they should be injected with borax and saltwater solution while still fresh. i preserved a velvet rack perfectly without injecting them. i put the rack in the freezer for a whole year and then soaked them by completely submerging it in borax/salt water solution for a month and then letting it dry. if you feel any slipage while it is drying out, resubmerge and let it soak longer. there should be no odor if done right.