Stubborn Exterior Mildew
This is a photo of mildew on the underside of a porch ceiling stained with Rubio Hybrid Wood Protector with extra M1 Mildewcide added: https://imgur.com/a/lbMsHS1. The substrate is Doug Fir, which was stored under cover, then sanded and stained on the bench, prior to installing in Aug 2023. Zero water exposure – except for our copious morning dew (central TX).
I’ve removed mildew in this exact situation (same stain, same building), except the substrate was Southern Pine, using diluted bleach. But I’ve never seen mildew here that looks quite like this — and *nothing* will get it off. I tried diluted bleach at the usual dwell time before scrubbing, then 20 min, 30 min, and 1 hour. I tried 70% alcohol, hydrogen peroxide, vinegar, and pure bleach. I could try your favorite magic cleaner… but it’s hard to imagine when bleach does *nothing* (except wear the surface of the wood). Thoughts?
Again the only variable (compared to situations in which I got the mildew off no problem w/bleach solution) is that it’s Doug Fir.
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Replies
Have you tried the commercial siding cleaning solutions and scrubbing with a rag undiluted?
Consider trimming the trees a few hours a day of sunlight would likely fix the problem.
Walta
What cleaners do you have in mind? Mold Armor, etc. say to use only on non-porous solutions. I ordered some Concrobium today because it says it works on wood, though it gets extremely mixed reviews. There are no trees nearby... this is the underside of a porch roof, on the east side, just doesn't get direct sun.
Lysol and Mold Armor are what I've been using for this before, but it's hard to remember which one worked better for me, it's been a year or two since I've done it last time. I've also had some really good stuff used for gunsmithing that I've got from https://gritrsports.com/ but at this point it's just a label-less bottle, so can't recall what was that...