Balloons are made of highly elastic rubber. After inflation, the internal air pressure is higher than the external air pressure. After being punctured by a needle, the gas in the balloon will be ejected quickly. Because of the good elasticity of rubber, the holes will become bigger and bigger in the process of gas ejection, and the ejection speed will become faster and faster. So it feels like it's going to explode at once. The elasticity of transparent gelatin is poor after being stained with transparent glue, which also limits the elasticity of rubber skin on balloons. Therefore, the elasticity of the balloon surface is greatly reduced, and it will only leak a little when it leaks, rather than expanding the breach, so it will not explode. In short, because of the small elasticity, the breach will not expand.