Pics of trucks in Primer Paint

[markeb01]

Originally Posted by Dan in Pasadena

Thanks markebo1,
I (obviously) know NOTHING about spraying Rustoleum or anything other paint. I've only ever used ordinary mineral spirits to thin or clean it up. I know you're not telling me/us to use that, so what do we use?

Experiment with the thinning ratio or where do we start?

The at-gun throwaway water filter is sufficient because I always had the impression you were supposed to use that WITH the permanent at-compressor type water separator?

I just went out in the garage and looked at a can of gloss Rustoleum. The instructions say “If thinning is necessary, thin material only with mineral spirits or acetone”. Most people that buy this type of paint are going to use it for some type of household project and aren’t aware there are any other options available beyond what their local hardware store carries. If the paint is going to be applied with a spray gun and it’s too thick to flow through a spray gun, thinning it will allow it to feed through the spray head. In addition to getting through the gun, mineral spirits will tend to make the paint more “runny” during drying, while acetone will tend to cause it to dry significantly faster. If a “flat” paint is being sprayed, acetone will generally make it dry very fast (the more acetone the faster the drying) to the point it comes out looking rough and chalky. Spraying paint straight out of the can will also work, but requires a large tip in the spray gun or the paint will clog the gun. This is why people say they use a “primer gun” which generally has a very large tip to flow heavy solids paint.

Whether spraying straight from the can or by using mineral spirits or acetone, the main variable is the thickness of the paint. If it’s too thick the finish will orange peel because it doesn’t flow out well during drying, if it’s too thin it is more likely to produce runs especially on the vertical surfaces.

This is why I always use Acrylic Enamel Reducer when spraying any enamel paint. It’s more expensive and must be purchased at an auto paint supply store, but it allows you to change the properties of how the paint flows and the finish it produces. I learned these concepts years ago when all the cars I painted had a gloss finish. If I painted on a cool day, high speed thinner would tend to make the paint set up faster so it didn’t sag or drip. If it was a hot day, slow speed thinner would allow the paint to flow out better for a nice smooth gloss finish. On an average day when I might be able to use normal or medium speed thinner, I would try to lean toward a bit more slow thinner in the mix, so the paint would really flow out into a beautiful glassy smooth finish, just short of producing runs. This is the mix I used to paint the grille and front bumper with Rustoleum gloss white.

Acrylic enamel reducer contains more expensive chemicals designed for automotive paint. In addition to better managing the speed of drying, it also produces a nicer looking finish.

Which speed thinner to choose depends a great deal on when you intend to paint. For a relatively inexpensive way to experiment, I’d suggest start by getting two quarts of acrylic enamel reducer. If it’s cold, buy and quart of medium and a quart of high speed thinner. If it’s hot, try medium and slow thinner. Start with the medium speed thinner. Mix up a small batch and shoot a test spray on something (old toys, a dead garbage can, whatever is available). If it doesn’t produce what you want, change to or add the other speed thinner and just keep track of what mix produced which result. Disposable paper cups are convenient for measuring small batches of paint. As mentioned earlier it sounds complicated but really isn’t. It doesn’t take that long to mix up a batch or to find out if you like the result.

I’ve used both PPG Delstar and Dupont Centari acrylic enamel reducer because it is what my local paint shops carry, but any name brand will work just fine with hardware store enamel. In the PPG line the breakdown by part number is:

DTR600 Fast (below 65 degrees)
DTR601 Moderate Temperatures (60-75 degrees)
DTR602 Medium Temperatures (70-90 degrees)
DTR604 Slow - Hot Temperatures (85 degrees and above)

In the Dupont Centari line the part numbers are:

8034S 65-75 degrees
8022S 70-85 degrees
8093S 70-90 degrees
8096S over 90 degrees

The part numbers may change between quarts and gallons, but the above provides a reference point so you know what to ask for.

And yes, a permanent water separator is essential or the disposable filter at the gun can be overwhelmed and fail. If you have the option, it’s better to mount the separator farther downstream from the compressor as it will collect more water than being mounted directly to the compressor outlet. Before I had a hard line system I mounted the water trap half way across the garage from the compressor and connected it with a piece of hose, and it did seem to help collect more water.