What should I consider when making homemade steam distillation equipment?
Steam distillation is used to convert catnip leaves to concentrated catnip oil. There is an Instructable that I've followed in the past to make what they call kitty crack.

It's relatively simple, at least the distillation portion. The leaves are placed in a container on a heat source and water is added. The collection is boiled and the vapor containing water and oil condenses on an inverted lid over the container. Gravity pulls the condensate to the center where it drips into a smaller container on a stand in the middle of the concoction.



It's using ordinary household materials, including loads of ice! I've forgotten how many times I had to refill the inverted lid due to the heat transfer.

The chemical aspects of the catnip process will be different from your selected herbs, I'm sure and I can't advise that portion, but I suspect you have a few leads for processing the condensate.

I processed about a pound of catnip leaves and recovered a couple grams of concentrated kitty crack, which seems tiny, but they were dry leaves. Your herbs will probably have more oil than dry catnip. Running the same batch of leaves about five times means each sequence will be more water, less oil, but ensures maximum recovery.

I dumped the leaf mush in the yard in view of the security cameras. There was enough catnip remaining in the mush to attract more than a few local felines for a stoner session.