Paint Prep Question for Trunks Options

[aggiezig]

Hello 914World!

I'm getting ready to spray the trunks and cabin of my 914 with color. They have so far been coated with two coats of epoxy primer and then seam sealed. My question is, do I need to spray some other sort of primer first before applying color, or can I apply a couple of coats of single stage color straight on top of the epoxy primer?

I'd love to get everyone's thoughts, especially from those more experienced with paint than myself.

[mgphoto]

Interior and trunks do not need sealer which is the next step before top coat.
Epoxy, body filler, sealer (not seam sealer) than top coat and clear.

[jmitro]

agree; only thing I would add is if the epoxy primer and sealer are vastly different shades, you may end up with a slightly different shade of topcoat on the trunk than the exterior. also, be sure to scuff the epoxy well before the topcoat

[aggiezig]

agree; only thing I would add is if the epoxy primer and sealer are vastly different shades, you may end up with a slightly different shade of topcoat on the trunk than the exterior. also, be sure to scuff the epoxy well before the topcoat

Good call. I will have to find an epoxy sealer that is similar in color. I used white epoxy primer for everything and the top coat will be Mexico Blue. No paint expert here, but I would think a light epoxy sealer would be ok to use under that color.

[mgphoto]

I used Southern Polyurethane epoxy which when diluted with urathane reducer becomes a sealer, the hot rod crowd loves this stuff.

[MarkV]

I used rattle can SEM epoxy primer on the bare metal and sprayed it with single stage PPG with a catalyst. It's been like 10 years and it holds up fine.

[McMark]

agree; only thing I would add is if the epoxy primer and sealer are vastly different shades, you may end up with a slightly different shade of topcoat on the trunk than the exterior. also, be sure to scuff the epoxy well before the topcoat

Good call. I will have to find an epoxy sealer that is similar in color. I used white epoxy primer for everything and the top coat will be Mexico Blue. No paint expert here, but I would think a light epoxy sealer would be ok to use under that color.

Just use the same products in the same order for the trunks as you will/did on the exterior. Or if you're not painting the exterior, than just accept that the trunks won't match exactly.

Using a tinted sealer/primer is less necessary if you're using quality paint. Cheaper paints tend be semi-transparent, so it takes more coats to cover up any variances (and by variances I mean like the yellow trunk with gray stripes above). But if your trunks are all primered in one color and you don't have variances then you don't need to worry as much about that transparency issue. Or just use a good quality paint and use 3-4 good coats.

Primer color will affect the final color, but there are a bunch of other aspects that affect final color, such as: Paint brand, mixing ratios, number of coats, skill of the painter, even age (old PPG paint won't necessarily match new PPG paint, even with the same code). There are a VAST number of reasons why the only REAL way to make sure everything matches is to do the whole car at once. Or train a long time to be good at color matching (it's a skill far beyond paint color).

People pretty regularly get the impression that the 'paint code' is some sort of guarantee of color accuracy (I thought the same thing when I was starting out), but as your dig deeper into the process you realize what a sham the paint code is. It's only ever a ROUGH approximation of the right color.

[bbrock]

I used Southern Polyurethane epoxy which when diluted with urathane reducer becomes a sealer, the hot rod crowd loves this stuff.

I'm using PPG which is supposed to be the same - add reducer and it is a sealer - at least if I'm reading the tech sheet correctly.

[IronHillRestorations]

I'm approaching this as I get further along in a major restoration. What a paint rep told me is that with the epoxy primer there's a time frame you need to work within, 5 days IIRC.

If you wait too long to topcoat you have to sand the primer. So on what I call 'secondary surfaces"; trunks, engine bay, etc, where you won't be using a sanding primer/filler, you prime it and then finish coat it as soon as possible for best adhesion. Exterior, what I call "primary surfaces" it's epoxy paint followed with filler, and then sanding primer.

It's been over 10 years since I've been into paint and body work this deep, and much has changed in that time.

[mgphoto]

I used Southern Polyurethane epoxy which when diluted with urathane reducer becomes a sealer, the hot rod crowd loves this stuff.

I'm using PPG which is supposed to be the same - add reducer and it is a sealer - at least if I'm reading the tech sheet correctly.

