Primer, needed or not?

[Ray Von]

Hi all,

I am thinking of using the predicted warm weather to spray paint, in the garden, some plastic kit buildings and vehicles with primer prior to brush painting later on.

Just wondered what people's thoughts and feelings were on this subject, is it indeed necessary / of benefit? The kit is N gauge, and the primer is bog standard grey, which also raises the question: is there any advantage to white primer over grey or vice versa?

Cheers, Ray.

[Scottish Modeller]

Hi all,

I am thinking of using the predicted warm weather to spray paint, in the garden, some plastic kit buildings and vehicles with primer prior to brush painting later on.

Just wondered what people's thoughts and feelings were on this subject, is it indeed necessary / of benefit? The kit is N gauge, and the primer is bog standard grey, which also raises the question: is there any advantage to white primer over grey or vice versa?

Cheers, Ray.

Hi Ray,

 

I've always regarded the Primer/No Primer discusion as a bit of a lame duck.

 

It doesn't depend on weather or anything like that.

 

It depends initially on the material you are painting and then on the colour you want it to be finished in.

 

So - the material question.....

 

Metals - use metal primer as it creates a key for the topcoat to stick better to.

Plastic - use plastic primer if you want to, don't if you decide not to.

 

Colours - use the recommended primer colour for the top coat you will be applying.

 

Yellow top coat - use white primer

White top coat - use white primer

Grey top coat - use grey primer

Blue top coat - use grey primer

Red top coat - use red primer

Black top coat - use black primer

 

For red brick buildings use red primer without any top coat

 

Edit - To add 'for brick buildings I use Halfords Red Oxide as the primer and final coat. This is then weathered with colour washes which, with care, can represent the mortar between the bricks. can represent the varied colours that bricks realy are. Brindle is about the best way to describe this finish.'

 

I'm sure you get the idea!

 

Thanks

Edited May 26, 2017 by Scottish Modeller

[PaulCheffus]

Hi all,

I am thinking of using the predicted warm weather to spray paint, in the garden, some plastic kit buildings and vehicles with primer prior to brush painting later on.

Just wondered what people's thoughts and feelings were on this subject, is it indeed necessary / of benefit? The kit is N gauge, and the primer is bog standard grey, which also raises the question: is there any advantage to white primer over grey or vice versa?

Cheers, Ray.

Hi

 

Personally I only use a primer when I have a mix of materials such as brass and plastic to give the top coats a consistent undercoat.

 

Cheers

 

Paul

[brossard]

I agree it's a personal choice.  I like to use primer because bare plastic can be a bit slippery and may need two coats.  I certainly agree with Phil about undercoat colour, very important IMO.

 

John

[Ray Von]

Cheers guys,

 

Really helpful stuff. I do find plastic very slippery to paint directly onto, and I have found the finish a bit streaky. I only meant that the nice weather would mean that I could spray paint outdoors to my heart's content btw! Rather than choke on the fumes indoors! :-)

Edited May 26, 2017 by Ray Von

[Andy Hayter]

Plastic ideally - and metal for that matter - should be gently washed in mild detergent and allowed to dry before painting.

 

In the case of plastic, this is to remove any mould release agents that will be on the surface.  In the case of metal to remove solder and flux residues - and you may well need something a bit more aggressive than mild detergent.  Some plastic kits are much worse than others.  Many you would get away with without the washing - but it is still a benefit.

 

Your aim is a clean and dry surface to paint onto.

 

Most plastics do not need an undercoat, but will frequently benefit from one.  One major exception is Airfix figures.   These are (or at least were) moulded from a plastic that takes paint badly.  There have been many tricks to get around this but a once over with the undercoat can is a simple solution.

 

Regarding buildings, I generally paint before assembly rather than after.  Usually the kit will contain sprues in self coloured plastic and painting these while still on the sprue is pretty straight forward - with or without undercoat.    Doing things at this stage means that the fine parts are still on the sprue and not attached to the model, where there may be a change of colour - for example window frames set into a wall opening. 

[Ray Von]

Very helpful, I never considered the residue from the moulding process! But I get what you mean.

[Kris]

I generally prime anything that I paint, personally I feel this gives better results. 

[devondynosoar118]

Primer is there to provide two things, a colour block to build on and a key surface for coloured paint to bond to. All plastic kits are poor surfaces for paints to adhere to. Primer is designed to overcome this by having a high particulate count and less thinners than topcoats. On large plastic pieces and oily plastics a toluene based adhesion promoter is also a good idea. This is not really a problem in N. Washing parts to remove moulding release agent and surface contamination is a good idea,

In metal painting an etch primer is worth considering, especially on non ferrous metals like brass which oxidise quickly.

I find Halfords grey excellent for general modelling, Games Workshop Chaos Black is good too and if you want a base colour and primer Army Painter coloured primers are great as well.

Not priming is a poor substitute for proper prep in my experience.

