Primer paint

[Russell Reay]

My cowl is seriously pitted. I have applied layers of filler and sanded them down trying to eyeball and feel when things are smooth enough to paint. Unfortunately, after priming it is not uncommon to note a divot which needs filing or an edge that wasn't adequately smoothed. Is it possible to use rattle can primer (Krylon, Dupli-color, etc) as a guide coat to reveal these flaws, and after correction, shoot with air-powered expensive primer with hardener. My greatest concern is that I don't want to be required to remove ALL the cheap primer in order to assure adherence of the good stuff (Acme Finish 1 DTM high build primer). Recommendations please

[bobbader]

My personal suggestion ............ the cheap primer is THE CHEAP PRIMER! You’re using it to save time & money ......... right? Don’t get me wrong, in their own way, Krylon and Rustoleum are respected brand names in spray can products. And, since they’re sold in places like Home Depot & Loews, they can really be had for cheap. That said, if you use them for guide coats, you would be doing yourself a favor to remove even the slightest amount of them from your job before proceeding. Why? Because they are, at best a simple enamel based product that may not be compatible with the more expensive lacquer or urethane product you’ll follow up with. Time and money saved just went out the window. SEM is a well regarded name in the body shop industry for aerosol and non aerosol products. Pricey at anywhere from $15-20+ per 15oz can. But, a much better guide coat choice, and probably available as “guide coat”, as opposed to store bought Krylon primer. Sources like Eastwood & TP TOOLS carry it or other reasonable like quality alternatives. Do yourself a favor............ don’t skimp on a $5 alternative to save $10 over the cost of the whole job. Cutting corners is not the way to go with paintwork. The end result still relies on everything under the topcoat to make that topcoat perform at it’s best.

Good luck with your project. Bob Bader

[Terry, NJ]

What Bob said! Don't mix primers! They may show in the final coat. It's too much work to have that happen. Good luck with the job! I remember when I was where you are. Hey! I almost forgot, Happy New Year!
Terry

[Kevin in NJ]

You are doing it wrong.

Your error is trying to level on the metal. You need to have the filler coat the whole surface. You cant have metal through and have a level surface. The metal is too hard and you will always have a dip at that edge.

There are various ways to tackle the problem. The optimal way is an epoxy primer per instuctions. Then in the recoat window put down filling primer and level. Trying to not get through to metal. You goal is to have a level coat of primer with no metal showing. then you are ready to for the surfacer and paint.

For quality paints at reasonable prices https://www.southernpolyurethanes.com/

[chrs1961815]

As Kevin says, you should not be sanding it down that far. Best bet now is to spray some epoxy over it. SPI's products are great, I would use some of their epoxy over it. DP90 is about the worst epoxy you can buy. And omni mp282 is thin and takes a lot of coats to make progress.

[Russell Reay]

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Originally Posted by Kevin in NJ

You are doing it wrong.

Your error is trying to level on the metal. You need to have the filler coat the whole surface. You cant have metal through and have a level surface. The metal is too hard and you will always have a dip at that edge.

There are various ways to tackle the problem. The optimal way is an epoxy primer per instructions. Then in the recoat window put down filling primer and level. Trying to not get through to metal. You goal is to have a level coat of primer with no metal showing. then you are ready to for the surfacer and paint.

For quality paints at reasonable prices https://www.southernpolyurethanes.com/

This is all news to me, but very much appreciate the info. I have been warned that epoxy is very resistant to sanding, suggesting to me that I need to guard against sags and runs. What are 'recoat window' and surfacer? I have heard others praise SPI, also.

[Kevin in NJ]

I called up SPI many years ago and talked to the owner.

So first you have to understand how coatings adhere to a surface. This is generic from glues to paints. There needs to be a proper roughness to the surface for the molecules to grab on and hold to a surface. This varies depending on the type of molecules formed as a coating does its chemical reaction. Being generic here you have to take time to learn about each process.

The epoxy does a great job of filling in all the light scratch. Like that of sandblasting or the grit paper as required according to the manufacturers datasheet. While epoxy is going through its curing process the surface has microscopic holes. At the end of the recoat window these holes close off leaving a very smooth surface. A very molecularly smooth surface that will not allow much to attach very well. The epoxy cure rate is affected by tempurature.

