Priming Question

[zachb55]

ok, im FINALLY getting to the priming stage of my car. I already put a layer of etching primer on a while back, but now that all of my body work is just about done, im going to be putting on the gray primer which will be right before my paint if i understand correctly... my question would be this "how many layers of primer should i lay?", "what grit sandpaper should i use before my first layer?", "what grits should i go through and end at?" and i guess ill ask some other sanding and layering questions about painting later when it comes to my topcoat. thanks for the info,

-Zach

[EScanlon]

Once you're done with the body work and ready for primer:

1) Using a quality Wax and Grease Remover, wipe off the WHOLE car.

Procedure for this is to get one rag cloth that's been moistened with the W&G and another to wipe dry. Wipe with the moistened cloth a section about 2' x 2', then before it has a chance to evaporate, wipe dry with the dry cloth. Get to all edges, underneath areas, ANYWHERE that you can access.

2) Inspect the car completely.

If any of the original finish is still showing, make sure that you've sanded it so that there is no SHINE left on it. If there's shine, paint / primer won't stick. You could wet sand if there's any doubt as to how smooth this area is (320 grit is ok) or you could use a 3M Scotch SCUFF PAD. This is something that looks a lot like one of those green pads you would use in the kitchen but it's designed for body work. You can get it in Brown (coarse), Green (Medium), Maroon (Fine) or Grey (Extra Fine). At this stage a Maroon should be fine.

2a) If you've wet sanded or scuffed any areas, make sure you W&G those areas again.

3) Mask any areas that will NOT get primered.

4) W&G car again. Make sure you use fresh clean rags, change your dry rag often, and also your moistened one. Ratio should be about 2 dry to 1 wet.

This may seem like overkill, but you would be surprised how many times I've seen paint jobs ruined because this was done only once or twice. Your body exudes oil, if you touch the car barehanded you'll leave residue behind. As you've been working on it, scuffing, masking, etc, you will have left behind little dabs of skin oil. These can cause fish eye, crazing, lifting, to name a few.

5) Allow the car to "breathe" about 30 mins or so in the paint booth. This is to allow whatever W&G residue you didn't wipe off evaporate.

6) Mix your primer according to directions.

Now let me digress.

Primer Filler: This is the primer to use to lay down a coat of material that you will be Wet Sanding smooth. This is the one that will make your final paint look like glass.

There is High Fill and Regular Fill.

If you are experienced doing bondo / panel repairs, then you can get away with Regular Fill.

If you have any doubts whatsoever as to how smooth the PANEL is overall, I would use High Fill. Yes it's more work to sand a High Fill primer panel down, but the results SHOW.

Believe me when I tell you that you will SEE any imperfection in the panel once you finish painting. A dark paint will literally HIGHLIGHT any sub surface irregularity. A light color paint will not show it as readily but to the trained eye they're still visible.

The intent of FILL primer is to provide a sandable surface that you will then sand smooth so that when the paint is applied it will reflect just like if it were a mirror. And like a mirror, it doesn't take much of a distortion to show up.

Sealer Primer: Sealer does exactly what the name implies. It seals the base materials from the topcoat. This type usually has SOME fill material, so yoiu can sand it smooth also. However, you must NOT cut through it to the base or you will have to shoot another coat. It's purpose is to SEAL.

Depending on what type of repairs you've done will dictate whether you should or MUST use sealer. Bondo, if mixed properly and worked properly and most importantly NOT FRESH (within 48 hours), should be ok without Sealer.

Red Cap, if applied thickly, MAY require sealer.

Fibreglass work, almost without exceptions, SHOULD be sealed. Fibreglass resin tends to leech for MONTHS and it will cause paint both Lacquer and Acrylic Enamel to craze, lift, fish-eye, haze to name a few. I personally will not primer and paint over fibreglass work without Sealing it.

Plain Sealer: This has NO fill in it. You can use this just prior to painting if you have any doubts as to the base. Usually this stuff is also called "non-sanding". That is, you don't have to scuff off the top skin. Note however, that this is usually only for a limited amount of time (24-48 hours usually).

