Those turned out great. Another perfect use for soft washing. No wand strokes in that stone!

AC

Nice work steve

Thanks all of you for the compliments.

This is the power of networking. We take a little bit from the many professionals on this forum and others and find the right blend for our company. We also hope what we share is of value to the group too.

Doug, I have to tell you the schooling made a huge difference in our confidence. Now, we just need miles of roof under our belt!

Sincerely,
Pap Pap

Steve, I have a customer with very similar material.  As you can see in my photos I'm not getting the job done. What is your secret. This is a $7 million dollar home and I really need to get it cleaned.  There are many other opportunities with this customer.

Thanks John. I have read some posts about "pre-soaking" with Greenwash. What do you think. This will probably take 3 coats.

Robert
I have been off the grid for a few days.

When we have really badly infested capstone, we go nuclear... Like John says, Layer it and when I get all done there are times I will leave a coat on the caps to just soak in and get the deep stuff.

As far as tile grout goes, it is tricky. You never know what has been spilled or tracked into it. It is cement based so you can use a hot mix. Always test any dark grout color to make sure it will not white out when you treat it. It may not have been grouted with a polymet modified exterior grout, so it could lose it's color.

AC is right, pressure does not remove embedded biology or some stains. The wrong tendency is to get closer with the wand. Do not do that.

I will use a White Tip on my pressure washer dialed way down so we can loosen the embedded dead bacterias and dirt etc after the chemicals dwell for awhile.
Just remember sandstone is layered sediment rock, so it can be delaminated with too much pressure. Sometimes what we reveal is the sins of the homeowner and his previous personal power washer sessions. They have a tendency to get real close to the grouted areas to get the deep stains out. When they do, they picture frame the soft tile edges. Not good

We have a 36 year installation background in flooring, so we have a level of confidence on what we are looking at and set expectations accordingly. I always remind the homeowner that grout is the weakest component in the tile installations. You have 3 sides of grout with cold joints, so it just lays there by gravity. Organic growth and dirt will fill the fine cracks caused by the grout shrinking and cracking along the sides of the tile.

If that tile is limestone, it will be very soft. If it is travertine, the small holes really hold a lot of grit and dirt.



Last point: If the biology has been eating that stone cap for a long time, it will have pitted the surface and that will affect the visual outcome you can expect.

AC Lockyer wrote:

---

I often add pixi dust (sodium peroxy mono persulfate) to my mix at about 4 oz per 100 gallons.

My kids college ACU in Abilene, TX spent #380,000.00 having the wand strokes removed from one of their buildings a couple years back.

AC

---

Do you use PixiDust above 40 degrees? Do you use it to activate a flat mix (how old max) at any temperature? It is a catalyst or an oxidizer? What's the difference ;)

AC, the $380K tab for pressure washing damage would be a heck of a selling point. Do you have an article or website you can share?

Troy, does your Doheny's work in all temperatures?

Still learning,

vic