Star pump
From PyroGuide
Star pumping is a simple and fun method of manufacturing pyrotechnic stars. Pumps can be used to create stars, comets, crossette stars and more. There are several devices that can be used to pump stars, ranging from cheap home made devices like a plastic tube, or modified syringe, to more expensive devices like commercial metal star pumps like the one in the picture.
A metal star pump is a simple tool consisting of aluminum slotted sleeve and pinned plunger. To operate, retract the plunger till the pin clears the slot, press the pump into the damp composition till full, then simply eject finished star, prime and let dry.
Pumped stars have the advantage of offering you consistent size so all the stars you make burn out at the same time, giving the effect a more professional look. This is especially effective when the stars are used in aerial shells. Another plus of star pumps is their ease of use, and the fact that they require no special skills, which can be necessary in other star-making methods such as rolling stars. Pumped stars are often seen as ideal for roman candles, though they are not limited to these fireworks, and nor are roman candles limited to pumped stars. Pumped stars differ from Comets only in their size, and intended use. When a pumped star is called a comet is not defined, and will vary depending on context and personal opinion. Pumps for these can also be either created at home, or bought.
A complete tutorial on how to pump stars using a modified syringe can be found here.