If you've ever wished for an acrylic paint that dried slowly, more like oil paint, you now get it in the form of Open Acrylics from Golden. It looks and handles like normal acrylics, but makes blending colors something that can be done leisurely.
Having heard quite a bit about how Golden's Open Acrylics did indeed stay workable for ages, making them more comparable to oil paint than normal acrylics, I decided to do a bit of an unfair test. I tried the samples I'd received on a piece of unprimed paper and then left it overnight near the night-storage heater. So not only was it on a very absorbent surface but also near a dry heat source.
The result? Thin paint dried very quickly (not a surprise), but slightly thicker paint was still tacky the next morning, and clumps were totally workable and had not skinned over. It may look like normal acrylic paint, but it's not.
I've only played around with some samples so haven't yet used it extensively enough to confidently say how it handles glazing. But given that the paint can be "reopened" if it's not totally dry it will require some timing adjustments compared to normal acrylics at the very least. Working wet-on-wet requires more discipline to prevent overworking because you can keep going for so much longer.
Overall I think Golden's Open Acrylics are an exciting development in acrylic paints. I envisage mixing normal acrylics and these depending on what I'm painting, as sometimes I want paint to dry very rapidly and sometimes I want time to consider and blend.