Playing around with Golden Open acrylics, which have a longer drying time than other acrylic polymer paints. So far, it's promising enough to keep playing with. While it does dry more slowly, it gets gummy rather more quickly than is comfortable. Definitely has a greasier feeling to it going on, too, and I'm tempted to try to beef it up with some dry pigment.
on paper with pastel, 22x30in.
on panel, @ 7x10in.
on canvas stretched on panel, 9x12in.
on paper, 5.5x4.5 in.