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Mysterious substance on bathroom walls

Looking for some insight as to what could be on our upstairs bathroom walls. In this picture you can see what I'm referring to. The substance builds up on all four walls, usually higher up in the bathroom. I would describe it as orange-ish and slightly tacky/sticky or dry to the touch. Typically after a shower it's easily wiped off the surface, but will come back regularly.

We have a crawl space behind the bathroom, and I've recently noticed the same in a few areas there as well.

Is this mold? Could it be originating from the fan vent, the roof or paint? We've lived in the house for 2 years and it's always been like this.

Thanks for any help you can provide.

A. Spruce
Re: Mysterious substance on bathroom walls

That nasty brown gook dripping down your walls would be you, partly. When you shower, the oils in your skin, bath products, etc become atomized and airborne. These airborne particles pick up dust that is in the air. The walls are cool, the moist air is warm, causing condensation of the moist air onto the walls, depositing all the dirt, oil, and other contents onto the walls with it.

Simply wiping the walls down periodically will keep the brown spots and streaks away. Installing a good bathroom vent fan on a timed switch will go even further to reduce these deposits on your walls.

Re: Mysterious substance on bathroom walls

I suspect that your venting is insufficient. Check your fan, service it if needed or replace with a more powerful one. Then run the fan longer.

Also, clean these spots after every shower with a bleach-water solution.

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