What kind of containers are suitable for the collection and shipment of samples of in-service lubricating grease?

The preferred containers are open mouth jars made of unbreakable high density polyethylene or other materials that are impervious to grease.  Although glass containers are impervious to oil and grease, they may break.  Some commercial testing laboratories supply sample kits that include a sample container, a label, and a pre-addressed box for shipping.