AZDoug

What are your opinions,a nd why on what to use over sanded original fiberglas as a base primer?

Polyester gelcoat? Catalyzed urethane primer? Anything else?

Thanks,
Doug

Jim Dillon

Doug I see you posted over in the painting forum as well and you will find there are differing opinions in this regards. In your other post you stated you have a painter and I would assume you have seen some of his work. If you have not since this is something you want to last a long time it may benefit you to do so. If he has experience with Vettes he more than likely has run into which products work best and will have products that he feels most comfortably with. I have prepped and painted a pretty fair number of Corvettes (admittedly pre-1984 cars) and have used a number of different products. On my present 2- 62 Vettes I used epoxy primer as the base primer on the black car and polyester primer on my candy red car as the body was pretty rough and had some of the ill effects of stripper from the prior owner. If your car is pretty nice which appears to be so, after stripping it may not need a foundation primer to cover a multitude of sins but instead need a primer that is made to be used over bare fiberglass and then from that point surfacer (I would assume 2K) would be used until the surface is ready for sealer or finish paint. There are some primers that are not meant to be applied directly over properly cured polyester so always check the manufacturers product sheets and/or websites. Check with your painter and also talk to your paint jobber to get his input for the progression with the materials that you are going to use. I have had the best success with epoxy primer (PPG DP) as an adhesion primer both with Corvettes but in industry as well when adhesion problems were encountered. If your painter has a good product for a base primer and your homework shows that to be the case then run with it.

I am not an advocate of gelcoat as it was originally designed to be used in molds with a chemical bond with the polyester substrates and any use over a cured fiberglass surface has to be by mechanical means. I am still waiting for any studies that show this not to be the case and would hope that I am in error as it would be very helpful if there could be some type of chemical bond when applied to properly cured fiberglass panels. Polyester primer is not gelcoat it is polyester primer, nothing more.

As to your painter using Sherwin Williams, I have used this paint and found it to be a pretty decent paint although I have not been overly pleased with their reducers and the overall depth of their product line. If your painter is familiar with it he may know all the little tricks to push it into the show finish category. I like PPG because they have a very large product line and I have had real good luck with it. There are some tri-coats that PPG has in their product line that have some tints in the midcoat and I have found them pretty easy to spray. I sprayed my red car with the tri-coat candy red.

Also I would not make a practice of sanding your basecoats unless the product sheets allow this. There are some basecoats that are sensitive to this procedure so once again defer to your product sheet.

There are many ways to skin this cat. If you have some confidence in your painter and his work and you study the product sheets you have a pretty decent chance of getting the job that will justify all of the money you are going to spend on it. Hope this helps. Good luck-Jim

highschool67

I like PPG K series. #36
Great sand/fill/high build and tintable.
I shoot single stage urethane top coat typically.

AZDoug

I have a painter in mind.

Not commited. Still need to look some more. Seems decent, work looks good. Not sure what he wants to do it what is ideal for me. Maybe his way is best, maybe not.

The difference between what is best for me and best for him, is durability, straightness, minimal shrinkage and deep glossy paint on my end, and what is best for him is satified customer with as little hassle as possible while maximizing profit.

Here we get into durablity. What looks good now, may still look good in a year, but will it still look good in 15 years? Will the paint shrink,and check, will the body repairs show tehmselves over time, etc.

Garaged car, of course, not parked in the sun everyday, all day.


That is why i am asking.

Thanks,
Doug

aworks

Jim pretty much says it all in his post. I am not in the gelcoat camp either. What primer to use depends on the bodys cond. If the body is a nice clean orig. one then I would use PPG DP epoxy primer for the base and go right over that with PPG K38. If the body has alot of work done to it then go with a polyester primer. There are to many to list. Slick sand is one that is used alot. the one I use most is made by Valspar.

Brian G.

Jim Dillon

Doug, if it was a straight body I would also use the PPG epoxy and a quality 2k primer (surfacer) such as Brian suggests. The only thing I might add would be to encourage your painter to use either heat lamps or the strong AZ sun in between coats of your surfacer to help it cure fully and shrink sooner rather than later. If you go look at some of the tri-coats that PPG offers you may get an idea for some nice colors. Now that you have all that high dollar powertrain you need the paint to match-Jim

Olustee bus

Everyone will say I am crazy but I have heard (and it is what I did) to use a metal etching (self etching) primer on raw fiberglass as the first coat. I know, why would you use metal/self etching primer on fiberglass. That is for use on metal where it adheres to metal. Follow that with a polyester (filling) primer and then a coat of urethane.

