The grenadilla wood that is used for making clarinets really will not absorb bore oil. Many people feel that oiling a wooden clarinet is totally useless, and certainly, using the wrong oil is a bad idea. I don't think it is possible to prove that oiling will reduce the likelihood of the instrument cracking.
However, I still oil the instruments I recondition. I take off the keys and oil the outside and inside of the instrument, including inside all the tone holes. I always oil the bore at least twice. The reason I do this is:
So, bottom line, oiling the bore is a good idea. Oil the outside if the wood begins to appear dull and dry. You don't really have to take the keys off to do this as you will only really need to oil the surfaces that show. If your pads are of the traditional bladder type, avoid getting oil on the pads.
I recommend that oiling should be done once per year. A newly reconditioned clarinet that was previously stored for many years may need 2-3 oilings in the first year of being played regularly again.
What oil should I use to care for my wooden clarinet?
I now use Bore Doctor, sold by Doctor's Products. See the subpage for more on this.
Do not use petroleum based oils.
I previously used apricot oil from Pakistan. The reason was simply that my daughter and son-in-law work there. They bought a recorder there for me, and the maker recommended using this oil. I have found that it has nice qualities: It is not as heavy as the purified linseed oil and soaks in better. And it smells delicious while I am putting it on. But it does harden like many other vegetable oils, and this will clog the pores of the wood. This is what makes the oil sold by Doctor's Products is better.
Do NOT use linseed oil that is thick and smelly, or the kind that is used for finishing furniture! This will ruin your instrument!
You can find some good discussion on bore oil at the ChiffandFipple Flute message board. (This is a message board about Irish flutes, many of which are made of wood.) See the subpage article. It is probably not a good idea to use purified linseed either!
What about waxing clarinet wood?
My source for oil linked above also sells a very special wax. Doctor's Products recommends using both IF you are using their wax. Using normal car or furniture wax is not a good idea. See Dr. Omar's advice on this on this subpage: The Doctor's view on Oiling vs. Waxing
Discussion about waxing can be found at woodwind.org. If you search that forum, I'm sure the topic has come up multiple times.
Extreme treatment: In depth article promoting oiling using organic, vegetable based oils: Life Everlasting for a Good Clarinet, by Larry Naylor. In my [philpedler's] opinion, this is over the top.
Oiling the key mechanism
Please, please do this once or twice per year. One doesn't use bore oil for this! Any light oil will do, like 3-in-1 oil, or sewing machine oil. I like to use a blunt syringe for getting into tight places. (Computer printer re-inking kits often include these.) Oil the keys in the crack between the post and the key, wherever they move. This not only keeps the keys moving freely, but it also prevents the screws from getting rusty and stuck.
Valentino pads are not degraded like traditional pads, but you don't want to leave moisture in your clarinet to mold and smell!
DON'T use those thick 4 inch square swabs made of artificial chamois.
Muncy Winds has nice silk clarinet swabs. I like these because they don't get caught inside the upper joint, and they are efficient so that only one time through is usually enough. Just make sure that the trailing end of the swab does not enter the horn folded up, where it might get snagged by the tube of the register key.
A great alternative is to dry out your clarinet more like most flute players do. Get a nice big man's handkerchief or bandanna, and use a chop stick or small dowel to push it through.
When you are done drying your instrument, it is best to NOT put the wet cloth inside the case. You want to allow the horn to dry out and don't want to trap moisture inside the case.
In some very dry climates, some people like to leave a humidifier inside the case.
DON'T use “Pad Savers”!
They are really Pad Destroyers. Pad Savers are fluffy rods that one is supposed to insert into the clarinet after playing. I think the problem comes from students (always in a hurry after band) not swabbing out the clarinet first. Then the Pad Saver traps moisture in contact with the pads. You want the clarinet and the pads to dry out after you play. For best results just swab out the clarinet, and let the remaining moisture dry out naturally.