I've been keeping my eyes open for small, cheap, clear plastic bottles (not too tall, not too wide in diameter) with screw caps, that would be appropriate for small-batch ink mixing. I found an unexpected and cheap source: coin storage bottles, three for $1 at a gold/silver/coin dealer.

They come in various heights and diameters. The containers designed to hold dimes have a perfect diameter & height for my small ink mixing tests. I wouldn't store the ink in these bottles long-term, but I did fill them with soapy water & kept them upside down for a couple of days with no apparent leaking.

Petra

I wonder if anyone uses the ink sampler containers for ink mixing as well....

And an unrelated question... How do you make best use of the last ammounts of ink in an ink bottle / container?