Different guns for primer and paint?

[jmoffett]

What is the purpose of spraying primer and paint out of different guns, other than perhaps tip size? Last week I sprayed Z-chrome Rust Defender with an Astro Pneumatic standard gravity feed gun with 2.0mm tip and it did ok but it seems like I had to use alot of material to get complete coverage. It took nearly a gallon to cover a hood, two fenders, a tailgate, and cowl cover for a '63 Chevy pickup.

Today I needed to spray some Por-15 Tie Coat Primer on my Mustang and decided to use my new Astro Pneumatic HVLP gun with 1.5mm tip just to see how it sprayed. It took about half a pint to fully cover the entire jamb area of a door, the door hinge jamb on both sides of the car, and the entire taillight panel and trunk jamb area. The HVLP gun gave me complete coverage on the first pass.

I realize the two materials have varying thickness, and the tip sizes are different, but I'm not sure I'm interested in using anything but the HVLP gun anymore. Is there any reason to have two guns?

[Serge]

Well, it's convenient...you don't have to change tips on the guns...but more important, the guns won't ruin a job...

I have dedicated guns for primer, basecoat, clear, mud and a couple used for every thing else like ss urethane. The reason being that:

1) The primer gun sees only primer. Primer hardens real fast. I use epoxy exclusively so when it jams in the gun it's difficult to clean, thus could create problems in my top coats. If I have problems with a gun while doing primer it's not that critical, you take it appart, fix it and respray...sand...not a big deal...(1.6 or 1.8 tip)

2) The basecoat gun sees no catalysed products. It's easy to clean (basecoat is easy to disolve, even after its hardened). It's used for color, and has a 1.4 tip...

3) The clear coat gun will never spit a black spec of old basecoat in the middle of a white hood...or worse, a spec of metalic glitter in the middle of a black hood...The idea here is that nothing but clear stuff goes in that gun, so it's not risky...(1.3 tip)

4) A cheeper gun with a 2.0 tip for mud (polyester sprayable putty). Never put that stuff in a gun you like...

5) The other guns are don't care gun. One is a touch up (lph-50LV) the other a full size (lph-400lv) These I clean carefully and treat to anything I have to shoot that is not base or clear. They see some thinned epoxy and the full size gun is used as a sealer gun (switched to a 1.5 tip for sealer).

Just 2 cents...
Serge

[Andy]

I agree with Serge about not using your good top coat gun for primer, unless you take extra time and clean it very thoroughly. Primer is more difficult to clean out of a gun than top coat paints.

I have another question on primer guns. I have been using my old Binks #7 gun (1.8 tip) for primer. I also use it with a pressurized cup for heavier materials ( sprayable filler, etc.). It seems to work ok for this. Would I be any better off to buy a new HVLP gun for primer? What should you look for in a primer gun?

[isprayum]

3) The clear coat gun will never spit a black spec of old basecoat in the middle of a white hood...or worse, a spec of metalic glitter in the middle of a black hood...The idea here is that nothing but clear stuff goes in that gun, so it's not risky...(1.3 tip)

Amen to that. This is one rule I have reluctantly learned to live by