Ok, I received my sand blaster today and tried it out using baking soda. I could not get the baking soda to syphon up the tube into the mixing chamber and ended up having to use it inverted, tapping it againt the table every 5 seconds or so to ensure a flow.
So I know it is caking up, but how and why? Humidity is under 50% so that is not an issue. The baking soda was from the kitchen and free of contaminants.
I was using about 40 PSI as per instructions.
Any ideas?