Why primer?

This is the place to get answers about painting, weathering and other aspects of finishing a model.

Moderators: DasPhule, Moderators

Post Reply
TheIrishAvenger
Posts: 341
Joined: Sun Oct 10, 2004 2:04 pm
Location: Evans, CO-just south of the festering Greeley Mall gang-wars

Why primer?

Post by TheIrishAvenger »

Hi guys,

A couple questions. What does primer DO, exactly? What makes it different from regular paint? Can I use another flat paint in substitute for primer-just any old color?
I'm working on a PL TOS Enterprise and sanding down all the seams and filling them. I'm too broke to be able to go buy primer right now, so I was wondering if hitting it with some regular flat spray paint (Model Master SAC Bomber Tan) would hurt it any just to show up irregularities in the surface. Anybody got thoughts?

Thanks,

Chris
"Some say the alien didn't die in the crash. It survived and played poker and drank whiskey with the locals, until the Texas Rangers got wind of it and shot it dead."
Digger1

Post by Digger1 »

Primer gives paint something to cling to while it dries. Flat paint can generally work, yes but I think there are special properties that primer has that flat paint doesn't.

Primer also lets you see imperfections in the model surface (seam lines, pits, holes, accidential knife scribes etc.)
User avatar
Kylwell
Moderator
Posts: 29643
Joined: Sun Nov 02, 2003 9:25 pm
Location: Lakewood, CO
Contact:

Post by Kylwell »

Primer, in general, is hotter (meaning it sticks to more things better) and somewhat thicker. It levels the playing field when using disparate materials making painting easier. It's also handy when you've got a plethora of colors, due to putty, plastics, etc, to find the flaws.
Abolish Alliteration
User avatar
Owen E Oulton
Posts: 2216
Joined: Thu Jul 03, 2003 10:30 pm
Location: Ottawa, ON Canada
Contact:

Post by Owen E Oulton »

As noted, many primers are "hotter" than enamels, but this is not always a good thing, depending on the model itself. For plastic model kits, a flat modelling enamel is often just as good as a primer. While a primer coat is good at giving an even "tooth" to the entire project, this is less important for models than for such things as automotive paintjobs.

The one thing a flat primer or enamel coat will do is to highlight various imperfections which may not be visible otherwise. F'rinstance, say you have two different colours of styrene joined together, with yet a different colour of putty at the joint. The high contrast between the putty and parts makes it difficult to see that there's a fine groove left which requires more putty work. A single flat colour coat makes it far easier to see the shadows and highlights on the edges of the imperfection.

Where primer really comes into its own in modelling is when you are using various dissimilar materials - resin plus styrene plus epoxy putty plus white metal plus photetched brass is a not uncommon mix. All of these materials take paint differently, but a primer coat can even all this out, giving a consistent surface. Is is important when dealing with this sort of mixed surface to mist on the first two or three coats of primer before putting on an opaque coat - even primer likes to have something to grip.
...Only the dead dreams of a cold war kid...
TheIrishAvenger
Posts: 341
Joined: Sun Oct 10, 2004 2:04 pm
Location: Evans, CO-just south of the festering Greeley Mall gang-wars

Post by TheIrishAvenger »

Wow, that was very helpful. Thanks guys!

Chris
"Some say the alien didn't die in the crash. It survived and played poker and drank whiskey with the locals, until the Texas Rangers got wind of it and shot it dead."
max142
Posts: 666
Joined: Fri Jul 12, 2002 3:21 pm
Location: Va Beach, VA
Contact:

Post by max142 »

for good cheap primer hit up your closest Wal Mart or K Mart, or similiar store and get the cheapest primer in the automtive section....about .99 cents...saver your good paint.

