What is sealer?

I'm and old guy so cut me some slack on this question.

I see references in threads that mention to apply sealer over primer before the top color coat. WTF is sealer for and do you have to use it?

In my ancient history we just used primer and then painted on top of it.

 

I am a greybeard and I'm as lost as you unless they are just referring to primer/sealer. HRP

 

Typically, your last application of primer isn't covering 100% of your car, there will be spots where you sanded through to the old paint, or maybe even metal on a panel edge, etc. Sealer gives you a uniform 'seal' over the entire car so those edges don't show up later. It also helps fill any teeny tiny imperfections you might have in the primer.

 

I'm no body man but a primer with sealer simply means it keeps the moisture out vs primer without sealer (etching, high solids, etc.)

Primer with sealer has been the norm for some time now, and as far as I know is just the progression of paint/ paint quality.

 

Back in the day, days of Velva-seal ect..., You used sealer when you painted a car over the OEM finish to help in case of a reaction between the new and old finish. You don't have to use sealer over Urethane primer, but it does help to use a tinted sealer under the topcoat as far as coverage goes. And, if you get a chip, it won't stick out like a sore thumb. I still use velva seal. Also most of all the sealers now are catalized. Lippy

 

A good catylized sealer will help hold down all the body work. It also makes the car one even shade which helps when the color you are using is transparent and doesn't cover as well as others. It also fills sanding scratches and makes a smoother surface to lay the paint on. You can paint without sealer too. It is not a mandatory step.

You guys beat me to it. Im slow. Good info above^^.

 

A guy that clubs seals ?
Do I win something ?

 

When a Canadian says he is "going clubbing" he doesn't mean the same thing you mean.

 

One application of a sealer, is adding a sealer agent to your last coat of high-build primer, this helps prevent the scracth or sand lines you may see as your body filler shrinks and pulls the finish paint into the scratches, which will show up in your paint job. May only be noticeable if you look at the surface at a certain angle and in certain light. It can take a few years to show up.

This is how it was explained to me by several guys who have done body work over the years. I have had this issue pointed out to me in various cars at shows.

FWIW

 

Solvents in the paint aren't supposed to penetrate thru the sealer where they might raise any edges of small cut throughs in the primer surfacer, or soak into scratches in the primer surfacer and make them show (raise). In a perfect world you wouldn't need sealer. In my experience, its cheap insurance against very minor imperfections one may have missed.

 

Hey JonF,

A sealer IS necessary for preminum paint work for the following reasons: It provides a uniform base upon which your top coat will adhere to, it will seal previous coats of primer & surfacer BUT it's not its' job to keep undercoats from shrinking! Primer surfacer is porous by nature, and if just painted over without a sealer being used, can lead to dry or dull spots in your top coat, and poor colour holdout!

 

oh i finally get it "what is a sealer"?
a guy who clubs seals
might help you guys to see it all together
haha

 

Etch primer is the stinky green shit you put over bare steel, fill primer is the yellow stuff that you block out after your mud work is done, and sealer primer (or epoxy primer) is usually grey and goes on before paint. Helps keep the paint from mapping or reacting with filler and old paint underneath. DP90 is sealer.

Three different things called "primer" which all have a different use, causing confusion.

 

Its for HOLDOUT,or the ability of your topcoat to not show impefections in the primer coat or a sand thru in a tiny spot of your primer.....The gloss could be spotty or inconsistent in spots if sealer is not used......

 

That's the way I learned it.

 

Ah so, wise ones. I am now not confused at all and I thank you all.

 

If the surface you are painting looks like this-you should use a sealer before your top coat

 

Just for the sake of clarification, would it be advisable to use epoxy over bare metal (in place of etch primer), filler primer, then another round of epoxy as a sealer prior to the finish coat?

 

I have used epoxy primer that states it can be reduced and used as a sealer before top coat. I believe it was mixed 1:1 over bare steel and 2:1 or 3:1(?) as a primer sealer before top coating.

 

Ok, you spend all that time block sanding primer and it looks perfectly smooth, then you spray on a coat of sealer. If you get orange peal in the sealer do you block that smooth too, or spray finish color over an orange peal surface?

 

This is an excellent question that I would like to se an answer from some pro painters.

 

Interesting, but I don't think pro painters would have layed down orange peel to start with...but let's see what they say

 

The way I learned (or re-learned) was epoxy primer, followerd by fill (hi-build)primer. The sealer is done on paint day, think of it as your first layer of paint. The ppg I used is acrylic, so it sets-up fast. One coat, flows and lays down smooth. Check for runs, ect. if sanding is required in spots,touch-up the sealer then start spraying your basecoat. If you sand the sealer before laying on your basecoat, it will lose it's sealing capacity. I was spraying silver, so a pre-mixed light gray was perfect, but could have been tinted to whatever is required.
It's got a nice sheen to it, so an added plus is you get a good visual on your bodywork before you spray that expensive stuff on.
<<<<<<<<see my avatar.
P.S. I'm definetly not a pro, but I do spend a shit load of time researching.

Let me add some stuff I learned that can save a lot of work...off the subject of sealers, but nonetheless..You definetly don't want to have to block sand epoxy primers if you can help it. If you use the windows correctly, you can lay down your epoxy, let it cure (check the mfg's spec sheets for the windows(time)), and just scuff it prior to laying the first coats of hi-build. If you go beyond that window of time with the epoxy, it will have to be sanded rather than just scuffed...and you won't like doing that. I let my high build cure for as long as I can before blocking. It shrinks alot. After blocking is complete, I spray one more coat of high build and let it sit until paint day is close. Final blocksanding is done just prior to the sealer coat, etc.
One note of caution with the high build: I mentioned it shrinks alot..at least the Matrix brand I use, so after curing, and prior to blocking, check any tight inside corners (door jambs, trunk gutters, raingutters, etc), to make sure the primer is "tight" in those corners and hasn't pulled away from the epoxy primer.

 

I do restoration of small pieces. I have been using single stage acrylic enamel with 4:1 paint to reducer and 1/2 of a hardener for some time over a 2K primer surface. First, self etching primer is applied over bare metal. Every once in a while I (today as a matter of fact) I get a severer reaction to the primer. Is it that there is too much solvent in the paint? I do first spray a light coat of paint and let it tact off before I hit it with the final wet coat.
Should I be using a primer sealer before the topcoat?

 

I doubt too much solvent. Is the primer dry as per tech sheet? Are you mixing paint companies products? I would not add another product until you figure out what's going on. Primer sealer/sealers are not a cure all or crutch. They can be very useful however.