








The Tantalus Cup






Step #1: Prepare the cup.

Ctesibius and the Tantalus CupCtesibius and the Tantalus CupCtesibius and the Tantalus Cup
  • Drill a 1/4" hole lengthwise through the stem of the drinking cup.
  • Next, file several openings in the bottom lip of the cup, to provide an exit for the liquid when it drains out.

Step #2: Make the siphon (Option A).

Ctesibius and the Tantalus CupCtesibius and the Tantalus CupCtesibius and the Tantalus CupCtesibius and the Tantalus Cup
  • Option A: Pill bottle.
  • As shown in Diagram A, insert the 2-1/2" tube about 1/2" into the hole you drilled. Fix it in place with the silicone sealant, then seal the joint all around.
  • File a 1/4"×1/4" opening in the lip of the bottle. Apply sealant to the lip (don’t plug up the opening you just cut), invert the bottle over the tube, and press it into the bottom of the cup. Let dry.

Step #3: Make the siphon (Option B).

  • Option B: Plastic tube.
  • Following Diagram B, insert the 1"-long aluminum tube halfway into the plastic tube, then insert this assembly into the hole in the cup. Seal the joint with silicone and let dry.
  • Bend the plastic tube into a loop, taking care not to kink it, until its open end is ¼" above the bottom of the cup. Fix with a cable tie.

Step #4: Make the siphon (Option C).

  • Option C: Glass tube.
  • Buy a 6" length of glass tubing if possible. If not, use the edge of a steel file to notch the tubing, wear heavy gloves to break it to length, then sand or fire-polish the sharp broken ends.
  • Mount and light a propane or butane torch securely, donning heatproof gloves. Referring to Diagram C, rotate the area of the tube to be bent in the center of the flame until it softens. Remove and quickly bend it around the metal rod to form a 180° U.
  • Once the tube is cool, insert it into the hole in the cup and seal the joint with silicone. A polycarbonate wine glass adds some class.

Step #5: Using the Tantalus Cup.

Ctesibius and the Tantalus Cup
  • The legend of the Tantalus Cup is that it was designed to teach moderation. The cup appears normal enough, except for the column or figure inside.
  • If you pour a moderate amount of wine into the cup, you can drink out of it in the normal fashion. But if you fill it to the brim (actually, to any level over the height of the siphon assembly) the cup will empty itself. Every last drop will siphon out, and you won’t get a drink at all.


This project first appeared in MAKE Volume 35, page 134.
William Gurstelle

William Gurstelle



  1. Antonios says:

    You have to go a little back in history
    This cup is a Pythagoras invention around 500 years BC

In the Maker Shed