I always clean my paint brushes after using them for painting interior walls. My usual routine is to rinse them under water and clean them out with a combination of a wire brush and a brush comb, but this isn't working for primer.

The primer I'm using is so thick that it's practically glue. Rinsing under water doesn't do anything at all, and I would need to comb for days to get this stuff out. I'm sick of throwing away brushes after a single use. Maybe the answer here is to use a different primer?

The primer in question is a 5-gallon can of Kilz Original Interior Primer.

  • Have you tried soap, hot water, soaking?
    – jwh20
    Nov 5, 2020 at 18:56
  • I have tried soap, but the stuff is so gummy that I've had limited success. But perhaps the answer is just: more soap Nov 5, 2020 at 20:30
  • 2
    Well if this paint is really oil-based as @Ecnerwal indicates, then soap and water is not going to work.
    – jwh20
    Nov 5, 2020 at 21:11
  • I buy brushes at garage and estate sales for cheap. If I'm going to use them again, I wrap them in a plastic bag. Otherwise just toss them. Life is too short to spend any time cleaning brushes. Nov 6, 2020 at 5:44
  • @SteveWellens With latex paint, that is just wasteful. Water-based paints clean up so laughably easily that why on earth wouldn't you? Mind you 99% of my painting is alkyd (which is a task to clean), epoxy, or LPU (both uncleanable, into the trash it must go) so I stock over 100 brushes. So I know my subject matter on cleaning brushes. The problem with tossies is they are cheap brushes. Better off getting a good brush and taking care of it... when that's possible, lucky you! I can't. Nov 6, 2020 at 17:45

2 Answers 2


The results I get for that product name indicate that it is oil based.

As such, water cleanup won't do.

You should (before painting, with a clean brush) dip your brush in paint thinner and wipe it out so that the deep parts of the brush are -pre-loaded with thinner rather than paint.

When done painting, you need to clean the brush with paint thinner, not water.

You can also use paint thinner to make the thick paint, thinner (better just the tray or cup you have out to paint from, not the whole bucket, and if you are painting from the whole bucket directly, stop doing that & use a tray or cup...) but don't overdo that (there are typically directions on the side of the can/bucket for what range of thinning is acceptable.)

  • I don't know about the rest of the country (or world), but in California the instructions usually just say "do not thin this product", which I believe is to ensure compliance with VOC regulations. Of course this has nothing to do with how much you can actually thin the product.
    – The Photon
    Nov 6, 2020 at 4:34

You've made a leap of assumption that all architectural paint is water-based. That's wrong, but if you want that, it's perfectly possible to paint a house using entirely water-based products. You just have to avoid higher-performance products like Kilz Original.

There are different kinds of paint. You need to read the labels.

The paint label will specify what to use for a reducer (aka "thinner" that makes the paint thinner). Whatever that "thinner" is, you can use that for cleanup solvent. Some paints will recommend another chemical for cleanup if the reducer is too expensive.

Now, Kilz Original is an alkyd (read: oil-based) paint. It says "Do Not Thin", because if you reduced it with paint thinner, the paint-in-pot would exceed the allowable VOC limits for some regional Air Quality Management District somewhere, and they don't know where you'll paint it. VOCs are mineral solvents like gasoline that evaporate and cause regional smog. Los Angeles being the poster child for this; their rules are far more draconian than everywhere else.

The Kilz label indicates using mineral spirits for cleanup; that covers a wide variety of products including paint thinner, literal mineral spirits including odorless, etc. In the halcyon days of my youth before anyone knew better, we used to use 60 cent a gallon gasoline, of course disposal was an environmental nightmare even then. Nobody wanted bare spots on their lawns.

I'm pretty good at cleaning brushes with just a couple of ounces of thinner. I paint stuff I don't want til the brush goes dry, re-whet the brush in contaminated thinner, work that in, paint stuff again til the brush goes dry, re-whet, then use rags to soak the thinned paint out of the brush.

If you have been using water to thin alkyd paint, that would only make it thicker still - and spoil it too!

It really helps to use the right brush, though.

"Normal" hardware-store rollers can be used with alkyd paints/primers like Kilz Original. However "normal" synthetic brushes will not perform well with alkyd paints -- with alkyds, use natural-bristle brushes. Conversely, do not use bristle brushes with waterborne paints -- they will water-log and perform badly.

Bristle brushes are readily available, in any quality from cheap Indonesian chip brushes to badger brushes like your great great grandfather used. I use the cheapie brushes by the 24-36 box, because the LPU paint I like has very expensive solvents, and I'm not spending $10 in solvent to save a $8 brush lol. So the idea of lovingly caring for an expensive brush is pretty alien to me, but in the 20th century many painters did that their whole careers. All paints were oil-based then.

  • Thanks, this is hugely helpful. I did manage to rescue my (non-bristle) brush using some paint thinner, but it definitely occurred to me today that I may just want to get some cheapies for the primer. Nov 6, 2020 at 4:49

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