Gray Primer VS White Primer

All my life I have used white primers on just about anything. I do this having the knowledge that it's easier to cover light colors with darker colors. So...I guess the big question is, Why do some people swear by the use of gray primer over white? Seems to me that one would have to use more color coats to cover up the gray primer. Especially if your finish coat is white. What gives?

Not sure? Maybe they might like the sanding characteristics of the gray primer?

It depends if the final top color can cover the gray primer without bleed through.

Some colors such as yellow or bright red seem to do better for me when they are sprayed over a white base coat.

The auto-body tech's use alternating, contrasting color primer coats to see the high and low spots when wet sanding and prepping the surface. You could do the same when filling spirals, etc. but a rockets surface area is pretty forgiving for little details, so probably not real necessary unless your looking for that level of detail.....

Everybody seems to recommend "automotive" primer over regular primer, and my local hardware store only carries the automotive type in gray, so that's what I use. I haven't had any trouble painting gloss white or gloss yellow over it, so I have no reason to try anything else.

I've done my share of sanding primer over the years but nothing works like really fine steel wool IMO. The finer the better. It covers a lot of area fast and leaves a very slick surface.

SCP said:

The auto-body tech's use alternating, contrasting color primer coats to see the high and low spots when wet sanding and prepping the surface. You could do the same when filling spirals, etc. but a rockets surface area is pretty forgiving for little details, so probably not real necessary unless your looking for that level of detail.....

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I use the alternating method, but aside from detetcting low spots, which isn't real critical I use mainly to warn me how far I have sanded through the primer. It works well in the way.

For me there's nothing special about grey... but the filler primer I use (Rustoleum automotive sandable filler primer) only seems to come in grey. I wish it came in white, as I often prime with white (to give a good uniform easily color-coated surface) after sanding down the gray.

Getting back to the original question of white vs gray primer - For me it depends on the situation. I've used both and either one will give a good base to do your final coat over. When I use gray primer, I usually use a light gray that even white will cover. The difference is what I'm shooting the primer coat on. White primer doesn't always give a good base coat over dark plastics such as black (some Estes nose cones) or red (Maxi Alpha III fin can). Gray primer will usually cover the dark colors better with fewer and thinner coats. If you are worried about the gray showing through, use gray for the first coat or two, then switch to white. This is just my technique, brought over to rocketry from both my days painting wargaming miniatures and my days building plastic models in our local IPMS chapter. So YMMV.

I found some white primers did not seem as sandable as the grey.
Another thought if you don't have or like the white primer is to give a light coat of silver over the grey primer before the top coat of white.

Dupli-Color makes a white sandable primer. I have used it and it covers well and sands easily.

The high build automotive primers seem to come mostly in gray. The big box stores carry white primers but they seem to be less bulky than is desired.

This will be like a fingernail on a blackboard to some but I've found the Kilz and Bullseye 1-2-3 spray primers in white work exceptionally well for my mailing tubes and LOC tubes. Goes on heavy, takes about a week to cure, and smooths out quite nicely using a 3M or Norton sanding sponge. Then I overcoat the initial layer with a Rustoleum white primer if I'm shooting my usual fluorescent pink. If I'm doing a darker color, the gray Rusto primer works just fine.

Lest anyone get the wrong idea, I use Rusto Plastic Primer for LOC nose cones and let it cure for the recommended 7 days before doing anything else. Of course, I prep the surface before hand with washing, 60 grit to raise some "hair", etc. Yes, it still chips but only if I manage to hit the lone rock on the field.

Dupli-Color also makes black sandable primer. It produces a nice matte coat. My Astron Cobra clone looks so good in it that I am just leaving it in primer for now.

Gary Byrum said:

All my life I have used white primers on just about anything. I do this having the knowledge that it's easier to cover light colors with darker colors. So...I guess the big question is, Why do some people swear by the use of gray primer over white? Seems to me that one would have to use more color coats to cover up the gray primer. Especially if your finish coat is white. What gives?

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Actually Gary:
The soilds in various color primers are there for differing purposes. Some of the darker color primers Black, & Browns have the largest and heaviest particles along with some of the "HIGH Build" primers these base primers are used to cover serious surface scratches, minor dents and dings
Then there are the general purpose Auto Grey primers: these have medium solids used for priming over orbital sander wheel scratches, minor surface scratches and tiny surface irregularities. Multi coats with these primers can cover even deep dents and seams.
White Primers traditionally have super fine soilds: they are intended as spot & finishing primers over grey & other color prmers to check for minor surface blemishest before first color coats. White primers are always the last primer used as the very last feather coat after all the other surface prep and repairs are done.

