Devilbiss JGA 503 and Sikkens

[Mikec35]

I have a JGA 503, not sure how to tell what tip it has. I will be using Sikkens color build primer-sealer-hardener and Autobase plus paint. Is this gun ok for these products? I am only going to paint the door jambs, trunk and the cowl area on my car. Also, my compressor is a 30 gallon, 5hp, not sure of cfm.. I am hoping it is enough for these small areas.. I wouldn't mind getting an inexpensive newer gun if it would paint better and save me from wasting this expensive paint. Any suggestions? The tech sheets say for the primer to use .071-.087 tip and for the paint to use 1.3-1.5 tip for hvlp gravity feed, and 1.8-2.2 tip for hvlp siphon. Any advice would be greatly appreciated!!

[Phil V]

Look on the air cap and there will be some numbers stamped that will read most likely either 80 or 9000. If its the 80 air cap then its good for primer, acrylic enamel and lacquer but NOT for acrylic urethane single stage or clear coats. If the cap is the # 9000 then it will work with any paints, including the acrylic urethanes.

[Phil V]

You air compressor will work OK for doing door jambs, etc. Its not big enough to do a full paint on the outside of the car.

[Mikec35]

It has 80 stamped on it. Is it worth buying a 9000 cap or should I just invest in a hvlp gun, maybe something like the devilbiss finishline? By the time I buy the cap and when you figure the paint transfer efficiency with the JGA maybe a new gun would be better? This paint and primer is expensive, I would like to waste as little as possible...I appreciate your responses..

[Phil V]

The #80 air cap that came on your gun from the factory is excellent for primer, lacquer, acrylic enamel and even the basecoat for a BC/CC paint job but it does a poor job with acrylic urethane single stage and clearcoat. A new #9000 air cap will set you back about $75.00 which is about half way to paying for a new Finishline III HVLP gun.

To be honest with you the #80 air cap might work fine for doing just door jambs and under the hood/trunk area. I just wouldn't use it for spraying the full outer surfaces of a car.

The Devilbiss JGA series of guns are in my opinion the best all around spray guns ever made. I have one with the #9000 air cap and still use it relatively often. I do have an Iwata LPH 400 LV for spraying large areas of clear (like a full paint) but my old JGA gets used for most spot jobs and panel painting etc.

You mentioned transfer efficiency between the JGA and an HVLP. That would be applicable if you were doing a full paint on a relatively large vehicle but cutting in a car (doing the jambs, under hood/trunk) you will notice very little difference in material savings using an HVLP as opposed to the the old JGA.

[Mikec35]

Phil, Thanks for all the advice.. The #80 cap is a 1.8. Instead of getting a new cap, couldn't I just adjust back the fluid knob a turn or two?

[Phil V]

Mike, where the problem arises with the old JGA spraying urethane topcoat paints is that the air cap wasn't designed to break up the urethane topcoat paints into fine enough droplets (atomization). It worked fine for lacquer and acrylic enamel because it was not an issue about how fine the paint droplets had to be when they came out of the gun. Acrylic urethane is a different story, it has to be atomized fine enough or it will go on with serious orange peel, dry spots and even runs. Picture in you mind trying to spray a car with one of those homeowner type Wagner power painters. The droplets coming out of the Wagner is huge compared to an automotive type spray gun.

There are ways to "cheat" the gun into bettering the atomization with the #80 air cap. Raising the air pressure and cutting back on the fluid is one way, over-reducing the clear is another way to increase atomization. At that point your paint transfer efficiency will drop down to around 30% (70% end up in the air as overpsray). Shine die-back is directly proportional to how much reducer you ad to the clear. The more reducer you add to clear the more its going to shrink and cause die-back or dulling of the paint shine.

I'm sure you can get away with your JGA with the #80 air cap for doing the interior and cutting in the door dambs, under hood and inner trunk area. Spray some junk parts first to get a feel for the gun and the material you plan on spraying. It may seem like wasting expensive materials but in the long run its a lot cheaper than redoing everything you paint because of runs and dry spots.

[Mikec35]

Is it any more difficult to use a HVLP gun? I saw a craftsman HVLP gun, which is made by devilbiss on clearance for $69. It does not say what size tip it has, but since its newer I am sure it will probably work ok.. I am now thinking of buying this gun instead of trying to make my other work..

[Len]

Since there has been a little confusion about HVLP I pulled this explanation from an old archive to better explain the difference.

There are two things that differentiate conventional from HVLP spray guns.

1. "Transfer Efficiency” means the percentage of material that goes from the cup to the surface being sprayed. HVLP needs to transfer 65% or more of the material to the surface.
2. Pounds per square inch (PSI) of air pressure measured at the "air cap" of the spray gun. The air cap is the part that surrounds the fluid tip where the paint comes out. Less than 10 PSI is required (behind the air cap) for a gun to be HVLP. This cap pressure usually doesn't need to be measured because it's controlled by adjusting the inlet pressure and the correct inlet pressure will result in the correct cap (outlet) pressure.

The old "conventional" spray guns atomized well but transferred as little as 25 to 40% of the material to the surface while having a pressure 20, 30 or more PSI at the air cap. The latest technology is the "compliant" spray guns that meet legal requirements in many states because they transfer 65% or more of the material to the surface but they have a pressure at the cap that exceeds the 10 PSI so they cannot be called HVLP.

There are pros and cons to all the variables because when you increase performance in one area you suffer in another. For instance when you decrease the pressure with HVLP you also decrease the ability of the air to break up the paint into very small droplets. At the other end of the equation when you increase pressure you generate better atomization but you lose transfer efficiency because the increase air generates effects that cause the paint to go into the air and not on the surface.
The compliant guns have a lower pressure than conventional but not as low as the HVLP. With the better engineering these compliant guns are better in some ways and not as good in other ways when compared to both conventional and HVLP.
Judging which spray gun to purchase is almost like judging which car to drive; you want to calculate....

1. Fuel consumption or in the case of the spray gun its "air consumption" meaning CFM needed to power the tool. Will your compressor keep up?
2. "Performance" Will it fit you needs? Will it generate the result you want?
3. "Cost" Does it fit your budget? If you spend too little you could possibly get an inferior tool and if you spend too much you may be waisting your money.

I find that a "good" HVLP spray gun will atomize well and be much easier to handle while a compliant gun will move faster, atomize better but won't handle as well as the HVLP. What this means to the user is that the results with compliant may be smoother and faster but they probably won't be as consistent as HVLP, especially for the painter that doesn't paint frequently to boost their skill level.

With reduced pressure at the cap you generate less of an "air pillow" on the surface which means that the changing angle of the gun doesn't drastically effect the result on surface like it does with higher pressure at the cap and a more dense air pillow.

Personally I really like the consistent results from my HVLP gun because I tend to polish most of my work and, since I'm no longer a production shop that needs to meet deadlines on my jobs, I don't need a gun the applies the paint quickly. With their consistency HVLP guns tend to generate much less overly wet or dry areas that result in dull spots and runs while making the material go a long way with it's good transfer efficiency. I also find that it's a lot easier for me to generate a high quality job with a little orange peel followed by polishing than it is to generate a good job that has runs and dry spots needing repair. However, if you're looking for speed as well as meeting the legal requirements for a paint shop business in your area OR you're painting daily OR have a limited air supply it may be wise to look at compliant or conventional spray guns. There's something for everyone.