Thinning paint - measuring?

Depends on a few things.  What's the brand of paint?  Is is Acrylic, enamel etc.?  Is it gloss or flat?

I can give you an example based on the paint that I use most, which is Mr Color.  I tend to thin the flat paints close to 50/50.  The gloss paints get thinned a little more, probably 45/55 or 40/60.  I always use Mr Color thinner to thin the paint and regular lacquer thinner to clean the airbrush.

I tend to just eyeball the ratios, though.  I don't use anything to measure it exactly.  I just shoot for what seems like 50/50 to start and then I'll add more thinner or paint if I don't like how its coming out of the airbrush.  What I do is keep some Mr Color thinner in a plastic bottle with a pointy tip (that looks like a ketchup bottle in a diner) so I can just squirt in a few drops at a time.  You can get these bottles in various sizes at Hobby Lobby or Jo Ann's.  I have other bottles full of lacquer and enamel thinner, too.  Be sure to label them if you do this.

I mix the paint and thinner right there in the cup that attaches to my airbrush and stir it with a toothpick or chopstick from a Chinese restaurant.  I have a bunch of chopsticks from Pei Wei.  These make great stir sticks.  And the price is right.

Hope this helps a bit.

I have these Tamiya mixing sticks that I use for my painting needs. One end looks like a screwdriver blade that I use for stirring, and the other end is a tiny spoon/scoop. I use that end to measure in drops of paint and count them in. Then I use an eye dropper to add thinner at whatever ratio I choose. Depending upon the paint I use anywhere from a 2 parts paint:1 part thinner to 4:1. Like the recommended rule goes, thin your paint until it is like milk in consistancy on the side of the mixing jar.

I use a siphon feed airbrush (Badger) so I mix in the bottles.  These botttles are straight sided (cylindrical) so you can see the height of the paint, and if you pour slowly and carefully the thinner will sit on top of the paint and you can see how much you have added. I use a 1:1 mixture, so I pour in a little paint, then pour thinner in on top of it to the same height.  You do not need to be super precise- like to the nearest percent.  A ten to fifteen percent tolerance is good enough for most paints.  You can do that by eye.

I should mention that I use an eye dropper if I need to mix the paint exactly.  So if the instructions call for 30% C308 + 70% C305 then I will put 3 drops of C308 and 7 drops of C305 in the jar.  I have an Aqufina bottle lid with lacquer thinner standing by to suck up into the eyedropper to clean it out before I dip in into a different bottle of paint.  Then I will eyeball the thinner.

I use disposable 3ml pipettes to measure paints into airbrush cup. I picked up a case of 500 on Amazon for about $15. I use one for the paint and one for the thinner. They have measurements in .5 ml on the side. I portion them right into the cup and mix with a brush. Always put the thinner first.

I have found that using a syringe to draw up the paint works great. I can pull 1 part from 1 colour, draw a little air and clean the tip then draw the next colour and so on, then draw the thinner, draw some more air cover the tip shake the syringe and then deposit it mix right into the airbrush. This way the I can have a supply of what ever colour I mixed available for a couple of days, almost like a wet palette for brush painting.

How do you clean the syringe? In between the colors, do you use some thinner to clean? I have some syringes so this technique is interesting to me as a way to do it.

Thanks,

Mike