Paint primer question

[pflaming]

What is the reason for three or four primer/sanding sequences prior to applying the color? Seems when I sand primer, I always take some off. I know primer does NOT cover a poor surface, but does several coats in effect fill 'microscopic' holes tha makes for a very smooth surface.

Edit: Is the last coat of primer sanded also?

[Plymouthy Adams]

priming multiple coats will allow you to fill all the tiny imperfections and sand scratches in the primary body work..the primer surfacer and the finer grit of paper and using soapy water as a media to prevent clogging and give lubrication makes for a very slick finish..the use of a squeege during wet sanding will show all the small pits/sand scratches that will yet need primer applied..(wet dot stay behind)...once the pits are gone some use a guide coat to help eliminate waves on a long panel..I like to use the largest block sander suitable for the panel and the longerst stroke to help prevent waves

[Dave72dt]

You use progressively finer grit paper each time you sand the surface. You could sand it with one pass with 80 grit and paint it but every sand scratch would show in the paint. The next sanding session is with finer grit to remove the coarser sanding scratches, and the next is finer yet to remove those sand scratches until you get to the grit the paint's P sheet recommends. General rule of thumb is 400 grit minimum for a solid color and 600 min. for a metallic. The coarser grits remove the material fastest but leave the deepest scratches.

Sealer is sprayed after all the sanding is done and is normally not sanded. It does however have a time window when the color needs to be sprayed and if you're doing a BC/CC it usually has a time window too. Get all the P sheets for the materials you intend to use, and make sure they are compatible.

That's the really short version. They write books on this stuff.

[JBNeal]

I've read several books (found several at the library and picked up a few online) and have practiced with different techniques, and multiple thin coats with progressively finer sanding grits provides glossier top coats, even with flat paints. I've also painted without sanding between coats, and the surfaces can be rough which can be a problem with coating durability, as rougher coats are more susceptible to chipping, and generally look like carp. When I painted my home LPG tank last year with a foam roller, I wet sanded between coats with 120, 320 & 400 grit with impressive results. For a much glossier finish, I could have progressively gone up to 1600 grit for the mirror finish...but for the LPG tank, I figgered 400 was good enough. With this finish, lines can be seen in the finish from the foam roller, but from 20 ft away, the tank's flat aluminum finish will blind ya in the summer sun

[55 Fargo]

There is even polyester filler primers out there, shoot with a big spray tip like say 2.0 to 2.2, you could bury 80 grit scratches like nothing, with 1 pass. I have heard of guys burying a quarter that was taped onto some panel for a test. This stuff kicks hard though, so you need to get the gun cleaned fast after shooting it. But for a wavy pitted scratched panel, could work great.

I use 2k urethane high build primer, it blocks and wetsands very nicely....

[Dave72dt]

There is even polyester filler primers out there, shoot with a big spray tip like say 2.0 to 2.2, you could bury 80 grit scratches like nothing, with 1 pass. I have heard of guys burying a quarter that was taped onto some panel for a test. This stuff kicks hard though, so you need to get the gun cleaned fast after shooting it. But for a wavy pitted scratched panel, could work great.

I use 2k urethane high build primer, it blocks and wetsands very nicely....

For that polyester filler primer, I believe the recomendation is to not wet sand it. Dry sand it all you want but it contains a lot of talc which will absorb moisture if wet sanded and come back to haunt you after it's painted. It needs a 2k primer over it for wet sanding.

[55 Fargo]

For that polyester filler primer, I believe the recomendation is to not wet sand it. Dry sand it all you want but it contains a lot of talc which will absorb moisture if wet sanded and come back to haunt you after it's painted. It needs a 2k primer over it for wet sanding.

