Working with Brass Car Sides

[Tom Todd]

I have several Brass Car Sides and American Model Builders core kits. As I haven’t built any of these yet. I’m looking for any and all tips on the construction process. One question is: How do I prepare the brass for painting?

Tom Todd

[robert3985]

Tom ( @Tom Todd ) , I've built a dozen or more of these both for myself and for friends.  All I did to prepare the brass for painting was to totally degrease it, using Bestine (Heptane) and a medium stiff boar bristle brush.  (edit) I also took the protective coat off by cleaning in my ultrasonic cleaner before assembling, then using Bestine after assembly.  It's been a few years since I've built one of these, and my old brain forgot about the ultrasonic cleaning step.

Also, instead of acrylics, I use enamel based paints, allowing about three days at room temperature between maskings.  I much prefer Scalecoat II over just about any other model paint, 'cause it gives me a lovely, glossy finish...smooth as glass and doesn't hide details, and makes decaling a cinch.  I don't use a primer on brass, and so far, for the past 35 years or so, I haven't needed it using my airbrush properly.

(edit) On metal models that aren't a composite of plastic/metal, I bake them in my little toaster oven on a slab of 1/4 I've cut to fit.  I also put a precision thermometer in the oven so I can see the dial through the oven window to make sure the temperature doesn't get over 175 deg. F.  I pre-heat the oven to get the temperature regulated, then I bake for 30 minutes which works for most N-scale brass.  Temperatures around 200 deg. F start discoloring the paint, which is particularly noticeable with Armour Yellow Scalecoat II.  The way to tell if your enamel-based paint is cured is to smell the model.  If you can still smell the paint thinner, then you need to bake a while longer.  Cured enamel doesn't smell like paint thinner.

Make sure that you stir your paint instead of shaking it.  I use the Badger battery-powered mixer, and it dissolves all the pigments in the jar quickly and gets rid of any enamel based globs or strings.  (I also use it on acrylics)

If you etch the brass with vinegar or scratch the surface with fine sandpaper or 3M pads, a proper coat of Scalecoat will show all the scratches and etch pits.  That's the beauty and the curse of it...makes you be sure the finish you're painting is as flawless as you can make it, especially for diesel and steel/aluminum passenger equipment.

Make sure you have a oil/moisture trap on your airbrush hose and compressor, especially if you live in a humid clime.  I like the inline Paasche airbrush moisture trap, which is available through Dick Blick for a few bucks.  It's very cheap insurance and easily splices into your airbrush hose.

Cheerio!
Bob Gilmore

[DKS]

If you etch the brass with vinegar or scratch the surface with fine sandpaper or 3M pads, a proper coat of Scalecoat will show all the scratches and etch pits.

A vinegar bath does not leave any visible defects, unless perhaps you leave it in for a few hours, which is not recommended. A few minutes is all that's needed, and I can report that it does enhance the adhesion of paint to the surface.

[nickelplate759]

I'm pretty sure that Brass Car Sides puts a clear protective coat on their sides.  You might want to strip that before painting.

[thomasjmdavis]

I'm pretty sure that Brass Car Sides puts a clear protective coat on their sides.  You might want to strip that before painting.

I think you are right about the coating, but whatever they are coated with sticks to the brass VERY well- and some paints stick to the coating better than they stick to the brass [edit- see the BCS instructions in nickelplate759 post below].  I paint almost exclusively with water soluble acrylics - fast dry, low VOC, non-flammable all enter into the consideration for me.  And I am happy with the finish I get with modern acrylics. 

None of which is meant to contradict Bob Gilmore's advice- if I had a proper spray booth, and an area separately ventilated from the rest of the house, I would probably be using Scalecoat II as well.  But for my circumstances, acrylics have worked well, and I felt more comfortable in the days when I was teaching my (now adult) kids to paint.

Some other considerations....
On the BACK of the sides, I usually sand around the edges to rough up the surface a bit (and remove any coating), which helps with glue adhesion.  I paint the inside of the sides with primer or some light color before assembly. Once that dries, I put masking tape over the window openings from the inside- so that paint overspray from the outside finish does not get all over the interior of the car.

