maintenance for brass reeds

[Wolf Molkentin]

Hi everyone,

 

as I‘m owner of two very different brass-reeded instruments I have two concerns:

 

Could I attempt to improve the voicing (top of the line Wheatstone reeds in particular, only one or few) without taking the risk of breaking the reed?

 

Could I add solder (by heating the reed from underneath, as usual)?

 

Many thanks in advance - ?

[David Hornett]

Solder weighting:

 

I believe 'brass' reeds are really phosphor bronze. I have tip weighted phosphor bronze reeds with solder, however have always used a heat sink just below the solder point so any excessive hear does not alter the reed's temper. I don't know if a heat sink is necessary, but just play safe. The heat sink is a shim of brass bent back on itself to form a small clip that is interference fitted over the reed tongue just behind the solder point.

 

david

 

 

[Wolf Molkentin]

Hi David, thank you for the advice!

 

As to the heat sink I opted against it when weighting a lower reed for the first time, as it might increase the amount of heat required to get the solder melting.

 

My son told me that non-steel springs shouldn’t be tempered as the carbon of steel would be missing. He only mentioned the melting point, which should not be within the reach of any soldering iron.

 

But I take it from you that on the reeds mentioned the solder appears to have been applied to the „brass“, which would be good news.

 

Any experience with correcting the voicing / setting of those reeds?

 

Best wishes - ?

[David Hornett]

Hi Wolf,

 

When heated, non-ferrous metals soften, the temperature for this to happen is dependent on the alloy. In fact, I believe non-ferrous alloys, such as brass, gradually harden at fluctuating low ambient temperatures, and also by working / moving the metal, called work-hardening (such flexing also causes non-ferrous metals to break more easily, e.g., reeds and springs). Copper and brass pipes when submitted to fluctuating ambient temperatures (around engines / water pipes) will become brittle and split, rather than swell, as they would in an unhardened state when first installed. This site may explain this more clearly: http://www.totalmateria.com/Article71.htm 

 

So, some ferrous materials can soften if heat is applied, even below what would be the normal tempering heat, and the copper-based ferrous metals conduct heat very rapidly. It is my understanding, but I cannot recall from where this was sourced, that if a length of metal is reduced in size along its length and heated at one end, the reduced section will get hotter than the non-reduced section because more heat is carried through the reduced area. If I am correct in this, the the thin belly area of a reed will get hotter than the reed tip if it is thinner in cubic cross-section than the tip, but I could well be wrong, as I cannot remember the source. But this is why I use a heat sink, just in case.

 

I hesitate to suggest any ideas on voicing. I use the same technique as on steel reeds: hold the middle down and gently raise the end, then take the pressure off the middle and flip the reed to see where it returns to. I am certain though, that others may disagree with this method (I am very interested to hear how other members do it). With 'brass', if the point of natural resistance is passed it is the same as work hardening and there is a good chance the reed will one day break at the point this has occurred.

 

(Other members may be clearer on this, I have always read Dana's contributions with great interest. I studied metallurgy when I was 17,  52 years ago, youth and the passage of time could well have modified reality.)

 

As a point of interest, I purchased a 'brass' reeded Lachenal EC on eBay some years back and no fewer than 4 reeds were broken, only one at the root, the other 3 at the tip. I have never seen a steel reeded instrument in this state.

 

David

[Wolf Molkentin]

David, thank you so much for your insightful and in-depth considerations. With them in my mind I felt ready to take the risk of cautiously lowering the gap for three slow-to-speak reeds to a satisfiable degree. The reeds are of high quality, nevertheless there are three steel replacements on the side I‘ve been working on. Time will tell, and I‘ll keep working rather carefully.

 

Soldering might happen tonight...

 

All the best - ?

[Wolf Molkentin]

so it’s hooray - after having improved the voicing where unavoidable I weighted the two Ab reeds down to the F - everything was straightforward as with steel reeds, with the exception of the scalpel work to reestablish the clearance, as brass (or phosphor bronze) would probably not withstand the steel blade - so I chose the (extra carefully applied) file for that step of the work too.

 

thank you once again David, your replies - beyond providing certain knowledge- assured me of not planning to do a totally loony or undefensible thing!

 

all the best - ?

[ttonon]

"I believe 'brass' reeds are really phosphor bronze."

 

David, I'm interested whether this is true.  If anyone else can provide reliable information, I'd appreciate it, because I just posted a file that shows calculations comparing brass and steel tongues, and I assumed brass reeds are the common alloy 260 brass.  However, there's not too much difference in the pertinent material properties between brass and phosphor bronze, though I should know what the true situation is.  Thanks.