Yup, its not for surfacing in the sense of final blocking and wet sanding, it is a major high build, then you block, and shoot on say a good 2k urethane primer surfacer.... ps like spraying body filler or glaze, then its time to primer over it and block to perfection

[chopt50wgn]

I had put a couple of coats of epoxy primer on my wagon a few years back. Most of the body was down to bare metal so I shot on 2 coats of Dupont epoxy primer. The epoxy primer allows you to have a good water proof base to apply bodywork over it. So after getting all the bodywork done I was now ready for the final coats of primer.

I sanded the body with 80 grit , then 180, 150, and finally 320. Then applied 3 coats of filler primer. Let that dry for a whole day. Then started the wetsanding with 400 and the squeegee. That took about 25 hours over 2 days.

Now ready for the topcoats of epoxy primer. The filler primer is polyester and must be topcoated if you are going to subject the body to the poutside elements, which I am. I am going to drive the wagon in primer for a year before I paint.

All said and done, I have about $450 in materials and about 50-60 hours in time. Add up those hours against a shop at $75 an hr. and see how much you can save doing it yourself.

[pflaming]

I just read six (6) good ways to paint and six (6) good reasons for original patina! The expense of a GOOD paint job then is in two things: prep and the cost of paint, not to mention the reputation of the man with the gun. I've made a wooden model of my father's 34 D John Deere, and I'm ready to pain, thus my question.

A neighbor friend who is an immaculate hobbiest said that chrome paint makes a very good primer on wood. I'm going to experiment with that today.

I'm still on a 10# lifting restriction on my back, which is healing very nicely.

[Jeff Balazs]

I have some questions inline with this topic.

I have been working on getting my truck down to bare metal and need to get it primed soon. Can epoxy primer be tinted? I want to go with a light tan color and one of the non epoxy systems I have been looking at offers tinted primers.

Also what is the minimum set up required to spray epoxy? I have a pair of oil type 2 cylinder compressors that I can hook up in tandem to get about 10-12 CFM with 80 gallon reserve. I don't want to spend more than is necessary on a gun that is only going to be used for this one project. Also what respirator etc....do you recommend for this?

Thanks for your input.

Jeff

[austinsailor]

not sure about epoxy, but the polyester heavy fill primers, which you might use, can be tinted with normal fiberglass tints for polyester resin or gel coat.

I use it like a guide coat, but you could easily tint it to near your final color so scratches wouldn't show so bad, which is what I'm guessing you would be doing it for.

Another thought. If you spray it with epoxy and let it sit for more than a day or two, you must sand it before the next coat. If you cover it the same day, maybe up to 24 hours later, no sanding is necessary. A chemical bond is made instead of mechanical into the sanding roughness, which is going to be better anyway. If you put a sanding primer, like the high build polyester stuff, over the epoxy, it is much easier to sand, and you're going to sand that anyway.

[chopt50wgn]

As far as respirators go you want to use a good 3 inch filter respirator. There are many on the market and you may find one at your local paint supply place or you can look at Eastwood.

As far as a gun goes you will need a gun with no less then a a 2.0 nozzle to shoot filler primer. That should dry for at least a day before wet sanding. You should also wet sand with no less then 400 before applying a topcoat of epoxy primer to seal everything.

[Fernando Mendes]

Now I use this ruler to a good mixture.

[Plymouthy Adams]

Now I use this ruler to a good mixture.

I admit while that will give you proper fluid ratio mix in reducing..it does not in any manner substitute for a viscosity cup...not all paints are created equal in the base forumla as per thick/thin..and the most recent paint I bought for some work it's recommend thinning would work well for brush/roll application, would not spray if your life depended on it...

I usually mix my paint by first pouring the color into the mixing container.., then in a small pryex graduated clyinder add the hardener and then add about 1/2 the recommended reducer reducer to that..then mix to the base paint..then adjust the viscosity by adding the reducer to get a smooth shooting mix..

when shooting small items I have a chart on the wall for my paint/hardener ratio by 20z paint increments for fast accureate measurements..

I found the larger mixing less than handy for get an accurate ratio..

