Blotching on siding?

I was at my parents shore house in NJ this weekend and noticed they had some blotching on their siding. In person its more noticeable from a side angle rather than straight on.

Anyway, they had someone powerwash it last year and they believe it was straight pressure, i.e. no chemicals. Just curious if anyone can tell from the pics if this is definitely oxidation or if maybe something else is going on…

looks like a hot sh mix and it dried on it. I would try washing it with a hot mix as well as see if it goes away.


Not necessarily a hot mix but definitely not enough rinsing. House wash mix, dwell, rinse, rinse and then rinse! GL!

1 Like

Hi, it’s been a while but wanted to update. I ended up rewashing with about a 2% mix, let it dwell and then rinsed like crazy but it still essentially looks the same. New images attached. Do you think the mix wasn’t hot enough? FWIW, it seems to be pretty badly oxidized as this side is always in the bright sun and when i rub my finger, a good amount shows up on my finger.

Assuming a hotter mix/dwell/rinse/rinse/rinse doesn’t do anything to help it, what are my options? Is it basically just time to get a brush and manually scrub? It’s not a huge area so I don’t mind manually scrubbing if that will take care of it.

FYI, this is my parents house so it’s not a huge deal (they don’t seem to care at all), but I really would like to fix it for them (really bothers me every time I pull up to their house). Also, I see it as a good learning experience because as I was researching more about getting into this business, oxidation was one of the things that scared me the most. So now I get to see what seems like a pretty bad case first hand and would love to see thru resolving it.

Any thoughts/suggestions would be really appreciated?


1 Like

What was your surfactant and which nozzles did you use? It looks like disturbed oxidation to me but I could be wrong. I’d try to scrub with a purple degreaser.

1 Like

I used Elemonator and the 1st story chemical then rinse nozzles of a JROD for my 4GPM/4000PSI belt driven PW (sorry, I’m not real good with knowing the nozzle numbers/degrees and whatnot offhand, which I assume is what you were looking for).

So purple degreaser would be something like Zep? Dumb question, but would scrubbing with that take the oxidation off the siding or does it just smooth it out/blend it in better, so to speak?

Use the same nozzles to rinse as you do to soap (0040/2540) the others are high pressure and shouldn’t be used to rinse in most people’s opinion. Zep purple or any sodium hydroxide based degreaser which will be purple. It will take off the oxidation so make sure you do the entire side. Maybe do the bottom panel first and see how well it works and go from there. Clip a rag to a brush on a pole or use a soft bristle brush.


Thanks for the info, really appreciate it!

1 Like

No problem, let us know how it turns out.

1 Like

I’ve scrubbed oxidation off with purple degreaser. I pumped sprayed it on with a 1/3 degreaser and 2/3 water. Brushed with a medium to soft bristle brush. Don’t let it dry on there.


How close are you to the surface when applying and rinsing? Even when applying, you should stand back about 6-7’ or you will disturb the oxidation.

Had a similar issue, I pump up sprayed the whole side with 6% and it came out perfect instantly.

Are you a troll?

1 Like

This post was flagged by the community and is temporarily hidden.

My parents actually had another company do their house last year before I started doing PWing, and they left this miss. And I’m pretty sure they used pressure only (no mix), so that probably explains the disturbed oxidation (if they were just blasting high pressure all over the siding).

1 Like

Thanks for the info. Approximately how long did you leave it on total (total time from spraying, to scrubbing, to rinsing off)?

Maybe 5 mins dwell time. I sprayed small sections, scrubbed and sprayed. It was hot out so I was rinsing it quicker than I wanted to but it come out perfect.

1 Like