This page is about looking after 19th century original flutes. http://www.mcgee-flutes.com/flutecare.html
All woodwind instruments require the same general care. Given that care, there is no reason why they should not be in perfect playing order in another few hundreds of year’s time. The rules are simple:
Always mop out your flute thoroughly after playing. Otherwise, the moisture from your breath will soak into the instrument and cause it to crack or raise corrugations in the bore. Mopping also polishes the bore, preventing the build up of roughness and ridges that weaken the tone.
Prepare a piece of absorbent cloth (old T-shirt material is good) that will just pass through the narrowest part of the flute. I find a strip about 250mm (10") long and 75mm (3") wide about right. Attach this to the end of your cleaning rod.
Mop out the foot joint and body sections first, as these tend not to be so wet. No point in distributing moisture from the headjoint throughout the rest of the flute! When you mop out the headjoint, fold the cloth back over the tip of the cleaning stick to get right into the corners near the stopper. Twist the rod both directions to remove as much water as possible.
If your flute has a metal tuning slide, remove the slide from both the headjoint and body and mop any moisture out from the ends of the tenons and the insides of the sockets. This is important as the endgrain of wood soaks moisture up very quickly.
What happens if you don't clean your flute. This cork stopper was taken from a German flute whose owner admitted he never bothered to clean out after playing.
The cork of the stopper can be seen as the dark brown patch on the right hand side. On top of that is a cracked crusty layer of something organic - probably based on Guinness. On top of that is a vibrant growth which clearly enjoys the lifestyle. There was more but it came off in the battle to release the stopper from inside the head. The inside of the head was lined in similar accretions, the flute now plays considerably better with them gone.
Treat a new flute gently. For the first week, limit your playing to sessions of about ten minutes in duration. Mop out the flute and give it a rest to dry out for a few hours. Slowly increase length and frequency of playing over the next few weeks.
If you're playing for a while, it's a very good idea to mop out every 30 minutes or so. Preventing the build-up of moisture achieves two things. The flute is less likely to be damaged and it is easier to play and sounds better.
If possible, leave the instrument's case open after mopping out. This allows the remaining moisture to evaporate.
Never leave the instrument in a hot place, such as a car, mantelpiece or window sill. This invites cracking.
Regularly oil the bore with proper bore oil (not vegetable or machine oils). I use and recommend LeBlanc's Bor-seal, available from most music stores or me. Oil the flute each week for the first month, then each month for the first year. After that, twice a year should be enough.
Prepare a small piece of cloth for oiling your flute. I find a piece about 75mm (3") by 40mm (1 1/2") useful. You will find that until the cloth is saturated in oil it tends to rub off as much oil as it applies. For this reason, I recommend soaking the piece in oil and consequently keeping it in a small plastic sealable bag. Otherwise you will find your supplies of oil diminishing quickly and you won't be really sure whether you are applying enough.
The bore must be quite dry before oiling, and a few hours or preferably a day should then elapse before the flute is played. Strip the flute down to its component parts, removing tuning slides and stopper. If you have keys, either remove them or slip pieces of plastic sheet (or cling wrap) under the pads to prevent contamination by the oil.
Attach the oily cloth to the end of your cleaning rod (try to minimise skin contact with bore oil - you don't want your pores sealed). Squirt a little bit of oil into the bore of the flute and use the cloth to distribute it uniformly throughout the bore. The bore should glisten with the oil, but there should be no blobs or runs forming. If the bore doesn't look wet, add some more oil.
Because endgrain of wood absorbs water so easily, make sure to oil any endgrain areas where moisture might gather. Examples include the bottom of the sockets and the ends of the tenons (the parts that plug into the sockets). If your flute has a metal tuning slide, this applies to the ends of the tenons that plug into it.
Do this in each section of the flute and set it aside to dry. Pack your piece of oily cloth away in its bag and store it with the oil. Carefully reassemble the flute when the oil is dry, remembering to reset the stopper to the correct position as shown on the other end of the cleaning stick.
The outside of the instrument can be oiled with bore oil applied with a cloth. Buff off any excess oil with a soft cloth. You can also use furniture polish.
Do not leave the instrument assembled for long periods. This compresses the tenon cork, requiring the cork to be replaced earlier.
Use cork grease on the tenon corks as soon as you detect any sign of resistance when assembling your flute. Keep the cork grease with the flute so that it's always available.
For best results, massage the grease into the cork with your fingers. Grease the inside of the socket too. If resistance persists, seek attention from the maker as the socket wood might have swollen and could jam.
If a joint becomes loose, have the cork replaced by the maker or a qualified woodwind repairer. As an interim measure, you can wrap some waxed dental floss around the joint. Do not use cotton thread as this can swell with moisture and jam the joint.
If a joint jams, do not attempt to force it. Leave it for a few days without playing. The swelling should go down. If jamming persists, seek attention from the maker.
The rings on the flute sockets are not just decoration - they are vital to preventing the thin socket wood from splitting. If a ring comes loose, do not assemble the flute, but seek attention from the maker or a qualified woodwind repairer.
Dirt building up inside tone and embouchure holes can affect tuning and tone. Do not use anything harder than soft wood to remove it. Be especially careful of damaging the edge of the embouchure hole.
Be careful while cleaning or oiling not to damage or dislodge the cork stopper in the head-joint. You can check the position of the stopper by inserting the cleaning rod up the head-joint backwards. With it touching the face of the stopper, the mark engraved near its end should appear centrally in the embouchure hole. (This assumes that your cleaning rod is calibrated for a conical flute and not a modern cylindrical flute. The mark should be 19 mm from the end of the rod.)