Premium crafting slots might be bugged, unless I'm misinterpreting. It states:
"Impurity is halved, and purity is doubled."
However Aluminium is going from 1.5 impurity to 1.25 impurity, instead of 0.75, as expected.
The line of code that says `impurity *= isPremium ? ((impurityBase - 1) / 2 + 1) : impurityBase;` - I'm not sure why it's subtracting one before the division, and then adding one back, but without those 1's, it comes out to the expected amount (0.712499999 because of the 0.95 on the line before it) It looks like you're only having the decimal portion, but if so, then it's definitely not as described.