Gel, yes. A medium for acrylics that thins and makes more transparent the paint. I wondered what it would look like to have multiple transparent layers. This is the result after some red and blue layers of ink:
Looks good, I think. How about some colour consistency with another layer of blue.
Yeah, the second stage result was less good. A uniform blue layer on top:
The uneven colour looks interesting, but not sure it quite works as multiple layers of colour coming through. Might have to be more careful in building up these layers.