When replicating CD’s a “glass master” is made as part of the process of manufacturing. The glass master is a high quality mold made from your audio master. So when someone refers to a “glass master” they are not talking about your audio files, but the physical replication model made from your music.

Making a glass master is a one-time process. Once made it can be used to replicate thousands of CD’s. Often glass masters are stored for a period of time, so the manufacturer can make “re-orders” at a later stage.

Some manufacturers charge separately for creating the glass master, some factor the costs into the price per unit. Ask about this upfront to avoid unexpected costs. Also if you expect to need re-orders of the CD ask them about their glass master archive policy.

There are two processes used to manufacture CD’s and DVD’s: duplication and replication. So what is the difference between the two?

CD duplication is similar to burning a CD/DVD on your personal computer. A duplicator extracts data from your master disc and writes it to a blank disc. The difference is that these duplicators can do it for hundreds of CD’s at a time, making it faster than what you do at home. Additionally the duplicated CD can be label printed so the end result looks like a proper CD.

  The benefits of CD duplication is that it can be done for low quantities.
  CD duplication usually costs more per unit.
CD replication is the process used for high volume manufacturing, like all the CD’s you find in      brick-and-mortar stores. A glass master (more on that below) containing your audio data is created      from which a so called “stamper” is made. The stamper, in turn, is loaded into an injection molding      machine that creates CD/DVD replicates. Lastly the product is label printed to finish it off.
  The benefits of CD replication is that it can be for high quantities and a lower price per unit
  The drawback is that you need to pay the setup costs for the creation of the glass master
  CD replications usually starts at 500 copies minimum