Synthetic bagpipe bags, although relatively new to the piping community, have come a long way in a short period of time.
Originally made of no more than a synthetic, airtight material, synthetic bags were flimsy under the arm, when not inflated, and were somewhat challenging to strike in and stop. Over the years, bag makers have added a variety of options including hybrid bags that include a thick, hide-like material over the airtight membrane. This gives the bag a solid feel under the arm and provides for better starts and stops.
Synthetic bags have a reputation of being easy to maintain. In my experience, that is a true statement. The primary task is making sure that the bag is airtight. As with any bag, you should check your bag on a regular basis. With a synthetic bag, that starts with a solid "tie-in."
Tying in a synthetic bag is a straightforward task. Even the earliest synthetic pipe bags were equipped with rubber collars for the drone stocks and this feature has changed little. For the drone and blowpipe stocks, use a touch of dish washing liquid. Swab a bit of it on the inside of the collar with your finger. Insert the stock into the bag and press it into the rubber collar. Cup the rubber collar between your thumb and index finger and press the stock into the rubber collar with the palm of your other hand. You should be able to feel the tie-in groove slip into the seat of the collar. You can verify this visually by inspecting the joint. You should see the base of the collar seated in the tie-in groove. After you have verified that the stock is properly seated, use a dry cloth and wipe off the excess dish washing liquid from the stock.
The chanter stock can be problematic, just as with a standard hide tie-in. An airtight tie is crucial. To start, stretch a rubber O-ring in the chanter stock’s tie-in grove, then position the stock in the neck of the bag. This O-ring will create the needed airtight seal against the bag. Make sure that the O-ring is perpendicular to the neck of the bag, then mark it’s position with a piece of tape. This will provide you with a reference for the hose clamp that typically comes with your bag. Another optional step might included cutting a 1-inch width of bicycle tire tube and stretching that over the tie-in groove and O-ring before slipping it into the neck of the bag. This will insure an even tighter seal. Place the hose clamp over the O-ring and then tighten the clamp. As you tighten the clamp, smooth out the skin so that it doesn’t develop any folds. A fold in the skin will provide a channel for air to escape. If you're feeling ambitious, and are not a fan of the metal clamp, a normal tie-in with standard cord is also possible at this point.
Once tied in, a synthetic bag will not require seasoning. But, any bag, and synthetic bags are no exception, will need to be checked regularly for air tightness. In my experience, the first spot that you should check is the chanter stock tie-in. If you are using an O-ring and a hose clamp to tie in your bag, make sure that the O-ring is perpendicular to the neck and ensure that the hose clamp is centered over the O-ring. Often, you can cure a leak around the chanter stock by tightening the clamp every so slightly. If you inflate the bag and listen, you can often hear the air escaping and as you cinch down on the clamp, you can hear the leak close.