Old timer at the shop swore by blending primers and it backfired on me

This guy Mike who's been painting since the 80s told me last week to mix a little hardener into my epoxy primer to speed up drying in my shitty unheated garage. I did it on a door panel I was fixing up for a customer's F-150 here in Buffalo. Panel looked great at first but after 48 hours the primer started cracking like crazy all over. Now I gotta strip it back down and start over which is like 4 hours of sanding I didn't plan for. Mike says he's done it a hundred times but maybe my garage was too cold or I put too much hardener. Any of you guys ever tried this trick or am I better off just sticking to the mix ratio on the can?

3 comments

3 Comments

stellat467d ago

Did you check the temp rating on that specific hardener? Some of them stop working right below 60 and just mess up the chemical cure. Mike might have been running a heated booth back in the day and forgot what cold garage life is like.

pat_murray537d ago

I mean, yeah, that temp thing bit me once too. I'd let the parts warm up in the house overnight before mixing anything and it still came out tacky.

wren2306d ago

Nah, I gotta push back on that a little. Look, I know it sounds like I'm making excuses for the guy's bad advice, but temperature is usually way more critical than people give it credit for. Even if the parts felt warm to the touch after sitting in your house all night, the core of a resin tube or hardener bottle can still be cold if your house isn't kept super toasty. Plus, different batches of hardener can have slightly different cure windows, and a tiny drop in temp can mess with the chemical reaction in a way that feels like a different fault. I'm not saying Mike is right, just that I've seen people blame the product when it was really just a borderline cold snap and a slightly slow cure that needed more heat than a living room gives.