Hi Steven:
X-Jet
Last week we washed a 4-story office building. Assignment was to get it ready for new stain.
Cedar lap siding, built in 1974, probably hadn't been stained in 15 years.
Used a 40-ft bucket lift and an M5 X-Jet.
Lots of green and yellow algae deeply dug in along the lower edges of the boards. Pretty much laughed at 1%. So, stepped it up to 2% and the original stain started running off. This revealed a ton of black algae/mold all over the boards. This was problematic because the building owner had hoped to have it retained with semi-transparent.
Consulted with my buddy Mike Rego about stripping it. Really tough to do because of the massive amount of black and that these were vertical surfaces. We mutually decided on a hotter wash mix, get off as much as you can and tell the building owner that he'd have to go to a solid stain.
Talked to the building owner and he agreed to go solid. So, stepped it up to 3%-4% and it cleaned up pretty good. The painting contractor was impressed.
One thing about it though, the amount of rinsing needed was incredible!