An egg piercer is a kitchen tool that is used to break a tiny opening in an egg shell to prevent the shell from cracking and the yolk from turning green while boiling. This tool is typically a sharp steel pin that is housed inside a base and that protrudes only when an egg is pressed onto it. An egg piercer also can be used to prepare egg shells for crafts.
The base of the piercer typically is spring-loaded, so when the operator presses the egg down on the piercer, the needle will pop up and poke a tiny hole into the shell. An egg piercer can come in a variety of shapes, sizes and colors to fit any kitchen décor. Most piercers are not much bigger than the eggs themselves and are small enough to fit into a drawer for storage. They can be made of stainless steel or plastic, and some even are shaped like a hard-boiled egg. Some people simply use a push pin to pierce an egg shell.
Air inside an egg expands as it heats up during boiling, and this can cause the shell to crack. Having a small hole in the large end of the egg allows air to escape gradually, which prevents the shell from cracking. All eggs have an air pocket at the larger end. When piercing the egg shell, the pin should go deep enough to pierce the shell where the air pocket is but not deep enough to puncture the inner membrane. If the inner membrane is punctured, the insides of the egg will come out while it is cooking.
The green ring that forms around the yolk of a hard-boiled egg is from sulfur. When the sulfur cannot escape from the egg shell, it turns the yolk green. When an egg piercer is used to create a tiny hole in the egg shell, the sulfur can escape, and the yolk will not turn green.
Some people enjoy decorating empty egg shells. This delicate craft requires the removal if the insides of an egg without breaking the shell. An egg piercer is perfect for the job. Two holes are needed, one at each end of the egg. The crafter can then blow the insides of the egg carefully through the egg piercer hole by blowing into the larger end of the egg. Once all the contents of the egg have been removed, the egg shell can be decorated.