# How to clean a granite marker

**URL:** <https://boards.straightdope.com/t/how-to-clean-a-granite-marker/35447>\
**Category:** Factual Questions\
**Created:** [October 3, 2000, 3:34am UTC](https://boards.straightdope.com/t/how-to-clean-a-granite-marker/35447 "2000-10-03T03:34:46Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\
**Post date:** [October 3, 2000, 3:34am UTC](https://boards.straightdope.com/t/how-to-clean-a-granite-marker/35447/1 "2000-10-03T03:34:46Z")

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I want to clean some lichen from my grandparents headstone. It’s growing in the rough engraved areas. I was thinking some bleach water and a toothbrush would be good for this. Bleach water will kill the lichen and help with it’s removal. Is the bleach going to harm the granite? I don’t think it’s strong enough to etch it, is it?

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**Author:** ![LazarusLong42](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@LazarusLong42](https://boards.straightdope.com/u/LazarusLong42)\
**Post date:** [October 3, 2000, 4:54am UTC](https://boards.straightdope.com/t/how-to-clean-a-granite-marker/35447/2 "2000-10-03T04:54:44Z")

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Bleach will not etch granite, no. In fact, I can’t think of a chemical that will etch granite besides hydrofluoric acid, which they use for etching glass (granite is about 70% quartz, which is in turn the same material as glass).

Since you can’t exactly buy HF at your corner store… I’d say you can use anything. I would recommend SimpleGreen or trisodium phosphate; those may break up the lichen more effectively.

LL

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<div class="post-metadata">

**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\
**Post date:** [October 3, 2000, 11:19pm UTC](https://boards.straightdope.com/t/how-to-clean-a-granite-marker/35447/3 "2000-10-03T23:19:19Z")

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Thank’s for the answer.

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**Author:** ![bare](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bare/32/471_2.png) [@bare](https://boards.straightdope.com/u/bare)\
**Post date:** [October 4, 2000, 3:00am UTC](https://boards.straightdope.com/t/how-to-clean-a-granite-marker/35447/4 "2000-10-04T03:00:18Z")

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Muriatic acid is the common item used for cleaning stone. It is available in hardware stores. Follow the directions on the container.

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**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\
**Post date:** [October 4, 2000, 9:31pm UTC](https://boards.straightdope.com/t/how-to-clean-a-granite-marker/35447/5 "2000-10-04T21:31:40Z")

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Thanks for the input.