Primer Cure Time Questions

P

PatG

Hi Guys

Well, I just shot my first test panel. Used epoxy primer and covered with one coat of Featherfill G2. After 24 hours (and temps in low 60’s at best), I lightly sanded with 600 grit and then shot three metallic red PPG DBU and three coats Universal Clear. Clear went down great – so far, so good. Now we’re at Day 4 and I’m starting to see sand scratches telegraph through red metallic. I’m guessing that the epoxy and Featherfill did not have time to fully cure out prior to covering with red. So, my question is two-fold. If I’m going to just shoot epoxy and then block and paint, what is cure time to avoid these sand scratches? If I’m going to shoot poly primer or urethane primer (I also have SPI Regular Build Primer which I’ll be using in the future), what is cure time to avoid these scratches? Thanks for the tips.

Pat
 
All I can say:

I remember back in 80's BF Goodrich, Classic and a couple of big name paint companies sponsored a effort to test cold temps on automotive grade solvents and certain resins.
The conclusion, 58 degrees all of them tend to get real lazy.

So if it is 65 out, then the metal temp is 60-58 degrees, usually 5-8 degrees cooler then air.
 
i have learned my lesson . imho anything sprayed from a gun in temps under 70+ will laugh at you. it just does not work. at 60 it will all but stop . may be dry to the touch but until it gets some heat in it the game is in time out .
 
PatG;17338 said:
Hi Guys

Well, I just shot my first test panel. Used epoxy primer and covered with one coat of Featherfill G2. After 24 hours (and temps in low 60’s at best), I lightly sanded with 600 grit and then shot three metallic red PPG DBU and three coats Universal Clear. Clear went down great – so far, so good. Now we’re at Day 4 and I’m starting to see sand scratches telegraph through red metallic. I’m guessing that the epoxy and Featherfill did not have time to fully cure out prior to covering with red. So, my question is two-fold. If I’m going to just shoot epoxy and then block and paint, what is cure time to avoid these sand scratches? If I’m going to shoot poly primer or urethane primer (I also have SPI Regular Build Primer which I’ll be using in the future), what is cure time to avoid these scratches? Thanks for the tips.

Pat
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Your test panel was metal? You sanded the metal with 80 grit? you shot epoxy and waited how long before the G2 went on? Both the epoxy and G2 were 24hrs old when it was sanded with 600 and painted? One thing that's very important here: Epoxy is slow curing (think 7 day recoat window) but if you apply urethane or poly primer over it to soon it will delay the clear even more, in extreme cases you'll see major contraction and splitting of a fast curing primer. Cure time is very important with all products. I doubt the 600 grit scratches had anything to do with the results.
 
My favorite saying is all paints are made to work at 70-75 degrees and 35% humidity, that means in Georgia we can paint maybe, one day a year for three hours.
Anything colder or hotter it is up to the painter to adjust with activators, proper grade reducers and flash times.

I'm not sure what really are the worst conditions, high heat or cold weather.
 
I know I am anal when it comes to epoxy now. I will shoot poly over epoxy in 24 hours and let that thing sit for a 5-7 days with a min temp of 65 degrees before I start blocking. I try to always let 2k primer sit up atleast 2 days before sanding.
 
Another 2 cents is that the rule of thumb for refinish material is to never put something fast over something slow. But that basic rule gets violated when laying epoxy on metal, then switching to a relatively quick drying primer-surfacer like poly or 2K urethane. So knowing you are breaking the rule, extra flash time between the two different primer types is called for, the more the better.
 
I know I am anal when it comes to epoxy now.
Click to expand...
me too! ive watched it fisheye on bare metal in cold temps and i too love the 70 and up for epoxy. i dont have a problem shooting base or clear in the cold.
 
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