Temperature also effects viscosity. At one point, and maybe still, the US paint industry used a standard of 77F to check viscosity. All paint was brought to that temperature before the lab tested it.

In reality, for our usage, all this technical stuff isn't necessary. Skrez is looking for a simple, reliable, way to make his paint viscosity into a reliable and repeatable form for spraying.

The best advice that I've received, is to adjust your paint to the consistency of milk. This has worked well for me.