What can I mix with paint to avoid mold?

Question

I am helping a friend painting his garage. He has lots of problems with mold because it's an underground garage.

He already bought the paint. I know there are some additives you can buy at specialized stores, to avoid or delay mold but I am actualy looking for something home made.

Is there anything, that one has usually at home, that I can mix with the paint to delay fungus?

We cleaned the walls with bleach, and I thought of mixing some bleach in the paint, but I am not really sure that would work or even if it's advisable.

Answer 1

Depending on the paint you bought, you may be able to add lime which is a mold inhibitor due to its pH.

If you can still return the paint, making your own milk paint (aka casein paint) at home is an option. Milk paint has the property of being a natural mold inhibitor if done correctly. Numerous recipes (and youtube videos) can be found online with a quick search depending on your application.

Answer 2

There are washes and primers that can be used before painting to kill and inhibit mold.

One example: http://www.homedepot.com/p/Zinsser-1-gal-Mold-Killing-Primer-2-Pack-276049/205009921

Edit: Just noticed you're asking for a home made solution. You mention bleach, but not if you're talking about chlorine, hydrogen peroxide or something else. Chlorine might kill off existing mold, but as it's a quite volatile gas, the effect probably won't last long. I wouldn't try to add anything home made to the paint, as you may ruin the properties of the paint itself.