The Fountain Inkstand: A Cork That Cuts the Cup Off From the Fountain

"In the construction of modern inkstands, various devices have been used to keep the air from the large body of ink in the fountain, so as to prevent the evaporation of the acid ingredients, which evaporation makes the ink too thick for use; also to prevent the liability of the ink in the cup to overflow by reason of the expansion of the air in the fountain when the inkstand is left exposed to the sun or the atmosphere of a very warm room." "The tunnel shaped cup g has the tube h h extending from its bottom to the bottom of the inkstand, and the lower end of said tube is fitted with the cork i i which bears against the layer of cork j j fitted in the bottom of the inkstand as above described; and this cork i i operates as a piston in the cylinder b b."

**Fountain.** Glue a disc of cork sheet in the bottom of a glass jar with a metal lid. Drill a hole in the lid for a piece of PVC pipe, push it through so it stands 2 cm above the bottom, and seal it: the cylinder. **Cup and piston.** Cut a length of clear vinyl tubing to reach from 3 cm above the lid to the cork layer, and push a cork plug into its lower end with a small side hole cut just above the cork. Fit a PVC reducer from the assortment on its top as the cup. Slide it into the cylinder and clamp it there with a hose clamp at the height that keeps the cork just off the layer. **Test.** Fill the jar half with ink, screw the lid on and press the tube down once to fill the cup, leaving about 0.5 ml of room. Stand the inkstand in a bowl of water at 35 °C, read with the thermometer, for 20 minutes with the tube raised (cup open to the fountain) and watch the cup. Refill, press the tube down so the cork seals on the layer, clamp it, and warm it again. Compare with the notebook.

**Francis Draper** of East Cambridge, Middlesex County, Massachusetts, received US 7,885, dated 7 January 1851 and reissued on 2 April 1861 as No. 1,164. His inner cylinder was cast in one piece with the screw cap, and the cup had a double-threaded screw working in the cylinder, so that turning it lowered the cork piston and pressed ink up into the cup. He also wrote that the cylinder could be left out, or the cork put straight on the cup's tube. **Honest limits.** A jar, a PVC pipe, a vinyl tube and a hose clamp stand in for his cast cylinder and screwed cup. The notebook treats the trapped air as an ideal gas at constant pressure; its volumes and temperatures are examples. Your warm-water test is the result.