Red Cap or Top Cap: This is thickened primer. You can obtain this in various colors and sanding consistencies. There's Red, Lite Blue, Lite Green, Yellow. The difference in the color usually denotes how "sandable" it is. The more sandable the Top Cap is, the easier it is to remove it and hence harder to gauge when you've FILLED the imperfection you're looking to get rid off. (Remember, that's HALF the purpose of primer / filler and the ONLY purpose for Top Cap)

Ok, got all that?

I'm going to parse this out into two postings so that the server can "page" if necessary.

Enrique

[EScanlon]

Before you primer, you should have an Organic Vapor Breather. This is the type that has those 2 charcoal canisters and / pre-filters on each side of the mask. They're there to block the overspray that WILL be floating around that you do NOT want in your lungs or nose.

Please, DO NOT ASSUME THAT A SIMPLE PAPER FACE MASK IS ADEQUATE! But then again, they're your lungs, if you feel you will be a good candidate for a Lung Transplant in the future, ignore this warning.

7) Fill your paint gun with primer.

I tend to only fill it to about 3/4 of the cup. This way you won't be dripping on the car as you do the roof, hood. Even then, I will usually tie a rag around the cup top to catch any drips out the vent hole.

8) Check your spray pattern and volume on a scrap piece of cardboard, metal, etc.

Your paint gun should allow you to adjust the width and the amount of paint you will be spraying. The adjustment down to a SPOT is for shooting into tight and deep recessed areas. The width is so that you can adjust how much overspray to the top and bottom of your pattern gets thrown out. The volume needle determines how much paint you will be spraying at one time.

Personally, I like to set my pattern at a straight up and down fan, measuring about 9-12" tall when about 12" away from the metal. A single steady pass should leave enough color that you can tell you've misted it completely, but you don't have complete total coverage. This is commonly referred to as a Single Pass Mist Coat. A Double Wet coat is TWO passes, but this time on each pass you've thoroughly wetted the surface. The volume needle will regulate how much paint you're shooting, the next variable is your coating speed.

Obviously the FASTER you move your hand accross the panel, the LESS paint you will get on it. Conversely, the SLOWER your pass, the MORE paint you will get on it. You need to be careful as you don't want to put the paint so lightly that you will be putting it on "DRY" and not so heavy that you cause it to "SAG" or RUN.

9) Make your first coat a thorough LIGHT Double Wet.

The main intent here is to get a good even coat AND to get the sequence of panels down pat. What's a sequence of panels? Ahh, here's where technique is very important.

While you are primering, you are practicing your technique in painting AND how to "flow" around the car. If you do this just right, you will NOT have a Dry Line left. Do this out of step or in a haphazard manner and you will have a Foggy look afterwards, where the newly applied paint didn't flow into and blend with the prior paint pass. (That's what a dry line is.)

Thankfully, primer is very forgiving about dry - lining. PAINT however is NOT.

I would start midline on the roof, go from the windshield all the way to the hatch window, then back and forth all the way to one side. As you approach the side edge, shoot it from the top down and on the back stroke, from the bottom up (under the gutter). Carry this stroke down the back window edge.

Quickly, step over to the other side and do the other half of the roof, duplicating your pattern. Remember, shoot the rail AND the pillar, but don't get crazy about getting too far down the pillar.

Go back to the first side and pick up on the pillar and paint down the pillar to the back of the hatch and down the top of the rear fender.

You get the idea? The idea is to shoot a complete area or half an area, carry the paint line (the leading edge of where you are applying paint) forward and before it has a chance to dry, you go back and pick it up on the other edge and paint the next area or the other half. The intent is to NEVER let the paint line dry and carry it forward until you finally meet it to itself at the opposite end of the car from where you started.

Imagine that you are pouring the paint from the top and you want the paint to flow from panel to panel all the way from the point where you start pouring to the final and furthest edge of the car. Just like an animated cartoon. The paint ideally will never have stopped at any edge, and will have flowed evenly.

Ok, this gets you through the first coat.

10) Depending on how much primer filler you need to apply, shoot another 2-3 coats over the whole car, waiting 15-30 minutes between coats depending on temperature, humidity and thickness of your previous coat.

Got all this?

Next post.....

[EScanlon]

Now you've primered the car. Wait at least a couple hours before going in there and removing any masking you may have done.

The next steps will determine how good your final paint job will look, so be meticulous in doing them well.

After waiting at LEAST 24 hours, and LONGER if the temperature is low, humidity high, or you've shot a THICK coat of primer.

