Painting best surface preperation

[Charles A.]

I am painting a 67 coupe that has been stripped and the fiberglass is pretty rough. We have re glassed where appropriate and sanded.Unsure of the best preparation before painting. My painter says 3 choices: 1. gelcoat. 2. epoxy primer or 3. polyurethane coat. Which one is best?

[Don H.]

Re: Painting best surface preperation

I am not an expert but since no one has replied I will jump in. I think most shops wanting the best and longest lasting finish will gel coat. Don H.

[Charles A.]

Re: Painting best surface preperation

Thanks Don. Is there someone who knows about all three methods?

[Richard H.]

Re: Painting best surface preperation

I would recommend epoxy primer. It should be block sanded and then re-applied. Continue process (spray/block sand) until waves in glass are eliminated. It is then ready for top coats. If you want to keep it looking original, just shoot the primer one time and leave all the waves in the glass.

[Doug F.]

Re: Painting best surface preperation

charles, i get the body work done sanded to 80 grit, then i apply a couple of coats of a polyester primer surfacer, i use evercoat slick sand, then i block that out to 120 grit or so dry, i follow that with polyurethane primer, i use valspar colorfil 092, i like it because you can choose a color that will match your top coat color,block sand wet, repeat this process until your at about 600 grit, then it's ready for the top coat of your choice. since i've been using this combo i've never had a problem with shrinkage or any other subsurface issues, be careful when picking a shop, us painters are the worst of the lot.

[Charles A.]

Re: Painting best surface preperation

Thanks. I use to sell DuPont paint back in the acrylic lacquer days but know what you are talking about. Fortunately I have a great painter but he has only used epoxy primer in the past and there are a few sanding marks that can be seen at just the right angle on a roadster he did for me. Will the urethane fill better then the epoxy?

[Tom A.]

Re: Painting best surface preperation

Charles, If you want the best possible hold out for the long term, I would suggest you use spray gel coat. The problem with epoxy or urethane primers is that they use very aggressive solvents. Your fiberglass is old and dry and will absorb solvents readily, eventually this will come back in the form of surface shrinkage as the solvents finally work there way out. Gel coat will create a barrier that helps prevent solvent absorption into the original glass. There are as many opinions as there are painters but at this point you don't want to save a little expense or time only to find in years to come than a little more effort might have prevented problems not easily solved after all its all done. I have been doing Corvette bodies for over 30 years and have tried every method out there to create a long lasting finish without repairs coming back to haunt, including some very expensive high build polyester primers. The only thing I have found to give consistant results without fail is spray gel coat (not the hard surface marine variety). I'm from Texas any heat and sunlight here tend to exagerate the problem. This is just my experience and doesn't mean that others have achieved good results with other processes, I tend to overdo my base because it's cheaper than reworking later. Good luck with your paint. Tom

[Sandra H.]

Re: Painting best surface preperation

Tom,
Is the gel coat used just as a sealer, or does this also make the 'fuzzy' areas lay back down?
Can gel coat be sprayed way before anything else.....I would like to get the 'fuzzies' under control before it gets worse, but don't plan on painting the car for quite awhile.
And can I use the same sprayer that I would use with the top coat of paint? I have several sprayers here.....I'm assuming the DeVilbiss I have is the one to use for the top coat.
And ....what size compressor do I need? I have a new one that I've used for varnishing wood panels, but don't know if it's the right one for car paint.
Any clarification would be a help.
Thanks, Sandy

[Tom A.]

Re: Painting best surface preperation

Sandra,
The pupose of gel coat is to seal the porosity of the fiberglass surface. It will seal your "fuzzies". I would sugget spraying 4 to 5 coats of gel coat just on the fuzzy areas, allow them to cure, block sand them with 40-80 grit sandpaper then gel coat the entire surface. This will build up the fuzzy areas (areas that for whatever reason have had a portion of the resin washed away) then level the strands sticking up. This can be done before body fillers or after. The prefered method would be to finish repairs first then seal the whole area with gel coat.
A top coat spray gun may not have an adequate flow rate for gel coat as it is a very thick material to be sprayed. The gun will need to have as large an orfice size (the size of the opening the material goes through to create proper atomization of the material sprayed) as possible, If you have an old cheap pressure pot gun for use with latex paint it may work as the pressurized pot forces the material through the spray tip (orfice). Be sure and clean your gun immediatley after spraying or if the gel coat starts to thicken (harden) in the gun. Clean with acetone or lacquer thinner (automotive grade not hardware store or home grade). I can not stress enough the importance of cleaning completely and without delay. If the gel coat hardens in the gun you might as well throw it away as cleaning will be nearly impossible.
Your compressor size will depend on the cfm (cubic foot per minute)output of the compressor as compared to the cfm flow rate of the gun you are using. You might get by with to low a volume on many paints by just waitng for the compressor to catch up but gel coat is time sensitve and waiting is not an option. Under normal circumstances you will have barely enogh time to spray the materil and clean your gun before the material starts to set up. I hope I have covered all your questions, if not leave another post or e-mail me at automospe@aol.com. I would be glad to help any way I can. Thanks
Tom

[Sandra H.]

Re: Painting best surface preperation

Just one more question, Tom.
Can I gel coat and then wait, probably for quite awhile, before painting?
Most of my other questions are answered, I think, in the Eckler's fiberglass repair book that I have.
Thank you, Sandy

[Tom A.]

Re: Painting best surface preperation

Sandra,
You shouldn't have any problem leaving the surface with gel coat for a long period of time. I would avoid leaving it set in the sun as this may deteriorate the surface eventually and I would not cover the surface with anything for at least 2 weks to allow all solvents or vapors to escape completely. Good luck with your project.
Tom

[Sandra H.]

Re: Painting best surface preperation

Thanks Tom for your part in my education. Best, Sandy