What is this on the block?


On a job cleaning a building with some split cinder block ( at least that it’s called around here). What it is not-
Mold, algae, mildew or anything organic or soot.
I have used straight SH, 30% Sodium Hydroxide.

Not sure what to do? Acid?


I have also tried heat up to 190 degrees with no dice.


turbo nozzle ?


It looks like its part of the color from the casting. Maybe just me and my screen…


No on turbo nozzle.

Not sure about casting color. It is not consistent in that only a small% of the total blocks have this. It only shows on the north side of the building where the mold/algae was the heaviest. But it is not mold/algae - I put 12.5% on it and continually reapplied for 30 minutes (while doing other things) just to see if anything would happened.

Showed my Prosoco shop here today and they are at a lost as well. He gave me a stain remover sample to try which I believe is just muiratic acid solution of sorts.

I almost positive is was nothing I did, as I used the same chem and process over the entire building and only in this one area was it showing.


Scrape it with something and see if it’s part of the block?


Send the pic to info@eacochem. Mike is the guy you will talk to, incredibly knowledgeable about all things stone and rocj cleaning related. Also very willing to help.


Acid burn ?


Maybe. I am going to test a small area with some acid and see if it either cleans it or duplicates it. Will let you know.


Maybe light efflorescence? Could try some 600 by prosoco or some Muriatic. If you already finished the job, what did you end up using?




Might be efflorescence.

At first I was thinking someone before had cleaned with an acid or something, but I noticed it on a newer building the other day that I am fairly positive has not been cleaned with the same appearance.

I have not yet done anything to my job (commercial property and PM has not brought it up) but in the next day or so, I am going to try a Muriatic solution to see what happens. I am also running by the Prosoco shop here in a bit and ill see if they have any 600 samples that I can get 1 of and try that as well.

Will update