What is "birthing," and how do I do it?

The term "birthing" refers to the removal of the fully colonized PF cake from its glass jar. This can be achieved very simply. If you are going to keep the cake intact (growing as a cake) be sure to be careful and not break the cake (its hard to break if it's fully colonized, so don't be too gentle). You'll need a fork (or something to scrape the dry vermiculite layer off with), a wastebasket, and perhaps a large ziploc bag. Unscrew the jar lid, and turn the jar upside down (on its lid) while supporting it with your hand. The cake should slip down and fall onto the lid being held by your hand. Slide the glass jar off of the cake. Remove the excess vermiculite into the wastebasket, and handle the cake as little and as gently as possible. Overhandling can cause a bruising and bluing of the mycelium. Alternately, you could birth the cake into a ziploc to reduce waste - unscrew lid, place upside down lid and jar in bag. Simply open the jar up in the ziploc, where all of the vermiculite and excess will fall into the bag - instead of having to hold it over a wastebasket.