Bondo kept sagging on a vertical quarter panel for 2 days straight

I was fixing a 2012 Civic today, the quarter panel behind the driver door had a dent about the size of a dinner plate. First pass I laid the filler on too thick, left it for 20 minutes, came back and it was dripping like a melting candle. Took me 2 full days to figure out the trick was doing thin coats, like 1/8 inch max, and adding a touch more hardener when the shop temp drops below 60. Even then I had to use a heat lamp for the last coat to get it to set up before it slid. My foreman finally walked over and said "you're mixing it like pancake batter, add less filler next time." I sanded it down today and it finally holds its shape. Anyone else fight with vertical panels this bad or is it just me?

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elizabethhayes1mo ago

Oh man, I feel your pain on this one lol. I remember reading in a body shop forum that temp and humidity are like half the battle with filler, and your foreman is totally right about the pancake batter thing. Thick coats just trap solvent and they never cure right, they always sag or fish-eye on you. I had a buddy who swore by warming the panel with a heat gun before he even mixed, said it gives you a fighting chance on cold days. Also, I learned the hard way that you gotta wait for it to really kick off before you even think about walking away, like touch it and if your finger comes back clean you're good. You probably already know this now, but for anyone else stuck, thin coats and patience beat everything else every single time.

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