While it is quite true it is easier to apply lighter colors over white base. Most experienced modelers use flat white Paint as the base coat over grey prmer to check for imperfections rather then the much more expensive white finishing primers on the market.

As I've mentioned many, many times: most Prrmers are MENT to be almost completely sanded off between coats. Because Primers are a sacrificial coating I always look for and use the cheapest grey automotive primer I can get my hands on. When working on Showpiece or Museum models I'll use a cheap matt or semi-gloss white to look for surface blemishes, but to be honest over the last 5 or 6 years I doubt i've needed the matte white under anything including Yellows which are by far hardest color coating to get to look good aside from mirror metal finishes.

Just a note about all matallic colors: If your really want them to "PoP" they should be applied over Matte or Gloss black base coats, which work best over dark or black primers

It all comes down to experience and of coarse personal preference. It is However nice to know what the different primers colors are ment to be used for.

Micromeister said:

Actually Gary:
The soilds in various color primers are there for differing purposes. Some of the darker color primers Black, & Browns have the largest and heaviest particles along with some of the "HIGH Build" primers these base primers are used to cover serious surface scratches, minor dents and dings
Then there are the general purpose Auto Grey primers: these have medium solids used for priming over orbital sander wheel scratches, minor surface scratches and tiny surface irregularities. Multi coats with these primers can cover even deep dents and seams.
White Primers traditionally have super fine soilds: they are intended as spot & finishing primers over grey & other color prmers to check for minor surface blemishest before first color coats. White primers are always the last primer used as the very last feather coat after all the other surface prep and repairs are done.

While it is quite true it is easier to apply lighter colors over white base. Most experienced modelers use flat white Paint as the base coat over grey prmer to check for imperfections rather then the much more expensive white finishing primers on the market.

As I've mentioned many, many times: most Prrmers are MENT to be almost completely sanded off between coats. Because Primers are a sacrificial coating I always look for and use the cheapest grey automotive primer I can get my hands on. When working on Showpiece or Museum models I'll use a cheap matt or semi-gloss white to look for surface blemishes, but to be honest over the last 5 or 6 years I doubt i've needed the matte white under anything including Yellows which are by far hardest color coating to get to look good aside from mirror metal finishes.

Just a note about all matallic colors: If your really want them to "PoP" they should be applied over Matte or Gloss black base coats.

It all comes down to experience and of coarse personal preference. It is However nice to know what the different primers colors are ment to be used for.

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+1 , filling with white is a PITA. I would spend 3 or 4 cans just to fill seams. (16.00)
i can go buy a quart of transtar high build for 13.00 thin with acetone or laquor thinner and fill seams or holes with 1/2 the ammount of primer.

(since your sanding it all off anyway!)

when i wrap phenolic tube with FG, i do 1 coat of filler/epoxy to fill the weave, then i use transtar 6004. Takes only 2 or 3 coats. you can also use more thinner, and get "basecoat" ready surface.

Also, on the side note, if your buying a "professional" grade paint. Color formulators can tell you what the base coat color should be. Some are white some are black and some other colors such as chromate green.

but, thats onlyl if you want to obtain a forensicly determined color as on the color chip. Most of us wouldnt even see several shades difference anyway.

I almost always base coat white.

I like gray primer because it's easier to see flaws compared to white.

If I'm painting the rocket a light color I'll spray a coat of white paint first.

simple,, and paint wet sands nicely as well, without absorbing moisture like primer does

Stymye said:

I like grey primer because it's easier to see flaws compared to white.

If I'm painting the rocket a light color I'll spray a coat of white paint first.

simple,, and paint wet sands nicely as well, without absorbing moisture like primer does

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Agreed that white paint can cause snow blindness.

Micromeister said:

Most experienced modelers use flat white Paint as the base coat over grey prmer to check for imperfections rather then the much more expensive white finishing primers on the market.

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Micro, I'm usually pretty good at reading between the lines and if I didn't know better, I'd say your interpretation of an "experienced modeler" requires the need to know how to put the big finishing job on your rocket. Are you saying that because my finishing techniques aren't top shelf or that I lack good finishing techniques that I am not an experienced modeler?

