A printed balloon is a printing problem disguised as a party supply. The substrate is not flat, not rigid, and not the same size at the press as it is on the day. Natural rubber latex tapped from Hevea brasiliensis is compounded with sulphur, zinc oxide, accelerators, antioxidants and pigment, then held in suspension at roughly sixty per cent solids. Aluminium formers are dipped in a calcium nitrate coagulant, dried, then plunged into the latex tank. The salt destabilises the colloid at the surface and a gel film builds within seconds, thickness governed by dwell time, viscosity and former temperature. Rotating brushes roll the open end into a bead. The films are leached in warm water to strip residual salts and soluble proteins, then vulcanised near one hundred and twenty degrees Celsius, where sulphur bridges lock the polyisoprene chains into a network that recovers its shape after six hundred per cent elongation. Then comes the hard part. Ink. - The balloon is inflated onto a ma...