old Conn metal question

[GC]

I recently acquired a Conn monster Eb that was made in 1925. It seemed to be made of yellow brass, but some of the corrosion spots have a red core. I thought it might be red rot, but after shining a flashlight down the bell I found that the yellow brass plating ends about a foot and a half down and the lower interior of the bell and the bottom bow are red brass.

It looks to me as if the horn was made of red brass and given a coating of bright (at one time) yellow brass. Is yellow brass over red brass likely to be something that Conn did at one time, or is it probably something done later by one of the owners? The horn is unusually resonant and mellow, and I attribute the sound to the red brass body. Why cover something like that up?

[imperialbari]

I tend to doubt your interpretations of your findings. Aside from a few specialty horns made out of nickel silver, most old brass instrument were made out of sheet brass adhering to the respective national standards for military cartridge metal. The Boosey & Hawkes shop foreman around 1980 told that the absolutely worst of these standards was the one of the US. And that was the exact reason why US made trumpets and trombones had a superior sound.

I have two Conn sousaphones from before 1930 and one from 1946. The older ones have the more punchy and resonant sound.

I have seen red rot, but not in anything but spots. The red colour covering larger area that I have seen is rather a certain honing component, that I don’t know the name of. It occurs, when the instrument was no thoroughly cleaned before being shipped from the factory.

I never heard of anything being plated with brass. I am not even certain that is technically possible.

Klaus

[Donn]

I have seen red rot, but not in anything but spots. The red colour covering larger area that I have seen is rather a certain honing component, that I don’t know the name of.

You could be thinking of rouge, a reddish abrasive mineral.

I have a 1926 Conn (actually Pan American) Eb tuba with yellow plating that extends 12 inches (measured vertically) into the bell and then ends abruptly, but it's gold, not brass, common with silver plated instruments of that era.

[imperialbari]

Yes & yes!

I hage heard the term rouge in this context, but din’t remember it when writing.

My old Conn 40K is gold plated over silver plate. The gold is thin and it is pale, where the silver shines through.

Klaus

[GC]

I'm trying to keep an open mind here, but I don't think you're correct in this case. There is no silver on this instrument, nor is there a spot of lacquer anywhere. The plating does not look like gold, either. It has the characteristic yellow brass look, and gold does not make corrosion spots like this horn has in the outer plating. The bright yellow coating does not scratch easily like gold does, either. Wherever the holes go through the yellow outer layer, there's red underneath. Wherever I've Simichrome-polished away the corroded spots, there's red underneath. Inside the bell where the bright plating ends, the metal is distinctly reddish. Looking inside past the bell to the interior of the bottom bow, it's red.

It might be that the red is rouge, but why would it be underneath yellow plating? If it actually is rouge, how would I test it?

When I first began to look up this topic, I came across a picture of a red-brass Conn monster Eb from the same general era that had been restored, polished, and relacquered. It was an utterly gorgeous instrument. Of course now that I'd like to find the picture to put a link in this post to show that red brass Eb's do actually exist, I can't find the picture again. #!&*%!@%

[Wyvern]

As can be seen on video of the tuba for sale, tarnished brass can have a red appearance viewtopic.php?f=4&t=36994

I have been mistaken into thinking tarnished yellow brass is red brass. I think that is what you are also doing

[Matt Walters]

Actually, I have seen with my own eyes many older Conn, King, and York brass instruments that have a more redish hue than standard C26000 "Cartridge brass, 70.0 Cu, 30.0 Zn" horns have.
According to "Machinery's Handbook 25" (Earliest copyright 1914 and I know more recent versions have been published.), The list of uses for C26000 does not include musical instruments.
However, C24000 "Low Brass, 80.0 Cu, 20.0 Zn" has listed "Excellent cold workability. Fabricating characteristics same as C23000[Red brass]. Uses: battery caps, bellows, musical instruments, clock dials, pump lines, fliexible hose."
Some earlier American made horns were built with C24000.
Heck, I know for a fact of a Holton bell that looks to be mostly C26000 with a big "V" notch seam of redish C24000 or C23000 in the flair area. I think it is very possible that a bell of that era have a bell flair that was yellow brass with the stack being low brass.
I've not seen your horn up close, but I can also imagine that tarnish over Low brass (as someone else menetioned) could seem like yellow brass over red brass. When my York CC is tarnished, it looks all yellow brass, but when I polish it up, you can clearly see the difference between the low brass bottom bow and the yellow brass bow guard I put on it.
Ever wonder why there are so many great old American horns surviving in great shape when newer ones don't? Could the alloy have something to do with it?

[Donn]

It might be that the red is rouge, but why would it be underneath yellow plating? If it actually is rouge, how would I test it?

Wouldn't spend much time on that hypothesis.

Of course now that I'd like to find the picture to put a link in this post to show that red brass Eb's do actually exist, I can't find the picture again.

I think what's called for here is a picture of your tuba, showing the phenomena you're trying to describe.

[oedipoes]

Yellow brass can corrode in a way called 'dezincification'.
The zinc in the alloy will move away, the copper stays behind, in the same physical shape but more porous than the original brass.
This is called 'red rot' and will lead to leaks in the brass instrument.

For larger areas of 'red' appearance, I think Neptune points in the right direction.
Also my old kaiser showed large reddish areas of tarnished yellow brass. (see picture below)
After much polishing, it disappears, an I got the shiny yellow back.

Just my thought.