In the words of Vern Estes quote/unquote:
"I do not have the patience to do a good finish job. I just want to get something that works and “watch her go.” I admire those that have the patience to do beautiful modeling work. After spending hours and hours getting it just right I often wonder how they have the courage to press the button."

I would NEVER question that mans experience as you should never question some else regarding their finishing experience.

ps....grey (better understood as Grey....a biographical name) is not a color. GRAY is a color. Grey is a variant.

I've been using gray primer as the first coat (as Micro mentioned, it's a bit heavier/covers more imperfections), sand it to what I want and then hit it with white primer, sand that too—where and if I think it needs it. Then, whatever color paint I'll be using. White enamel primer is particularly nice for airbrushing acrylics. It gives a bit of a surface for the acrylic to adhere to.

Gary Byrum said:

ps....grey (better understood as Grey....a biographical name) is not a color. GRAY is a color. Grey is a variant.

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"Grey" is the British spelling, as in "grey colour." In the US, we would write it as "gray color."

https://en.wikipedia.org/wiki/Grey

I have always seen the main purpose of primer as promoting the adhesion of the paint coats. With the exception of special automotive high build primers, I have never used primer as a surface filler. During the finishing process, I fill and repair any surface defects (including tube spirals) and get the surface nice and smooth before I apply the primer coat. Then it's one primer coat, followed by the paint coats. The primer coat has to remain there, and not be sanded off, in order to do its job.

MarkII said:

I have always seen the main purpose of primer as promoting the adhesion of the paint coats. With the exception of special automotive high build primers, I have never used primer as a surface filler. During the finishing process, I fill and repair any surface defects (including tube spirals) and get the surface nice and smooth before I apply the primer coat. Then it's one primer coat, followed by the paint coats. The primer coat has to remain there, and not be sanded off, in order to do its job.

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You don't want to sand THROUGH the primer, but sanding the primer coat down is pretty much necessary IMHO...

I usually put 2-3 coats of primer on a rocket, sand most of it off to get a baby-butt smooth finish, then put the color coats on...

But, you're right-- you DO want a smooth even primer coat before you put the color coats on... If I sand through anywhere I put another light primer coat on in those spots and sand lightly to get a uniform primer surface before painting...

later! OL JR

MarkII said:

"Grey" is the British spelling, as in "grey colour." In the US, we would write it as "gray color."

https://en.wikipedia.org/wiki/Grey

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Please don't lay that "Sheldon Cooper" anal retentive crap on me. This is America. Not England.

luke strawwalker said:

You don't want to sand THROUGH the primer, but sanding the primer coat down is pretty much necessary IMHO...

I usually put 2-3 coats of primer on a rocket, sand most of it off to get a baby-butt smooth finish, then put the color coats on...

But, you're right-- you DO want a smooth even primer coat before you put the color coats on... If I sand through anywhere I put another light primer coat on in those spots and sand lightly to get a uniform primer surface before painting...

later! OL JR

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Yes, I often give the primer coat a very light sanding to remove any subtle differences in texture. It isn't always necessary, though. I do all of my fussing to make the surface smooth before I spray on the coat of primer. If primer is applied evenly on a smooth base, it doesn't need any sanding.

Using primer as a surface filler is a bit like putting on multiple pairs of underwear to hide a beer gut.

Gary Byrum said:

Please don't lay that "Sheldon Cooper" anal retentive crap on me. This is America. Not England.

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Yes, and that's why I spell it g-r-a-y.

Baaazingaaa!!!

I thought the "bazinga" was implied.

MarkII said:

Yes, I often give the primer coat a very light sanding to remove any subtle differences in texture. It isn't always necessary, though. I do all of my fussing to make the surface smooth before I spray on the coat of primer. If primer is applied evenly on a smooth base, it doesn't need any sanding.

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My primer often comes out a little "fuzzy", both looking and feeling, so I end up sanding it lightly. Any idea why that happens to me?

UrbanKnight said:

My primer often comes out a little "fuzzy", both looking and feeling, so I end up sanding it lightly. Any idea why that happens to me?

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that's common with sandable primer.
unless your spraying krylon primer ... it's more like a paint, not meant to be a "sandable to dust" thing... I hate it.

I'm using Rustoleum automotive primer. It seems that a few light passes with 400 grit sandpaper makes a smooth surface that the paint sticks well to.