That is what a corvette restorer told me.

tomply32

oh boy here we go again ,as i have said before if it works for you then use it but.PLEASE GET INFO FROM A PROFESSIONAL CORVETTE RESTORATION CENTER IN YOUR AREA THAT HAS RESTORED HUNDREDS OF CORVETTES NOT JUST A few.beware of putting an etching primer over glass and applying polester primer over it you are asking for trouble there, the two depending on manufacturer can be incompatible believe me.your car is made of polester resin and glass what makes more sense here.most people do not understand the workings of gelcoat or the correct application procedures(polester primer,sanding gel)in the corvette body industry(not boat or moldmaking or other).i will rest my case at this point .good luck on your project.

vettnut

I use Evercoats Featherfill. Some people like gelcoat. Again, what does your painter think? If he doesn't know then maybe he should research it or find someone else. Important! Figure out the recipe first. Then cook. Today's epoxy primer sucks ever since they removed the lead,IMO. Gelcoat or Evercoat's Featherfill are both Polyester products. Polyester is also in your fiberglass resin and body filler. One big happy family. DG

Kensmith

Totally agree. Whatever you use, make sure you stick with the same product manufacturer. I like PPG and get great results.

AZDoug

The person i am considering sez:

block the glass, apply a catalyzed urethane medium build primer. Long block, apply another coat of same medium build primer If NECESSARY,
long block, apply paint.

It is not a no hit body, as i grafted on a couple GM replacement fenders 34 years ago,and ground out a bunch of bondo on the front and layed in glass mat where the bondo was, but all in all, it isn't a bad body, and it isn't full of bond.

Doug

Jim Dillon

The great thing about this forum is that none of us know all about everything so it is helpful when we can go to the forum on our weak points and get some helpful direction. I know it has helped me on a number of occasions so I try to help others if I can.

Tomply you are correct that most people do not understand the workings of gelcoat. Production Corvettes have never had gelcoat nor do they need gelcoat except maybe in the rarest of circumstances. It is also tricky stuff to work with and is not meant for novices. Many of the guys on this forum are very knowledgeable and do not have to defer to any Corvette shops on many of the issues. A lot of personnel in the Corvette shops could learn from some of the guys on this forum. When I was born my grandfather was the world's largest car collector and I was hanging around his restoration shop by the time I could crawl. I went to work in his paint shop in 1964 and have been painting ever since. I had my own restoration shop for 16 years but since my restorations on 1930s luxury cars cost over $100,000 it did not give me an opportunity to work much on Vettes other than my own and for friends. I also during that time did show work for GM and handled fleet projects with GM and later TMC. One of the problems I worked on was a massive paint failure with the primer breaking down within itself which in turn shut down all production for a couple of months. When an assembly plant is shutdown and the problem is paint let me tell you firsthand the scrutiny is quite extreme. I pushed for DP epoxy primer as the solution and we ended up using DP40/401 after running 100s of tests. It is pretty decent stuff and my experience shows it works. The surfaces we had to cover were rubber, stainless steel and fiberglass. It is true that the new DP formula is lead free but I have not found any failures. Can't swear to it but I still tried some adhesion tests and found it to be very good. In the paint forum you made reference to a problem with GM and sealers (or epoxies) one I am not familiar with but if there was such a problem as you state then I would appreciate being specific so I can look into it. I do not want to preach as to the benefits of epoxy primer if there are other problems with it.

That being said I have probably painted 50 of Corvettes over the years (my first was for Autorama in 1969). I have worked with fiberglass molds and panels and am pretty familiar with both tooling gel and finish gel. Gelcoat is not meant to be applied mechanically, it is a chemical process that is applied wet to a mold and bonds chemically to the polyester soaked cloth or mat. It is true that some fiberglass panel manufacturers have suggested the use of gelcoat over their panels but that is because they screwed up in the first instance and made defective panels. These defective panels would never be accepted in industry as there is never any need whatsoever to put gelcoat overly a properly made panel. They are accepted in the Corvette industry because the options are limited.

Also just because all of these products are based in a common product, that being polyester resin does not mean that they can be used in a helter skelter manner. Would you pour liquid polyester over a properly cured fiberglass panel? I wouldn't and keep in mind that polyester resin be it as a gelcoat or a pure state (free of mat or cloth) is very brittle. It gains it strength only when it truly bonds to the surrounding layers,

Evercoat makes gelcoat and they make slick sand. Their product sheets refer to slick sand as polyester primer and not as gelcoat or sanding gelcoat. I believe referring to polyester primer as gelcoat just confuses the issue and novices start asking should I be using gelcoat.

