I was patching up some holes/ scratches on a fiberglass panel and layed some bondo on it (not overly thick). I let it go overnight, but when I had a poke at it the next day, it was still sticky, you could scrape your fingernail across it and end up with some under there. I realised then that the stuff I used was probably "off" (or maybe the hardener was). Will the stuff eventually harden up? If it is to stay sticky, whats the best solvent I can hit it with to remove this mess? The weather forecast for here is about a week of over 100 degrees, maybe that will help?
Acetone usually works, but it might affect what's under the filler. If the hardener is old, it doesn't work very well. "Old" means older than about 6 months.
You've used bondo before, right? You aren't just talking about the tacky surface are you? If it's soft all the way through, I'd scrape most off with a chisel. Grind the rest with an old disk. Then throw the disk away.
In this situation I've applied a thin layer of filler mixed with extra hardener over the soft filler. It'll harden up.
Remove it with a putty knife and get some new hardener and do it again. it is usually the hardener that goes bad as it is the catalyst. SA trick that a body and fender man/fiber glass body builder told me about bondo on glass is to mix it with fiber glass resin and hardener. 3:1 bondo to glass. It is just the way that he does it, it may not produce the results that you require.
Two more trains of thoughts,If you are familiar with Bondo and have used it in the past,did you use enough hardener and how cold was your shop,cold weather will greatly reduce drying time. HRP
I am guessing that it was not cold enough in his shop in Australia during the summer to slow the cure down to a days time. It could just be the skim on the top that stays sticky. Some lower quality fillers don't have the additives required to stop that from happening. Try sanding it, if it remains soft and clogs your paper after that first top coat has been removed then you need to take all off. If it is fine after that initial sanding it will be fine but you might want to buy better filler in the future as sand paper ends up costing much more than filler when you have to throw it away all the time because your filler clogs it up. If it is still soft, as mentioned, it is probably bad hardener. Scrape or sand it off and start again. Make sure you use enough hardener 2% by weight and never store your hardener where it is exposed to UV as that increases the deterioration of MEKP substantially.
My daughter let some of those "traveling" body men do a fix on her pickup. They bondoed it up, primered it and sprayed on a guide coat. She never got it repainted. When we junked the truck 10 years later, you could still dig the bondo out with your fingernail.
Body filler is talc, like baby powder, if it isn't covered with real paint (not primer) it will absorb water like a sponge. I am not surprised it was soft after 10 years of exposure.
When I do scratches or pinholes,i use an ultra fine glaxing putty or a stop putty,only those with hardeners,with body fillers[bondo]they are cheap,so get quality stuff,if it's tacky after 10-15mns =not enough hardener or it's too cold,should be min 24d cel,make sure from the start you press the filler firmly into those small areas so it gets right in,good luck,Gaz!
DOH!...Just because it's the dead of winter in my neck of the woods don't mean everybody lives where it's cold where they are... HRP
If the fiberglass panel is made with Epoxy resin not polyester resin the bondo will never harden. Plastic Filler is polyester base and the two don't work together. One way to get thru your problem is to lay a good coat of epoxy primer on the fiberglass panel and bondo on top of it. you will need to Scrape it off clean wash it with acetone and start fresh. You can put epoxy resin over polyester resin but not polyester resin over epoxy.
Interesting, I would have thought you could drop a blob of catalyzed bondo in oil and it would still cure. Cures in my hair overnight. BTW have you tried urinating on it? I see guys doing bodywork and they often say "Piss on it" right after applying bondo.
This is not true if the epoxy is already cured. You cannot mix the two resins but they will not affect one another once cured.
Moisture and humidity can affect drying time for filler too.Interesting post about pissing on it; that must be why body shop guys usually drink lots of beer- then they'll never run out of "curing fluid" !!
Just scrape it off and clean the rest off with some lacquer thinner and a scotch rite pad. Please don't piss on it. Don't listened to anyone telling you to put more on top, that will not work and will just create an unstable surface and WILL fail sooner rather than later.
It looks like I got me a bit of scraping to do. Iv'e used bog for years, but it has always behaved itself. It sounds like the hardener has crapped itself. The layer is only 1mm thick, and it is soft all the way through. It would have nothing to do with the temperature, it's a pleasant 97 degrees outside, but it will get hot next week.
OMG .....it must be brutal down there is SC in the " dead of the winter". What ....40 degrees over night for a low....20 below here this morning.
Sir I am not trying to get off topic of start a dispute, but I disagree 100 % with your statement. Vinylester resin is the only other option when trying to cross both Epoxy or Polyester. Vinylester will coat over the top of either dried product and harden appropriately. I do agree with you that the products cannot be mixed in liquid form.
I usually say "piss on it", put down the hammer and dolly, and that's when I get the bondo out. Maybe the wizz is a good bonding agent?
You may disagree but you are incorrect. I work for a filler company and I am pretty well versed in what our products can be used over and a fully cured epoxy will have zero affect on the hardening of a body filler Not to be a dick but to make sure I was not talking out of my ass and spreading false info I called our lab to confirm and they concurred with my statement. Now an Epoxy that is not fully cured will result in these types of situations.
Imo,filler will cure layed down on most surfaces but not necessarily bond to it,i've used it many a time to repair cracks and chips on my workshop floor[concrete]still good after 20plus yrs !
Please tell me you are using a professional-grade product and not a Bondo branded product, from the auto parts store.
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