Primer _ sealer

[Tony P.]

Im painting my 57 and want to know the difference between primer and sealer. Does the car just need primer or sealer before painting?

[Gary C.]

Re: Primer _ sealer

Tony,

IMHO if you don't want the paint to spyder crack a '57 needs to be gelcoated.

Search the forum for gelcoat - there are several threads on that subject.

Gary
....

[Chris S.]

Re: Primer _ sealer

to answer your question
primer is a undercoat designed to bite into the substrate (fiberglass or metal) and for some thing for the top coat to adhere to
Sealer should be used as the last topcoat before basecoat to seal down all body work, plastic filler etc... from bleeding thru into the basecoat
There are many different combos
There are primer surfacers etc
Best advice - stick with one paint line and follow there recomendations from begining to end
Gelcoat - IMO - is a thing of the past
I use a Slick Sand - it is a 2k - very heavy polyester primer surfacer AFTER I am done with all my body work
I like it since it is MEKP activated - just like resin

http://www.evercoat.com/productdetail.aspx?pid=28

I like to block this first, then prime, then block, then prime, then final block w 600, then sealer, then basecoat, then clearcoat
for cracks - V groove them with a dremel from beginning to end - I fill cracks with Glasin - other guys use other products
you have to V groove cracks and address them individually - or they will come back up thru. Takes lots of time

But use sealer just before basecoat.

[Tony P.]

Re: Primer _ sealer

Thanks for your help

[Tom A.]

Re: Primer _ sealer

I would suggest you research spray gel coat further. Gel coat will seal the fiberglass to prevent solvents from migrating into the fiberglass. These solvents will eventually come out and leave fiberglass shrinkage. Slick sand is a good product but does not seal the surface well and has solvents of its own which will soak into the fiberglass.In my experience it's good for the short term but will not hold out long term. It is a great high fill primer and cuts down block sanding time. There are many opinions on this subject you just don't want to short cut the fiberglass work it's the hardest part of the restoration to have to redo. The solvents used in today's finishes are very aggressive and can soak in deep.

[Tony P.]

Re: Primer _ sealer

Thanks,thats why I'm asking questions! Im trying to doit right the first time.

[Chris S.]

Re: Primer _ sealer

I would suggest you research spray gel coat further. Gel coat will seal the fiberglass to prevent solvents from migrating into the fiberglass. These solvents will eventually come out and leave fiberglass shrinkage. Slick sand is a good product but does not seal the surface well and has solvents of its own which will soak into the fiberglass.In my experience it's good for the short term but will not hold out long term. It is a great high fill primer and cuts down block sanding time. There are many opinions on this subject you just don't want to short cut the fiberglass work it's the hardest part of the restoration to have to redo. The solvents used in today's finishes are very aggressive and can soak in deep.

I do agree about the solvents being aggressive - It is prob the number one cause I see in paint defects - many guys rush the process and do not let all the solvents make their way out of the undercoat(s). They then become trapped and can cause a redo.
I will bake my body work with a infared lamp - I also set glass/body work out in the sun in summer - let the glass go thru many heat and cooling cycles - more the better
I do disagree with the S Sand comment I have used it long term and have personally seen numerous BG and NCRS cars go long term with S Sand but to each their own - you need to find a process that works for you - Best advice - use one paint line/system - follow their recommendations and directions - if they are followed failures, are minimized. Talk in depth with your painter or shop.

[Domenic T.]

Re: Primer _ sealer

Tony,

We have had 100% sucsess with a good 2 part epoxy primer/sealer which does both.

It cures and the solvents are solid after the cure time.

I apply the first coats in white then tint the primer on the next coats I sand and avoid going into the first coat of white.

A good shop will give you something to tint the primer with or you can use a different color primer for finish work.

The 2 part epoxy primer will lock down old glass that grew hair and keep it from photographing, ( when the weaving and repairs you covered show thru after shrinkage).

ALL non shrinking primers will shrink a little and the longer the cure time the better.

The post that talked about trapping solvent and running into problems is true, I know that for a fact as I lost some stripes 2 weeks later.

We had to conform with CA paint standards that required a 2 part clear coat to cover a solvent based paint and it trapped the solvent (reducer) and the paint wrinkled 2 weeks later.

If the gell coat is anything like the stuff they use in the boating industry I would recomend the 2 part primer.

DOM

[Tony P.]

Re: Primer _ sealer

Thanks everyone for your input.This site is how I do my research being a new commer to restoring and Corvette repair.