You also stated in one of your earlier paint forum posts that epoxy primer will not penetrate the substrate as your polyester primer will (what you refer to as sanding gelcoat). For all of us out here that apparently are clueless about gelcoats I am not aware of any chemical penetration of a cured substrate by polyester and if such is the case I would be most interested in following up on it.

As a restorer of Corvettes I am sure you are very familiar with them and if you and even most reputable Vette shops as you claim use your method that is fine but I believe there are other methods that are available and if it inspires some healthy discussion then so be it as in the end it will only help all of us get a better product in the end. -Jim

aworks

Again Jim has made his point very well. I'm not a back yard guy that has done one or two vettes in my time.I have owned my body shop since 1983. I can not count back far enough to tell you how many I have done. But I can say it's well over 30. And I also own a few that I did years ago. So I think I can back up what I am saying. That said, Every guy has his own ways of doing things.

As far as using DP over bare glass, There is no problem when using a urethane primer over that. If your are using a polyester primer then apply it over the bare glass.

When I started working on these cars we used Laq. paint and primer. The stuff now is way better then back then. Bottom line is it,s your car so do what you want. Brian G.

Scott Marzahl

Self etch primer followed by polyesters is a disaster waiting to happen.
Feather G2 was developed to help combat those disasters with self etch primers but why bother.

I'm in the epoxy primer camp followed by a either quality 2k high build or polyester like Slicksand followed by a seal coat of epoxy, then color.

Lots of ways to approach this, good luck Doug.

67pete

Nobody has really mentioned Lacquer...pros & cons?

AZDoug

Questions:

What exactly is meant by quailty 2K primer?, I know what quality refers to, but 2K?

DP epoxy, is a generic abreviation , or a specific item?

Jim: You said you did autorama once. i assume that meant like arrow stright, Detroit auto show type stuff; can that look be had using yours, or Tomply's suggestions as stated already? Any special other steps to get perfect body/paint, other than just time and elbow grease?

Brian: Please clarify. "As far as using DP over bare glass, There is no problem when using a urethane primer over that."

Are you saying no problem using urethane primer over bare glass, or no problem using urethane primer over DP?

Sorry for the rudimentary questions, bit I know a whole lot more about mech/elec stuff,and next to nothing about paint.

Thanks,
Doug

Thanks,
Doug

Scott Marzahl

DP epoxy primer/sealer is a PPG product, it comes in various colors ie DP90 is black. Staying with the PPG line a quality 2K (two part, build primer) would be K36 or K38 which is applied directly over the DP, ideally within the allowed time window of less than 7 days to achieve the chemical bond.

You can also check out the SPI website for their products and a brief read on the perfect paint job. You get a lot of high quality product for the money, downside is limited colors.

http://www.southernpolyurethanes.com...ct%20paint.htm

aworks

Right on the money. PPG's DP epoxy primer is the best there is. Use it just how Scott said. You have some excellent advise here.

Jim Dillon

Doug to be perfectly honest the 57 Vette I did for autorama back in 69 was a B/G drag car and certainly was not laser straight. I have done a number of cars including Vettes to be laser straight, but I also try to weigh the fact that excessive film build is not optimum. If there is enough surfacer on the car they can be made laser straight, the only potential problem being that someguys apply so much primer surfacer that it may border on the absurd in terms of film build and then you have a chipping problem.

DP epoxy primer is PPG's epoxy system although today it is lead free so it is now called DPLF 90 if black, 40 if green etc. 2K primer stands for 2 komponent meaning it has a hardener. Primers used to dry by evaporation of the solvents (thinner) but with 2k the hardener speeds up the cure and there is a combination of chemical reaction and evaporation of solvents (to a lesser degree). As Brian suggested PPG K-38 is a very good 2k urethane primer. I use it and I also use some of the PPG shopline 2k urethane primer as it is a bit cheaper. If I may make a suggestion a way to get them laser straight while still watching your film build would be for instance to shoot DP 90 which is black and then shoot K-38 which is yellow. Block the K-38 (using blocks in a NE/SW direction and then a NW/SE direction) until you just start to break thru to black and stop in that area or panel as you have blocked it straight (hopefully) and removed much of your film build without disturbing your adhesion coat of DP. Spray a bit more of your K38 and do again if necessary until it is straight (easier said then done of course). I have watched guys spray 2 gallons at a time of 2K surfacer and sand a bit and shoot more and I cringe a bit. Shoot as much as necessary but hopefully most will end up on the shop floor in the way of powder.

I would not use urethane primer over bare glass. Great paint but I believe epoxy primer to be better at adhesion. Also I would never use a wash etching primer over fiberglass. That is a whole other subject but I cannot see an upside for putting acid laced primer on a fiberglass panel.-Jim

stratplus

Where is the painting forum?