 

Tom

[ttonon]

"It is my understanding, but I cannot recall from where this was sourced, that if a length of metal is reduced in size along its length and heated at one end, the reduced section will get hotter than the non-reduced section because more heat is carried through the reduced area. If I am correct in this, the the thin belly area of a reed will get hotter than the reed tip if it is thinner in cubic cross-section than the tip, but I could well be wrong, as I cannot remember the source. But this is why I use a heat sink, just in case."

 

David, from how I understand what you mean, you are wrong, unless the Second Law of Thermodynamics is wrong.  When the tip of the tongue is heated, there will be a monotonic decrease in temperature down to the riveted end, and heat will flow in that direction, as well as outward to the surrounding air.  If the belly of the tongue would get hotter (higher temperature) than parts closer to the tip, heat would flow backward, against the Second Law.  Heat flows down a temperature gradient, like water flows downhill.  I do however think it's safer to provide a heat sink, because of the annealing affects of elevated temperature, as you mention.

 

In my edit, I add:  The idea that "more heat is carried through the reduced area" is erroneous.  Heat flow is determined by 1) the conductivity of the material, 2) the temperature gradient, and 3) the cross sectional area of the part.  All three of these are multiplied together.  With a reduced area, less heat flows, restricting the heat flow that tends to cool the tip.  If you maintain the same total heat flow with the soldering iron, the consequences are that the temperature of the tip increases, increasing the temperature gradient, and increasing the heat flow through the thin section so that a new equilibrium is reached.  It's the same with water flow in a pipe a reduced section of pipe does not carry more water flow, it only serves to increase the pressure upstream of the restriction.

 

Tom

Edited June 13, 2019 by ttonon
Add a paragraph.

[David Hornett]

Hi Tom,

 

Thank you for replying concerning reduced belly size in transmission of heat, I was very unsure when i made the comment. (But even so i would still use a heat sink just in case.)

 

I was much more sure of phosphor bronze, although I need to explain.

 

1, I replaced the non-steel reed tongues in a 'brass' reeded Jones concertina with steel a few years back. The replaced reeds were not the yellow of brass, but the more ruddy colour of phosphor bronze which I had become familiar with when repairing high end chromatic harmonicas, Hohner CX 12 (note one Hohner site gives these reeds as 'brass', another as 'phosphor bronze'; they certainly have the latter's colour)

 

2, A few years ago i also tuned a Lachenal, which had the same ruddy reeds.

 

3, But, after your above comment i went back through my collection of old reed pans, and yes, to my surprise I found Lachenal reeds which were the ruddy hue of phosphor bronze AND others which were the yellow of brass, and some german silver, so quickly learnt not to generalise.

 

Below I have images of these reeds clipped over a clock spring -- although the colouration did not show as well as I had hoped on the photo, the difference can still be discerned:

 

From left to right: Hornett steel reed, Lachenal German silver, Lachenal brass (alloy shoe), Lachenal 'phosphor bronze', overlaid with Jones 'phosphor bronze'

 

??

 

All the best

 

David

[ttonon]

Hi David, thanks for the info.  I can see the color best I think in the second photo, and I agree that the second and fourth tongues from the left are probably not brass.  The third is surely brass.  Interesting.

 

Tom

[Wolf Molkentin]

throughout the same colour and thus not that significant, here‘s a shot of some Wheatstone „brass“ reeds, responsive and rather loud, but nevertheless with the clear bell-like tone (which I‘d hesitate to describe as just being „mellow“) in the higher range I am familiar with from my (very quiet) George Case...

 

possibly true brass here?

 

best wishes - ?

[ttonon]

5 hours ago, Wolf Molkentin said:

possibly true brass here?

Yes, that definitely looks like brass to me.  Thanks.

Tom

Edited June 16, 2019 by ttonon

[d.elliott]

A little bit about metallurgy, setting aside the super sophisticated super-alloys,  only steels can be hardened and tempered, a process which takes carbon in and out of solution in an iron based crystal matrix. Brass is copper matrix with zinc, Bronze is copper with tin plus stuff, including phosphorus. Brass/ bronze can only be annealed by heat (softened) usually from anything around 400 C  upwards subject to composition. Copper alloys cannot be hardened by heat.