While thier grap a tube of Bond Spot putty and Glaze...another $2.00
TheIrishAvenger
Posts: 341
Joined: Sun Oct 10, 2004 2:04 pm
Location: Evans, CO-just south of the festering Greeley Mall gang-wars

Post by TheIrishAvenger »

Well, I WAS using some primer from Napa, or rather, was GOING to use, until I tested it on a scrap piece and found it comes out WAY too "liquidy". Too runny. Would've had to throw on four or five very light coats before it even became opaque, to avoid that runniness.
As for putty, you mean Bondo Glazing and Spot Putty, right? Already picked up a tube of that. Pretty good stuff. Seems just like another putty I used a few years ago, but forget the name of it. Might've been Squadron. Much cheaper tho. Thanks again!

Chris
"Some say the alien didn't die in the crash. It survived and played poker and drank whiskey with the locals, until the Texas Rangers got wind of it and shot it dead."
User avatar
Kylwell
Moderator
Posts: 29643
Joined: Sun Nov 02, 2003 9:25 pm
Location: Lakewood, CO
Contact:

Post by Kylwell »

Personally, I've given up on cheap primers. Last coupla ones I tried either never dried, where way too thick, or just didn't have the coverage. Tamiya white fine primer, covers anything and has no problems.

I would be curious to see a study done on various primers, to check coverage, thickness, opacity, etc.
Abolish Alliteration
Digger1

Post by Digger1 »

Don't forget, too that paints in aresol cans tend to dry more slowly (if at all) when the humidity is high. The outside relative humidity should be under 60%. Modelers in the bible belt can forget about painting their models.
User avatar
Owen E Oulton
Posts: 2216
Joined: Thu Jul 03, 2003 10:30 pm
Location: Ottawa, ON Canada
Contact:

Post by Owen E Oulton »

Well, I WAS using some primer from Napa, or rather, was GOING to use, until I tested it on a scrap piece and found it comes out WAY too "liquidy". Too runny. Would've had to throw on four or five very light coats before it even became opaque, to avoid that runniness.

Sure you shook it up enough. You should shake a can of primer vigorously for at least a minute and a half (90 seconds), longer if you can do so without your shoulder dislocating (ouch). The old "grab the can and give it a quick shake" doesn't really cut it.
...Only the dead dreams of a cold war kid...
User avatar
TER-OR
Site Admin
Posts: 10531
Joined: Thu Jul 11, 2002 7:05 pm
Location: Conjugate imprecision of time negates absolute determination of location.
Contact:

Post by TER-OR »

THis belongs in FINISHING.

For styrene, I don't bother with a primer - the base color or perhaps white if I'm doing light colors on dark plastic does the job. That will let me see any errors which must be fixed.

If you're using lots of different materials, that's another story. Or metal miniatures, then I use a primer.
Raised by wolves, tamed by nuns, padded for your protection.

Terry Miesle
Never trust anyone who says they don't have a hobby.
Quando Omni Flunkus Moratati
Warped Speedster
Posts: 1589
Joined: Mon Sep 02, 2002 4:45 am
Location: Phoenix

Post by Warped Speedster »

I don't usually use "Primer" but the last time I used Testors spray primer it orange peeled and took about three days to finally dry. I live in Arizona where the humidity is not a problem so I don't know what caused the tackyness or the wrinkles. I shot it on regular AMT plastic which should've worked fine.

As it turned out the wrinkles ended up looking good anyways. It was just a round cover plate that I primered. It kinda gave it a rough cast look.

Still weird though. :?
Did I just see a Ford fly by?
User avatar
Lt. Z0mBe
Posts: 7311
Joined: Thu May 29, 2003 1:46 pm
Location: Balltown Kentucky, by God!
Contact:

Post by Lt. Z0mBe »

Warped Speedster wrote:I don't usually use "Primer" but the last time I used Testors spray primer it orange peeled and took about three days to finally dry. I live in Arizona where the humidity is not a problem so I don't know what caused the tackyness or the wrinkles. I shot it on regular AMT plastic which should've worked fine.

As it turned out the wrinkles ended up looking good anyways. It was just a round cover plate that I primered. It kinda gave it a rough cast look.

