Cracking with Water-Borne Clear Over Milk Paint

Hard clear coatings over softer color coats can be problematic. June 9, 2007

I have been spraying water based varathane over milk paint using the Wagner conversion gun, and sometimes experience either cracking when it dries or hazing. There is probably a very simple solution that I'm unaware of, as I'm quite new to this.

Forum Responses
(Finishing Forum)
From contributor P:
I can't offer any answer to the problem, but I was curious as to why you would spray, or apply anything other than oil, over milk paint.

From contributor K:
Sounds like the milk paint wasn't completely dry. You might want to seal it in with SealCoat next time.

From contributor M:
Milk paint can be tricky with topcoating compatibility problems. I have had problems and have had to strip and start over. Old Fashion Milk Paint Co. sells a clear for this purpose. Various sealers are potentially a problem. Call Old Fashion and order the clear.

From contributor P:
What's the reason for the clear? I've used milk paint for years but have never put any sort of clear on it. To me the beauty of milk paint isn't fully realized until it's had years of wear applied. I would think that encasing it in plastic would be somewhat self-defeating.

From contributor J:
I had a similar problem when I tried waterborne lacquer over paint. I had very fine cracking of the topcoat. I was used to spraying solvent based, which you can put on a little heavier. I found that with the waterborne, very thin coats when spraying solved the problem of cracking. I did totally sand bare and started over. It was a pain.

From contributor A:
A good rule of thumb is don't put a hard coating over a softer coating. Don't know about milk paint, but paint in general tends to be soft compared to a hard, brittle coating like lacquer. Cracking is exactly what you'd expect to see if you do this.