Slick Sand or ???

[bill3337]

I'm redoing my '67 Camaro that I've had since new and am an amateur painter, having painted only my other two cars in the past. I've done a lot of metal work on the car, using NOS panels and had the entire body sandblasted inside and out with crushed glass. I've applied two coats of SPI epoxy primer over the bare metal and will now do some minor skim coat work with Evercoat Rage Ultra (unless there is another better version), followed by another coat (maybe two) of SPI epoxy, then would like to apply final coats of something (epoxy high build, Slick Sand or 2 part urethane high build) for final blocking. I've only recently heard of high build epoxy, but assume it might be tougher to block than Slick Sand? I assume Slick Sand or some other polyester primer is preferred over 2 part high build?

 

['68 Coronet R/T]

Generally, polyester primers (Slick Sand, Featherfill, etc) are only used when the car needs extensive skim work done on the panels. Think of them as spray on body filler.

I usually lightly block sand the epoxy primer to see what condition the car is in. If there are only a few low spots here and there, I use filler, extending it beyond the low spot and block sand feathering it into the epoxy, then shoot 3 coats of 2k build primer and begin the guide coat, block sanding process.

If, on the other hand, there are lots of little dents and areas that need filler, I shoot 2 coats of polyester primer, guide coat and begin the block sanding process. When it looks good, I shoot 2 coats of 2k build primer and move to my finish sanding process.

 

[shine]

I use slicksand or epoxy only . I would think the camaro would be fine with epoxy only . Let it set covered overnight give it more body to build .

 

[bill3337]

I use slicksand or epoxy only . I would think the camaro would be fine with epoxy only . Let it set covered overnight give it more body to build .

Thanks Shine, it will need some skimming over ground welds etc and will block the skimming before applying more epoxy over the skim coat. Once that epoxy has cured I'll see if blocking the epoxy will be enough on it's own. What's it like to block sand? Here's a couple pictures of it with it's initial epoxy.

 

[shine]

Sands great .Don't need a guide coat .

 

[theastronaut]

I like epoxy to seal the metal, a skim coat of filler over the whole panel to correct the overall shape and make it 100% straight, then 3-4 coats of poly. Poly builds over body lines and edges so they can be straightened/sharpened up while blocking- epoxy isn't thick enough for that. If you're going for factory correct body lines then poly isn't really needed. I have shot a few spot repairs with three coats of epoxy, then blocked with 180 and wetsanded with 220/400 to prep for paint- it builds enough to cover filler if the filler work is smooth, level, and sanded to at least 220. Epoxy shrinks, so let it cure for a few weeks before final blocking.

 

[shine]

i experienced no shrinkage with the epoxy . 6 total coats of epoxy .

 

[theastronaut]

I've left a few oz in a mixing cup and it shrinks up and pulls away from the sides of the cup much more than poly primer does, poly cures into a full size puck if left in a cup. That's not a realistic "on a panel" comparison but it's something to watch for if applied thicker as a build primer.

 

[Chris_Hamilton]

@theastronaut I asked you in another thread but you didn't reply, so I'll ask here.
How is chip resistance doing it this way? For stuff that doesn't get driven I would guess it's no problem, but how does poly hold up to something that gets driven? I know what my experience with it has been in the past which is why I'm leery of it. What has been your experience?

 

[Barry]

I've left a few oz in a mixing cup and it shrinks up and pulls away from the sides of the cup much more than poly primer does, poly cures into a full size puck if left in a cup. That's not a realistic "on a panel" comparison but it's something to watch for if applied thicker as a build primer.

??
Was it reduced?, I have never seen this and I've tested to 4 inches thick let set 9 months to fully cure and still flexible and not pulled from sides?
Then took a sledge hammer and it did not hurt the epoxy, bounced off the cement.

 

[Barry]

I've left a few oz in a mixing cup and it shrinks up and pulls away from the sides of the cup much more than poly primer does, poly cures into a full size puck if left in a cup. That's not a realistic "on a panel" comparison but it's something to watch for if applied thicker as a build primer.

Where do you get epoxy shrinks, as you say?
I have mixed epoxy left in quart painters pail weekly from inch to 3 inches thick and never seen it pull from the sides.
Shrinkage is way better than any polyprimer or 2k primer, so I would like to know how you come up with your facts?
Strength? Poly primer cant hold a candle to it in any way or form.
We have vette shops that use it all the way through because, at a car show, they would see soak up a year or two later with the poly.
The one shop won't touch your car if you dont have six figures.

