Lead Tubing in Spool Box
By Bruce Clark
In response to Michael Amoroso's question about lead tubing on an Ampico drawer and the possibility of corrosion from inside out, there is a good possibility that it could be deteriorating. The first stage is pinholes. (Notes or controls receive the wrong signal.) The second stage are sections that crumble. Test it out. Cover the tracker bar with masking tape, and test each tube for leaks.
There is also a possibility of it being in good condition and lasting another 70 years. If you test it and do not find any leaks, keep it as is. If leaks develop in a few years, it is not a monumental job to replace the tubing at a later date.
Over the years, I have treated the inside of the lead tubing with shellac, but this is very tricky, and has to be done with great care and speed. Otherwise any remaining shellac would set up inside the lead tubing and block it permanently.
The amount of lead deterioration seems to depend upon the level of air pollution which may have traveled through the tubing over the years, or the possibility of differences in quality in different batches of lead. I have seen some that only deteriorated in one small area, but the rest was in good condition. It seems where the original lead was coated with shellac, there is no deterioration. The corrosion occurs where bare lead is exposed to air. (Sometimes)
Another puzzlement that I have seen is lead elbows connecting supply tubes. The same piano can have very good lead elbows, and some very bad ones. Others have all bad or all good elbows. Perhaps it depends upon the formula used to produce the lead? Different batches produced different longevity? I have had good luck in saving partially deteriorated lead elbows by dipping them in shellac.
New lead is not the easiest to work with, but it can be done. I have also seen lead replaced with neoprene, which has worked out nicely, and made the drawer of the Ampico much lighter.
Lead tubing was originally sealed with burnt shellac. Epoxy is a definite no.
Bruce Clark
Tuner from 1946 to 1996 |
(Message sent Sun 2 Mar 1997, 13:36:31 GMT, from time zone GMT-0500.) |
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