If you go past the recoat window you are likely setting up for the next layer to peal off in a nice sheet later. Epoxy past the recoat window must be sanded and you should put another coating of epoxy then the next coat on top.

The next coat can be polyesther filler for a filling primer. The filler will gets its molecules into the holes and then heat up at the surface and cause the epoxy to close in on the filler molecule.

Most modern primers, both filling and non filling, are isocyanate based urethane paints. These technically chemically bond into one large molecule.

You have options on how you level a panel. What is considered the best practice is to start with epoxy then some type of leveling. If the metal is close to correct level then you can get away with a few coats of a filling primer. Depending on how much you need to lay in you have options from manually laying out fillers from a can. These can be thicker for deeper filling or thinner for lite coats like filling pitting on otherwise level metal. There are also sprayable polyesther fillers. Then you have various thickness filling primer paints.

The skill is figuring out which products to use when. That is experience and pocket book. Buying lots of product gets pricey. I started with the thicker Evercoat fillers, a filling primer and a thin primer. When my metal work improved substantially I only use a thin polyesther filler for things like pit leveling. I had a filling primer that I could thin out and use as a surfacer too. I got to the point where I did not need much leveling. I did most of the leveling in metal. That did not happen overnight.

As you send you will end up with different color layers as you move along with the sanding. The goal is to never get to bare metal. So you will likely have a level surface but different shades. If you paint over this you will see the shading differences in the final paint (yes I did this and learned the hard way). So the last thing you do is a surfacer. That is a light coat of primer to make the level surface one color. You would use a light color surfacer for light color top coats and dark for dark colors.

Finally I will say you MUST be careful. The modern paints are dangerous!!!!! Keep your skin covered. The isocyanates cause and alergic reaction in some people that starts as a minor chest pressure hours later. Not being fully covered while mixing is one area where people have the most exposure. This gets worse with each further exposure. Once it starts you are done, no more painting ever. You need to be careful about exposing your familiy or neighbors when painting. You also have issues with breathing solvents that kill your brain, liver, and kidneys. A properly fitting charcoal mask will filter them out, but the issue is knowing that it is properly fitting.

If you call SPI they will help you understand the paints.

Hope this all helps.

[Russell Reay]

Thanks for the lesson. I spent some time on the SPI forums, and found more details expanding on your guidelines. Per respiratory safety--the only ventilation in my shop is to open the doors. If we are lucky, there will not be any paint spraying weather until April or May here in VT. I would like to apply at least one coat of something on my cowl in order to test-fit it to the frame, align the hood, and start on my huckster body

[hazelhoff]

Beware of choosing the primer color too ! Andalusite Blue requires a dark colored primer !

[Russell Reay]

Originally Posted by hazelhoff

Beware of choosing the primer color too ! Andalusite Blue requires a dark colored primer !

Gonna do chicle drab.

[old ugly]

Originally Posted by Russell Reay

Per respiratory safety--the only ventilation in my shop is to open the doors.

here is a trick for the home shop guys, an old cheap Swiss shop owner showed me. for small repairs he didn't want to waste time moving cars into the booth, washing guns and wasting gunwash.

good epoxy high build primer is your friend, but is really bad for your health. don't breath it in.

you can cheat a bit on the application.
use small disposable 3" rollers to apply the first coats of primer to a repaired panel. a little 3" roller and a plastic tray,cheap. mix the product as per the directions and roll it on. the roller will not leave a nice smooth finish like spraying but for the first coats of build it works good. a good primer will sand easy. the only issue is the roller, it may leave little hairs in the primer but i have never had any issued with them affecting the final finish.
always guide coat sand.
once you have the area level and ready for its last coat of primer you will have to spray the final primer layer so it is smooth. ventilate your area well.

[Kevin in NJ]

There are an increasing number of roll on paints and primers. I know the boat world is using them. I an not aware, but probably it is a good idea to look.