Edited May 26, 2017 by devondynosoar118

[lofty1966]

Grey primer is usually used under red top coat as far as I know

[Arthur]

 

I always Prime to get a single underlying finish on almost any kit in any materials.

 

I only use three colours

 

Grey for almost everything,

 

And for two colours which generally have poor opacity

 

Red oxide under red top coat.

 

And white where the will be a yellow top coat.

 

.

[Loconuts]

Grey primer is usually used under red top coat as far as I know

 

A friend of mine used grey primer on a LMS loco followed by Crimson Lake, result a nice fetching shade of pink. Rule of thumb is red oxide under warm colours and grey under cold colours and always do a sample before hand.

[stevejjjexcov]

White primer for white wagons, no top coat. Transfers then weather works for me!!

[sharris]

I didn't use primer on plastic to begin with, and managed to paint stuff, but when I did start using it painting seemed to get a whole lot easier.

[grahame]

One benefit of giving a model a coating of primer (grey in most cases for me) is that not only does it provide a nice matt surface for painting but it makes inspection of the model simple and it is much easier to see any modelling defects that might need addressing before adding the top paint coat.

 

Also I never use washing up liquid to clean models (of any material) as it usually contains lanolin (to help protect hands that do dishes) and glicerene (to make the crockery shine). Both can leave a fatty deposit that will make dirt stick but can prevent paint adhering. I use creme cleaner and an old soft toothbrush and rinse well with lots of warm water.

 

G

[dhjgreen]

One benefit of giving a model a coating of primer (grey in most cases for me) is that not only does it provide a nice matt surface for painting but it makes inspection of the model simple and it is much easier to see any modelling defects that might need addressing before adding the top paint coat.

Also I never use washing up liquid to clean models (of any material) as it usually contains lanolin (to help protect hands that do dishes) and glicerene (to make the crockery shine). Both can leave a fatty deposit that will make dirt stick but can prevent paint adhering. I use creme cleaner and an old soft toothbrush and rinse well with lots of warm water.

G

I agree with all the above. Cream cleaner and toothbrush was recommended to me by DCKits, works well.

[Anglian]

When I had the head of one of my car engines skimmed and the valves recut they asked me if I wanted it degreased and since it only cost £5 extra I had this done so I could paint it. It was this simple think that made the penny drop for me – don't try to paint over grease – it doesn't work.

 

When painting metal (brass and white metal) I now have rigorous process that has been giving me a result that I've finally been happy with. I use Vim with a toothbrush, rinse in warm water, then once dry I rub down with a kitchen towel soaked in cellulose thinners before rinsing again. Finally I leave the model in white vinegar for 30 minutes before a final wash off with warm water followed by air drying. I don't handle the model with bare hands as this can just put more grease down onto the surface. I either use latex gloves or cotton gloves depending on what stage I'm at. 

 

The whole point of my process is to not only clean the surface but to throughly degrease it. In my experience, this process, combined with the use of an acid etch primer made especially for 'tricky' metals, is the only way I have been able to get a coat of primer to chemically bond with the metal. In my view there is no point in priming if all you are doing is laying paint down over dirt, which is rare as you can generally see it, or grease, which you often can't see. When I was testing various approaches I found I could pretty much scrape anything off with relatively light finger nail pressure simply because it hadn't bonded into the metal properly. In the end I found the double degreasing process, first with cellulose followed by letting it etch in vinegar was the best method to give a very sound surface. Now I use this method I can't scrape the etch primer off with thumbnail pressure and it's pretty resilient to modest scalpel pressure as well i.e. you have to really want to scrape the paint off with a blade to shift it.

Edited May 27, 2017 by Anglian

[lofty1966]

A friend of mine used grey primer on a LMS loco followed by Crimson Lake, result a nice fetching shade of pink. Rule of thumb is red oxide under warm colours and grey under cold colours and always do a sample before hand.

When painting a wall (in decorating) its always grey.

[brossard]

I agree with Loconuts, I once used grey primer when painting an LMS coach.  After applying the crimson lake I got a sort of purple.  If you use a red oxide undercoat the final colour comes out in a much warmer finish.  Red is a translucent colour and the final shade is very much dependant on what's underneath.  It might be useful to note that LMS used a paint called "lake" as an undercoat.  This was basically red oxide.

 

John

[Petesquire]

I always Prime to get a single underlying finish on almost any kit in any materials.

 

I only use three colours

 

Grey for almost everything,

 

And for two colours which generally have poor opacity

 

Red oxide under red top coat.

 

And white where the will be a yellow top coat.

 

.

 

Halfords do a yellow filler / primer.

[Vespa]

I am using some primers as the finished coat. Black is very good for all black chassis and locos. I have also sorted brown primer for BR vans and coach interiors (the wood panelling) and grey for coach roofs footbridges and the like. I did a kit of Penydarren and sprayed the coal tender brown U/C then misted it in black U/C and it looked like aged wood.I think that there are many car sprays out there that are suitable for lots of things. I had a list but cannot find it at present so if anyone else has a link let me know.

