Acrylics should never be thinned with more than 25% water. Why? Too much water will upset the balance and spread the acrylic polymer too thinly so the molecules can't reconnect properly to form a stable film. Instead you should dilute with an acrylic medium, which is essentially the same as the paint but without the color pigment. This way you are adding more of the acrylic/water emulsion to keep the formula and film stable.
When wet, an acrylic/water emulsion has a slightly milky appearance and becomes transparent as the paint dries. This milkyness slightly lightens the value of the color. As water leaves the emulsion, and the binder clarifies, the value of the color darkens. This color change is commonly called the wet-to-dry color shift and is most noticeable with dark transparent pigments like alizarin and less noticeable with light opaque pigments like cadmium yellow. Our inhouse chemists are at the forefront of acrylic technology and use the latest acrylic resins available for Liquitex materials, providing you with the best wet clarity possible.
Acrylic paint films aren't keen on the extreme cold, so don't attempt to roll, unroll or flex acrylic paintings in temperatures below 45ºF as they will be more brittle.