I use PollyScale Acrylics about 90% of the time, and Model Master acrylics the other 10%. I find that the PollyScale paints are usually thicker, and need more thinning to airbrush well, while the MM paints need only a little thinner added.
I used to use distilled water to thin the paints, but I had mixed results. Sometimes they'd go on well, other times I'd get lousy coverage. I thought the problem was my thinning ratio-- "milk-like consistency" is still a rather vague guidance. At the time, I disliked airbrushing-- only doing it if I had no other option.
Then I read a tip that recommended the use of windshield washer fluid for thinning acrylic paints-- for me that made all the difference. Now, every time I airbrush, I get great results. The WW fluid (I use the cheap stuff from a gallon jug, sold at discount stores all over) has some detergent in it, which helps to break the surface tension of the water-based paint, allowing it to flow more freely. I use the blue tinted stuff, but the color has no impact on the color of the paint- even when painting with white or light yellow.
Now that I'm using the right thinner, I find that the mixture is nowhere near as critical as I once thought. I used to mix in a separate bottle, and try to add about 33% water. Now, I don't have to mess with that level of precision-- here is what I do:
I stir the paint thoroughly in the bottle, using a wooden coffee stirrer stick. I then use a plastic squeeze bulb pipette to get some paint out of the bottle-- I take the paint form the middle of the volume- to minimize the chance of picking up the little pieces of crud that may be floating or at the bottom of the jar. I squirt the paint directly into the color cup of the airbrush.
I keep a small plastic spray bottle with WW fluid at my painting desk. I take this bottle and give a squirt or two of WW fluid into the color cup. I use the same pipette to stir the mix, and suck it up into the pipette a couple of times, to be sure that the paint and the WW fluid have been well mixed. My paint does have the fabled "consistency of milk", which means it is clearly too thin to use for bush painting. I would guess that the mix is roughly one third WW fluid, two thirds paint, but that is a rough estimate.
I airbrush at about 15 psi. I do a couple of test passes to see if the paint is flowing well. If I'm not getting a good spray pattern, that means that the paint is too thick, so I'll add little more WW fluid, mix, and test again.
After I've painted the model, I wash the brush out right away. I have a sink next to my painting station. I rinse out the color cup, and wipe the inside with a damp paper towel to get most of the paint out. I then crank up the air to about 50 psi, and submerge the entire front end, cup and all, into a big cup of warm water and blast away. If I'm painting with more than one color, I will do so now.
When finished for the day, I clean with water, and then I then add a little household ammonia into the cup and repeat the process, with the nozzle of the airbrush under water. Blasting the ammonia into the water contains the ammonia vapors.
Acrylics dry fast, and stick like crazy to metal. Eventually, despite regular cleaning, I'll get some paint buildup in the airbrush. Once every month or two, I clean the airbrush with lacquer thinner, which dissolves all the dried paint and really cleans out the brush. I do this cleaning outside-- I don't do any spraying of paint thinners in my basement workshop.
This is my experience; your mileage may vary....
I only use lacquer thinner when giving the airbrush the "overhaul" type of cleaning. Lacquer thinner will dissolve in short order any dried acrylic paint that is clogging the airbrush. If the brush is a little dirty, I can get away with just spraying some thinner through the brush. (I do this outside.) I recently gave my brush a thorough cleaning- the first in about 9 months. It was still spraying fine, but the trigger was sticking, so I knew it was time for a disassembly-type of cleaning. I took it apart, and soaked the nozzle and other small parts in lacquer thinner for a couple of hours. (The only part of an Iwata that you can't soak in lacquer thinner are the rubber O-rings-- the metal parts are not harmed.) I also used a q-tip (cotton bud for my UK friends) and a microbrush to get all the crud out of the corners. After re-assembly, the action is like new- no sticking at all on the trigger mechanism.
Windshield Washer fluid is great for thinning paint, but doesn't seem to be any better than water for cleaning the airbrush. When I'm in a longer airbrushing session, where I'm going to be painting different colors off and on over an hour, I'll shoot some Windex (ammonia based glass cleaner) through the brush after I finish with a color-- that does clean out the brush a little better, and prevents clogs from forming.
Someone asked about using lacquer thinner in an Aztek--
I owned an Aztek before upgrading to my Iwata. I used acrylics exclusively in that brush, as well. I found that spraying water or even airbrush thinner through the brush would not get all of the paint out of the nozzle-- over time it would build up. I used to regularly take the nozzles apart and soak them in lacquer thinner- sometimes for days if I forgot about them. The nylon and metal parts of the nozzle were never harmed by this, and sure came out clean. I never used oil-based paints in my Aztek, but I know several folks who do regularly. There is no harm down in spraying lacquer thinner through the Aztek to clean it, but you should not soak the plastic body in it-- it will eventually degrade the O-rings sealed inside.
A couple more airbrushing comments/tips:
Brett Green, the editor at HyperScale is a master at airbrushing-- he uses an Aztek airbrush. He is sponsored by Testors, and has some helpful 3-5 minute long how-to videos on the website you can watch. In general, the plastic modeling sites have a lot of useful info about airbrushing, and are worth a look.
I buy my airbrushes and equipment from Bear Air. They have great prices and service, and offer a 45 day trial period when you buy a new airbrush. (Usual disclaimer applies- I'm just a happy customer.)
Testor's acrylic Airbrush cleaner is good stuff, but expensive at $10 a bottle.
I don't know what is in it, but it seems to be a bit better than straight
ammonia for cleaning at the end of a session. An advantage of the Testors
cleaner is that you can soak your airbrush in it indefinitely- a good option if
you don't have the time or motivation to do a more thorough cleaning after an
airbrushing session.
{Bill Michaels}
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