When 3d printing clay, a 5ml syringe makes a handy “squeezometer” to test clay consistency. Just pull the syringe apart, grease the plunger to reduce friction and poke some prepared clay in there. Then steal the kitchen scales and push the syringe down until clay just starts to emerge slowly. It’s very rough but still a useful test. You can calibrate it for the clay that works with your extruder. I am generally in the range 2.5 to 3.5 kilo of force. A small difference in softness can make a big difference to print quality.
Source: Make Your Own Ceramic 3D Printer Google+ Community