[Russell Reay]

"good epoxy high build primer is your friend, but is really bad for your health. don't breath it in.

you can cheat a bit on the application."

Are you saying to apply epoxy with a roller, thereby avoiding the fumes associated with spraying, or avoid all epoxy fumes by using a non-epoxy primer ??

[chrs1961815]

Rolling is better than spraying when it comes to fumes but they are still there. Not using epoxy is a bad option considering you can just wear a respirator and all will be fine.

[Oldbluoval]

And rubber gloves…
Avoid skin contact as mentioned previously

[marc silva]

The way to avoid this is to spray on a sealer coat tinted close to the color you are spraying. Then you apply the color.

[BRENT in 10-uh-C]

Everyone has their own different method of 'cooking', ...so I am trying to stay out of the kitchen however I do think there are some comments that are maybe not be totally factual in today's technological world of paint.

Just remember, that products in the paint world are ever-evolving. Something that was the hot ticket a year or two ago is very possible to be outdated technology today. I have factory reps in here ever 90 days or less showing me stuff and telling me stuff that was new just a few years ago that is now obsolete. Let me offer my opinion by saying that if you find yourself needing a darker primer to achieve a uniform color coating, then that generally tells me the quality of the finish-coat needs to be changed as a paint that is that translucent generally does not have enough pigments -or a good quality pigments in them.

As far as roll-on primers, we have been monitoring this for several years however the issue right now is the lack of adhesion of heavy mil thickness applications. I think the technology is coming however right now there is an adhesion problem. Most applications where that product is used does not need to have a high-build filling characteristic, and is more about an adhesion promotor or what is called a surfacer.

Based on Russell's pictures, at this time of writing my choice of primer would be the Evercoat Optex SuperBuild 4:1 primer which is a hybrid epoxy primer with an extreme amount of filling qualities, -and it is DTM. Also, it sprays and dries in a few hours in an opaque pink color so you can tell when it has fully cured, ...then it sands to a light gray/whiteish color that makes it very easy to know what areas have been sanded and what has not. Even though it is an epoxy, it does sand and feathers out very nicely which is typically uncharacteristic for a regular epoxy. We block-sand this primer to 240 grit, and then follow up with a polyester hybrid surfacer called Finishsand. The benefit with this primer is it is also DTM and easily block-sands to 400 grit. Therefore if you have sanded thru the SuperBuild, you can use the Finishsand directly onto the bare metal. You can also use Evergold Putty over the top of either primer if you have a pinhole or an imperfection show up.

Both of these primer products have taken away the need for a sealer to be applied before spraying the finish-coat, ...and quite frankly since most companies have gone away from offering a sandable sealer, it doesn't make much sense to block-sand to 400 grit and then spray a sealer that just reintroduces a layer of orange peel for the finish-coat to be sprayed onto.

Again, everyone has their own preferred method of cooking materials they want to use so I am not saying my recommendations are the best, but you must also remember that most products are geared for the collision industry and not the restoration industry.

[Russell Reay]

I appreciate all the input. The last time I did any serious painting was 15 yrs ago.

[old ugly]

Originally Posted by Russell Reay

"good epoxy high build primer is your friend, but is really bad for your health. don't breath it in.

you can cheat a bit on the application."

Are you saying to apply epoxy with a roller, thereby avoiding the fumes associated with spraying, or avoid all epoxy fumes by using a non-epoxy primer ??

the roller will save your shop from overspray getting everywhere. the fumes are still bad, you need to wear all the ppe.

you will find that overspray from the epoxy primer will glue itself to everything in your shop and any of the other cars it comes in contact with.

with the roller you can do small areas without having to mask up the rest of the car your working on as well as having to cover everything in your shop.


yes you want to use a good epoxy primer

[nkaminar]

Regarding painting boats: After a while the gel coat becomes dull and needs painting. The boat shops will spray but a boat owner can do a decent job with a roller. The reducer used is for brushing so it does not evaporate immediately. The amount of reducer is critical to produce a smooth finish. After the paint is rolled on it is dry brushed. As the name implies, the paint is brushed with a soft dry brush in horizontal and vertical directions. If done right it can be almost as good as spray job.