Using Dry Powder Guide Coat

M

milanomaroon

Promoted Users
I am getting ready to put another coat of epoxy primer down. I used a dry powder guide coat both during and after blocking to check for low areas and scratches. Not all of the powder has been sanded off. I haven't tried washing yet but did spray some wax and grease remover (700-1) and wiped it down. Is it OK to spray epoxy over this? It's almost as if it has been stained into the existing primer. By the way, the existing primer is several years old and fully cured.

Thank you in advance for any replies.
 
I was hoping a pro would respond but to be honest I would not lose any sleep over it. Clean it and spray your epoxy…

Mandatory backyard hack disclaimer inserted here.

Don
 
dhutton01 said:
I am assuming all of that several year old epoxy has been sanded. :)
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yes, it had been blocked with 320 several years ago but I never had time to go further with sealer and base. so re-sanded with 180 now and used guide coat to make sure i didn't miss anything. my plan is to apply several coats of epoxy primer (only using epoxy), sand with 320, then down to 600, seal, and base / clear. will want to use guide coat again to make sure i didn't miss any scratches. sound ok?
 
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milanomaroon said:
yes, it had been blocked with 320 several years ago but I never had time to go further with sealer and base. so re-sanded with 180 now and used guide coat to make sure i didn't miss anything. my plan is to apply several coats of epoxy primer (only using epoxy), sand with 320, then down to 600, seal, and base / clear. will want to use guide coat again to make sure i didn't miss any scratches. sound ok?
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That is a good plan. I've been told that nothing adheres better to spi epoxy than, spi epoxy. So your plan to spray a sealer coat before base / clear is a sound preferred method, especially if its sprayed somewhere within the 7 day window after your last blocking of spi epoxy for best adhesion. As an example, it has been said to spray sealer say on a Friday evening, and spray base the next morning.
 
I think the point jcclark is making is valid. Since you are only using epoxy primer, there is no need to apply a sealer coat. Simply block sand it flat, then begin your finish sanding prior to paint.

As for guide coat, I use it at each stage of the finish sanding. You do want to be sure it is all sanded off, otherwise what you are seeing is either a low spot or sanding scratches filled with guide coat.
 
'68 Coronet R/T said:
I think the point jcclark is making is valid. Since you are only using epoxy primer, there is no need to apply a sealer coat. Simply block sand it flat, then begin your finish sanding prior to paint.

As for guide coat, I use it at each stage of the finish sanding. You do want to be sure it is all sanded off, otherwise what you are seeing is either a low spot or sanding scratches filled with guide coat.
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I'm assuming jcclark is basing his opinion on the epoxy being sanded and prepped for base coat within the 7 day window?

What if it took the OP two weeks sanding the epoxy in preparation for base, Wouldn't that be a mechanical adhesion after base was sprayed in lieu of a chemical adhesion one gets when spraying base over fresh epoxy sealer?
 
MJM said:
I'm assuming jcclark is basing his opinion on the epoxy being sanded and prepped for base coat within the 7 day window?

What if it took the OP two weeks sanding the epoxy in preparation for base, Wouldn't that be a mechanical adhesion after base was sprayed in lieu of a chemical adhesion one gets when spraying base over fresh epoxy sealer?
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The OP did say he was getting ready to spray several coats of Epoxy. So the assumption would be he will be working on freshly sprayed epoxy.

I agree with applying a fresh coat if he lets it sit too long.
 
'68 Coronet R/T said:
The OP did say he was getting ready to spray several coats of Epoxy. So the assumption would be he will be working on freshly sprayed epoxy.

I agree with applying a fresh coat if he lets it sit too long.
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So that does bring up a question. If after the next 2 coats of epoxy which will be applied over cured epoxy (but sanded with 180 grit) I run over the 7 day window as I block and finish sand, can I spray reduced epoxy sealer and then base or do I have to start over with sanding 180 grit, more epoxy and finish sand?

The timing can be a killer...
 
The recoat window challenge of epoxy only work. This is why a lot of folks do their finish priming with 2k sprayed over epoxy in the recoat window. Then they are not fighting the recoat window…

Mandatory backyard hack disclaimer inserted here….

Don
 
It's my understanding that SPI Turbo prime has little to no shrinkage compared to other 2k primers.
 
The key is flash time. Too many guys rush through the primer stage and thereby trap solvent in the lower layers.
I found this out the hard way. It wasn't SPI primer but my first attempt blistered and cracked because I put heavy coats on too quickly.
 
What is the time window to put base over 2k primer?.....Say 2k sanded to 600, and 2 k sprayed as a sealer?..
 
You do not want to let any build primer sit exposed for very long because they absorb contaminants quite easily.

The SPI Tech Manual states:

Sanding: Depending on how you applied it and current temperature this primer should be ready to sand in 45-60 minutes. If sanded primer has set more than 24 hours you must scuff first with a gray scuff pad or equivalent before applying another product.
 
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