Any flute can very slowly go out of adjustment as cork, felt and leather compress and as pads wear, shrink and expand due to changes in temperature and humidity.Additionally, the headjoint cork can shrink over time causing air leakage by the headjoint crown.
Lots of small leaks on several keys are often not as readily apparent as one large one, yet they still affect the response, pitch and focus of the tone almost as much as one big leak. As these problems can creep up over time, they are not as easily noticed so the flutist tends to compensate by pressing harder and/or changing their embouchure. Many times they are unaware that there may be a problem with their flute and assume that the problem is with themselves.
There are a few techniques that you can use in order to determine if your flute is playing up to its potential or not.
A. Checking for pad leaks. The first thing that you can do is visually inspect the pads. Look for tears or spots where the pad has worn through. A flashlight can help with this. Sometimes you can see a small spot of white felt the size of a pin head showing through. That is a leak! Also inspect the pads as you press the key cups down to the toneholes. On professional flutes we seal leaks as narrow as .001″ (one thousandth of one inch) which are very difficult to see with the eye alone. So if you are sure that you can see a leak just with your eyes, then it is probably a fairly large leak as handmade flutes go. Most pads have a ring on them which is dust that collects as the pad is pushed down against the tonehole over and over again. When you are inspecting the pads for leaks with the pad pushed down against the tonehole be sure that you don’t mistake this circle of dust as a leak. The next test you can perform is while you are playing long tones on the flute. Using a very light touch push the keys down very slowly. If the pads are very level and sealing well the tone will “pop out” just as the pad hits the tonehole. If there is a small leak, the tone will start shallowly and will be unfocused as the first part of the pad hits the tonehole, then the strength and focus of the tone will increase as the pad is pushed harder and the remaining portion of the pad hits the tonehole. Using this technique may take a little practice.
A note of caution: Many flutists use cigarette paper to clean their pads by putting the paper between the tonehole and the pad, pushing the pad down and pulling the paper out. Over use of this technique will cause wear and tear on the pad skins. We once saw a 6 month-old flute with virtually every pad worn out because the flutist thought she was doing a good thing by cleaning her pads everyday. For more information on how to clean your pads, please refer to the article, How should I clean my sticky pads?
B. Checking the headjoint cork for leaks. Dip your middle finger in water and place it over the embouchure hole. (The water is to seal the cracks between your fingerprints.) Place your mouth on the open end of the headjoint (the tenon that fits into the flute body). Create a partial vacuum in the tube by sucking on the tube. It usually takes 4 to 6 sucks to remove most of the air. If there is a good seal of the headjoint cork you should be able to maintain the partial vacuum for at least 6 to 8 seconds. If there is a significant leak in the headjoint cork it will be difficult to form suction for more than a second or two. If this is the case you will need a technician to install a new headjoint cork.
C. Bent keys or tubes. Any time that you bend your flute tube or keys, you can be sure that you will have a leak.
D. Lost Motion. Don’t confuse lost motion with a leak. A flute can be in good adjustment as far as the notes coming out clearly, yet the instrument can still have “lost motion”. An example of lost motion would be the following: When you press the A key (2nd finger left hand) the upper B flat key goes down with it. When lost motion exists the upper B flat key does not move exactly at the same time as when you press the A key, but just a 32nd or a 64th of an inch later. This may seem like a small thing, but it makes the action of the flute seem sloppy and imprecise, yet it is not a leak as long as they both hit their toneholes at exactly the same time. The lost motion can be removed by a flute technician.