18th Birthday Cake Fountain. 18th birthday is an important milestone. By celebrating the 18th birthday, we say goodbye to our childhood and celebrate the beginning of adulthood. That is why it is usually the 18th birthday that is celebrated in style. And because we want you to be able to celebrate your 18th birthday "properly", we have prepared several colour options for you. You can find the complete range of 18th birthday party decorations in the section Party - 18th birthday. You can inflate the balloons with helium.