How to Prep Oily Fiberglass For Glass Work

Kid Vette

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As some of you know I need to graft in some panels in front of the differential to clear for the aluminum Dana 44 I'm installing. Both the existing panels and the ones I will be installing are coated with oil from leaky seals on the differential. Any suggestions on how to clean off all the oil to prep for glassing these in? :confused:
 
start with a scraper and get all the thick stuff off the fiberglass......then some cleaner like "crud cutter" or "simple green", a brush, then some engine degreaser.... I try to use as little as possible because that crap is expensive at $4 for a can, but it's very convinient to use in the spray can.... the simple green cleaner is only $7 a gallon but works almost as good.... mineral spirits works pretty good too....

don't cut or sand before you got most of the grease off...
 
Acetone is an excellent degreaser but I don't know what it would do to the fiberglass.
 
I'd use citrus based degreased to begin. Once the grunt of the grease is gone, I'd go acetone, one acetone soaked towel to apply, one dry and clean one to wipe it out immediatly (it you leave it it will attack the fiberglass).
Then only I'd start sanding/scrapping.
 
Thanks for the replies! I guess another question is how critical is it this gets super clean? I read somewhere that a glass repair is only a mechanical bond, net chemical. I'm not going to paint this so maybe it isn't so critical?

Also I came across this method on the internet, "Here is a method of removing oil contamination from fiberglass. First scrape off as much as possible with a plastic or wooden scraper. Then bake in the sun or heat with a heat lamp or hair dryer, and then apply talcum powder. If there is oil present it will be drawn into the talcum powder much like speedy dry floor absorbent. Vacuum it off so you do not spread the removed oil around. When you feel the talcum is no longer absorbing anything wash with Dawn soap and hot water. Repeat until there is no oily residue. Finish up with waterborne wax and grease remover. Using a pump garden sprayer; mist the W&GR on. Then use clean rags to wipe it off."

I think the focus of this method is to pull the oil out of the fiberglass rather than rub it in. Sound like it might worK?
 
I'd use citrus based degreased to begin. Once the grunt of the grease is gone, I'd go acetone, one acetone soaked towel to apply, one dry and clean one to wipe it out immediatly (it you leave it it will attack the fiberglass).
Then only I'd start sanding/scrapping.

Instead of acetone, you can use lacquer thinner. It evaporates a little slower than acetone and so it's a little more economical to use. However, evaporating slower, it may attack the fiberglass a little more.
...........
My 68 had significant oil leaked from the valve covers and who knows where else. Over the ages the oil, and in some places engine heat, had turned the oil into an almost varnish like substance; i.e. a substance permeated with sand...there's a lot of sand in the air here. I scraped it off with a putty knife and a rotary wire brush powered by an electric drill. ...then next countless swabbing with at first acetone and then later lacquer thinner. The upside was that once I got all this stuff off and cleaned, I had a frame that was as pristine as the day it came from the factory. Breathing acetone and lacquer fumes, particularly while drinking wine, stresses your liver. I stopped drinking for about 9 months. To do it over, I'd definitely wear a face mask with charcoal filtration.
 
definitely wear a mask......

mechanical bond? it sure is important the resin can properly adhere to the old fiberglass. If it's oily/greasy it will not adhere.....

if possible (like the fender flares) I like to hit the surface with 60-80 grit for some "extra" grip.....
 
I'd use citrus based degreased to begin. Once the grunt of the grease is gone, I'd go acetone, one acetone soaked towel to apply, one dry and clean one to wipe it out immediatly (it you leave it it will attack the fiberglass).
Then only I'd start sanding/scrapping.

Instead of acetone, you can use lacquer thinner. It evaporates a little slower than acetone and so it's a little more economical to use. However, evaporating slower, it may attack the fiberglass a little more.
...........
My 68 had significant oil leaked from the valve covers and who knows where else. Over the ages the oil, and in some places engine heat, had turned the oil into an almost varnish like substance; i.e. a substance permeated with sand...there's a lot of sand in the air here. I scraped it off with a putty knife and a rotary wire brush powered by an electric drill. ...then next countless swabbing with at first acetone and then later lacquer thinner. The upside was that once I got all this stuff off and cleaned, I had a frame that was as pristine as the day it came from the factory. Breathing acetone and lacquer fumes, particularly while drinking wine, stresses your liver. I stopped drinking for about 9 months. To do it over, I'd definitely wear a face mask with charcoal filtration.

Another reason I use acetone over paint thinner is its relative harmlessness.
Overall low toxicity and so far no proof to be carcinogenic.

I'm probably unscientific on this, but I don't like the idea of oil/petrol-based products soaking into my fiberglass.:bonkers:
 
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