Body repair and paint

[Ray C.]

I have the body repairs 98% complete and will soon be ready to start the paint process. I have used PPG DP primer-sealer for a sealer-guide coat and for a base to apply additional plastic filler if needed prior to applying K-36 high build primer and then Duraclyr lacquer.

I have been told recently that DP should not be used on bare fiberglass and if it is used, a 7 day drying time and a light sanding is required prior to applying any high build primers or finish paint. I called PPG tech-line yesterday and this was confirmed by PPG.

I would like to shoot a guide-sealer coat of a different color prior to applying the K-36 high build primer. Does anyone have a recommendation to what would be the best product for this application?

Thanks for any help!

Ray

[Chuck S.]

Re: Body repair and paint

I have the body repairs 98% complete and will soon be ready to start the paint process. I have used PPG DP primer-sealer for a sealer-guide coat and for a base to apply additional plastic filler if needed prior to applying K-36 high build primer and then Duraclyr lacquer.

I have been told recently that DP should not be used on bare fiberglass and if it is used, a 7 day drying time and a light sanding is required prior to applying any high build primers or finish paint. I called PPG tech-line yesterday and this was confirmed by PPG.

I would like to shoot a guide-sealer coat of a different color prior to applying the K-36 high build primer. Does anyone have a recommendation to what would be the best product for this application?...

(1) Based on what others have said here, I would gelcoat any new resin/mat repairs or repro panels and let it cure WELL before paint.

(2) This is the first I've heard that DP can not be used on bare fiberglass. Unless PPG has revised the product sheets, properly prepared fiberglass is was specifically itemized as a suitable substrate. If you asked PPG Tech Service if DP has to be sanded after 7 days drying time, their answer would have been an unqualified "Yes".

(3) DP is not a sanding primer...application of a guide coat over DP is a waste of time and material. ADHESION to the cured DP is your objective, not leveling. You can tell where you've scuffed DP without a guide coat...sanding flattens the eggshell gloss.

If leveling is your goal, apply your guide coat AFTER 3-4 wet coats of K36 and sand it smooth. You can buy guide coat products in aerosol cans...there's no point in overworking the solution. Guide coat is applied sparingly, not to full hiding; Apply just enough to sand off everywhere but the low spots...the nozzle on the aerosol can is designed to give you a fine splatter coverage that works well without wasting material or increasing your work.

[Dick W.]

Re: Body repair and paint

I have used DP for many years on bare fiberglass with NO problems. If you do not top coat it within 7 days you have to scuff it before you apply another coating. I have used the DP, followed with DP, sand/block and anywhere we went to bare glass spot that area with DP, immediately prior to applying color we use DP reduced 100% as a sealer. While this is drying you mix your color and immediately start painting.

We never use/used any gelcoat products, the DP gives you chemical adheasion, the K-36 gives you the primer/filler that gelcoat does, so why be redundant. The first car we did this way was painted 23 years ago, and to this day, other than waves in the glass, it looks like it came out of the spray booth yesterday. Ever car we have done this way has not had any problems with the paint. We just followed PPG's instructions to the letter, no variations.

[Chuck S.]

Re: Body repair and paint

...We never use/used any gelcoat products, the DP gives you chemical adheasion, the K-36 gives you the primer/filler that gelcoat does, so why be redundant...

To clarify my post, Dick, spotting repairs and painting reproduction panels with gelcoat as I described is not intended to promote adhesion or provide leveling. Gelcoat is essentially an additional layer of catalyzed resin applied to SEAL solvent volatiles and/or SEAL pre-existing oil and grease stains that can not be effectively removed to prevent paint problems.

Maybe DP primer is enough to seal these problem areas, but I remember there has been evidence to the contrary (see archives). Limited use of gelcoat as described seems prudent to me. I don't know if it works EVERY TIME, but I do know that it is the solution of last resort.

I would only use gelcoat on fresh lamination repairs or reproduction panels; clean, original fiberglass should be fine without gelcoat in my opinion.

[Gary C.]

Re: Body repair and paint

Everyone has their opinion whether to use or not use gelcoat. Don't know about C2/3's as my paint experience is with C1's primarily '57's. If you don't use gelcoat all over on a '57 you can expect to have spyder's in a couple of years or less. That's been my experience. It's better to be safe. JMTCW, Gary....