Source: http://www.balloonhq.com/faq/making.html#general

HOW TO MAKE LATEX BALLOON

Balloons are manufactured from a liquid rubber called latex. The balloon gets its color from the pigment that is added to the latex.

The natural rubber latex that we use comes from the sap of the rubber tree , Heveabrasiliensis. Once removed from the tree, the sap is called latex. To make this suitable for balloon production, curing agents, accelerators, oil, color, and water must be added. After these are added, the completed latex is put in an open top tank, and the balloon form, which is in the shape of a balloon, is dipped. Before the form is dipped into latex, it is dipped into a coagulent that causes the rubber particles of the latex to collect on the form. This coagulent is calcium nitrate, water, and/or alcohol. After the coagulent coated form is dried, it is then dipped into the compounded latex. Then the latex coated form passed through a set of revolving brushes that rolls the balloon neck into the bead that is used to aid in the inflation of the balloon. The latex coated form is then washed in hot water to remove any unused nitrate. Following the leaching, the form is put in a 200-220 degrees Fahrenheit oven to cure for 20-25 minutes. When cured, the rubber balloon is removed from the form (stripped).

HOW TO MAKE LATEX BALLOON AT HOME

The man who invented and patented the Geo, Ron Prater from Indiana, made all his prototype balloons at home, and vulcanized them in his kitchen oven (of course, his dad was a chemist at Pioneer Balloon Company...). I have a newspaper article (that was reprinted in a clown magazine) which discusses this.

Regarding making balloons at home, I've watched the hand dipping process and it's a snap. One good person with a few hundred dollars invested could make a gross in about 12 to 16 hours. At that rate, the cost would be prohibitive. - Marvin

Procedure to Manufacture a Latex Dipped Item

• Stir latex coagulent (the talc generally powder settles out). Transfer to vessle suitable for heating. Warm coagulent to 130-140 degrees Fahrenheit (warming is optional and is used mainly for fast production).
• Warm former or form for 3 minutes at 170-175 degrees Fahrenheit.
• Dip warm former into coagulent (coagulent should be under constant agitation).
• Dry coagulent coated former in 170-175 degree Fahrenheit oven for 3 minutes.
• Dip dried former in 70-75 degree Fahrenheit latex.
• Leach latex coated former in 175-180 degree Fahrenheit water for 15 minutes.
• Cure latex on former for 20 minutes at 200-215 degrees Fahrenheit.