Feather Fill G2(bondo) won't cure

mvernon · Jul 22, 2019

Hello all,
I have been working on repainting my Bridgeport mill body , knee. I cleaned all paint and bondo off. Then I primed with pro form epoxy. That seems to go well. After that hardened I proceeded to spray 3 coats of Evercoat featherfill G2 from a new can I just bought letting the coats flash off for about 10 minutes as the directions instruct you to do so. The problem is after 3 days I can still scrape the filler off with my finger nail. And it is to soft to sand with out clogging up then sand paper. I have used the proper amount of hardener and sprayed at 71 degrees with 60% humidity. Will this cure or do I need to sand off every bit and start over. Which I really wouldn't want to have to do. Please give me good news!

Thanks Matt.

Bill Simmons · Jul 22, 2019

I would contact the manufacturer. There are good videos saying sandable in 3 hours. I would also try a paint forum as opposed to a machining forum. It is a paint problem, not a mill problem.

mvernon · Jul 22, 2019

Bill Simmons said:
I would contact the manufacturer. There are good videos saying sandable in 3 hours

I will try calling them tomorrow

rons · Jul 22, 2019

Use a heat lamp on one spot. If the cure is accelerated in that spot then you can work the lamp around.

They might tell you to lightly sand and apply a thin coat.
Don't know exactly what you did but just a thought. A flash coat does not equal the thickness of a regular spray coat. I suspect you went on too thick and all you need is some lamp work.

mvernon · Jul 22, 2019

rons said:
Use a heat lamp on one spot. If the cure is accelerated in that spot then you can work the lamp around.

They might tell you to lightly sand and apply a thin coat.
Don't know exactly what you did but just a thought. A flash coat does not equal the thickness of a regular spray coat. I suspect you went on too thick and all you need is some lamp work.

Would a regular heater work or does it need to be an infrared heater?

Bill Simmons · Jul 22, 2019

A regular heater would work, or a space heater. Don't you have a heat wave there now? What did the excess material removed from the gun or the inside of the mixing cup do? Videos indicate get it out of the gun in 45 minutes or lose the gun. I do not think excess thickness would cause a failure to set with this type of material. The videos spoke of large builds filling pin holes. I assume no reducer is used as you want it thick but if used was it the right stuff?

rons · Jul 22, 2019

mvernon said:
Would a regular heater work or does it need to be an infrared heater?

If it was me I would just use a 100 watt light bulb in one small area and not too close to cause more problems.
Just warm up the surface and see. If it causes some curing to complete then maybe heating the space over night would solve the issue.

bmikkalson · Jul 23, 2019

Did you add the hardner?? Should be 1 little tube to 1 qt

mvernon · Jul 23, 2019

bmikkalson said:
Did you add the hardner?? Should be 1 little tube to 1 qt

I know I sound like I am a moron. But yes I added the hardener.

mvernon · Jul 23, 2019

First mixture was 8oz to 5ml of hardner
2nd and 3rd was 16 oz to 11ml of hardner

Mark Rand · Jul 23, 2019

Assuming it's a styrene type filler with a benzoyl peroxide hardener. How old was the hardener. It can go off. Older resin usually cures more quickly, but if the peroxide in the hardener has decayed, then it won't kick off the styrene hardening.

If it's a polyurethane or acrylic with an isocyanate hardener, then that ain't the problem.

mvernon · Jul 23, 2019

So I have decided to remove it and start over. I have scrapped as much off as I can. Now what? I don't want to smear it into the cast iron. The Date on the hardener is from feb 2019

ORAGRAG · Jul 23, 2019

mvernon said:
So I have decided to remove it and start over. I have scrapped as much off as I can. Now what? I don't want to smear it into the cast iron. The Date on the hardener is from feb 2019

Use acetone to clean up the rest.

mvernon · Jul 24, 2019

ORAGRAG said:
Use acetone to clean up the rest.

That didn't do much. Think I could wet sand blast it off?

DDoug · Jul 25, 2019

mvernon said:
That didn't do much. Think I could wet sand blast it off?

try lighting the acetone & bondo soaked Bridgeport on fire..... :nutter:

rons · Jul 26, 2019

You should have learned by now one thing:

Don't cover large areas with one big bleeding batch.

wesg · Jul 26, 2019

FWIW. my limited experience using bondo to finish MDF molds for CF parts.

Thin layers were always sticky unless I upped the hardener ratio. I was guessing it was because the thin layers didn't generate enough heat to cure well.

I also found if I bulled my way thru sanding, once I got thru the surface it was hard enough to sand halfway decent.

It's supposed to not fully cure if it has contact with air, so the next coat will chemically bond?

Whatever, hated that crap. Never mind the stench. If I ever need to do it again, I'll pay whatever EPOXY filler costs.

bmikkalson · Jul 27, 2019

Did you figure it out?

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