white spots in mirror blue and mirror black

[Desert PC]

Has anyone had issues with tiny white spots (looks alot like paint overspray) with tiger mirror black and mirror blue? I've used the same bag(s) of powder on several bike frames and noticed the last frame done in blue had the spots-- I gave the customer a discount and everything was good.

A week ago, I did some bike parts in mirror black and had the same white spot problem, but attributed it to contamination. Tonight, I shot a frame in mirror black, and s**t, the same white dots appeared. I have done at least 5 frames in mirror black and every one came out near perfect. I'm almost certain it is not outgassing or contamination from a bad color change over as I have done 8 colors without issue, and none of them was white. I have a china gun with a cup (hopper on the way). Powder is stored indoors at ~77 or below, packed in plastic bags, inside Ziplock containers with desiccant in the container.

Is it possible that as this powder 'ages' it can take on this white spot behavior?
Has anyone else had this problem? I plan to order more blue and black and do side by side comparisons on equal substrates, cleaning, curing and see if the problem disappears with fresh powder.

Desert PC
1offpowdercoating.com

[Auto-Cycle PC]

Re: white spots in mirror blue and mirror black

What kind of booth a filter system are you using? I get the same thing when my filters needed cleaned before I added a final filter to my booth. I know thats where it was coming from because the same powder came out great if I sprayed it without the booth fan on.

[Desert PC]

Re: white spots in mirror blue and mirror black

Thanks for the potential cause. I have a homemade booth with pleated filters and a fan behind them, but I have not thought to change the filters. What's odd is I do many different colors and I have never seen the tiny whites dots in anything but mirror blue, and now mirror black.

[Auto-Cycle PC]

Re: white spots in mirror blue and mirror black

For me they usually show up in the black and I get red/pink specs in my white. After I clean/change the filters it goes away. Cleaning filters will make it as bad or worse if you dont have a good final filter. So you might be better off changing filters if your not running a final filter after your fan.

Think about it like this the air exiting your booth is the same air it is pulling back in, and if powder is passing through your filters it is being pulled right back where you are spraying your part.

[Guest]

Re: white spots in mirror blue and mirror black

Maybe your desiccant is getting into your powder? I had one of the packets leak and do the same thing.