11) Scuff the whole car with a Grey Scuff Pad or very lightly with a Maroon one.

The intent of this is to remove any overspray "dust" and to very VERY lightly cut the skin on the primer. You're not looking to sand with this, just to knock off any surface crud that may have stuck to the primer.

12) Using 360 or 400 grit paper, a sanding block, and a rag that's dripping wet with water, start sanding the roof of the car.

Work your sanding so that you are using SHORT diagonal strokes in a lengthwise orderly manner. Using keyboard symbols what you want is this:

\ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ ==>>

Hopefully you can see what I mean.

If you use strictly linear strokes there is a HIGH probability that you will end up "grooving" the primer. That is, due to the unevenness of the pressure you will be applying to the sanding pad, AND the tendency of humans to do linear movements by moving their hand from close to their body to extending their arm all the way, rather than side to side (if you do that you'll have an ARC). What will happen is that the sanding paper and block will cut deeper grooves under the areas of high pressure.

By using short diagonal strokes, you use the SIDE of your hand AND you are cross hatching the stroke with the return stroke.

13) As you sand each panel, use copious amounts of water to flow away the cut primer. Every so often, use the edge of your sanding block, or get a rubber squeege and squeegee the panel "dry". Look at the reflection of the water as you squeegee.

If the panel has been sanded smooth and even, you should be able to see an EVEN satin moistness. If you see SHINE, more than likely that is a SHALLOW area in the primer. You can continue to sand the panel down to meet that shallow OR you can apply Top Cap Primer to fill it. This is where experience is your best bet. What some guys would Top Cap, others would sand smooth and the reverse. You just have to develop a feel for how thick your primer is, and how much more sanding you can do before you cut through the primer to the metal.

Remember, if you cut through to the metal, or the base coat, then you must repaint that area so that you can once again blend it in.

14) Continue sanding the whole car until you are finished. If you find that you have some areas that need Top Cap, you can either apply it to just that panel and keep on going, or wait till you finish sanding the whole car.

Note, since Top cap is basically thickened primer, you will want the panel to be bone dry, AND you will have also given it a good wipe down with Wax and Grease Remover. Just like you did to primer the car originally.

Apply the Top Cap with a rubber squeege or one of the smaller bondo spreaders. Squeeze it tight into the scratch or shallow and smooth it off as best as possible while still building it up so that you can sand it smooth. Remember, it's purpose is to provide material to be sanded smooth. If you skimp, you'll more than likely have to re-apply. If you go overboard, you'll be sanding that much longer.

Personally, to sand the Top Cap, I use 320 grit for Red, and 360 for Blue / Green and I haven't used Yellow in so long I don't know if they still sell it, but 400 there.

Test the panel for smoothness every so often until you can readily see that it's smooth.

Some people will shoot a very light mist coat of offsetting color paint on top of the primer as a GUIDE COAT. This is an excellent idea if you shot extra thick primer, or HIGH fill primer or even if you're not quite expreienced enough to make sure you sand the whole panel evenly and smoothly. It's no shame to use it as it is a helping tool. It's also excellent at pointing out shallow area's in your panel.

Well, there you have it. I've tried to be concise, and although that may get a chuckle or two out of everyone, go ahead and check out any book that deals with painting and tell me how well I did.

Hope this helps.

Enrique Scanlon

[zachb55]

Whoa man, blew me away with that, i dont think a book could have done any better... thats somethin i wold want to put on my site if its ok with you, im sure it will help alot of once confused amatures that havent done this before... i have another question though, i used a green primer that was a sealer and an etcher i think, i put that on before i did alot of my body work because a big reason was my leaky ceiling which was allowing moisture to get on my roof which i had done hours of bondo work on. i sanded through it to the metal in a lot of the places where i did body work but i only sprayed it on the main shell of the car and not the doors, valance, hood, hatch, or any other parts that came off, should i respray the entire thing (including those other pieces) with this sealer just to have a uniform coating? i also did use a fiber hair product and i would assume that has the same properties as fiberglass might? i hate to make you type anymore, maybe someone else will contribute this time, but after all this work i want to do it right no matter what!

-Zach

[EScanlon]

Zach, by the way, I'm here in Vancouver, Washington. So if you want, I could meet with you and take a look at your car and give you some advice right there. Just a thought for you. PM me and we can exchange phone numbers.

