Thinning Enamel Paint

Thinning paint for spraying has gotten a little tricky now that the solvent content of the paints themselves has been cut back by regulations. May 7, 2007

I'm in the process of painting kitchen cabinet doors. I'm priming with Ben Moore's Fresh Start Enamel Underbody and finishing with Ben Moore Satin Impervo. Both products are being sprayed with a CA Technologies HVLP. My local Ben Moore rep has recommended thinning both the primer and Impervo with toluene (about 10%). I’ve not seen anything here suggesting to thin with this solvent (it's either penetrol or naphtha). Has anyone used this or compared it with other solvents? Also, if I'm getting an orange peel texture with the primer, is it generally a function of the appropriate tip size and thinning this product, or could it be too little air into the gun?

Forum Responses
(Finishing Forum)
From contributor D:
Thinning today’s alkyd paints with 10% of anything gives you paint with the consistency of mud, and thick mud at that! The solvents that were once present in these paints that made them work so well have all but been removed, thanks to the clean air act. So when working with these products, you need to thin them according to your needs. Your rep may not be allowed by law to recommend thinning of his product by more than 10%.

That said, thin your paints with regular old paint thinners. VM&P naphtha is a fast drying thinner. Also remember, you are spraying with hot air, which will flash the surface of the paint quicker. Thin and test. Add some penetrol to the paint as well. This will help to keep it wet. Don't worry so much about the primer coats. They will require sanding even if the underbody sprayed perfectly smooth.

Be more concerned about coverage. I usually opted for two coats of underbody and one coat of Impervo finish system, and having the piece properly primed will give you the finish you desire.

From contributor M:
Either paint thinner or naphtha work well with the alkyd Ben Moore, and as contributor D said, you will find you will thin more than 10 percent. I find I am thinning Impervo 15-20 percent, depending on the time of year. Naphtha does help dry quicker. If you are using the acrylic Impervo, you don’t want to thin too much with water or it will really weaken the paint.

From contributor L:

I've been thinning my BM Fresh Start with regular paint thinner. About 3/8 cup to 32 oz primer. For the acrylic about 2-3 oz of water to 32 oz of paint. I use a cheap Husky pressure cup siphon gun and get outstanding results. If this is going inside, I would suggest using BM Super Spec primer. It dries in 15-30 minutes and can go on as smooth as glass for the second coat (sanding the 1st coat with 220). The Super Spec doesn't have as good a build as the Fresh Start, but if you are starting out with smooth surfaces, you shouldn't have to worry.

From the original questioner:
Thanks for the responses so far. Today I thinned it a bit more than 10% and I'm getting the underbody to spray very much to my liking (i.e. smooth). I also appreciate the responses to the suggested solvents. I'm sticking with my toluene mix for this pot. I'll try penetrol when this is empty. Guess my original question should have also asked what the heck the difference between all these solvents is? Anyone have an idea why the rep would have suggested toluene?

From contributor R:
I thin it with lacquer thinner. Dries fast. You might need to thin more than 10%. That sounds still too thick. You need a well heated shop to have it dry, unlike pre-cat. If it were me, I would use pre- or post-cat vs oil paint. It will come out much better and quicker and you can get it to match any BM color.

From contributor A:
All of the painters in our neck of the woods use naphtha. It speeds up the drying slightly, whereas adding paint thinner or mineral spirits will slow it down to a crawl. Toluene is a pretty fast evaporating solvent. It might mess up how the paint levels and flows.

From contributor N:
Penetrol for both primer and finish! I have been doing this for over 16 years and this is a great system. If latex, use Thinx, a latex paint thinner. This stuff is unreal!

From the original questioner:
Thanks, contributor A, for your response regarding tolulene being a quick evaporator. Seems there are a few “standard” solvents that keep coming up to use as a thinning agent and toluene isn't one of them. I sincerely appreciate the responses - very helpful!