Blending clay for vessels

Blending clay for vessels-

So, I have been experimenting with blends of the Derbyshire clay and other clay bodies. I have found that the pure derbyshire clay is very difficult and often unsuccessful when thrown due to the amount of sand in the clay. it feels as though I can 'pull' the put up really high, but the sand starts to slump the clay. It feels a bit like when you are walking along a beach, when you take your foot away from the waters edge how the sand fills the space immediately. Its very odd. Adding porcelain has seemed to help the vessel 'stand up ' better and be lighter.