Still weird though. :?
What kind of AMT kit was it? I had the same mystery problem ona '71 Duster model. Nothing would stick to it. Not primer, not enamel, nothin'. Basically, the paint would peel off like old latex siding paint.

Z0mBe

www.sigmalabsinc.com


Onward, proud eagle, to thee the cloud must yield.
User avatar
Owen E Oulton
Posts: 2216
Joined: Thu Jul 03, 2003 10:30 pm
Location: Ottawa, ON Canada
Contact:

Post by Owen E Oulton »

I don't like Testors' grey primer at all. I've never had good results with it.

My favourite primer is one that's currently available in Canada at Wal-Mart under their ColourPlace house brand. It used to be available under Canadian Tire's Armour-Coat, but Canadian Tire changed manufacturers. It took Johnnycrash Fleming and myself the better part of a year to track down the actual manufacturer using the product code on the bottom of the can, and then to find out who they supplying that particular primer to. It comes in oxide red, light grey, white and black. When Canadian Tire carried it, they also had a darker grey available that Wal-Mart doesn't carry. Too bad, as it was my favourite, and I even used it as a colour coat on several models.
...Only the dead dreams of a cold war kid...
Warped Speedster
Posts: 1589
Joined: Mon Sep 02, 2002 4:45 am
Location: Phoenix

Post by Warped Speedster »

Z0mBe wrote:
Warped Speedster wrote:I don't usually use "Primer" but the last time I used Testors spray primer it orange peeled and took about three days to finally dry. I live in Arizona where the humidity is not a problem so I don't know what caused the tackyness or the wrinkles. I shot it on regular AMT plastic which should've worked fine.

As it turned out the wrinkles ended up looking good anyways. It was just a round cover plate that I primered. It kinda gave it a rough cast look.

Still weird though. :?
What kind of AMT kit was it? I had the same mystery problem ona '71 Duster model. Nothing would stick to it. Not primer, not enamel, nothin'. Basically, the paint would peel off like old latex siding paint.


Z0mBe
It was the AMT "Droid Fighters" kit from SW episode one. I was painting the round base that comes with the kit. Either the plastic didn't like the paint, or the paint didn't like that particular kit. Or it was a bad can of paint.

It sounds like your model may have somehow had some residue left on it from the mold. That would for sure cause problems with paint sticking well. Sometime you have to clean a regular plastic kit just like you would a resin kit. Soap and water, I guess.

It could also be that it was just a bad batch of plastic from AMT.
Did I just see a Ford fly by?
User avatar
TheMilkmanCometh
Posts: 4904
Joined: Fri Jul 12, 2002 12:08 pm
Location: ...is everything.

Post by TheMilkmanCometh »

You probably shouldn't worry about priming unless:

A) It's resin (and not in all sircumstances).

B) It is metal.

C) You are putting a metallic finish on it.
Sci Fi Smoker
Posts: 6042
Joined: Fri Jul 12, 2002 2:15 pm
Location: North Mississippi

Post by Sci Fi Smoker »

The primer I use isn't a primer at all. I airbrush Floquil Railroad Lettering Gray and check for seam imperfections.
A free man can never be defeated, he can only be killed.
big-dog
Posts: 6270
Joined: Wed Jul 17, 2002 4:46 pm

Post by big-dog »

I like primer, gives an even base colour to start your paint job from. Also lets you seem imperfections, those you can get away with, and those you can't. On Terry's advice I did switch to flat white for lighter coloured subjects as even light gray can give a bluish undertone and influence the base coat, as in turn yellow a light green.
Stand back, I don't know how big this thing gets.
User avatar
asenna
Posts: 490
Joined: Mon Jul 15, 2002 12:43 pm
Location: Toronto, Ontario

Post by asenna »

One very important reason to use primer which I don't think was mentioned is that it helps to prevent a static charge that attracts dust and thus makes for a cleaner and smoother top coat.

http://www.briansmodelcars.com/tutorial ... &CurPage=1
Post Reply