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Topic Review (Newest First)
05-07-2005 08:35 PM
Ratchet I should have read this post before I shot the base coat on my project today. Check out the attached picture the bumper cover has black primer on it and the rest of the car has grey primer. The main body of the car has two coats of paint on it and the bumper cover has 4.

http://www.hotrodders.com/attachment...achmentid=4903
05-07-2005 05:36 PM
cboy
Quote:
Originally Posted by BarryK
Now that he's got his story right, he is exactly right!
Actually it's...now that I'VE got HIS story right. He was right all the time, I just got the issue confused because I wasn't listening to him well enough.

And he did emphasize the Dupont research (which you mentioned). I think he said they now have 7 shades of gray for various color coats.
05-07-2005 06:32 AM
BarryK Now that he's got his story right, he is exactly right!

Dupont first figured this out a few years back and came out with their Value shades.

A lot of people laughed at the idea at the time because you would assume a bad hiding red would hide better over a red sealer. Wrong, it turns out it will hide better over the proper darkness of gray better. This has since been proven true with all colors.

No ones laughing now!
05-06-2005 06:03 PM
cboy Finally got a chance to talk with the Car Quest paint guy about his "gray is best" claim. Appears that baddbob and AC/DC had the right idea. He WAS talking about coverage of the color coat over the primer, not the primer itself.
03-03-2005 08:20 PM
AC/DC Could it be that he has a gray primer that is more expensive than his black primer? Just guessing, cause I can't figure out why he would tell you such things. I would now be careful in receiving advice from him. None of us a perfect and we all have opinions but what he said was strange.
03-02-2005 09:50 PM
MARTINSR "Solids", "Filling", not only does color have nothing to do with it, a 2.1 urethane clear has more solids than your average urethane primer by FAR.

S-W has a tintable urethane primer. It is a milky color as Barry discribed. You add toners off the mixing bank to make one of 28 colors. After mixing, when you spray it, it STILL is quite transparent. But until some super high solid low VOC primers came out it had the most solids of any primer they sold. It is one of my favorite primers and fills like mad.
03-02-2005 09:36 PM
sevt_chevelle Well PPG's NCP type primers come in three different colors a med green, gray and purple. If you look on the tech sheets for both products they have the same solids content and coverage per sq ft.

Color makes no difference on film build...Eric
03-02-2005 09:15 PM
AC/DC OK then. Refer back to BarryK's first post, he's got it right. Color makes 0 difference on fill.

Baddbob has a good post too.
03-02-2005 09:05 PM
cboy
Quote:
Originally Posted by AC/DC
When he said "best covering" did he maybe mean that when you shoot color over it that you could acheive coverage faster/easier? Grey does seem to be the best color to paint over. Just a guess on my part.
His argument was more about coverage and "fill for sanding" of the primer itself, not its effect on the top coat. I know this because we were discussing what I wanted for a top coat, which is a flat black which will appear to be black primer but, in fact, will be a finish coat to seal out moisture (like John Deere Blitz Black - although I'm going to use the Car Quest brand of flat black to achieve the goal). My assumption was that I would naturally use black primer to provide the best base for the flat black finish coat. And that's where he sprung the concept that there is a difference in the coverage and fill characteristics of the different color primers - regardless of the color of the top coat. And that gray was the best.

I really can't provide any of the specifics supporting his argument until I talk with him again. I was just interested to see if any of the experienced painters on the forum had ever heard of such a thing. And it doesn't appear they have.
03-02-2005 08:33 PM
AC/DC When he said "best covering" did he maybe mean that when you shoot color over it that you could acheive coverage faster/easier? Grey does seem to be the best color to paint over. Just a guess on my part.
03-02-2005 08:08 PM
baddbob Just my opinions-no scientific data but for me primer color offers only two functions. Primer color can help or hurt paint color coverage- some colors of paint cover some primer colors or shades better than others and can make a big difference on how much paint you will use. Also related to color coverage would be rock chip damage- major differences in color from paint to primer will show rockchips much more than if the primer was similar. Example-If I do underbody work all of my primers used will be black so future rock chips don't stand out.

Second function if you can call it that, contrast with guidecoat, when working on highend jobs where the primer is blocked and blocked and blocked to perfection I just plain prefer light colored primers. Dark color guidecoats contrast well with light colored primers making imperfections stand out really well IMO. When I use dark colored primers I spray a light coat of light colored primer on for use as a guidecoat but it just doesn't stand out as well and I find myself looking very hard to see any imperfections. Sometimes I do my heavy blocking with light colored primer and do my final sanding on dark colored primer just for better coverage, etc.

I haven't seen any differences in fill or sandability related to color, they all seem to work the same.

Dupont's valueshade system is a fine example of what primer color can do for you in reguards to paint coverage. Bob
03-02-2005 06:30 PM
cboy
Quote:
Originally Posted by BarryK
A further note, in the other two primers we make in buff and gray only and 90 percent of the sales is gray in those primers, so he probably knows this and is assuming why.
Actually he referenced some Dupont research that had been done regarding gray vs. other colors. Next time I'm in there I'll have to press him for some specific documentation. I've delt with this guy on other car related issues and he's always seemed to know his stuff. This is my first paint purchase from him however.
03-02-2005 02:26 PM
BarryK
Quote:
Originally Posted by Beenaway2long
I'd ask for a tech data sheet.

MY BET is that he has TONS of old gray that he wants to peddle.
************************************************** **
A further note, in the other two primers we make in buff and gray only and 90 percent of the sales is gray in those primers, so he probably knows this and is assuming why.
03-02-2005 02:02 PM
Beenaway2long I'd ask for a tech data sheet.

MY BET is that he has TONS of old gray that he wants to peddle.
03-02-2005 01:19 PM
BarryK That just kills me!
I hear from some shops that they won't use red because it will crack and some shops grey will crack.
Fill difference on colors?
Here is how we do it so you can figure out yourself if there is any difference at all in fill rate.
2500 gallon vat is the primer, its all made and in the color of the core resins, kinda a milky color. Now we add white tint to the whole batch because the first 500 gallons pour out will be white.
When that is done we will add x-amount of black to make our grey and we will pour out 1000 gallons. Next we will add black to the remaining so we have 1000 gallons of black primer. (tint is powder)

Fill rate difference 0.

Is there any difference? fill rate no, but the more black you add the
the slower dry because black is the slowest drying paint.
An example with the above primer at 30 minutes the white is ready to sand
the gray at 32.75 minutes and the black is ready at 35.25 minutes.
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