Solvent pop?

[56_Kruiser]

Was painting a panel today, with HOK Shimrin 2 base coat.

After getting a couple coats on, I noticed an area that the primer needed sanding down. I let the paint cure for an hour, then wet sanded the paint down to the primer and smoothed out the problem.

I primed the spot I worked, and a bit larger.

I let the primer (HOK Epoxy KD) dry for 2 hours, wet sanded, then started applying the base coat. And at the edges of the primer, where it turns from primer to previously painted base, I got solvent pop.

So, I'm assuming I needed more ddrying time somewhere.

I was hoping to smooth out the bad spot and get back to painting before 4 hours elapsed, at which point I understand I'd need to sand it all ... sort of a fresh prep, and start over.

So do you think it's unrealistic to try to do that repair in a 4 hour period? Did I not let one of them dry long enough, either the primer or base?

I'm not sure why it popped at the edges of the primer.

Any thoughts appreciated.

 

[56_Kruiser]

Also, to repair that, Can I just sand down and smooth up, or do I need to strip down to metal?

The pop does not look 'deep'.

 

[TAZ]

I would have thought that you could have repaired that without having to reprime. Just sand it smooth and repaint some base in that area.
The HOK bases are very transparent so it would take quite a few coats (maybe 4 or 5 or so).
I doubt if it's solvent pop, it could be a slight bit of wrinkling on the edges.

I think you can just resmooth that area, then keep dusting the base in until it's covered again. Don't just hammer it on though.

You should be fine without sanding the complete panel. I was thinking you had 48/72 hours, not 4 hours before you had to resand base.

 

[56_Kruiser]

I agree with you.

The reason I had to re-prime is because U just did sand through the primer, and with the translucent base I had to re-prime to get uniform color.

I believe the tech sheet for Shimrin 2 says a maximum of 4 hours between coats. It does not say to re-sand, but I take it to mean that. Probably should just to be safe, you reckon?

 

[56_Kruiser]

Boy, this forum software is really screwed up today. I get all kinds of program error message when enter a screen. I entered a post, and did a preview, and it showed the preview OK, but no post buttons. There was a blank message screen, with post button, but had lost all content. So, I'll try again...

I sanded the base coat today. It's been 24 hours since spraying it on. Interestingly, the sandpaper loaded up (per picture below). I changed paper as soon as i noticed it loading. Never wore out a sheet.

I was planning on painting in another 24 hours, but now I'm not sure I should. I still am surprised the paint raised around the borders of the primer spot.

 

[TAZ]

I'd say if you are waiting that long, yes, you should resand. Looks like you'll need to do a good resand anyway.
Keep in mind, when you spray those colors, you're supposed to put a very light base under the base to make it all the same shade. No need to reprime.
I think HOK suggest white. I normally take the basecoat white and add a touch of whatever color I am spray like "tangelo" into the white. This will give it a very nice light orange to spray the Tangelo over.

You should be able to just spray that base, then about 4-5 coats of the Shimrin base, then clear all within a 1/2 hour on a smaller panel.

 

[TAZ]

By the way, isn't that 'dry' sandpaper?

 

[56_Kruiser]

Yes, it is now all sanded. That paper is a wet and dry paper, 500 grit. I sanded wet, and had a small amount of dish soap in it to help prevent buildup, but as you see, it did build up. That's why it seems to me the paint wasn't curing. That was after 24 hours.

HOK tech had recommended KD3003 (yellow) primer. Having just broken through the primer, showing some dark, that's why I re-primed that spot.

The idea of tinted white is a good one. Too late now, but we'll keep that in mind in future.

 

[TAZ]

Okay, good luck on the recoat. Hope it works out for you.

I don't know why it took that long to cure or unless it's the primer that remained soft. Basecoat normally dries pretty quickly.