I run into this when cleaning flagstone,..it kinda flakes away in layers,..Yea,.I think it's just an age and abuse of the elements type thing. Maybe salting them makes them worse? But,,..I simply evaluate it and tell the customer what I'm dealing with,...and they will be chemically cleaned with minimal use of pressure,..usually a basic rinse. And that will take care of their flagstone. But there's been many times that I've seen it so flaky that it needed cleaned up with a broom and a bucket before even starting. I do have a few customers who seal it,..and that does seem to have helped the flaking,..and also makes the colors of flagstone "pop".

*I've mentioned many times over the years how hard flagstone is to clean,..it holds mold worse than anything else I've ever seen,..and pressure won't clean it anyhow,..usually takes multiple coats of really strong SH and NAOH mixed to get it all out.

**One change in the above statement,..I have one other thing I run into that holds mold REALLY bad,..and fortunately I don't run into very often. But I clean the pool furniture and the pool lining at a Country Club ,...the mold that is created by those tanning oils and Sunscreens is the absolute hardest mold to deal with,..12.5% barely touches it,..and the mold is weird looking,..big black circular spots,..never seen anything like it,...but I hate it,Ha,Ha,..


Jeff

Jeff call charles at eatoils.com.
I believe BT200 may work on the oily molds.

Sample products is very reasonable so you can try it

Thanks Steve,..I am going to check into it,..because I have ALL those damn pool chairs to do again this year,Ha,Ha,..

Jeff

Thanks Jeff for the help. I also deal with a black stain around my liner every year...usually when it's first open Leslie pools sells a product ( can't remember the name of it ) But wiped on ...wiped off. I will see if I can find it.

Thanks Patrick,.Yea,..I'll take any advice or recommendations, I can get for this type of mold. It's the chairs that are REALLY resistant to even 12.5%.

Jeff

Jeff I hear good this about Dragon Juice. Check it out mydragonjuice.com/