Glass jars are often used to store food items and spices. Airtight glass jars ensure that whatever is stored inside stays fresh by preventing air from entering the jar. Rubber and cork line the lid to provide a tight fit for the jar. You must properly maintain and clean the rubber and cork to maintain the airtight environment.
Apply a small amount of liquid dish washing soap to the lid.
Use a damp, soft cloth to wipe away the soap and any food or dirt from the rim of the lid.
Apply water to a cork lid. The water causes the cork to swell up and make for an airtight glass jar. To ensure a rubber lid fits snugly, make sure you've removed all dirt from the lid and seal. Rubber is added to the lid to make sure the lid fits tightly so there is no need to treat it other than clean it.