Dust coat over reactions.

[Edward Yemm]

I’m spraying some 1K base over a couple of areas on a recently painted 2k clear surface. Cut through with the polisher as it slipped and rolled over the edge. Not going anywhere near the edge of a panel with it again. Going to do the edges by hand in future. I’m getting some reactions. I could use my barcoat but some people say it’s not very reliable at times. It can fail over time. I know that, sometimes less paint is better over any reactions. Does this light dusting technique work everywhere with all paint systems? I tried doing it over a very small reaction earlier but didn’t have any joy. I turned my fluid right down to 1/4 of a turn. Tried just pulsing the trigger on and off and that little reaction just kept creeping back through. I got fed up and just cleared over the top of it in the end. I’ve got another area with a far bigger reaction that’s not going to hide so easily under the clear. Maybe I need to leave longer than 20 minutes between light dust coats? Maybe I need the gun a long way from the panel or perhaps I should reduce or increase my thinner. Not sure on the next thing to do?

 

[Edward Yemm]

Also, it’s worth pointing out that my mixed basecoat has been sat around for a few days. Leftovers from another panel. I had a bit of a reaction on that panel. Same issue. Recent over spray clear, but I managed to sand it between coats and then the base eventually covered what little was left of it without any further reaction.

 

[Edward Yemm]

I’m also perplexed as to why the recent clear is so dull with fresh clear over the top of it. I’ve done a spot spray area of base on a door before. Then I re cleared the whole door over sanded clear. It wasn’t dull looking then. Maybe it’s just because my recent clear is too fresh? Have I no other option but to re coat the whole panel?

 

[MG David]

I assume this is solvent base coat. In a similar situation, where I sanded down a defect in the clear and went through, I have had the same issue with the new base coat reacting with the earlier basecoat when patching.

A technique I haven't tried, was used by the guy on the http://www.mckennasgarage.com/xke/index.htm website, was to paint rub through using a mix of base and clear. He uses a number of other techniques depending on the severity of the rub through and his wish to experiment.

 

[Edward Yemm]

I assume this is solvent base coat. In a similar situation, where I sanded down a defect in the clear and went through, I have had the same issue with the new base coat reacting with the earlier basecoat when patching.

A technique I haven't tried, was used by the guy on the http://www.mckennasgarage.com/xke/index.htm website, was to paint rub through using a mix of base and clear. He uses a number of other techniques depending on the severity of the rub through and his wish to experiment.

Thanks for replying. I just read this after I’ve started spraying. Yes. 1K solvent base coat. I’m at this stage now. As long as these two little reactions don’t spread I think they will be hidden ok by the clear. They may look a little different to rest of panel but I’ll see how it goes. If the reaction gets worse I’ll try what you suggest. I’ve tried acetone thinner in the past. It doesn’t always work. I was considering mixing some 2K thinner into my 1K base. See if that helps. I’m dusting this on for now. Fluid half a turn out and spraying 1-2ft away from panel. The other day I sprayed more and more paint over it to see if that would work. I was left with what looked like a bin bag over the panel. Paint wrinkled and lifting. Was just like touching a plastic bin bag. Very flexible.

 

[Edward Yemm]

This BMW metallic is a bastard for it. Never had this issue when painting cars years ago.

 

[Edward Yemm]

I think those two little reactions are actually just cracks left over from the reactions the other day. I’ll tell you what I’ve found makes reactions worse.

Panel wipe.

I purposely didn’t use any today. I just dragged a wet microfibre cloth over the panel when I’d finished sanding. Less reactions if any.

 

[steveo3002]

its kinda the norm to get reactions over fresh clear coat ...the basecoat solvent just attacks the edge

sand it smooth with 1000 or so , then carefull light dry coats to cover it

if you can walk away from it to let it cure longer then do so

 

[Edward Yemm]

Still going on nice and smooth. Maybe reactions need a few hours to air out after sanding? I’ve come back to this panel after a day away from it. No hassle today.

 

[the snooper]

I've never had a problem with reactions over 2k clear, and it suggests that the 2k isn't yet cured, are you using standard activator ?

 

[Edward Yemm]

its kinda the norm to get reactions over fresh clear coat ...the basecoat solvent just attacks the edge

sand it smooth with 1000 or so , then carefull light dry coats to cover it

if you can walk away from it to let it cure longer then do so

Yes. I tried that on Saturday. I think I was rushing it between coats though because the tiny reaction over my re sprayed other area of the arch kept creeping back. It’s just noticeable. Only just. It’s right next to my finger. Right on the edge. That line of metallic particles. It will do.

 

[Edward Yemm]

I've never had a problem with reactions over 2k clear, and it suggests that the 2k isn't yet cured, are you using standard activator ?

Extra fast activator. It does seem to be recently painted stuff I get reactions with. Maybe I should be leaving the infrared lamp on it for 1/2 hour before tackling fresh paint.

 

[the snooper]

Extra fast activator. It does seem to be recently painted stuff I get reactions with. Maybe I should be leaving the infrared lamp on it for 1/2 hour before tackling fresh paint.

It's hard for anyone to give you definitive answers over the internet as you can't see the finish properly, I'd only use fast a activator, if it starts to cure to quickly before flowing out you'll not get the best finish and will have to work more to get the shine you want

 

[Munkul]

When it's hot, you want slower thinners and slower activator. Too fast - you'll have problems...

Your photos aren't really helping, TBH. Can you take better ones?

 

[Edward Yemm]

It's hard for anyone to give you definitive answers over the internet as you can't see the finish properly, I'd only use fast a activator, if it starts to cure to quickly before flowing out you'll not get the best finish and will have to work more to get the shine you want

It’s a 2K set my Mrs picked up for me last August. I didn’t know much about hardener and thinner speed so just used what they’d sold her. It’s ok. You get a good finish as long as you slow the gun down and pile it on.

 

[Edward Yemm]

When it's hot, you want slower thinners and slower activator. Too fast - you'll have problems...

Your photos aren't really helping, TBH. Can you take better ones?

Yes. I know now. Thanks. I was using what my Mrs picked up for me last August. I didn’t know what was what and just used what they gave her. Fast is ok as long as you move the gun slower. The finish is too heavy in orange peel otherwise. I’m just about to run out of this 2K. Got medium everything on order now. Should arrive today. I’ll try some more photos.

 

[Edward Yemm]

It’s back. Put the paint on a bit heavier and it crept through somewhere else. I’ll just dust in this area and fill the rest in normally as it is behaving now.

 

[Edward Yemm]

Meant to upload this.

 

[Munkul]

I see the crazing now. It's drying too fast IMO

 

[Edward Yemm]

I see the crazing now. It's drying too fast IMO

Thats medium base coat thinner mixed 1:1 with 1K solvent base coat. It’s sprayed over 2K clear where the crazing is. Perhaps a slow 1K thinner or even a medium 2K thinner would be better mixed with the base coat? Or maybe I can just add another 50ml of base coat to the mixture so it dries slower?