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Sometimes I just sit and think. Other times I just sit.
eracode:
@David321 Any update on this - eg did the acid get the stains off?
Getting there, it has not been as effective as I would have liked though.
I have had to wait for weekend days when it is cloudy and slightly cooler (rare at this time of year) to apply the acid otherwise it dries on the bricks to quickly (something you cant let happen).
I have been mixing the acid at the strongest recommended dilution which is one part acid 10 parts water, and leaving on the bricks for about 10 mins, spraying more on if it starts to dry so the surface stays wet.
I then use a strong circular brush that attaches to my drill for the scrubbing, the mortar is slightly loose from the acid by this stage which shows the acid is working to a degree.
After the scrubbing the bricks need another rinse with acid as the brush drags dissolved mortar over the face of the brick, something I imagine would look absolutely terrible if I were to let it dry like that.
Then I have been giving it a good rinse with water from the hose to get all the acid off.
As the bricks and mortar are quite porous they hold water and look darker than the rest for a long time, i'm talking a few days at least, so the the results of my work are not known until a few days later.
The result of the two areas I have done at the moment, is an improvement, by about roughly 50%. Its a lot of work and I believe it will take a few applications, I am still not 100% sure if it will work to fully remove the staining but ill have a better idea after a few more applications, when free time and suitable weather coincide.
It has been the most effective product I have used so far so ill keep using it. I am going to use a stronger dilution next time as I am not as worried about the acid burn staining to the bricks that can occur after reading online about the dangers of using to strong dilution. I straight acid on one of my spare bricks and saw no damage to it as a result so I am thinking ill step up to 1 part acid 5 parts water next time.
Here are some pictures of a small area I did which has my best results so far after 3 applications, it certainly has improved, there is still a bit there though, picture looks better than it does in reality.
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