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I am about to retuckpoint my exposed brick wall with a custom mortar mix (1x hydraulic lime, 2.5x sand). Once I am done, I plan to clean the residue and other dirt from the bricks using muriatic acid.

My question is: what is the minimum amount of time I should wait for the mortar to cure before it is safe to apply muriatic acid over it? Is a couple of days enough? I have heard that masonry mixes (concrete/mortar) take as long as two weeks to fully cure, I was unsure whether it is safe to bring it in touch with a substance as potent as muriatic acid during that time frame.

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Curious about the lime mortar.. is it a NHL based? Do you have old, soft bricks or some other reason for using a lime mortar outside? –  HerrBag Jul 5 '13 at 21:45
yes, the house (and its bricks) are 104 yrs old. also, i think the lime-based mortar (white) looks better. also, it is inside, not outside –  amphibient Jul 5 '13 at 22:22

1 Answer 1

up vote 2 down vote accepted

I would scrub with water only @10hrs - 48 hrs.

I wouldn't use muriatic/water until 3-4 weeks. Be sure to add acid to water, not water to acid. An 8:1 (water-acid) mix is a good place to start.

Pre-wet the wall and any plants nearby. Rinse off then neutralize with ammonia or baking soda and water.

Old clothes, rubber gloves, eye protection. If you use it any more concentrated, organic respirator.

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i have added water to acid before and had no problem. why do you say the opposite? –  amphibient Jul 5 '13 at 22:26
Small amounts of water (into acid) could potentially boil, spraying a (mostly) acid solution. –  HerrBag Jul 6 '13 at 0:22

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