I have been restoring many old flutes for Lark in the Morning lately, so I thought I would share a few observations, do's and don'ts. If you have an old instrument that needs repair or restoration, I recommend finding a competent repair person to handle the task rather than doing it yourself. Finding a competent repair person isn't easy, however. The lot of most wind instrument repair persons is repairing band instruments of the grade or high school variety; they may not be aware of your instrument's historical setting, higher quality (say you have a Rudall and Rose), or they may not be familiar with working on dried, old, brittle wood. You might contact the local symphony organization or a local early music group to find where their members send instruments for repair. There might even be a baroque flutemaker living somewhere nearby who could recommend someone for the task. You can always contact Lark; we may be able to repair it for you, or know of someone in your area. If you do decide to work on your instrument yourself, I recommend the following approach.
First: Find out all you can about the instrument's history and where it was made, etc. This is so you can assess the instrument's possible importance and value. For example, you have a flute made by Rudall and Rose that is in fair condition, but the keys are all there, it has a few cracks and the cork is missing. In your research, you could learn that Rudall and Rose was a highly respected 19th century firm that made flutes of the highest quality. You may decide that your lack of experience in repairing flutes merits taking this instrument to someone who has worked on a Rudall and Rose. However, say you have a German flute stamped Sears and Roebuck (believe me, they do exist). If the repairs don't seem that extensive, you might gain some satisfaction by repairing it yourself. The crucial point is to be aware that if you have a very rare and possibly very valuable instrument, please don't run the risk of ruining it by attempting to repair it yourself unless you have the appropriate expertise.
Second: There are three basic principles I use when restoring instruments. These are always foremost in my mind when I look at work that needs to be done.
1) Any repair work done should be reversible if at all possible. Some future restorer may come up with a brilliant way to repair something. Make it easier for him/her by making your techniques possible to undo. Realizing that those who may come after us may know more than we do is a healthy attitude.
2) No alterations to make the instrument "better than the original" should be attempted. A major problem in restoring old flutes has been their poor intonation. Some of this is because someone else tried to adapt the instrument to changing pitch standards, or tried to get a bigger sound out of it, without any awareness of the physics of the instrument. The result was commonly poor intonation, lack of balance, and worst of all, poor response.
3) All repairs to be done, especially if radical, should be undertaken only after sufficient practice on test pieces, or, as is the case at my shop, a junker instrument. For instance, I had one flute in the shop that played excellently, with the exception that the bottom notes below E were very sharp (70 cents or more). Before I extend the instrument by grafting additional wood onto the lowest tenon area, I did a dry run on my junker flute to determine if it would work structurally. The repair was very successful, and I avoided a few mistakes by working on the test piece. Had I made those mistakes on the flute, I would have ruined it.
Third: Have all the necessary tools and equipment on hand. This, fortunately prevents most of us from being too eager to work on our treasures. Most people don't have a fully equipped woodwind turning shop in our garages. Some of the repairs I will describe don't require this; some, like the tenon graft mentioned above, do.
I would like to say a word about Superglue. Although it, and the acetone used to unglue it, is very poisonous to work around, it is commonly the restorer's best friend. I use two kinds, one with very high penetration and low viscosity, and one with gap filling properties and higher viscosity. Both are available at hobby shops, where I recommend purchasing them. The ordinary hardware store varieties just don't seem to work as well and are much more expensive. DON'T BREATH THE STUFF and avoid getting it on your body, anywhere.
The most common problem with old flutes is checking or cracking. Most of these will be minor and local. Some will extend the length of the joint, usually the headjoint. One will often find old cracks that have been pinned along the length. I avoid pinning, although I have a word to say on that matter, shortly. Most cracks can be dealt with and rendered stable by simply filling with a small bead of superglue along the length. It is a good idea to mask the surrounding wood with masking tape beforehand, or you may have an additional problem. Go slow and glue a small section at a time, rather than the entire length. You will breathe less glue this way. It will also leave an unsightly dried bead of Superglue that can be worked off with a xacto knife (be very careful not to cut into the wood), scrapers or tiny files, and lastly, fine sandpaper. I recommend leaving the glueline, as filing and sanding will require that the area be refinished, which I will discuss later. Problems also occur when the cracks are in the sockets or tenons, across holes, keyblocks, or the blowhole. Then it is best to seek some advice or help. Some cracks, such as at tenons, may be made strong and stable if the surfaces to be glued are painted with a dilute solution of baking soda water, which makes the Superglue stronger. Tenons with many cracks require radical treatment: if they are not too thin they can sometimes be turned thinner and an overlay of matching wood may be applied. Sockets crack because the tenons fit too tightly (the cork lapping sometimes swells if it isn't greased well), and sometimes require pinning. If pinning is to be done, I select the spot(s) where pinning will be most effective. For pins I use hardened brass wire (from hobby shops) glued in with penetrating Superglue. I try to make the pin shorter than the hole and I tuck it in so that the ends don't show. The holes can then be filled with Superglue and wood dust made from lightly sanding the area glued, or better yet, from a scrap of the same wood. I do not recommend pinning if you have had no experience at it.
If keyblocks are split off and missing, new ones may be fashioned from matching wood and glued on. Drilling pin holes is very delicate work, however, so I won't discuss it much here. If the original blocks are present, glue them back on after painting both glue surfaces with the baking soda solution and allowing it to dry. Sometimes they will still come loose; in this case, the pieces need to be reinforced with pins glued to the body and the block. If metal posts are loose they can be glued back in place (after careful realigning) and will hold well if their bases are packed with dry baking soda.
Perhaps the biggest source of frustration with old flutes is leaks. If there is a leak anywhere, the lowest notes will be weak or will not respond at all. Mickie suggests finding headjoint leaks by immersing the headjoint in water and blowing through it (seal the blowhole with your finger) and this works pretty well, especially if you don't immerse it too long. Leaks come from many sources, usually cracks, ill fitting pads, springs that don't work (usually solved by rubber bands) and a variety of other subtle causes, such as loose tenons, old tenon grafts where the glue dissolved away, etc. Sometimes, oiling the bore is all that is necessary. Old pads may sometimes be rejuvenated by applying olive oil. Sometimes, the pad seats are dirty and require cleaning with a fine brush. Most of these repairs will be obvious and/or annoying. There should be no leak at the headjoint cork. Sometimes cork greasing is all that is necessary. The obvious course to correcting a leak is to eliminate it. Sometimes repadding is necessary. If this is all that is to be done, a regular repair person may be able to do it effectively and without risk. Sometimes the pads and seats are fine, but the keys work sloppily. Shimming the sides of the keyblocks with very thin brass is an old and effective remedy, as well as the less effective but more common rubber band.
Cosmetic defects are sometimes best left alone. Some scratches and nicks may be sanded away or filled with Superglue. If there are areas that are sanded, such as crack repairs, they will appear dull or matte compared with the rest of the instrument, which was varnished. French polishing with seedlac solution and lots of oil (almond or mineral) works well; a violin maker or repairer may be able to offer some help with this. The goal is to attempt to match the original varnish.
If your flute has intonation problems, DON'T attempt to modify it. That is my best advice. If there is an isolated sharp note, you can, of course, flatten it by adding a little wax to the hole. Usually, intonation problems result from improper cork positioning, leaks, which must be dealt with first, or previous tampering. Some notes were commonly tuned flat as compromises, such as the low D on many London made flutes. I have raised the pitch of these by adjusting the height of the c# and c keys. On many flutes used in Irish music, these keys will be missing. A radical method which I have successfully used has been to alter the sounding length by shortening the next to last joint, but this I do only if there is no alternative and the instrument does not belong in a museum.