Bag seasoning, which has been spoken of earlier, is a liquid that seals the pores and seams of a leather pipe bag to ensure that it is airtight. The properties of the seasoning also aid in keeping the bag soft and pliable. It should be applied according to the manufacturer’s instructions, which may or may not include heating before application. Do not boil seasoning as this can change its properties and cause damage to the bag.

During seasoning, the hide should be kneaded and rubbed to ensure the mixture is worked into the hide. With the stocks corked, the bag should be inflated and inspected for air-tightness. If leakage is apparent, stocks may need to be retied or the bag may need more seasoning. When you are convinced that the bag is airtight (even a small leak is annoying, especially when you're breaking in a new chanter reed) the corks should be carefully removed and the bag hung to allow the excess seasoning to drain. Once all excess seasoning has been drained from the bag, clean each stock to ensure each is clean and free of seasoning. Excess seasoning may build up on the inside of the stocks causing problems with reeds and steadiness.

Home recipes for seasoning have long been shared and used with varying degrees of success. These concoctions may or may not work well. I only suggest that the cost of commercial seasoning is a lot cheaper than that of a new pipe bag. The following recipe is from a catalog published by Henderson Bagpipes in 1920.
Interestingly, Henderson came out with their proprietary “NOLEKE” seasoning in a can a few years later.

Regardless of what you use to season the bag, I would leave you with a word of caution. Many a good relationship has been severely tested by matter of seasoning a pipe bag. It is better to season the bag when you are on your own for a few hours. This will give you plenty of time to clean up should one of the corks give way and seasoning explode all over the kitchen. I am the voice of experience on this matter.  Also, any fondness for the aroma is definitely acquired through the love of the instrument.
Many pipers will delight in the knowledge that alcohol is the recommended disinfectant for pipe bags. (Yes, that is a glass of Jack Daniel on my pipe box!) The amount of bacteria and germs that collect and breed inside a hide pipe bag is not surprising. For sheepskin bags, I recommend a disinfectant every month or two immediately prior to seasoning. For other hide bags, every month or two regardless. The alcohol content of a cheap grade of whiskey is sufficient to kill most if not all germs. I usually pour about two shots into the bag and one into myself, swill it around for a minute or two and pour out any excess. The small amount that does stay in the bag will evaporate quickly. Under no circumstances should 16 year old single malt Scotch be poured onto the bag. If in doubt, call me first.

Synthetic bags may be washed with a mild soap and water, and of course, a shot of whiskey for good measure.
Pipe Bag Seasoning