I have often had confused customers coming in to IFS looking for cork grease for their flute. And I end up confusing them even more when I tell them it isn’t recommended!
Cork grease is meant for….you guessed it, corks! And modern flutes do not generally have corks. (We do carry it for piccolos, which often do have corks.)
However, it seems logical to add lubricant when two metal pieces that are supposed to fit smoothly together no longer do so. In fact, this is the case for many brass instruments. But flutes are different.
The reason cork grease isn’t recommended is because the tenons (joints) of the flute are very closely fitted by the manufacturer. Unless something causes the tenon to go out of round or it gets dirty, the tenons should fit together very well without any type of lubricant. Adding grease can actually hurt the flute over time. Grease can trap small particles that will grind into the metal every time you put together and take apart your flute. This can wear down and scratch the tenons, requiring repair.
If the tenons are too tight, wipe them down using an untreated cleaning cloth. Be careful not to swipe the edge of the nearby pads on the body and footjoint when you do this as it can cause them to tear. You can also dampen your cloth slightly. In the past I have used damp paper towel for this since sometimes you will end up with a bunch of green or black stuff on your cloth. Yuck!
If the tenons are still too tight, bring it into your repair technician. Same goes for the opposite problem. If the tenons are too loose, bring it in. If you are in the middle of rehearsal and your footjoint goes flying off the end of your flute (trust me, they’ve seen it all in the repair shop), you can put some scotch tape on the tenon as a quick fix until you can bring it in to the repair shop. Scotch tape is not a permanent solution though as it doesn’t seal perfectly.
(On a side note, never grab your assembled flute by just the headjoint. If the tenons aren’t fitting properly you may end up with just a headjoint in your hand and the body of your flute on the floor! Instead, pick it up or hold it by the barrel. This is just below where the headjoint fits in and often where the manufacturer’s name is engraved.)