 

The only way to harden these copper alloys is by work hardening, rolling, cold drawing, cold forging. when I make brass reeds I buy rolled strip ten beat it down to section. Think of a cloth bag which has been filled with marbles (small glass balls) you can get hold of the bag, squeeze it and the balls will slide around inside, changing it's shape with little or no effort, now smash the cloth bag with a hammer shattering the marbles inside, and then try to squeeze the bag to move its contents and change it's shape. The splintered  glass shapes will lock up on one another and oppose any forces applied. When metal is first melted and cast, it's crystal structure is fairly globular. it is soft and easily bent. when it is cold worked, the crystal s get all broken up and resist deformation.There is also age hardening

 

If you are weighting reed tips to deepen their pitch you need to keep the strength in the reed 'belly' which is doing all the bending and springing work, whilst adding mass to the tip to slow the flexing down. Brass is like it's parent metal copper, extremely heat conductive a heat sink is essential otherwise the spring in the reed will become compromised. A high temperature soldering iron coupled with low melting point solder plus heat sinks to protect the working part of the reed.

 

There is age, or precipitation hardening of copper alloys, which seems to be a factor in fatigue failures. 

 

I have also noticed that some reeds are redder than others, at first I thought of phosphor bronze, and I read that this was the case, however I doubt it, the first patents of experimental pho- bronze metals was around the 1850, commercial availability in a usable form would be much later. I think we are just seeing a stronger concentration of copper in the brass alloy, but I have no means of proving now I am retired.

 

Dave 

 

 

[ttonon]

5 hours ago, d.elliott said:

when I make brass reeds I buy rolled strip ten beat it down to section.

Hi Dave, thanks for the descriptions.  Why do you cold work it?  I understand that brass usually comes in annealed, half hard, and full hard, sometimes with quarter hard increments, depending on how much cold working the material has in manufacturing.  To me, the manufacturer did a useful thing to provide material with definite properties that are probably uniform and consistent. What's the advantage of doing your own work on it?  Can you make a full hard material stronger by cold work?  Won't it start producing cracks?  Why buy a grade less than full hard?  Beating implies hammering, which suggests a rather crude method.  I suppose that if you have your own precision roller, you can avoid that, though still, why not use material with strict specs?

Best regards,

Tom

[d.elliott]

Hi Tom,

I simply want to get as close as is sensible to the final section, I take the remnant under the reed clamp as a guide, an ensure that I get the maximum amount of work into the structure before I start filing it away.

 

Different types of cold working have different different 'signature' crystal deformations. Rolling and drawing are not deep compression, that is most of the work is in the outer skin of the section, obviously thin section are pretty good. Forging by a GFM machine is not as good as by press, which is not as good as a hammer in terms of shocking and shattering the mid section structure. Admittedly my professional experiences were to do with ferrous alloys or super alloys, but I think that by following my path I am giving my reed the best shot of longevity. 

 

Half Hard & full hard are grade bands, I don't know the working history of what I have, and hardness seems to be as much graded by tensile yield rather than indent, but on checking annealed brass is about 90 HV; a full peak hardness at a 60% section reduction is around 183 HV, a mid range, half hard partial anneal or temper is around 110 HV.

 

Anyway banging away with a hammer 'beats' (sorry about the pun) tedious filing any day. I may be a bit cracked, but I have not experienced the problem of cracking in the stock. Is this cold working metallurgically necessary? I cannot test it, but it is both satisfying and can do no harm, an insurance? 

 

Dave

[ttonon]

Hi Dave, I understand.  You illustrate the difference between "hand-made" and "machine-made," and I don't mean those labels in the way used by Italian and Chech reed makers, but in the more general sense.  Before my questioning, I looked at it from an industrial perspective, but you have many more variables available "at hand," treating the fabrication more like an art.  Your cost is time, but hopefully artisan work such as yours can continue to be something people are willing to pay for, of course because of the superior result.  Thanks for the detailed info.

Best regards,

Tom

[Wolf Molkentin]

@d.elliott, thank a lot for your insightful explanations!

 

I‘d now like (need) to bring forward the other part again:

 

The brass reeds of my model 6 are, as mentioned, exceptional IMO: loud and clear with a good dynamic range and a beautiful tone.

 

Only issue is that some reeds, especially in the lower register, are a bit breathy, thus slower-to-speak at low pressure. What I seem to have observed is a tendency to improve on that when engaged frequently, but that wouldnt last.

 

I have already cautiously re-voiced some reeds in the middle of the range. As for the lowest reeds, there are already a few steel replacements, and I have mused about failed attempts to re-voice them being the reason for that.

 

So would the advice be to let these (brass) reeds alone and play the instrument in its present state (which would surely be an option), or try to set them (as they are indeed a bit high altogether) in a strictly cautious manner?

 

Many thanks in advance / ?

 

Edited June 24, 2019 by Wolf Molkentin
added info re current setting, model Nr corrected

[wunks]

Aside from the metallurgical considerations above, is it possible that when playing you subconsciously settle in to a generally uniform attack whereas the less frequently visited lower register requires a slightly different focus to sound well?  Put another way, are these reed anomalies an artifact of a some what "one size fits all" approach?.......?