My best beaver lure is fresh castors turned inside out and a pair or two left in the bottom of a 1 gallon jar with some oil from the oil stones drizzelled over them then sealed up and aged like that at least 5 years.I keep 5 big jars of them with a couple pair of castors in each and each year take the oldest ones out and put a couple new ones in to age.
The castors turn pure black and rubbery and are deadly for lure.A small crumb smells like a whole warehouse full of fresh castor.
I learned how to make that from old Pa Turner.
Any special reason why you use a 1 gallon jar for a couple pair of castors and a little sac oil?