Bubbles/holes appearing in powder paint during cure

[Blowtoad]

I've been encountering (what seen to be) bubbles that appear while curing powder painted jigs. It basically leaves a hole in the paint and is always adjacent to the shank or eye of the hook. Doesn't happen all the time but it has happened with several different colors, and boy does it look lousy! Can anyone lend me some insight into what's happening? and also how to fix/avoid it? Thanks!

[Apdriver]

Well dang. Never seen anything like it. What kind of paint you using? What’s your process? 

[Blowtoad]

3 minutes ago, Apdriver said:

Well dang. Never seen anything like it. What kind of paint you using? What’s your process? 

It's got me baffled tbh. All my paints are protec. Sprues twisted off, quick file, heat shrink on the eye, and dip. These are 1/16, cured for about 15mins at 300. Seems to mostly happen on my small jigs. 

[Jig Man]

How hot are you getting the heads before you dip?  Do you knock off any excess paint before you bake?

[Blowtoad]

8 hours ago, Jig Man said:

How hot are you getting the heads before you dip?  Do you knock off any excess paint before you bake?

Maybe 4 seconds rotated on the heat gun, knocking off excess after. You think it's a too hot/too much paint issue? When I do the 1/16 dips the powder almost always glosses over- okay or too hot? 

[Apdriver]

It looks like the powder is pretty thick. I would try to thin my coat, if I could. I think this would help but I’m not sure what may be causing the divot. Also, I am assuming you are dipping into jar without a fluid bed just by judging the thickness of your coating.

The best way to coat your jigs thin is with a fluid bed, imo. Secondly, you only want to heat the heads up just enough to take a coat of paint. The hotter the head when you dip it, the more paint it melts on the head. It’s a real balancing act and imo is best done with a heat gun counting seconds at the nozzle. Lastly, if no fluid bed, really fluff that powder before you dip and as you work, refluff it as it will tend to pack.

[smalljaw]

I've been using powder paint since 2003 and I've never ever come across that issue. I'm going to give a guess and say that if it is only happening with certain colors there may be an issue with the powder. It may very well be that there is excessive moisture in the powder and during curing it boils off but why didn't it happen when the head hit the paint in the first place? 

I'd send that picture to the people at Do-it, as I said, this is the first time I've ever saw or even heard of this happening. 

[mark poulson]

On 4/26/2022 at 5:45 PM, Blowtoad said:

I've been encountering (what seen to be) bubbles that appear while curing powder painted jigs. It basically leaves a hole in the paint and is always adjacent to the shank or eye of the hook. Doesn't happen all the time but it has happened with several different colors, and boy does it look lousy! Can anyone lend me some insight into what's happening? and also how to fix/avoid it? Thanks!

I started powder coating around the same time as Smalljaw, but I am only an occasional dipper, with nowhere near his experience or expertise.  In fact, over the years, most of what I know about powder coating I've learned from him, and other on this site.

But I guess I'm like most politicians.  I've never let my lack of knowledge keep me from offering an uninformed opinion.

So here goes.

In my limited experience with powder coating, I've never had that happen.  When the power is too thick it usually just sags, so I have thicker coat on the bottom of the jig when it's hung in the toaster oven and cured.

I notice that the bubbles appear where the hook enters or leaves the lead.

I am assuming you hang them all the same way, either hook up or by the eye.

So maybe there is something on the hooks that is released when it is backed, and bubbles out as it cures.  

If that is the problem, I don't know why it only happens with the white powder.

Do you use the same size/batch of hooks with other jig of different colors?

[cadman]

I have never seen that either . However, you will get fisheyes if the jig had small divots in there before powder painting. It almost looks like the paint is too hot, or could be a paint issue. You have a PM from me.

Edited April 30, 2022 by cadman

[Blowtoad]

Update after a while, bunch of changes and testing- I THINK on these jigs in particular, twisting off the sprue deformed the lead a little bit, leaving some gap between the lead and hook (when the jighead has some wiggle to it)- The air in that gap expanded and caused the bubble.

 

After dipping some new ones, I would put them back on the heat gun for 5+ seconds and pop I could see a bubble emerge at the shank or eye. Once that air was purged the melted powder seemed to backfill the hole and they're so far good to cure. A lighter coat of paint seemed to help as well. 

Thoughts? 

[Apdriver]

I think most of us use sprue or gate cutters instead of twisting just to prevent loosening the hook and the cutters leave a little neater separation. Glad you got it figured out.

[Slammingjack]

I hold the jig head and not the hook. Hold the sprue with a pair of big needle nose pliers. Rocking the pliers side to side.( not front to back). The sprue come off more evenly. If your lead is hard it may leave a hole in the top of the jig. I don't use hard lead.