.
• Apply a thick coat of the poultice to the stained area.
• Cover with a dark plastic (like a black garbage bag) bag; hydrogen peroxide will turn to water if exposed to light.
• Leave the mixture on overnight.
• Rinse the area with cold water and blot to dry.
• Repeat the process if necessary.

Deep embedded stains:
• Using rubber gloves mix a poultice of powdered whiting or cream of tartar with lacquer thinner into a paste.
• Use a rubber spatula and spread the poultice on the stain (about ¼” thick).
• Again cover this with plastic wrap and tape it down so no air gets in.
• Keep the granite poultice in place for 24 hours; depending on how discolored the stained area is you may want to keep it in place an extra day or two.
• After removing the poultice the granite may appear darker, it may take a few days for the moisture from the poultice to evaporate and the color to return to normal.

If you try a poultice and it does not work well enough, try using CLR (Calcium, Lime, and Rust Remover), dab it on and blot off with a clean cloth.

After you have cleaned your granite thoroughly apply a granite sealer, wipe on and polish it off, following the manufacturer’s instructions. This will help stop future staining. A sealer should be re-applied every 6 to 12 months.

Please post your results for us to see what worked for you!
Mrs. Clean