No, Clean hands and utensils will do. To minimize the chances of cross contamination between cultures it would be wise to keep Milk Kefir utensils for Milk kefir and the same with the other cultures. It is also not entirely necessary to use a new clean jar for your next batch of Milk Kefir. You can use the same jar more than once. Iron the cloth that you put over the jar because it kills mold spores and other bacteria that are unwelcome.