How I did did my mixed ink challenge in a collage. I used pipettes instead of the big droppers that came with the ink. I put them down into the water to set the focus on my camera. That helped.
Seven years and counting, and still enjoying every minute of it, although I don't have as much time to devote to photography as I'd like.
Christian,...
Thank you for the challenge (and a clue how to do it). You've pretty much done everything! How about getting up high and taking the photo from a perspective looking down? Hope that challenges.