Having introduced the collection and talked a little about their construction and my drive to engineer them, I want to shed some light on the theme.
The name kinda gives it away - they're based on the 4 classic elements - earth, air, fire and water. The 5th element is well, the 5th element. The 5th element is often balance, or aether, and here the 5th Hat features a little something of the other 4 Hats and brings them together as a collection.
I think the beauty of these designs is that you can see which element they refer to, yet if you view them through the lens of a different elemental theory, they still appear relevant and appropriate.
So let me introduce each Hat with it's element, and then I'll explain a little about the naming theory.
Fire - Azula
Air - Opal
Water - Katara
Earth - Toph
Balance - Korra
The astute may have spotted the naming theme already, and if you haven't, the Hats are named after characters in Avatar (The Last Air Bender)
Aran is a huge, huge fan of the animation series (as is Tom, to be fair) and can tell you all the characters, which elements they belong too, and what sort of mischief or mayhem they get up to. It's on our TV a lot, and whilst I can't say that the series directly influenced the designs, I can say that it's played a big part in the naming of the designs.
If you're not familiar with the animation (don't watch the film; it's rubbish) the characters are grouped by, and defined by, their elements, which are essentially nations. Amongst the population are those who can manipulate their element through special powers, and they are known as benders, and the practice as bending. Being able to manipulate air or any of the elements in this way seemed rather fitting to the manipulation of fabric, to the way that the short rows bend and divert the colours through technique. Naming the Hats after Benders was a natural step.
The avatar is a character that can manipulate all 4 elements, and creates peace and balance in the world; and so the 5th element Hat is named after one of the avatars (and, you may notice that they're all named after female characters)
Check the Wikia if you'd like to learn more - Avatar: The Last Airbender
The collection is due for publication on the 6th of September, give or take a day or two. Over the next few weeks I'll talk more about each Hat, it's key features and how it's name was chosen.