How to airbrush brass?

Discussion in 'FAQs' started by engineshop, Jan 5, 2005.

  1. engineshop

    engineshop Member

    I soon will receive an undecorated Key brass SP cab forward steamer and like to know if anybody has some advice how to airbrush a brass model. I would like to use waterbased colors like Polly S since I have a lot of experience with that paint on plastic models but I never used solventbased paint like Scalecoat 1.
  2. Blake

    Blake Member

    Polly scale is my favorite paint. It goes on nicely and is easy to clean up. With brass models, I disassemble them and soak the parts in Scalecoat II Wash Away to remove the clear lacquer that is applied to them at the factory. Then I wash the parts with warm water and dish washing liquid. I shake the water off of the parts and put them in a pan of white vinegar for about 1/2 hour. Wearing latex gloves (as not to get fingerprints on the model) I remove the parts from the vinegar and rinse with hot water. I then lay them on a paper towel until all are done. Next, I dry the parts with a hair dryer followed by a brushing of 70% isopropyl alcohol (available at any grocery or drug store) and another drying with the hair dryer. For the paint mix I use a 50 / 50 mix of Microscale gloss to Polly Scale paint (yes, they do work together). For thinner, I use a 50 / 50 mix of isopropyl alcohol (the same used for rinsing the parts) and distilled water. I thin the paint until it is the constancy of whole milk. Airbrush a light coat at first and follow with the hair dryer. The heat sort of bakes the paint on. Then just continue painting as you normally would using the hair dryer after each coat. I spray at 25lb. of pressure and keep the brush about 4" from the surface. Let the surface get wet with paint but not enough to drip. Polly Scale paint, dryad with a hair dryer is ready for masking or decaling almost immediately after it is applied. After decaling I swab the surface with a clean wet cotton swab to remove the decal setting solution that has dried on the surface. I follow that with a coat of Microscale Satin finish thinned 50/50 with the thinner mentioned above and then do the weathering. For the smaller parts I use 2 sided tape on a piece of card board to hold them in place while painting. For drivers I take an index card, punch a small hole in the center and then slice it from the hole to the edge. Slip this over the axle making sure the bronze bearing is behind the card. This protects the axles and bearings from getting paint in them. I clean the tire portion of all wheels with lacquer thinner on a pipe cleaner. When you thin the paint, do not return the unused portion back to the original jar as it will cause the remaining paint to dry out prematurely. I hope this all helps you. Any questions, don't hesitate to ask.
  3. jetrock

    jetrock Member

    Would you recommend a coat of primer under the main body coat? I am planning on repainting a couple of brass Birneys in my projects box--I have some Tamiya gray primer in a spray can which has provided good smooth results on white-metal kits in the past.
  4. sumpter250

    sumpter250 multiscale modelbuilder

    That's one of the better paint tutorials I've seen! Thanks.
  5. engineshop

    engineshop Member

    Thanks for your help.
    I have three questions. You said that you use a 50-50 mix of Microscale Gloss and Paint. Is the reason to do that, so you don't have to spray a coat or two of gloss after the paint is try to seal it for decaling?
    I assume you are thinning the 50-50 gloss/paint with the 50-50 alcohol/destilled water mix.
    Finally: Are you taking the drive/gearbox completely apart to airbrush the drive wheels or is it possible to take off the rods and cover up the rest while airbrushing. I am afraid I never can put it back together and was actually planing on using a hand brush for the drive wheels.
    I checked out your web site and I will be happy already if my model will look only have as good as yours.
  6. Blake

    Blake Member

    jetrock: I used to use an automotive primer made by Plasti-kote called Car Color #632 gray. I did some of my own testing and found that it was unnecessary. The Pollyscale adheres well to brass. The best paint for adhesion is Scale Coat, but it is solvent based which makes it a pain to clean up and the stuff takes about a week to dry even if you put it in the oven.

    sumpter250: Thanks Pete, wait 'till you see my next article in RMC. It will be all about painting.

    engineshop: I mix the 50/50 solution of alcohol and water and keep it in a bottle. This is the only thing I use for thinner. Just make sure you shake it up prior to using it. Yes, the 50/50 mix of gloss and paint is thinned with it. By mixing the gloss into the paint you get a much better finish. Putting a coat of gloss over flat works, but it is another thickness of material added to the process. I do completely disassemble the drives on steam locos. Mark the inside of each driver with a scribe. I mark them 1, 2, 3 and so on for the insulated wheel. I then mark the frame with a small "I" on the insulated side. I do the same on the tender. This eliminates the guess work when reassembling. You can also mark the inside of each rod. I mark them 1e, 2e, 3e...ect. for the engineer's side and 1f, 2f, 3f...ect. for the fireman's side. The valve gear can be painted all at once and when the paint is dry just move the rods around to loosen them back up. If you run into any problems just give me a shout. I'm sure you will do fine.
  7. CalFlash

    CalFlash Member

    IMHO you must fully disassemble a steam engine to properly. On of the biggest enemys of good paint adhesion is dirt or oil. You can only properly clean it if fully disassembled. You only need to mark drivers that may be in question. The geared one is no problem as is any with heavier counter weights leaving (usually) only the outer ones to mark.

    Hint: if you plan to weather the engine, the plated side rods and valve gear usually defiy good paint adhesion esp weathering. I bead blast them then washes or light airbrushing adheres fine. I think you could use an "air erasor" to do the same.

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