Step 2: Prepare the Balloon
I filled the balloon with coffee. I chose the cheapest and coarsest coffee in the store. I think that a coarser grind would provide more jagged edges for the coffee granules to lock onto each other when the vacuum is applied. I didn’t test it, so it remains s theory.
I decided to only fill the balloon about ¾ full of coffee. When the vacuum is removed the coffee needs some room to become a flowing powder again.
Next I used a craft pipe cutter to cut off about 5 centimeters of the brass pipe. You can get pipe cutters from hardware and craft stores. You could also use a Dremel tool or even a hacksaw.
The aquarium tubing was pushed onto the brass tubing, and then the tubing was inserted into the balloon neck and locked on with zip ties.