Epoxy 7 day open window

S

sprayerman

How many of you guys are shooting within this window without sanding first? Is spraying within the first day better than waiting 3 days?
 
I spary over unsanded epoxy all the time, within the 7-day window. I have never had any problems. I'm not sure what the ideal wait time is, but I know Barry would be able to tell you. I do know for 2k primer, I wait 24hrs and for poly-spray I wait 48hrs, although I'm sure I could wait longer without any issues.
 
For our shop and climate, 48 to 72 hours is ideal for most coatings or fillers to go on top of 2 coats of unreduced epoxy. Some like to hit it sooner especially if basecoat is involved, but up north we've learned not to rush it. Beyond 72 hours we noticed that it's best to scuff the epoxy before filler, though at that point it's still OK to prime it without sanding.
 
Thanks for the replies...

I guess I don't full understand how the chemical process works. When the epoxy is dry it's got a glossy slick sheen, everything I've learned in painting is to dull the surface? Not second guessing anyone here or the guys at SP, just would like to better understand things.

Maybe ground for another topic, but is it okay to just seal bondo and lacquer putty or does it need to be primed?
 
You will have a lot more problems spraying over lacquer putty than glossy epoxy, so you should use products with a hardner. I'm not a paint pro but I'll try and explain about the gloss.

It doesn't get any more glossy than clear coat, and the second coat of clear is sprayed over that glossy finish. Its because the chemical bond window is open and that window varies with different products, for epoxy its safe to say 7 days, so it is a deminishing window and the quicker you use it the better. That is of course after the proper flash time, which in some cases can be a day or two, which lets the solvents work their way out.

The reason for getting rid of the gloss before top coating an old paint surface, is because the only bond will be mechanical not chemical, and the gloss acts like a guide coat, so you know when you have sanded the whole surface. Seal your bondo with epoxy.
 
in my experience it seems bondo itself needs a few coats of epoxy over it because epoxy seems to soak in a bit before creating a solid coat. once it is all blocked solid and smooth then i seal it with reduced epoxy right before base coat. i dont use 2k primer.
 
Thanks for the replies guys...the clear analogy makes sense. I suppose it just feels strange for me to leave something so long.

Would there be any downfall to basing out with a fine silver metallic after 2-3 days? Or should I lay a grey basecoat then metallic for better bite?
 
form406;24214 said:
in my experience it seems bondo itself needs a few coats of epoxy over it because epoxy seems to soak in a bit before creating a solid coat. once it is all blocked solid and smooth then i seal it with reduced epoxy right before base coat. i dont use 2k primer.
Click to expand...

How long do you wait for the sealer before the base coat?
 
anywhere from an hour to not more than a day. i treat it like a base coat. do a search here its talked about a lot. it really helps base adhesion...
 
So this weekend I decided to shoot a few things. Knowing I was going to use my epoxy sealer I mixed it yesterday 1:1:1 with HOK med reducer and taped off the open top so the reducer wouldn't evaporate too much. Went to go shoot today and started around 11:30 AM applied a wet coat with a 1.0 t/u gun and here it is 2:00 PM and my sealer is still a little wet? When I started shooting it was 69 degrees I brought both my primer and parts in last night to keep them up to temp. It is now 74 degrees. Some of the parts are a little tacky while some have a wet film still. Should I wait until tomorrow and apply my base within the window or reseal then base?
 
I would wait then start tomorrow if it is dry to the touch and looks good go for the base.
 
Ok, best laid plans... I shot epoxy last sunday night. Meant to get it sanded in the spots that needed it, and reshot this week. Now it looks like i won't get to it until tomorrow. Do I need to verify that the recoat window is still open in some way?

Or do I know it's safe because it is at 6 days? Or am I counting wrong,and I'm right on the edge at 7 days?
 
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