My current build calls for several parts to be painted in 2 or 3 mixed paints. I‘d like to mix all these before hand and store in small glass jars with screw on lids. Does mixing paint reduce shelf life? If I mix them now will they be usable in 2 months? I’m sure adding the thinner should be done as needed.
Doesn’t matter the brand, you can mix for color and expect it to last long term if sealed up good. I’d avoid thinning it though till nearer ready time to paint. I’ve done this with tamiya acrylics, craft paints and enamels stored in little mixing bottles or even spare airbrush bottles.
I use Tamiya and mix it as well. Like Bish, I use old Tamiya bottles that I clean up real good. I tried other bottles and they dried up but the ones in the reused Tamiya bottles are good to go.
Try to mix all you need at once. An old house painter trick that probably isn’t done anymore- mix all your paint in a series of buckets poured back and forth. Otherwise you’ll see the variation bucket to bucket.
But don’t thin until use. That does seem to reduce shelf life or at least cause the paint to separate.
I second what Bill said, mix enough ! I screwed up a Duesenberg hood not following that instruction years ago. So if you have two different bottles of even the same color then mix them together and pour them back into the bottles before you even get started. That’s what I didn’t do, it wasn’t a custom mix but one ran out before I got to the hood. The second was not exactly the same shade. Now it doesn’t matter, it’s been 40 years and the model needs some freshening up, it’s on my list of to dos for some day.
With Testors enamels mixing does seem to reduce the shelf life a bit, and the life of an opened bottle is short enough anyway. Still, unless I take months to build, it usually lasts long enough. With acrylics or lacquers I have not had that problem. I like to mix up enough to finish the model, to keep a consistent mix.