"part" for airbrushing paint

[Anonymous]

I need to know, what exaclty is a "part" for thinning Polly Scale paints to be airbrushed. I know I need to thin the paint, but for example how would I thin paint using 75% paint and 25% thinner? How many "parts" and how to measure a "part". Thanks.

[Anonymous]

You can go to your local drug store and buy droppers or maybe even 2ml or 3ml syringes (without needles) for cheap, and use them to measure accurately.

[doctorwayne]

If you're using water-based paint, like PollyScale, the syringes, without needles, are a good idea.  Don't use them with lacquer-based paints, though, as the lacquer will "attack" the rubber seal on the plunger, causing it to swell.

For mixing paint, a "part" is a volume of ingredient, and can represent any measurement: an ounce, a cc, or a gallon, for example.  Or a part could be a drop.  My recipe for mixing the cream coloured paint used on TH&B diesels calls for 3 parts R-11 (Reefer White), 2 parts R-87 (Depot Buff), and 1 part R-31 (Reefer Yellow).  If I had 20 diesels to paint, I might use 3 oz. of R-11, 2 oz. of R-87, and 1 oz. of R-31, whereas if I only needed enough paint to do a bit of touch-up work on one diesel, I might substitute drops of paint in place of ounces of paint.  It's simply another way of expressing ratios of paint.  In your example of 75% paint and 25% thinner, the thinner is "one part", and since there's three times as much paint, the paint is "three parts".

Wayne   

[bobwhitten]

When instructions mention "parts", they are referring to equal measurements of paint and thinner. If the instructions call for 1 part thinner and 9 parts paint, they are saying to use any volume that you choose for both the thinner and the paint but to keep the ratio of of thinner to paint = 1/9.

For a 1 ounce bottle of Model Railroad Paint, you would use about 1/10 ounce of thinner and 9/10 ounce of paint for a ratio of 1/9. As suggested earlier, you will need some droppers or pipettes - and some small extra bottles which are available at the hobby shops.

Bob Whitten
Email: [e-mail]

[Anonymous]

Thanks allot for clearing that up for me. I have some pippets from a earlier project. BTW are the prototype boxcars undersides painted the same color as the tops? I have several Athearn kits that will be putting together but their undersides and frames are molded black, while a Bowser covered hopper car I picked up has the same color all the way around.

[doctorwayne]

Thanks allot for clearing that up for me. I have some pippets from a earlier project. BTW are the prototype boxcars undersides painted the same color as the tops? I have several Athearn kits that will be putting together but their undersides and frames are molded black, while a Bowser covered hopper car I picked up has the same color all the way around.

Different railroads had different practices for this.  Some roads even painted the truck sideframes the same colour as the carbody.  Check your prototype to be accurate, but after the cars were in service for a while, the accumulation of dirt on the underbodies made it difficult to be certain what colour they were originally.  Some roads also changed their painting practices over the years, so also check this if you're modelling a specific era.  Another painting practice that varied over the years, and is not always available with factory paint jobs, is the use of "waterproof cement" on car roofs and/or ends.  Not really cement as we think of it nowadays, this paint was usually black, and contained a tar-based emulsion that supposedly helped to waterproof these vulnerable parts of the car.

Wayne