Lumber and Siding - white film on painted (wood) siding

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bigbigwalleye
07-25-09, 08:31 AM
I had mildew on my painted (wood) siding, so I took a small test area and used 1/5 bleach, 4/5 water and a cup of detergent. This worked fine on the dark mildew. Now there are a few areas with a white film that doesn't come off with rinsing, but does come off with wiping. What could this be? And are there suggestions for removal (aside from wiping down the whole area)?

Thanks.

marksr
07-25-09, 03:57 PM
It sounds like the paint is breaking down and what you have is chalk. It can be difficult to remove and once removed, you usually need to repaint. If you can't remove all the chalk, add the appropriate amount of emulsa bond to the 1st coat of latex paint/primer. The EB will bind up the chalk allowing the paint to adhere.
bigbigwalleye
07-25-09, 04:36 PM
Ok, good to know. It does have a chalky feel to it. Does this only happen with latex paint?

marksr
07-26-09, 05:22 AM
It's more of a problem with latex but it happens with other types of paint also. Solvent based paints will adhere over some chalk [what's left after washing] but latex paints don't do well over any chalk - they tend to peel. Adding EB to the 1st coat of latex will allow the paint to adhere. Chalk is the substance that turns the tip of your finger white when you drag your finger tip across the degraded paint.