I recently re-grouted (mortar joints) our 1950 slate patio.
There are still some hazy patches of mortar on the slate. Is
there anything other than scraping or wire brushing it off the
slate? I know: should have been neater in the work… but I have
this mess now. I have use muratic acid to clean cement before.
Just wasn’t sure if there are new products for cleaning cement
If you have sealed the slate you will need to strip it first. I guess
you have not sealed it yet so mix 50% vinegar with 50% water. If the
water is hard use distilled water. Let it sit, but not dry out for 5
minues or so and then scrub with a nylon brush or a stiff bristle
brush. It may take a few applications but it worked well for a friend
who had the same trouble with an interior slate floor - by the way,
hazy patches on the mortar is common so it's nothing you did wrong.
I have a flag patio and I just added 800 sq/ft.
The real trick is to use a brush while the mortar is still fairly
fresh (set but not cured) I assume you missed that chance.
If this is really just a haze it will wear off pretty fast. Some
muriatic acid mixed about 1:20 with water will speed up the process.
You are probably going to be wire brushing or chipping out chunks.
The edge of a small pointing trowel works pretty good. It won't chip
the slate but it will dislodge the mortar chunks
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