I’ve done a ton of this (200,000 sq ft this year alone).
- SH is most likely going to add a mild orange hue to the finished product. My understanding is in the stone are ironites that react to the SH causing the slight organish color. You need to treat the entire wall and not spot clean to make it all blend together. I have not had a single homeowner / property owner comment on the hue, but it is something I see.
- Yes - it takes a strong mix. Usually, you will pressure wash with medium pressure to knock off the surface mold/algae. After that the stones will have a grayish color as the mold/algae is inside the pores of the stone. It is a process of applying chem, keeping wet and letting the chem soak in enough to kill the mold/algae. Be prepared for several (sometimes 3,4 or even 5 applications). Can be very time consuming. You are not washing vinyl here. Sometimes on tough spots, I spray chem and keep apply chem to ensure it stays wet and soaks in for upto 20 min dwell. I almost feel that apply to dry stone is better as you want the stone to soak it in unlike most substrates where you only want the chem on the surface.
- I have used a 2.2 gpm 12 v for chem application as well as pump-ups when I want to control spray more.
- You will be on a ladder for sure - you will not be able to do the normal DS, dwell and rinse like a normal housewash.
- You might consider Agent Halt (chlorine neutralizer) since you will be using a hot mix.
- You can use a product from Prosoco in place of SH called ReKlaim. It is not cheap and is just as toxic (it is basically hydrogen peroxide and sodium hydroxide). It does not bring out the orange like SH, but it is very expensive compared to SH and I don’t think average homeowner would pay the increased cost. It would work well in other situations such as heritage restoration or such.
- Because of the hot mix, you might want to add Arm and Hammer laundry soap as a scent masker along with your Elemonator. It will also help with the cling on the stone.
Here is a link to a post I made about a baseball stadium job I did that was covered in this stone.
You might notice in the video the orangish color I reference above. Some areas not at all, but others, at least to me, I see it. I also speculate that with mold, it is trapping water at/below the surface which might be interacting with the ironites in the stone causing the rust orange and that once cleaned the color is revealed. It is absolutely noticeable when I see someone clean this stone and only spot clean the mold spots.
Good Luck!
