Real Milk Paint ® will not stick to oil base finish. Minwax stains, varnish, enamels and polyurethanes are all in an oil base. The way to determine if a finish is oil base is to examine the instructions for the recommended thinner or clean up procedure. If the instruction recommends mineral spirits or naptha, the finish is oil base.
To make the milk paint stick to the oil finish you need a barrier coat. A barrier coat is a coat of finish between the milk paint and the oil finish. Before application of the barrier coat the surface should be cleaned with TSP (trisodiom phosphate) to remove any silicones or waxes, then scuff sanded for good mechanical adhesion.
There are four types of barrier coats we recommend: Ultra-Bond, latex, dewaxed shellac, and Sherwin Williams PrepRite Bonding Primer #643-160-30. Each will give different results.
Ultra-Bond is mixed with liquid Real Milk Paint ® for the first coat. Successive coats can be painted with unadulterated (pure) milk paint. Mix 25% Ultra- Bond to 75% liquid Real Milk Paint ®.
Real Milk Paint ® will stick to cured latex (30 days). If the latex is not fully cured crackling will occur. This is a nice reaction if you like crackle.
Real Milk Paint ® will stick to dewaxed shellac. Dewaxed shellac is generally only available from mail order companies. The shellac available at the hardware store has wax. Milk paint will crackle and slightly flake over the dewaxed shellac. This gives a nice antique over painted look.
For non-crackled milk paint, prime with Sherwin Williams PrepRite Bonding Primer #643-160-30. PrepRite comes only in white. Ask the store to tint the PrepRite close to the color of the milk paint color you chose. This will help to get better coverage from the milk paint. Follow the instructions on the can. Wait the full 8 hours before applying the milk paint.
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