Here's a related question: what exactly is acid bleed? Is it a reaction between the solder flux and the lacquer? Or can it happen on a sax with any sort of finish (even unlacquered or silverplated)?
My understanding of acid bleed is that it is due to residual solder flux that is insufficiently rinsed (perhaps trapped in little voids in the solder joint) before lacquer application. Over time, it diffuses from the joint, causing the brass to corrode and this, in turn, causes a failure of lacquer adhesion (why the lacquer flakes off). Plated horns get much more serious hot chem dips before plating that presumably cleans the flux better; also the plating is intimately bonded, and has anti-corrosive properties, as well as the fact that the solder does not get plated. This latter is different than the lacquer which effectively seals the corrosive material.
Does anyone know roughly how long it takes for flux beed to manifest? Is it usually fairly soon after lacquering, or is it possible that the process would begin long afterwards?
It can start appearing at least a couple of years after the causing event. It would be possible for flux to be trapped in a pocket within the soldering, and gradually corrode its way outside the soldering after quite a bit of time, and then start its visible manifestation - dark corrosion of the brass beneath the laquer.
I'll add that it's certainly possible to have this type of reaction on unlacquered brass, and it takes quite a bit of elbow grease to get this type of corrosion off of the brass.
Thanks Gordon. So unless my tenor was either resoldered at some point, or relacquered within its first couple of years, the lacquer's likely original. Huh.
I don't see acid bleed as any indicator of original lacquer or re-lacquering.
It is an indicator of flux (or other corrosive material) trapped at some time beneath lacquer.
I don't know much about acid bleed, but in terms of durability, the finish on my two silver-plated vintage tenors ('39 &'49) has held up far, far better than the lacquer on my more recent (mid '60s) mark VI. Maybe modern lacquers are better now?
The answers already said are correct. It is due to the flux on the body tube not being properly cleaned / degreased / prepared for lacquering.
I've never seen "acid bleed" on any plated horns. So therefore, it would have to be the reaction of the flux with the lacquer. Not exactly sure what chemical reaction is happening though.
It's corrosion of the brass beneath the lacquer. The lacquer just helps it to spread more, by capillary action, trapping the flux against the surface of the brass, beneath the lacquer, as the products of tarnish progressively lift the lacquer from the surface of the brass. Eventually the detached lacquer can peel away, leaving the corroded bare brass.
[All from my not-totally-infallible perspective and experience.]
Thanks for all the replies. Based on the pics simso provided, I'm starting to doubt whether the tarnish I'm seeing around the tone ring is acid bleed after all, and not simply the dark spots that are apparently common on vintage Bueschers.
Meanwhile, it's either amusing or a bit creepy that I just received an email from Amazon recommending an album by the sax quartet Flux. Coincidence?
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