I started using the Deltron, but found the SPI stuff is less than half the price.

[aggiezig]

I used PPG Shopline to tint my bedliner as that was the only paint available locally. I'm going to call around and see if I can find a better PPG for shooting everything else.

As far as color-matching goes... I plan to shoot the trunks / insides all at once, so at least they will match. Because most of these areas are covered with carpets or other stuff, I'm not too worried about it anyways. The nice thing is that all of the trunks have a seal to separate them from the body, so I don't think any slight color mismatch will be noticeable.

[jmitro]

I'm approaching this as I get further along in a major restoration. What a paint rep told me is that with the epoxy primer there's a time frame you need to work within, 5 days IIRC.

If you wait too long to topcoat you have to sand the primer.

that's my understanding as well, although I thought the cure time was much faster (1-2 hrs). probably best to consult your technical data sheet and/or your local paint professional on the flash/cure time

[mgphoto]

I'm approaching this as I get further along in a major restoration. What a paint rep told me is that with the epoxy primer there's a time frame you need to work within, 5 days IIRC.

If you wait too long to topcoat you have to sand the primer.

that's my understanding as well, although I thought the cure time was much faster (1-2 hrs). probably best to consult your technical data sheet and/or your local paint professional on the flash/cure time

3 day window for the SPI epoxy, if you go longer, sand and respray the epoxy, dry time is a few hours to top coat.

[Rob-O]

I used Southern Polyurethane epoxy which when diluted with urathane reducer becomes a sealer, the hot rod crowd loves this stuff.

I'm using PPG which is supposed to be the same - add reducer and it is a sealer - at least if I'm reading the tech sheet correctly.

If you’re using PPG’s DP series epoxy primer than that is correct. Difference between prime and seal comes down to how much reducer is in the mix ratio.

[Rob-O]

I'm approaching this as I get further along in a major restoration. What a paint rep told me is that with the epoxy primer there's a time frame you need to work within, 5 days IIRC.

If you wait too long to topcoat you have to sand the primer. So on what I call 'secondary surfaces"; trunks, engine bay, etc, where you won't be using a sanding primer/filler, you prime it and then finish coat it as soon as possible for best adhesion. Exterior, what I call "primary surfaces" it's epoxy paint followed with filler, and then sanding primer.

It's been over 10 years since I've been into paint and body work this deep, and much has changed in that time.

All that is still true. Guys thinking they can prime it and come back to it two months later and shoot a color on it typically would cause adhesion issues down the road. How far down the road is arguable of course.

[worn]

ROUGH[/i] approximation of the right color.

My paint guy got a formula for Bahia red and made it up for me. Later I had lost the formula and had him get it again from PPG headquarters. You guessed it. Close but not a match. I later found the first formula and it was different than the second. Same paint product too. DBC.

[Rob-O]

ROUGH[/i] approximation of the right color.

My paint guy got a formula for Bahia red and made it up for me. Later I had lost the formula and had him get it again from PPG headquarters. You guessed it. Close but not a match. I later found the first formula and it was different than the second. Same paint product too. DBC.

That happens frequently. Certain raw materials or pigments become obsolete. Or more frequently a pigment manufacturer produces a different raw and promises it can take the place of ‘x’ for less cost. So the paint manufacturer takes the deal on the new pigment and then has to remaster all colors that use that pigment. As mentioned in a post above, they guys in the tint lab are just trying to get the new formula ‘close’ using a color analyzer (see ‘Datacolor’ if you’re interested in finding out more about the machines and what they do). That ‘close’ is supposed to be within what the human eye can perceive. But there are all kinds of different aspects to that. Most effort is put forth on colors that are current. You can imagine that they’re not putting Bahia Red in the folder of colors that needs to get done ASAP. Usually what happens is that at some point you come up with a rough formula of how much of the new pigment you need compared to the old pigment. For example for each pound of old pigment we need 1.32 pounds of the new pigment in the batch.

The other reason for changing out materials is their effect on our ecosystem. The government phases out or bans certain materials all the time (think lead in house paints and heavy metals in automotive paints and other coating like chrome).