[48Dodger]

Current Poly-Primers can be wet sanded.

Two examples:

G2 Featherfill: http://www.evercoat.com/imgs/pis/FFG2%20pis%20sheet.pdf

PCL 901: http://www.pclautomotive.com/Product_Profile/polyprimer013007.pdf

These are maybe the most used poly primers (at least in my area).

Poly Primers have high build filler qualities, Epoxy doesn't.

Epoxy is expensive compared to Polys and in a lot of cases isn't needed.

The debate often continues between Epoxy and Poly without the advancements of new Polys in the argument, which include better filling, wet sanding, no shrinkage, and better final sanding. And when I say "better", I mean old Poly vs new Poly.

Not all Polys can go over Etching primers. PCL 901 doesnt do well, but G2 does. I prefer G2 FF, though the mixing has to more closely watched and the clean up almost imediate.

Quick shop story about my very first experience with the G2.

Mixing PCL is easy and forgiving.....this is what I was use to. So when I tried the G2, I mixed it with the same disreguard for exact measurements. No biggy, this stuff must be like the PCL. Well I put to much catalyst in, went to pick up the paint gun and the pot was HOT. I looked inside, and the primer was curning, making a ball...lol. Needless to say, instead of cleaning it up right then, I called the paint store and wanted to get their take on what was happening. Plus the counter guy is a friend and like talking shop with him. He pointed out that the G2 likes the mixing almost on the money etc....I went back to my gun....and crap. Took me a long time to clean that gun! Once I behaved and mixed it with the care its deserves.....works awesome everytime.

48D

[pflaming]

What is a sound way of painting an alloy wheel. I have this wheel and looking now for three more. I primer this and painted. How long will this last?

[Scruffy49]

If the clear anodizing or powder coat was left on it prior to painting, not very. Stuff doesn't give the primer a rough enough surface to get a good bite. The brush painted switch boxes on my motorcycle were peeling within a couple months... Sanded off the paint and the clear coating (factory mystery clear) and repainted. Paint has adhered well since 2003. Alkyd enamel.

[pflaming]

Do allow rims, such as these, have a factory clear on them which rejects paint? Whatever, if they are nicely wet sanded with a very fine grit, then primered and painted would the paint grip?

[Plymouthy Adams]

Paul, the wheel on the right in the above thread are the very tasteful Jeep Canyon wheels. These do have a clear coat from the factory..they can be dressed and recoated for great look. Also keep in mind that Chrylser aluminum wheels also come in argent tinted paint themes also. You can paint these wheels if you so diesire for good results..I have done clears in the past and I have painted with enamals all with excellent results and long lasting appearance.

I have a set of the canyons now that have had the centers opend up on the face without altering the concentric mounting, so to allow use on the front hubs of the older Mopars..these have also been milled flat in the center, drilled and tapped for Torq-thrust style spinner adapters. These will be recoated in clear once I get close to mounting them on the car.

[Scruffy49]

Anodized alloys I usually etch before painting. Oven cleaner. And yes it can destroy a wheel pretty easily. Powder coated I'll rough up with 150 grit and then start the priming process if I don't feel like stripping the powder off first. And I use rattle can wheel paint if I don't feel like breaking out all the gear to spray Deltron, Delthane, etc. I like those 2 because you can bury 320 grit sanding scratches... I hate sanding.

[Dave72dt]

Do allow rims, such as these, have a factory clear on them which rejects paint? Whatever, if they are nicely wet sanded with a very fine grit, then primered and painted would the paint grip?

The facrtory clear will take paint as does any clear coat but does need to be prepped for good adhesion. Sanding the clearcoat is a must and the use of an adhesion promoter in the tough spots will help along with light coats of paint. Most, if not all, of the newer factory alloy wheels will have the clear coat. Aftermarket wheels may not, especially older polished wheels. Thise will need to be prepped the same as any other bare metal surface.