What's the deal with dome?

If you spend any amount of time around disc golfers you may hear us refer to discs as being "domey" or that a disc has a lot of dome. Some discs are designed to be domey, they are meant to glide and offer some turn, other times you find a one off disc with much more dome than others of the same mold. It's pretty easy to see how domey a disc is from the side profile, but what makes some discs domey and others not when they are the same model? The simple answer is that the dome depends on a couple variables in the manufacturing process and it is sometimes tough to get consistent results. When hot plastic is injected into a mold, it is left in the mold for a brief time, this is the "in mold" cooling. The plastic starts to cool but can't deform as the mold holds everything in place. The disc is then jetted from the mold and the "out of mold" cooling begins. Like most solid materials, plastics expand when hot and contract when cooled. As a result, when a disc cools outside the mold, the thicker plastic rim contracts and forces the flight plate up, creating the magic dome. This little change in flight plate profile can make a disc glide further and even turn right more. The flight plate being pushed up can, in some cases, push the parting line down, leading to a slightly less stable disc. With an overstable distance driver, this can make that new driver fly a little straighter out of the box. In the photos you can see the difference in dome between 2 Shrykes from my bag. The darker shryke has significantly more dome than the lighter colored one. These are both star plastic the flatter one is a 2022, while the domey one is a 2023 they are both max weight. The flatter one is significantly more stable, and gets down faster than the domier counterpart. Next time you are picking up a disc in person check all the discs on the shelf, you may find one that has that little bit extra out of mold cooling, resulting in a beautiful little dome.