I was watching one of the more popular series of modeling videos online, and noted the host thins his Tamiya or Mr. Color paints right in the airbrush cup. Leftovers get poured straight back into the paint jar. Seems to work well enough, though I wonder how well the paint gets mixed. I use a clean separate jar to thin my paints though it does leave me with quite a few jars of thinned paint as I don’t want to pour it back into the paint jar and thereby bugger up my ratios in the future. I realise thinning paint is not an exact science, and often the mix is more intuitive than measured. I’m usually happy with a 1:1 ratio of paint and thinner so dumping thinned paint back into the jar would throw the ratio off, not to mention I like to paint straight from the jar for hand brushing and thinned paint doesn’t work as well.
My airbrushes are all siphon feed, so I thin in the jar. And usually in the proper amount (or close enough) needed for the task at hand. Any excess left over I will spray out prior to clean up. Pouring thinned paint back into the orginal bottle is a BAD idea, as it will shorten the life of paint in that bottle. I have used gravity fed airbrushes as well, and in those cases, mix the amount needed in a mixing cup prior to pouring into the airbrush cup.
Yup - The guys above are spot on I think. Many have pointed out, that pouring thinned paint back into the original jar can have negative effects on the paint within. I have seen this myself.
Mixing paint, additives and thinners in the airbrush paint cup, leaves the possibility of particle contamination from the brush, or whatever you might use for stirring.
I save the little plastic jelly containers from the coffee shop, being sharply cornered they are convenient for mixing and then pouring into the AB cup. It seems much easier and provides a thorough blending when done in other than the AB cup.
If you are thinning with hot lacquers or acetone, then plastic containers are not recommended. The aggressive thinning liquid could attack the plastic and affect the paint. Glass or metal is recommended for that.
I use gravity fed brushes and used to just mix paint in the cup of the airbrush.
I would put the thinner in first, then the paint after that - as doing the other way can result in the need to blow all the thicker paint through before you get to the properly thinned stuff.
I found that it mixed very well by stirring with a paintbrush and using some blowback to bubble it up a bit more.
The reason i stopped this is because of the brush mixing.
I had a blockage in my airbrush once and after sometime of stripping and inspecting, i found there was a small brush hair that had become lodged in the tip of the airbrush. I managed to blow it through, but, since then, i now mix in a separate small continer (i use the small plastic holders that tea lights come in) then pour it into the airbrush cup.
This way, i can make sure there are no hairs etc in the paint.
As for what to do with mixed paint - i discard it. I can normally judge how much i might need and discard the rest.
I have plastic 1oz shot glasses for mixing acrylic paint, and testors 1/2oz mixing jars for enamels and lacquer paint (Basically the same jar that the Testors MM paint are sold in). I have all gravity feed air brushes and I never mix in the cup. I will mix about what I need and will discard what is left over. But, I have put the cap on the mixed paint and saved it for another use.
But I once mixed lacquer paint in a plastic shot glass. Left for a minute, and came back to a real nice mess!
I thin paints by eye in the airbrush. I know that is not recommended. I mix custom colors in a small clear glass and thin it when I need a custom color, but not regular thinning of a paint out of the jar. Its a feel thing that comes after years of mistakes.
I personally use suction feed airbrush, so I already have lots of jars- mix up the colors I need early in the build.
But I have friends who have gravity feed brush, and many use the same bottles, those little 3/4 oz bottles. They use them just to store the thinned colors for a build, then discard excess and clean jars when build is done, just like I do.
I used to only use siphon feed airbrushes as well but now mostly use gravity-fed. I still have tons of mixing jars filled with paint as I could just pop on a siphon and airbrush away (after thinning, of course). These are almost all Testors MM acrylics and I’d like to get rid of all of it as I prefer Tamiya now.
Since switching to Tamiya and gravity-fed airbrushing, I find I use much less paint and have only a small amount left in the mixing jar. Good to know I should just toss it. The caveat to that is if I’m doing a project, I’ll keep the mixed paint until the project is done.
The online fellow I saw used a Tamiya stirrer to mix the paint in the airbrush cup and occassionally blew back the the airbrush for a better mix - and/or unclog the airbrush. Cleanup was done with a brush; I use cotton swabs when I’m cleaning.
When I do an airbrush session with a fairly common color like say flat black, I mix up a bunch of thinned paint, like an ounce maybe. I get out a bunch of kits from the stash and go through them, painting anything I expect to be black.
Makes the end toss/loss ratio to paint used minimum.
I use a gravity feed and mostly mix in seperate jars but, will occasionally mix in the cup for some spot work. I stir with a flat toothpick.
My additional tip to reduce toss/loss ratio is when I’m done with the job at hand I will grab one of my “stunt” models and practice patterns and techniques with the remaining paint. I at least get some skills training rather than toss the paint out.
If you are watching Andy’s Hobby HQ videos, he dumps unused paint back into the bottle. He uses only Tamiya paints to airbrush. So what he does when he opens a new bottle is to fill it all the way up to the top with Tamiya thinner. Now he has prethinned paint ready in the bottle for airbrushing. He builds fast so he uses this paint up pretty quickly.
I do not thin paint in containers any more. Too much of a waste, and time lost cleaning/wiping things. I pour the paint into my ab cup and add thinner then use a med size brush to mix and blend things. I have a jar of LT that I use to clean the brush then wipe it on a paper towel. I rather mix paint a couple of times rather than mixing too much and throwing the rest away.
As previously stated, do not pour the leftover paint back into the bottle cause it will eventually shorten the life of the paint.
I don’t know who started the idea of tossing thinned paint but I never throw out any paint. All of it goes right back in the bottle. Never had the slightest issue. I mix all paint in the cup. Thinner first, then add paint until it sprays how you want it to. Simple and foolproof. I see constant complaints that the hobby is too expensive. Throwing away perfectly good paint won’t help that.
I clean out old paint bottles for reusing paint. I store and label it. I know I am never going to remix a shade to match if I have to do TouchUp so this way I have some paint to cover missteps. Bob Gregory Ruining one kit at a time