At some point early on, you need to decide whether to have to roof come off, or have the floor come off.  I have always opted for the latter, as I have had a couple roofs with a bit of warp to them.  But have to admit that if the roof came off, it would be easier to access lighting, if you are planning to install it.  And if you have never done one of these before, be aware that the core kit was originally designed for use with .030 styrene car sides in Des Plaines models early kits.  There should be some strips of .020 styrene provided with the core kit to back up the brass sides so that they fit the rabbets in the ends and roof of the core, and shim out the floor to fit.  But in a couple cases where I bought core kits on the big online auction site, those bits were missing.

In general- lots of clamps. And ALL of the time you spend assuring good fit and squaring parts up will be time well spent.  And when in doubt, check the instructions that Dennis includes with the sides, or which can be downloaded from www.brasscarsides.com

[peteski]

I think you are right about the coating, but whatever they are coated with sticks to the brass VERY well- and some paints stick to the coating better than they stick to the brass.  I paint almost exclusively with water soluble acrylics - fast dry, low VOC, non-flammable all enter into the consideration for me.  And I am happy with the finish I get with modern acrylics. 

Interesting. I wonder if that coating (probably just over the un-etched areas) is likely the photoresist which protected the metal from the etching acid.  If that is it  then I'm surprised that it is so tough. I would expect it to come off rather easily.  Is the company that made this still around? It might make sense to ask what the coating is and what is their recommendation for prepping the parts for painting.

[nickelplate759]

The instructions that come with the sides say this:

"The sides are coated with clear Krylon acrylic spray. This coating may be left in place on the
rear surface, but should be removed from the front side prior to construction and painting. It may
be left in place on both surfaces, but at the risk that some paints, particularly those that are waterbased,
may not adhere as well. The acrylic coating may be removed with a paste-type paint
remover, acetone, orsimilar solvent. The sides will begin to oxidize as soon as they are stripped,
but this is only a cosmetic effect."

[nkalanaga]

I usually stripped mine with cheap industrial paint remover, which also removes any grease or grime, then paint with Scalecoat whenever possible.  Some colors they don't have...

Scalecoat can be baked on, which makes it even tougher, and almost any paint can be applied over it after baking.  If you start with light colored Scalecoat, it works fine as a primer.  It's one of the few remaining "old-school" paints, from when most scratchbuilding was either brass or wood, and is designed for use on metal, unlike most of today's paints.

[peteski]

Thanks George!  That sure clarifies things.  If it is an acrylic clear coat then vinegar will not be able to etch the brass. But it also appears that the coating acts as a primer for any additional paint coats.

[thomasjmdavis]

Well, if you are going to bake paint on the core kit, be darned careful about the temperature.

Thanks for finding the "official" instructions.  I went looking the other day and could not come up with that paragraph- must have skipped right past it twice or 3 times. 

So forget what I said above about not stripping the clear coat- I am sure that Dennis at Brass Car Sides has advise from a number of "best practice" level modelers and I am just one guy- who has never done a controlled study, even for myself.

[peteski]

I actually don't agree with the statement that the clear coat should be left on the back (gluing) surface.  If that  is done then the glue joint is between the core part and the brass sides' clear coat (not metal).  Normally, when I glue any models together,  I make sure that the mating surfaces are bare, down to the material the parts are made from. If there is paint, I scrape it off.  So leaving the clear coat on the glue side of the brass parts doesn't make sense to me.

[altohorn25]

I've built at least 20 or more cars using these sides; I've ALWAYS removed the coating from both sides of the side using acetone.  After removal, I assemble the car and prime it before painting it with acrylic paints (Model Flex or Polyscale).  Some of my cars are over 15 years old and I've never had an issue with the cars either coming apart or the paint coming off.

Nate

[nickelplate759]

I've built at least 20 or more cars using these sides; I've ALWAYS removed the coating from both sides of the side using acetone.  After removal, I assemble the car and prime it before painting it with acrylic paints (Model Flex or Polyscale).  Some of my cars are over 15 years old and I've never had an issue with the cars either coming apart or the paint coming off.

Nate

What do you use for primer?

[nkalanaga]

Tom D:  No, I don't bake the paint on the core kit, and wouldn't recommend trying it.  I paint the sides separately, bake them according to Scalecoat's recommendations, then glue them to the core.

All of my roads (BN etc) have the roof and ends a solid color, so matching the side stripes is easy - no match needed.  Just spray the core a solid color, and, if using Scalecoat, wait a week for it to dry.  For the BN black and GN "BSB" dark gray, I don't use Scalecoat, so those dry a lot quicker.

[altohorn25]

What do you use for primer?

Just standard rattle-can testors grey primer.