Whilst the craft of sax repair undoubtedly consists of a motely collection of arcane skills, unusual tools and noxious potions, there are a number of highly effective techniques that are nothing more than plain old-fashioned houskeeping - and if there's a surefire way to rejuvenate a grubby old horn it's to give its crook ( or neck ) a really good clean.

It really doesn't take long for crud to build up in this part of a horn, but no matter how fastidious you are with mopping the thing out you can't really do much to prevent scale forming - which shows itself as little whitish grey deposits. Even if there isn't any scale there's often a film of grease and fat and assorted other nasties that get left behind after a normal clean out.

So here's a safe and simple way of restoring a bit of sparkle to the bore of the crook - and thus to your tone.
You'll need a few items over and above water and detergent:

• A bottle of ordinary malt vinegar
• Something to bung the end of the crook up with ( a cork, blu-tack, tape, clingfilm etc. )
• A small screwdriver
• A crook brush ( a small, round brush on about a foot of flexible wire )
• Key oil
• A pipecleaner
  

Vinegar is ideal for this job. It's a weak acid - just about strong enough to soften or dissolve calcium carbonate ( scale ) and weaken the grip of fats and grease, but certainly not strong enough to do any harm to the metal or the finish on the horn - at least not unless you have a spare couple of weeks and a great deal of vinegar. It also acts in an anti-microbial fashion and is an effective agent for reducing the risk of contamination from the various bugs that thrive in the warm and wet environment of the crook's bore.

The first thing you'll need to do is remove the octave key.
I could say that you could get away with leaving it on - but there's going to be a lot of water and vinegar floating about, and as the rod screw and possibly the flat spring ( and certainly the spring retaining screw ) are made of steel it's well to get these items out of the way.
It's very simple, just undo the screw and pull it out ( you might need to use a pair of tweezers to pull it out - if you have to use pliers, cover the jaws with a piece of card or tape to prevent them scoring the screw ).
The key will probably pop off under the power of the spring...just lift it free of the crook by dropping it down over the crook tenon ( the bit that fits into the horn's body ). Don't worry about the cork - nothing we do is going to harm it.

You now have a 'bare' crook.
As this process is about removing the really stubborn crud that builds up inside a crook, it's a good idea to clean out whatever stuff you can to better allow the vinegar to get where it's needed.
Pop a drop of washing up liquid into a cup of warm water and, using the crook brush, give it a good scrub out - really work up that lather! I find it's worth slooshing the crook through with warm water first and letting it stand for ten minutes or so to really loosen up the crud...or you could just play the horn for a while, and kill two birds with one stone, so to speak.

You now need to stop up the mouthpiece end. I use a small cork, which is ideal if you have such a thing lying around, but if not you'll just have to improvise. You can use a large lump of blu-tack, or plasticine...or even a potato or piece of apple! All you really need is something that's going to be watertight for half an hour or so. Clingfilm might work, but I find the vinegar often seeps out over the cork and leaves it smelling a bit.
Likewise, the octave key hole needs to be blocked up. Blu-tack is ideal for this, but you might get away with a piece of tape or clingflim. Don't push the blu-tack right into the hole, it'll make it harder to get it all out later.
Here's one I did earlier...

What you need now is a sufficient quantity of vinegar to fill the crook.
If you're frugal like me ( or just a plain cheapskate...or the sort of person likely to curse me when you find yourself looking at a fish supper...and no vinegar ) fill the crook up with water, then tip the water into a cup, then tip the water out and replace it with that amount of vinegar.
If it's tenor crook you're doing, tip the mouthpiece end down a little...the bend in the crook can form an airlock which prevents the crook from filling properly ( makes a nice 'gloop' sound as the air pops out ). If you're vinegar-rich and don't want to faff around, about quarter of a bottle should be enough for the job.

If you really want to go the whole hog you can warm the vinegar before pouring it into the crook. I find this helps the cleaning process and speeds it up. For lacquered crooks I wouldn't heat the vinegar to anything more than 'hand hot'...i.e. you can place a finger in the heated vinegar and hold it there with no discomfort.
For plated or bare crooks ( or plain not that fussed ) you can take the vinegar higher, say about the temperature of a cup of tea. Don't let it boil though...it'll stink your house out, and I don't want you running the risk of scalding yourself when you come to fill the crook ( you'd be surprised how quick the metal will heat up...and if you're holding it, it's gonna hurt ).

While the vinegar's heating, consider how you're going to prop the crook up. It's got to stand for about half an hour and hold the vinegar in, so you need some way to support it. I have a very special tool for this - it's called 'a plate'. Yep, I just pop the pillars up on a plate and the crook sits there quite happily. Tenor crooks will need a slightly steeper angler because of that air gap ( two plates ).
I'd advise doing all this in the kitchen sink - if the whole lot takes a tumble on a table you'll have a cupful of vinegar to mop up, and the smell really lingers.

So, fill the crook with the vinegar ( hold it by the mouthpiece cork if using hot vinegar ) and pop it down to rest.
I generally find that half an hour is ample with warm vinegar, for cold vinegar it's nearer an hour.
Check on it every so often ( to make sure it's not leaking out, for a start ), and give it a bit of a shake to sloosh it all up. Don't worry too much if the vinegar doesn't come right up to the lip of the crook tenon, you can always wipe this part over later if necessary, but it's unlikely to be that gunged up anyway.

When the time comes to pour out the vinegar you might like to pour it into a cup. There's no real reason for doing this other that it might give you a small sense of satisfaction as you note just how dirty the vinegar looks ( certainly works for me! ).
Remove the stopper, and remove whatever stuff you have sealing up the octave key hole. It's worth running a pipe cleaner down this hole now, as there's likely to be residues in the tube...and perhaps even bits of blu-tack. Do this again just before you pop the key back on, just to be on the safe side.
Knock up another cupful of warm water with a little detergent added and give the crook a jolly good scrub out to remove any residues and any remaining vinegar.
Shake it out, dry the outside and then leave the crook to fully dry out.

Refitting the key is easy enough - poke the tenon through the 'ring' of the key and lift the key up and over the crook...being careful not to let the spring scratch the crook surface. The crucial part is to ensure that the spring seats on the little channel on the top of the crook. If the spring is loose, tighten up the screw a little ( it's only small, so don't overdo it ). Doesn't hurt to wipe the spring over with a little oil to help prevent it rusting...and pop a small drop of oil on the rod screw before you refit it. If you have a spare pipecleaner, clean out the key barrel beforehand...and give the screw a wipe too.
When fitting the rod screw, don't force it if it seems stiff - chances are you haven't got the key barrel aligned with the pillars. Give the key a jiggle whilst gently pushing on the screw. When everything lines up the screw should just slide in. Screw it up snug, and you're done.

If there's one drawback to this method it's that the extreme tip of the crook might not get cleaned, due to the bung preventing the vinegar reaching it ( though I generally find that some vinegar always manages to seep right to the end of the tip ). You can either wipe a little vinegar in the tip before you pop the bung in, or you can coat the last centimetre or so of the mouthpiece cork liberally in vaseline and simply up-end the crook in a centimetre of cold vinegar for half an hour or so.

If the job's been a success you should be able to see that the bore of the crook is nice and clean. It won't be bright and shiny ( as I I said as the start, vinegar simply isn't that powerful ), but it should be free of those whitish/grey deposits.
If not, repeat as necessary!

If you really must leave the octave key on I'd advise thoroughly wrapping it up in clingfilm, being very careful with the washout procedure, and leaving it wrapped until the last washout is complete...and giving the screw and spring a good oil afterwards, just in case.