Gun spitting excess powder

[pdeinc]

When I did my first part using black magic powder, gun performed well and I got a satisfactory coating on the part. I did some experimenting with air pressure and techniques and found that with too much pressure, much of powder blew past the part, lower pressure allowed the powder to be attracted to the part.

Did my second part last night, clear coated an automotive water pump. Using what I thought was similar technique, I had the gun occasionally spew powder, sometimes when the trigger was first pulled, other times when I shifted the gun abruptly. By the time I got a satisfactory coating on the part, the gun had probably spilled more powder than was on the part.

Thinking about it later, I had two thoughts. One, how is the PC process affected by ambient humidity? I'm in Florida and it was raining last night, probably 99% humidity. Powder was fresh out of the can tho.

Second thought was that if air pressure is too low, powder can accumulate in the barrel. I may need a different setup on my tank with a low pressure regulator, possibly mounted to my spray booth to control that initial burst of air that I observed. I may be adjusting pressure based on the initial burst and the subsequent lower pressure is inadequate.

[Noob2PC]

Re: Gun spitting excess powder

Thinking about it later, I had two thoughts. One, how is the PC process affected by ambient humidity? I'm in Florida and it was raining last night, probably 99% humidity. Powder was fresh out of the can tho..

Welcome to the CLUB!!! Yes, Humidity does affect the powder application greatly. I have dusted in all weather and all times of the day and if the humidity is up it is more difficult. I try to Sandblast when it is humid and PC when it is not as humid

Second thought was that if air pressure is too low, powder can accumulate in the barrel. I may need a different setup on my tank with a low pressure regulator, possibly mounted to my spray booth to control that initial burst of air that I observed. I may be adjusting pressure based on the initial burst and the subsequent lower pressure is inadequate.

I have 2 regulators plus the gun. I set the last one a 20psi and then use the gun for final adjustments.

[pdeinc]

Thanks for the response noob, can you explain your regulator config a little better? Are they both on the tank or some distance down rigid lines?

I have A/C in the garage so maybe I should crank it up a few hours before I'm ready to spray (or dust if that's a better term).

[Noob2PC]

Compressor / Regulator-----Hose----Waterfiler/Regulator-----Hose---Gun. .
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.Yes, Do the AC. I am About ready to add 3 more Shop Lights and a Window Mount AC unit. either that or I will be converting the 10x10 shed to a shop.

[pdeinc]

Interesting you mention the lights, I just added 3 more 4-bulb fixtures in my garage last weekend. I'm restoring my 65 vette and got tired of carrying the drop light everywhere I went. I already had 3 identical fixtures in there but they weren't in the center so needed more.

Thanks for the layout explanation, it's just what I am considering doing. And by the way, what sort of problems do you see when the humidity is up?

[Noob2PC]

Thanks for the layout explanation, it's just what I am considering doing. And by the way, what sort of problems do you see when the humidity is up?

I can't see cause sweat is pouring down into my eyes is one thing With High Humidity, I find it hard to get the right pressure for smooth dusting.

[pdeinc]

Well, I get the sweat problem when my head's over the sandblast cabinet looking downward for sure. Not to belabor the explanation, but 'right pressure' for dusting sounds like what I was seeing, when I had the pressure down where I liked the output from the nozzle, it seemed like extra powder was staying in the barrel. Is that similar to what you see?

[Noob2PC]

when I had the pressure down where I liked the output from the nozzle, it seemed like extra powder was staying in the barrel. Is that similar to what you see?

Yes, you need to turn up a tad more to help keep it out of the barrel. I also after each spray I charge the next part and shake the gun over it to shake out the powder stuck in the barrel. Not sure if it is the right way but it works for me.

[pdeinc]

Well, there was so much it the barrel periodically, I couldn't let that fall on the part. I'll try again this evening with the A/C on and slightly higher pressure.

Thanks for the advice.