How to kill green stuff on exterior walls prior to painting?

Pressure washer.

You'll need to get it off for the paint to stick properly. A tiny bit of copper powder in the paint prevents its recurrence. Tiny because the copper is toxic, and turns green or brown in time.

NT

Tabby wrote in news:f4896aff-fb84-46b3-af19- snipped-for-privacy@o20g2000yqk.googlegroups.com:

Thanks. Doesn't that discolour the paint, though?

Al

The Natural Philosopher wrote in news:ijqppf$bkr$ snipped-for-privacy@news.albasani.net:

I'll do that, thanks. I'd still like to make sure that every cell of green stuff is killed though, before I apply paint.

Al

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Try brushing one part bleach to six parts water. Its what they use to wash off 'growers' on grave stones.

If you use too much it does. It really only needs teh tiniest amount.

NT

Nope. BENZALKONIUM CHLORIDE.

I painted over tons of it. It stays dead under paint. No light probably.

pressure wash then water based exterior paint. take at least a year for it to start growing again..

"john reeves" wrote in news:ijrbck$7lv$ snipped-for-privacy@news.eternal-september.org:

Thankd=s for the tip. Bleach certainly seems to work well for mildew. Having said that, the last time I killed some inderior mildew with bleach, some other form of growth took over. It looked like white fluff! When I saw that, I thought "Ah, that stuff must LOVE alkalinity!! So I doused the wall with vinegar! No more white fluff, to date...

Al

"AL_n" wrote in news:Xns9E93B9C6AF8D1zzzzzz@130.133.4.11:

PS.. I tell a lie. I just had a look and the white fluff is back with a vengeance! I notice it is completely odourless, so perhaps it's not vegetable matter at all, but rather some kind of mineral crystalline growth.

Al

Google efflorescence.

The Natural Philosopher wrote in news:ik00pp$7d8$2 @news.albasani.net:

That's it! Thanks...