Dirty walls and ceilings - how to clean before priming


Old 07-12-07, 10:00 AM
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Dirty walls and ceilings - how to clean before priming

Hey y'all-

This 50-year-old neglected house I just bought has walls so dirty that you can see where the pictures were hung. It kinda looks like residue that you see if you burn candles everywhere; my guess is that it's the old residue from the use of the original furnace (no longer there). Anyways - these walls and ceilings look like they need a good scrub before I apply primer and topcoat.

I don't want to introduce any chemicals that will be absorbed into the existing paint which would adversely affect the primer coat. Given that, what's the best chemical to use with a brush to clean/wash the walls/lightly-textured ceilings before priming? Soap and water would be harmless enough, I suppose, but then i'd have to use a brush to scrub and then a clean-water rag to wipe up the residue.

I'm also planning to sand the walls (either before or after cleaning) to knock down a bit of the texture that has built up from 50 years of pain jobs. Knowing that, would one wash before sanding or just sand and not wash at all?

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Old 07-12-07, 10:40 AM
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If your local stores carry it, you should get TSP (Tri-Sodium Phosphate.) It will be in the paint department.

You will still need to scrub with a sponge and rinse (also with a sponge.)

I would follow up all this with a good stain-blocking primer, oil-based Kilz Original if you can stand it, a quality Latex primer (like SW PrepRite ProBlock) if you can't.

If there aren't severe visible smoke stains or odor, you don't need to bring out the thermonuclear weapon of primers, shellac.

I would still wash, but maybe you could do it after the sanding, unless the residue is so bad it will clog up your sandpaper. The washing after sanding will help get the dust off of the wall.

Old 07-12-07, 12:04 PM
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Good call, I forgot about TSP (and I have some!).

The dirt isn't such that it would clog sandpaper so I think I'll move forward with sanding and then wash afterwards. I need to get a good dropcloth with the vinyl backing to protect the wood floors against the tsp.
Old 07-12-07, 04:05 PM
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Make sure you rinse the TSP well, any detergent residue will adversely affect the paint If you have any doubts whether or not the stains might bleed thru latex paint - use a solvent base primer!

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