My roommate has an old mortar made from stone that had been outdoors for quite some time. She rinsed it thoroughly,put it in a big pot, and boiled it to kill any bacteria that could be crawling in there.

The mortar has great sentimental value for her, and I'm unsure about what products use for cleaning, if at all, since the stone might absorb the chemicals and render it unusable.

This related question seems to indicate that soap is not to be used with porous materials, such as stone. Why are stone ware and dutch oven items exempt from bacteria?

Before using it for food preparation, is there anything else we should do to avoid health issues? Can we use it already after boiling it?

3 Answers 3


What type of stone, lava, marble, granite? Bleach makes for a nice general purpose disinfectant, as it degrades on its own over time. Let the thing soak in bleach (1 part bleach 9 part water) for a few days then boil again, and you should be good to go; once you find a pestle that fits.

  • Hard to tell. It's light gray. Would someone be able to identify the material if seen? Commented Aug 2, 2015 at 15:48
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    Quite possibly. If the mortar is marble, a drop of vinegar on the bottom should bubble, at least slowly. Commented Aug 2, 2015 at 16:04
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    I'd rinse it, then let it cool and dry before using. Commented Aug 5, 2015 at 12:09
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    If there's residual bleach smell, rinse and let it sit for a week or so. Bleach degrades naturally. Commented Aug 5, 2015 at 13:45
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    I wanted to wait until we used the mortar, to confirm nobody died, before accepting the answer. However, it's been a long time and we still haven't used it, so I'm marking it as accepted as licking the mortar didn't send me to the morgue. Commented Jan 1, 2016 at 19:28

I think you are all obsessed with 'germs', cut off from nature so much you imagine everything a threat! You all need to get a grip! All you need to do with something left outside is wash it out with water, and if any stains some detergent. Children who grow up messing about in earth come to no harm, they have healthy immune systems which can cope with anything nature has. Same with dogs, kids who grow up with a dog and their less than hygenic habits are healthier than kids who don't, and get fewer childhood illnesses. Botulism? Are you mad? You could damge an antique mortar by boiuling it or using bleach. Get real, we are animals just like all others, we have an immune system. You have more to fear from the burgers America eats in vast quantities!

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    There is a partial answer in here, but it drowns in the opinions (the verdict isn't even out yet on that children/germs hypothesis). Please edit them out.
    – user34961
    Commented Jul 9, 2017 at 12:14

Boil in pressure cooker or oven.

I think the worst you have to worry about is Botulism, and it dies at 240.

So the pressure cooker would allow you to get the temp high enough to kill anything real bad.

Oven would work too, but be careful not to go too high because the stone could crack. And make sure to let it cool completely before you move it.

The vinegar is also a good thought. Not sure I would go the bleach route.

  • vinegar can mess up some kinds of stone used for mortars, proceed with caution and try on a non-critical spot first. Commented Dec 5, 2016 at 9:59

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