The corks play an important role for effective usage of the instrument: they hold it together. It has two main function: preservation of the cork and lubrication.
The manufacturers make the cork grease of different materials: soft wax, mineral oil or lanolin (wool oil). Most cork grease manufacturers do little more to their lubricant (typically an animal fat by-product or refined oil sludge) than to add a stabilizer and/or preservative. When added all up, this recipe is suitable for the cork's porous body. Even the so-called "premium" grades are
comprised of just two to three lubricants, while the most cork greases have six or seven. Popular cork greases contains the natural lubricants: beeswax, aloe vera and vitamin E oil. It may have different forms, but the most popular one is a form resembles the chapsticks or lip balm.
To grease the cork in proper way you need to keep an order: if you apply too much grease on your instrument it will smear all over the place and your clarinet can even fall apart during playing. If the grease wasn’t enough it won’t be effective.
Most woodwind instruments such as clarinet have a cork on one end of the mouthpiece. Take your cork grease and apply a thin layer on the cork, then rub it in with your fingers. Clean your fingers after this procedure to avoid the smudging of the rest part of the instrument. After that you may conjunct the mouthpiece and barrel. Next grease the top cork. Thoroughly clean your fingers not to soil the keys. Remove the tone hold rings and carefully grease the bottom cork. Connect the upper section with the barrel. Assemble the whole instrument.