Next:

Green Primer; sounds a lot like Epoxy Primer, or it could be some of the newer Acrylic Urethane. I don't paint the Acrylic Urethanes as some of them have some REAL hazardous fumes and I don't have a full face respirator with outside feed, and that's what I've heard you need.

As far as shooting just to get an even coat? I don't know that I would sand down to the metal just to get an even coating, now if you are ALREADY at the metal, then if it IS a Sealer Etcher, then by all means. An etching primer is always PREFERRED over bare metal, and under body work. However, if you've already past that stage, I wouldn't undo all the work just to use it. Mind you, this is all based on your having prepared the metal PROPERLY.

Bare metal needs to be etched or at LEAST D/A sanded with 220-360 grit. That way you'll have the fine swirls and ridges that the primer needs to make a solid bond onto the metal. If you did NOT prepare the metal, then you BETTER sand it down so that you can do it properly. At that point, use the Etching Primer.

When you mention the Fiber Hair product, I'm supposing you are referring to what we used to call "Gorilla Snot" or "Gorilla Hair". That's basically fibreglass strands in bondo. You probably SHOULD use the sealer over this, but if I recall properly, just fibreglass and bondo mix are ok. The substance you have to worry about is the RESIN that gets used with fibreglass strand mat or cloth. So try to remember if the stuff you used had a greenish tinge to it or maybe a brownish gray (kind of like caramel colored). That WOULD be a resin based bondo, and therefore should be treated as fibreglass. Another absolute sign that you were using fibreglass RESIN based material, is if the catalyst was a clear liquid peroxide. Usually you add it at the rate of 1 drop per ounce of resin.

If on the other hand you're talking the plain gray, or almost pale beige stuff, that's regular bondo. The hardener for this is typically a reddish toothpaste-like paste. I've seen blue, black, green hardener so that it isn't red is not an indicator.

Phrasing it another way, you won't go wrong using a sealer over the whole car just before the paint. It's just that most sealers aren't very high fillers, so it usually ends up being yet another step.

To describe the IDEAL procedure:

Body down to metal.

All seams seam welded and ground smooth.

Total Metal Preparation, whether by using an Etch Primer or a Metal Preparation Wash.

Perform all body work required to smooth body.

Primer with a Medium Fill or High Fill primer depending on the amount of body work done.

Wet sand smooth.

Top Cap and sand smooth. Re-prime if necessary and re-sand.

Wait at least a week. Inspect for any changes to the body due to shrinkage of the Top Cap.

Re-prime if necessary and re-sand.

Top the primer with Sealer, giving it a good uniform coat.

Wait overnight, then using a fine scuff pad, knock down any bumpies on the sealer.

Wax and Grease Remove

Mask

Wax and Grease Remove

Paint

Let it sit at least 24 hours before ANY reassembly, and the longer the better for anything that gets fastened to the body and presses on the paint.

DO NOT WAX FOR AT LEAST 3-4 MONTHS.

If washing is necessary, use copious amounts of water, a drop or two of detergent (the least amount possible) and the softest cloth you have and DO NOT APPLY STRONG PRESSURE.

As long as you give me credit for the posting you're welcome to use this elsewhere. The reason for the credit isn't for bragging rights but so that people know whom to ask and whom to blame.

Enrique Scanlon

[zachb55]

hey you highly deserve the credit for every right, i was once pretty confused but now i can consider myself one who has an idea of where im at in this process and what i have yet to do. th reason i asked about putting more of the green stuff on was just whether you thought it would matter in the finish if i started the primer on bondo in some places, sealer in others, and bare metal in some as well, but i think what ive learned so far is that this is no problemo. i sit thinking, a little worried that maybe i didnt do everything the way i should have, and that in two years ill be doing this all over again for that reason, but i guess when the time comes ill know how to do it just right. i would like to talk to you sometime, you seem like a really knowledgeable person, and i would like to do my senior project on something of the aspect of body work so im sure you will come handy there, but thats a bit in the future because im a sophomore right now so i got some time before then... man its weird, i got my car on the 7th of april 2002, i can hardly belive ive been working on it for almost a year, and i did most of the work in the last 2 months, i guess thats what happens once you get a license, you suddenly get a drive to get that car done. thanks for the info, ill be sure to let you know how it turns out.

-Zach