[57xx]

Halfords do a yellow filler / primer.

 

They do, but I wouldn't consider using it on a model, unless you wanted to obliterate all the detail, it's very thick and designed to fill.

 

On the original question, yes it absolutely worth priming. You will find the top coats going on so much easier and as others pointed out can affect the final coat's shading. You don't need to go to the expense of "special" plastic primers, Halfords acrylic cans do a very good job and will take either acrylic or enamel topcoats with no issues.

Edited May 29, 2017 by 57xx

[brossard]

I am using some primers as the finished coat. Black is very good for all black chassis and locos. I have also sorted brown primer for BR vans and coach interiors (the wood panelling) and grey for coach roofs footbridges and the like. I did a kit of Penydarren and sprayed the coal tender brown U/C then misted it in black U/C and it looked like aged wood.I think that there are many car sprays out there that are suitable for lots of things. I had a list but cannot find it at present so if anyone else has a link let me know.

 

Agree, I used red oxide with gloss varnish to paint the interior panels of my Kirk Gresley coach - I think it looks quite effective.

 

John

[Nile_Griffith]

Would agree that any surface plastic or metal benefits from proper prep and priming. I use acrylics and have started using a grey primer from a company called Stynylrez. I have always been a big fan of Vallejo primers but acrylic primers generally don't like to be worked with (sanding etc) until at the very least a good twenty four hours after the paint has dried and cured. The Stynylres primer seems much more durable even to working, even a couple of hours after painting.

 

I'd also agree with the comments that priming is an excellent way to check out surfaces, component fit and general look of your finished model prior to painting. It's not that rare that I've had a model that looked great at the assembly stage but then showed some small imperfections when a unifying coat of primer was applied.

 

On another tack with the primer colour discussion. A technique which is kind of showing good results for me, is varying the primer shade across the model. Most of the time I tend to use grey other than occasions when I'm spraying Royal mail Red (then I'll use a red primer). As I use an airbrush to apply my primer coats. I create varying shades of Grey primer by mixing grey and black primer paints together. Why? Well for example in under frame areas I apply a darker primer into the more recessed area's and a lighter grey on the larger more outward facing surfaces. As nothing in this world really appears as pure flat black (apart from maybe the inside of a coal mine with your eyes closed). As I start to build up my under frame colour by airbrushing my top colour in light passes, I start to achieve a bit of "dimension" as the darker shades of primer create slightly darker tones of top colour. I've tried these same technique with tank wagons and hoppers and found that you can loose a certain degree of flatness by creating a graduated or feathered effect between a dark primer sprayed into the recessed joins of body to frame. Military modellers have coined this technique as colour modulation. It does mean at the priming stage you have to give a bit more care and thought than possibly you would carrying out just a straight priming job, but so far for me it's provided some great finishes.

Edited May 30, 2017 by Nile_Griffith

[Vespa]

I am using some primers as the finished coat. Black is very good for all black chassis and locos. I have also sorted brown primer for BR vans and coach interiors (the wood panelling) and grey for coach roofs footbridges and the like. I did a kit of Penydarren and sprayed the coal tender brown U/C then misted it in black U/C and it looked like aged wood.I think that there are many car sprays out there that are suitable for lots of things. I had a list but cannot find it at present so if anyone else has a link let me know.

I found my old list of car paints. Some of which are still available in some car accessory shops.

Any roof grey Halford's plastic bumper

MR/LMS/BR red Rover damask red

GWR/BR loco green Rover Brooklands green

GWR/BR loco green Ford laurel green

BR diesel light green band Ford highland green

BR coach carmine Ford rosso red

BR coach cream Vauxhall gazelle beige

BR coach cream (well worn) Peugeot antelope beige

BR diesel blue VW Pargas blue

BR steam loco blue Peugeot royal blue

BR loco yellow warning panel Vauxhall mustard yellow

LNER garter blue/BR diesel blue, but slightly more blue Ford fjord blue, less green

LNER garter blue VW Pargas blue

LMS Coronation Blue Rover Pageant mid-blue

Stanier Coronation blue Peugeot royal blue

GWR or Pullman coach brown Rover russet brown

GWR coach cream Rover Primula yellow

SR dark olive green Land Rover Coniston green

LNWR/LYR coach plum lower panels Daewoo dark red

LNWR coach bluey-white upper panels Daewoo Casablanca white

CR steam loco Peugeot royal blue

SDJR blue Rover midnight blue

CR dark blue Rover midnight blue

Stroudley LBSCR ochre BMC tan

LBSCR umber Vauxhall Brazil brown

N.Staffs maroon Vauxhall Gambia red

NER coach red Vauxhall Gambia red

LYR coach upper panels Plastikote nut brown