Why primer?

[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

[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.)

[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.

[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.

[TheIrishAvenger]

Wow, that was very helpful. Thanks guys!

Chris

[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]

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

[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.

[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.

[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.

[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.

[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.

[Lt. Z0mBe]

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

[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.

[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.

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.

[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]

The primer I use isn't a primer at all. I airbrush Floquil Railroad Lettering Gray and check for seam imperfections.

[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.

[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.

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