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Make Pt1526
Inflating toy balloons with gas from the city mains – Modern Mechanix, June 1930.

GAS from the city mains can be used to inflate toy balloons with the simple inflating device shown in the drawing above. Gas as it comes out of the ordinary jet has only a pressure of a couple of pounds behind it, which is quite insufficient for inflating purposes.

Secure an air-tight tin can and fit it with petcocks as indicated in the drawing. Exhaust the can of air by filling it with water, closing the top petcock to prevent air from rushing in when the drain is opened. Now turn on the gas and the water in the can will slowly trickle out, forced by the gas pressure. When the can is full of gas, attach the balloon to the top petcock and then turn on the water supply from the mains. The water will increase the gas pressure to 40 pounds. The water, therefore, must be turned on slowly so that the balloon will not burst from excess pressure.

To fix the shroud lines around the balloon, which are necessary to support the basket, take a board and fix two brads in it, spaced apart to a distance equal to one-sixth the circumference of the balloon when inflated. Blow the balloon up gently with your lips until it is rounded out to the desired size. A third brad is driven into the board above the other two, and this distance equals half the circumference of the balloon. The bottoms of the shroud lines are left long for attaching to the basket.

A paper drinking cup is used for the basket. When the balloon is inflated and its neck tied with silk thread to prevent the gas escaping, fill the basket with half an inch of water and take out a teaspoonful at a time until the balloon rises. When cast loose it will stay low enough in the air so you can observe it for a long time. Before filling with gas, it is best to dip the balloon in talcum powder to prevent scratches from pricking the rubber and puncturing it.

In inflating the balloon, the neck is attached to the petcock through the shroud lines, as illustrated in the drawing. Be sure that the shroud lines are hung evenly so that the lily cup basket is directly under the center of the balloon. This insures an even, steady ascent.

Phillip Torrone

Editor at large – Make magazine. Creative director – Adafruit Industries, contributing editor – Popular Science. Previously: Founded – Hack-a-Day, how-to editor – Engadget, Director of product development – Fallon Worldwide, Technology Director – Braincraft.



  1. Adam Marksteiner says:

    What kind of gas was in the city mains that was lighter than air? Hydrogen?

  2. Rob R says:

    Natural gas. The exact same kind of gas we use now to heat our homes.

    Try googline: natural gas lighter than air


  3. Sean says:

    Specific Gravity -> Air = 1 @ (1.013 bar and 21 °C (70 °F))

    Specific gravity : 0.138

    Specific gravity : 0.55

    Specific gravity : 0.91

    Specific gravity : 1.105

    Specific gravity : 1.55

    BTW Rob R., Adam’s question wasn’t totally out of it. Given when this was written, mains gas could have been coal gas which is a mixture of Carbon Monoxide and Hydrogen, a byproduct of coking coal.

  4. Dave Bell says:

    AH, yes! Been there, done that…
    We used 1/2 mil dry cleaning bags, though. Much larger than toy balloons, and didn’t require the boost pump for pressure. That was in the early-mid 60′s California, so definitly methane, not coal gas.
    But the best “payload” was always a fuze!
    We were fortunate that none ever landed still burning, I guess.

  5. Anonymous says:

    It looks like with a little ingenuity, you could make an air compresser capable of light duty–like for an airbrush.

  6. Matt C says:

    I hope you don’t leave both the water main and gas main line turned on at the same time, otherwise it seems like you’d fill the gas line in your house (and maybe in your neighborhood) with water!

  7. drspectro says:

    My grandfather hacked the regulator on his gas meter at his shop, so he had pounds of gas pressure rather than ounces (not safe, probably not legal). My father and I filled baloons with the gas once. They floated but not enough lift to even put a string on them.