Oh we havent touched on flexibilty yet, tell me how good the poly is!

 

[theastronaut]

@theastronaut I asked you in another thread but you didn't reply, so I'll ask here.
How is chip resistance doing it this way? For stuff that doesn't get driven I would guess it's no problem, but how does poly hold up to something that gets driven? I know what my experience with it has been in the past which is why I'm leery of it. What has been your experience?

The cars/trucks I've used poly on don't get driven much, so I don't have any real world results on chip resistance. I have heard of guys shooting layers of softer primers over the nose of a car that they know is going to be driven to create a "cushion" effect to help absorb impacts and reduce chipping.

??
Was it reduced?, I have never seen this and I've tested to 4 inches thick let set 9 months to fully cure and still flexible and not pulled from sides?
Then took a sledge hammer and it did not hurt the epoxy, bounced off the cement.

Wasn't reduced, mixed 1:1. The pucks are around .40 - .50" thick and have shrunk down to around 3" diameter. I grabbed a couple different brand mixing cups and they measure roughly 3.6" inside at the bottom mold line. Both pucks are about 3". The undated one is roughly a year old, both are still flexible. After they dried a few weeks in the shop (already shrunk enough to be loose in the cup) I moved them outside to see how well the held up when exposed to weather. Maybe it was just this batch? I'll try again with a different batch, I'll be spraying black epoxy later this week and can test again. I'll leave it mixed in a couple of cups and test the pucks indoors and outside and see how it goes. I'll test poly primer again as well, last time I left mixed poly in a cup it didn't shrink this much.

 

[Barry]

Wow!
I have no answer, and hopefully, this is a fluke, but I take the blame.
Red is a small seller, and I would never grab a quart from inventory because we make the smallest batch we can where white, black, and gray im constantly stealing a quart of stock.
Now what I did do is the last batch of red I did adjust the formula and slight change on tint
To reduce the number of people that add a little black.

Also made enough to last a year.
I had a few painter pails of activated red from testing that sat on the bench for 2 to 3 weeks.

Text me if you want, and I will send you a quart to try.

Either way, whatever happened
Do not rate epoxy by your results
of that one batch or whatever
the problem was.

My test 4 wet coats with no flash time (abuse) all shrinkage you can see with the naked eye is gone in 4 hours at 75 degrees.

 

[Barry]

Another note on making pucks be it clear or epoxy set the painter's pail aside and do not touch for a few weeks because of thickness; there will be a lot of solvents trapped underneath in the painter's pail, and any movement in the painter's pail can cause the puck to come apart.
In a few weeks, carefully move the puck from the painter's pail, and you will see solvents that have been collected.
Set on the bench and let it finish curing; depending on thickness will decide the time.

 

['68 Coronet R/T]

I was wondering if it was unique to the Red epoxy, since I have never used it and also never had any shrinkage.

 

[shine]

hockey pucks are a piss poor way to gauge anything . the amount of solvent in an inch of epoxy in a cup is no comparison to a sprayed coat of epoxy . i have 10+ year old epoxy only jobs that have 0 shrinkage and no die back .

 

[theastronaut]

If the other colors don't shrink then I'll start using those. I usually use grey or black but had switched to red since this project will be painted red and that's what I wanted the final coats to be for better coverage.

 

[Chris_Hamilton]

Shrinkage in the cup in no way equates to shrinkage on a panel. I've never seen any noticeable shrinkage on the panel ever when using SPI epoxy. Finished a year long restoration of a black 72 C10 a year ago, which I used gallons of black epoxy. Saw it last weekend, no shrinkage, no dieback. I think you are making an assumption based on an apples to oranges observation.
Been my experience body filler shrinks more than SPI.

 

[ksungela]

The shrinkage you are seeing is normal in a cup and independent of epoxy color. Here is black epoxy compared to slick sand, both from the same size 3M pps cup. Although it may be alarming in this condition, we are not in the business of making paint pucks but painting objects with relatively thin layers of paint. The results from thin layers is different. I just completed a 63 SWC using black epoxy, SPI black base, and Euro 2020 and the results are stunning.
Slicksand, on average, builds 2-3 times more per coat than epoxy. This can change depending on how heavy you spray. I would estimate epoxy is twice as easy to sand compared to slicksand using the same grit paper.

 

[Chris_Hamilton]

Looks awesome! Incredible how you can find all those Vettes to restore and sell.