Golden Paints has introduced a new line called Open Acrylics. The idea is to offer acrylic painters a chance to really relax and take their time without the business of quick drying as in normal acrylics. The new product stays wet or tacky up to ten times longer than normal heavy-bodied acrylics. Further, they can be worked together with the standard products and made to speed up or slow down drying times according to percentages mixed.
I've been using them straight up and in various mixtures for a week or so, and I like them. Right out of the tube, or with the special thinner, you can be positively languorous--even in direct sunlight. I was blown away. They mix and blend like a dream, and false starts and boo-boos can be scrubbed into oblivion or gradated away with a rag. They stay water-miscible, so you can get effects you can't get with the regulars.
There are a few things you have to watch out for. The Golden Product Information Sheet is worth reading before you begin. For starters, the dedicated thinner contains no binders. It looks to me like there are a minimum of acrylic binders in the pigments anyway--but there is a volatile medium that is slow to evaporate. Golden recommends 30 days drying before final varnish.
I found that once things were going nicely I could force dry with moderate heat. This may not be advisable. Acrylics in general require curing rather than drying. Further, adherence or clouding problems may arise if you pile impasto or a regular glaze on an uncured surface. My advice is to consciously take a little longer between stages. This is good for the old creativity machine as well. Especially for those of us who multitask, the use of Open Acrylics takes the pressure off and lets you fool around more.
Because the Open Acrylics still have Golden's trusted richness, you can cut down your palette. I've been working with a small kit of six pigments: Titanium White, Hansa Yellow Opaque, Phthalo Blue (green shade), Phthalo Green (blue shade), Pyrrole Red, Quinacridone Magenta. You can mix some mighty sophisticated hues, including gorgeous darks and earth tones, from this tiny outfit. It's an education.
PS: "Due to the newness of this medium, some applications and uses have yet to be tested or fully explored." (Golden Information Sheet) - Robert Genn