Fixative for Herbal Bags?

I would like to know if you need a fixative for herbal bags and cushions or if you just dry them and put them in and then use them?

A fixative helps to preserve the scent of aromatic herbs. It absorbs some of the essential oils which would otherwise be lost to the air. Of course you want the essential oils to escape to the air – that's how you are able to smell the herbs – but you don't want the oils to escape all at once so the herbs quickly depleted. A fixative such as calamus or orris root powder helps to slow the loss of essential oils so the herbal mixture retains its scent longer.