 The Clarinet BBoard
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Author: john gibson
Date: 2003-04-07 00:58
Alright....
I keep having to have MPCs and tenons re-corked. They shrink and become wobbly. What the heck gives with this? I'm in Phoenix Arizona so maybe it's lack of humidity. What can I do to keep them "swelled" up so I don't have to keep paying for a re-cork? Can I soak them in water or something? This is getting old.....thanks for your answers....
John
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Author: Mark Charette
Date: 2003-04-07 01:16
john gibson wrote:
> Alright....
> I keep having to have MPCs and tenons re-corked.
John,
Have you tried any of The Doctor's Products? The Doctor has spent a considerable amount of time working on this and other problems. He's a sponsor, and I'll bet his stuff would help. Check his website at http://www.doctorsprod.com.
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Author: Henry
Date: 2003-04-07 02:12
Do you have a record of when the new corks were put on? When they are put on in relatively dry periods, the corks (and the tenons) should not shrink when the humidity picks up. To the contrary. On the other hand, when they are put on in relatively humid conditions, you may run into the problems you describe when the humidity goes down. Gordon (NZ) probably will have a sound opinion on this. Are you there, Gordon?
Henry
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Author: BobD
Date: 2003-04-07 15:27
Just a thought: On a new cork pre-treat it with paraffin wax. Rub it in real good to seal the cork.
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Author: jenna
Date: 2003-04-07 18:51
You could just throw a little dental floss or teflon tape on them to buy some time and prolong spending the money right away. I do this when I need a quick fix or don't have the money/time for a repair... so what if it looks a little funny? It gets the job done.
jenna
Post Edited (2003-04-07 19:51)
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Author: Gordon (NZ)
Date: 2003-04-07 21:31
1. Are you leaving the clarinet disassembled when not in use, so that the cork has a chance to 'recover'?
2. Are you using an unsuitable cork grease? Almost every product on the market is unsuitable. Some attack the structure of the cork, such that it loses its resilience. Some dry to leave a thick layer between the cork and the tenon socket, hence squashing the cork far more than it needs to be squashed when the joints are assembled. (another writer suggested paraffin wax for sealing. IMHO this does the same thing) Use Doctor's Products. These are excellent greases and seal appropriately.
3. Are you sure it is the cork? Most wobbly conditions are caused by too much difference between the diameter of the tenon TIMBER and the diameter of the socket. The difference should be no more than about 0.16 mm (0.006") I solve this by fitting silver caps to either or both ends of the tenon.
4. Is your technician fitting the corks too loosely - perhaps a result of matching to an in inappropriate cork grease. This needs experienced judgement in that before the grease is first applied, the joint should be almost impossible to assemble. After the grease is first applied it is difficult to remove more cork.
5. Is the tenon cork groove very deep - over say 1 mm? In this case a layer (say 0.5 mm) of far less resilient material should be glued on before the cork is. I use agglomerated cork (also called Hycotex, Rubco, Gummycork, Techcork, etc) Otherwise natural cork has too much 'give' for this application.
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Author: beejay
Date: 2003-04-07 22:23
When this happens to me, I soak the cork in a small glass of water for 30 minutes. That usually takes care of the problem.
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Author: Dan Shusta
Date: 2003-04-07 23:22
Something you might want to consider...I have Valentino synthetic cork on all of my personal clarinets...no problem with shrinkage or expansion and it seems to be impervious to whatever kind of cork grease I use. When properly installed, it lasts practically forever.
I am so pleased with this product that I would never go back to natural cork again.
Yes, it's that good. I hear that even Clark W. Fobes uses it on his repairs.
Just my $0.02 worth.
Dan
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Author: Gordon (NZ)
Date: 2003-04-08 02:05
Personally I have been very disappointed in Valentino cork for tenons, as it seems, have most technicians. It just does not have sufficient resilience - it compresses and stays compressed more than natural cork does, perhaps hardening in the process.
A newly available material that may be the best synthetic to date is a black material being marketed by Kraus. So far I have found it fantastic as a silencing material where there is a slapping action. e.g. on E/B key and the F/C crows foot. (I now use 7 quite different soft materials on clarinet mechanisms, each with special attributes for each application)
However I am reluctant to experiment on customers' tenons so far. No doubt a manufacturer will soon be using this and I can evaluate, as has happened with the Valentino product.
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Author: L. Omar Henderson
Date: 2003-04-08 17:42
With natural cork the trick is to keep it hydrated and the cubic cell walls of the cork cells swollen so that they maintain compression and rebound potential. One way is to seal the surface but with the irregular surface characteristics this is hard on a permanent basis. Another way is to impregnate the cork with natural plant oils which bind water tightly (Disclaimer - I sell a natural oil containing cork treatment). The energy of dehydration (moisture gradient from wet to dry) is not exceptionally great but over time it can remove a lot of water and cause the cork to shrink. With a sealant component and binding of water tightly by natural plant oils the cork is >100 times more resistent to dehydration (my calculations from experimental data). Petroleum greases will seal the surface but over time the cork cell walls collapse due to replacement of the natural oils with the petroleum grease and the cork will stay compressed and shrink. The proper plant oils could also be applied to the cork to retain water within the cork. Cork can be rehydrated and expand (if the cell walls have not fractured) but without an outer sealant or a buffer or reservoir within the cork, water is again easily lost due to dehydration and the cork will shrink. These shrinking, swelling cycles can also lead to premature failure of the cork function of compression and rebound.
The Doctor
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