Wim

[oedipoes]

picture after polishing

[Paul Scott]

Martins (or at least parts of them) were made at one time with the Low Brass (80/20) that Matt mentioned. It appears that they used low brass for the slides and slide crooks and possibly yellow "cartridge" brass (70/30) for the rest. Perhaps the thinking was that the slide parts should be more resistant to rot. I had a very small piece of a '36 Martin analyzed at a local foundry-this piece came from the first valve slide. It was found to be "low brass" with traces of antimony and lead. One of the engineers felt that the antimony might have been added to further reduce the chance of rot. You can definitely see a reddish hue in the slide crooks.

And yet I have a Martin catalogue from about 1919 that states, (capital letters are in their copy):

"MATERIAL-We use TRUMPET or YELLOW BRASS in all horns. This is very much harder to 'work' or 'form' than RED or LOW brass, requiring about 1-3 more time and labor. This means of course great increase in the cost of production, but we have the satisfaction if knowing we have a PERFECTLY FINISHED and HARD SHELL with an absolutely SMOOTH INTERIOR, the whole resulting in that perfect RESONANCE for which our Instruments are noted."

Funny twist on things, when now we tend to think that more copper is better!

[iiipopes]

Traces of antimony, lead, selenium, tin etc., were probably not added, but were the results of impure smelting or refining of the copper and zinc. After all, remember the purpose of "low brass" or "cartridge brass": made as cheaply as possible because it was expendable. So not a lot of time was put into the front end of the refining process.

The side effect is that these traces are exactly what make the brass superior from a brass instrument perspective, and for banjo rings as well.

[Ken Herrick]

I can not recall the specifics now, but back in 63, at Interlochen, Rex Conner was talking about variations in minor element composition of brass used by different makers at different times with varying amounts of lead and tin in the alloys. A couple percent of either could make a considerable difference in the workability and finished hardness of the brass and cause a considerable difference in sound. He said the old Beuscher he was then playing had a different alloy to what was in general use. I recall a very old Beuscher sax I once rebuilt seemed to also have a much harder than normal brass. Carl Geyer also said one of the things which made his horns different to others was a non-standard brass alloy.

One of the first times I visited Schilke about 65 his shop foreman, who had worked for HN White (King) said that in the 20s & 30s they and York were using an alloy which was not in general use and that Schilke was also using a non standard alloy which, as I recall, had some lead and tin in it. Ren also said a few times that his brass alloy was "different".

There are of course many factors, such as work hardening from drawing, hammering, and spinning, polishing, annealing, and tempering which can affect the final state of the metal and its affect on the sound of the instrument.

It would be interesting to cut a piece out of one of the CSO Yorks and have it met tested and compared with what is in other instruments!

Considering that tuba bells tend to be made of two or three pieces it is not too surprising that there could be variations in composition to make spinning easier.

[UDELBR]

I bought a sweet looking old Conn off That Auction Site several years ago, intending to do some Frankensteining on it. Once it arrived, I was dismayed to see the condition of some of the interior bows:





I asked several of the gurus here: most plausible answer to my ear was that back in that era (100 years ago) quality control on brass alloys wasn't what it is these days, and an occasional wonky batch would be produced. Apparently all repairmen see this kind of thing from time to time.

[Ken Herrick]

Looking at Joe's sousy makes me wonder about a possible, at least partial, cause for some of the failures. First, in the assembly stage, there is all the heat applied to solder everything together, then all the linishing and polishing and possibly shot blasting for frosted silver plate, then acid dipping etc. prior to plating or lacquering. And all that after the brass has been bent, hammered, annealed, tempered. hydraulicly expanded, etc. in the parts fabrication stage. Makes one wonder how the metal survives at all.

Think I'll go have a libation while I ponder the ramifications of the torture brass goes through to become a tuba - often only to be tortured even more by the people who own them.

Be KIND to your tuba - it's been to hell and back even before you got it!

[Rick Denney]

Pursuant to the original post: Surface dezincification is mostly harmless. It results from brass that is heated (significantly, but not necessarily to annealing temperatures) and cooled, and also as a matter of age. The result is a reddish surface that disappears with buffing.

Red rot is when dezincification happens from the inside out, creating pinholes and perforated sections in the brass. Red rot requires replacement of that part. Some alloys are much more resistant to perforating dezincification than others.

On the subject of cracks: Brass, like most metals, gets harder and more brittle as it is cold-worked. As you press it into shape, the grains of the metal align. That makes the metal stronger, but also more brittle. Metal that has yielded too many times will fatigue and break, just like bending coat-hanger wire back and forth repeatedly. Each time a bow is crushed and straightened, the metal work hardens, particularly at the spots where the creases are flattened out. This causes a pattern of brittleness through the brass. Often, metal that is overworked will crack, but not visibly--the crack will be on the inside surface or within the thickness of the metal. It takes some time for the crack to propagate, with repeated loadings, to the visible surface. Those cracks can also provide good spots for corrosion and dezincification to take hold, allowing the cracks to propagate even more quickly.

Preventing such failures is why metal is annealed, sometimes repeatedly, when it is being formed. Annealing heats the metal enough so that the grains diffuse into each other, but not so much that the metal actually melts.

Metal that has been hand-hammered, with successive annealing processes, probably has less internal residual stress than metal that was formed all in one process (just ask anyone who has tried to weld to an engine's oil pan, only to have it twist into a pretzel as soon as it got really hot). Shot-peening, contrary to expectation, and unlike sand-blasting, actually allows the metal to yield microscopically, removing a lot of residual stresses that can cause cracks to form and propagate later.

So: Surface dezincification is no big deal and polishes off easily. It is more a sign of the history of the environmental exposure of the instrument than anything. Cracking is not a sign of anything except excessive work-hardening leading to high residual stresses and brittleness that combine to promote fatigue cracking.

Rick "who imposes a strict no-sandpaper rule when having tubas repaired" Denney