Thread: Painting fiberglass

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When painting fiberglass what is the best method. I have never worked with fiberglass but was wondering if the best thing to do is lay a thin coat of bondo, sand, a few coats of primer, hand sand between each coat, and 8 to 10 coats, of paint, again hand sand between each caot, then a few coats of clear, wait a few days to a week, then polish???
This is what I have gathered from the few resources.

Does the glass have gel coat on it??? With base coat clear coat I never sand the base coat, everyone I've talked to on it sez that is a big no- no. Spray Tech is the expert, hopefully he will be around here soon.

Painting with modern paint systems is much more complicated than it seems at first glance.

First, go to this site and read the two articles under "How To" about preparing fiberglass for painting.

http://www.wescottsauto.com/site2003C/frame_specs.html

Then decide what type of paint system you want to use, and follow their instructions. I use Sherwin Williams basecoat / clearcoat system, and they are very specific about how to apply it.

If you're using basecoat/clearcoat, you typically DON'T sand the basecoat before applying the clear.

Also, unless your fiberglass body is totally gnarly, there's no reason to coat it with bondo. You just sand most of it off.

Originally posted by Grim
When painting fiberglass what is the best method. I have never worked with fiberglass but was wondering if the best thing to do is lay a thin coat of bondo, sand, a few coats of primer, hand sand between each coat, and 8 to 10 coats, of paint, again hand sand between each caot, then a few coats of clear, wait a few days to a week, then polish???
This is what I have gathered from the few resources.

Well it kind of depends on whether you have raw glass showing or not .
You dont want to just spread a coat of bondo over raw glass , as it will eventually soak and you will see it after a few months after painting .
What needs to be done is buy some fiber glass resin and mix ( real slow to keep out air bubbles)and mix just enough for the area then brush on real slow ( to keep from air bubbles) ,want enough on so when dry you dont sand through it and have to do it again.
Then all you need to do , is finish it off like you would a metal panel.

The correct amount of paint on a car is 9 Mills , thats around 3-4 coats of sanded primer , a coat of sealer , 3-4 coats of base, and 2 coats of clear( 2 more coats can be sprayed for later of the sanding and buffing . this way you have the required amount of clear covering the base for UV protection !!!!!
And its a NO NO on sanding a modern base coat, ( unless you hung a run in it , but it will need a few coats to get an even lay out of color.
Dont buy into the hype of all this sanding inbetween coats and then all the sanding of clear. Most of that was brought on by backyard do it your selfers that didnt do it for a living .
First choose a paint product ( PPG, Dupont, S-W, Sikkens.....ect) and use all the recomended products to go from start to finish.
If you follow directions you should have a very nice job when done .
SprayTech

From painting our boats I've found the original gel coat to be peppered with pinholes, I suspect aftermarket glass parts will be the same. A spray polyester surfacing agent like DuraTec works well for cleaning this up. DuraTec is basically polyester resin and microlite, a sprayable Bondo which you catalyze with MEP (just like Bondo and conventional polyester resins). You get 10-15 minutes pot life at 70F. Add acetone to thin it out. As opposed to using Bondo the DuraTec applies evenly, fills the pinholes, and sands like talc after curing for 30 minutes.

If you brush on a layer of straight polyester resin, use finishing resin which contains wax, or spray the surface with a curing film like PVA. If you uses laminating resin by itself the surface will remain tacky even when dry, it will gum up the sandpaper very quickly. Clean the wax or PVA off before sanding.

Be careful with the new parts before painting, gel coat is quite porous. It will absorb oils through handling which will cause problems when you start to paint. Even washing with acetone just gets the stuff on the surface. Best to avoid the problem by protecting as much of the part during mockups with a low adhesion protective paper like ProTex or Mask-Off.

Before doing anything with a new fibreglass part -- clean it well. The part will retain trace amounts of the mold release agent from manufacturing. Some of these contain silicones which are death to paint (unless you like the look of fish-eyes). If you start to sand before cleaning you transfer the silicones to the sandpaper then grind it into the gel coat.

As I stated my experiences have been working with fibreglass boats, but should be the same with fibreglass car parts.

Regards, Mark

Ok looks like a have a lot of reading and practicing to do, to be honest I have never worked with painting automobiles, but I have worked with painting computers and computer peripherals. But I am always looking for new learning experiences.

Some of my work (non-automobile)
http://img.photobucket.com/albums/v2...Dfinished4.jpg
http://img.photobucket.com/albums/v2...000/Final7.jpg