Reed "feet"... I Mean "tongues"

[JimLucas]

I just re-examined the reeds in that Jeffries with the Madras label on the (original Jeffries ) leather case,  and they definitely are odd, as I remembered.  Has anyone seen similar Jeffries reeds from the Praed St. period, or know of different steel being used in instruments that were to be brought to India?

Has anyone ever done rigorous chemical and/or crystallographic analyses of the materials in various different reeds?

 

Of course, we don't want to cut up or dissolve good reeds, but I believe non-destructive methods exist... e.g., neutron or x-ray diffraction for the crystal structure and neutron-activation analysis for the chemical composition. (I believe the latter is how they learned from one of Napoleon's hairs that he had been poisoned with arsenic.) I have no idea if these methods are commercially available, nor what they might cost if they are. But perhaps somebody with connections to a university with a well-equipped physics, materials science, or even archaeology department might be able to interest them in such a project. (Ph.D. thesis, anyone?)

[JimLucas]

I just re-examined the reeds in that Jeffries with the Madras label on the (original Jeffries ) leather case,  and they definitely are odd, as I remembered.  Has anyone seen similar Jeffries reeds from the Praed St. period, or know of different steel being used in instruments that were to be brought to India?

I don't know about Jeffries, but I've noticed several entries in the Wheatstone ledgers for instruments with "non-corroding" or "tropical" reeds. I don't think those are the exact words used, and I don't have time to dig for them now, but that's the import. Besides, the wording isn't always identical, but the idea is the same.

 

Unfortunately, there's nothing to tell us about the detailed composition in those cases... unless we find one and analyze it.

 

Hmm... does anyone here have access to period catalogs/price lists of such things as spring steel? E.g., I wonder if a clockmaker's supply catalog might list special non-corroding spring metals. If so, there might even be some information regarding composition, though maybe not. I wish I had the time right now to attempt that kind of research.

[Dave Prebble]

Hi,

 

You will have noticed I am sure that on steel reeds the underside of the reed very often retains its original blueing and shows markedly less evidence of rust than the top of the reed. This blue colour is a thin coating of a particular type of ferrous oxide which is chemically fairly stable and occurs as a result of the steel tempering process.

This oxide does much to protect the surface and preclude the formation of an altogether more invasive form of oxide we know as rust.

This oxide coating principle is put to good use in the bluing of gun barrels scientific and engineering instruments and the like.

The top of the reed generally has most if not all of the original coating removed when the reed is filed to shape and in subsequent tuning activities and is thus more vulnerable to rust attack.

 

There are 'paint on' chemical compounds available, known not surprisingly as 'Blueing Compound', that can be bought from Clockmakers or restoration materials suppliers. I have use this material to excellent effect on the restoration of antiques but as yet have never got round to experimenting on reed tongues though I feel sure that there is every likelihood of significantly increasing the corrosion resistance of reeds in situ.

Maybe one of you out there has already tried this or could be tempted to a little experimentation on some old reeds??.

 

I am reasonably sure that the process could be carried out on the tops of the reeds after final tuning but reed bottoms may prove a little more difficult. The thickness of the coating would be measured in microns and thus not materially affect the mass distribution along the reed.

 

If you do try this, read the safety precautions most carefully and adhere closely to the simple but essential safety precautions advised. These compounds generally contain complex cyanide salts and must be treated with due respect.

Blue the steel..... Not yourself!!!

 

Regards

 

Dave

Edited November 30, 2003 by Dave Prebble

[Paul Groff]

Jim and Dave,

 

Thank you for this information! I had heard of these "tropical" concertinas (I vaguely remember a reference to waxed woodwork and metal-cornered casework), but I wasn't aware there was written documentation that the reedtongue steel might have been changed as well.

 

I am neither a metallurgist nor a concertina maker...One of the makers could probably tell us much more about choosing, hardening, tempering, and otherwise treating steel for reedtongues. I found Geoff Crabb's article elsewhere on this site really interesting. In many Lachenal and Wheatstone reeds, blue (whether a natural "blueing" or painted coating) is visible on the underside, but many if not most Jeffries and early Crabb reeds seem to be a silver or straw color beneath. Some of the very early Lachenal steel reeds are also this color. I have figured this reflected less tempering (reheating to reduce the brittleness) of the steel after hardening, thus a stiffer material. But I have not tested this scientifically.

 

The reedtongues in the Jeffries that went to India are mirror-shiny silver on the underside and brilliantly bright on the upper side with the file marks from reducing and tuning. There is none of the typical rust-spotting or dark staining found on almost all reedtongues this old, despite the fact that the pair of tiny steel bolts of each reed have typical surface rust. As it happens, a couple of tongues were broken when I got the instrument (in unrestored condition) and another broke during the time I and my customers have owned the instrument. This tongue material may be a little less durable than the standard Jeffries steel, which rarely breaks unless really abused. Or the problem could be related to the fact that a few of the reedtongues had been flipped upside- down in their frames by some tinkerer in the distant past! (Colin Dipper mentioned that this practice was some kind of misguided fad that spread among concertina owners or amateur repairmen long ago) Still, 90% of the reedwork is dead original and that was enough to restore the rest. I have put aside the broken tongues and Jim can test their composition when he goes back to graduate school.

 

I believe I can hear a very slight difference in tone with at least one of the replacement reeds, but this may not be attributable to the steel the tongue is made of; other variables may also be different.

 

Paul

Edited December 1, 2003 by Paul Groff

[Dave Prebble]

Hi Paul,

 

I think you have the right idea now regarding the temper colours left on reeds by different makers. My suggestion regarding chemical blueing was as a possible means of increasing the corrosion resistance of the upper face of the reed where the original oxide film left by tempering has been removed by filing leaving areas more vulnerable to rust attack

 

Not everyone's cup of tea I am sure but just in case anyone out there is curious to understand a little more about reed steel, I have added below a, hopefully correct ;-) and understandable explanation of how hardening and tempering works.

 

The hardening and tempering process for carbon steel (from which spring/reed steel is made) is really a method by which the crystalline structure of the steel is altered and managed in order to strike a balance between hardness and brittleness suitable for the use to which the steel will be put..

 

When steel is heated to cherry red colour (approx 1500deg C), the crystalline structure alters to form Austenite If, however, it is cooled suddenly by quenching in a bath of oil, a new crystal structure, martensite, is formed. This crystal form is characterized by an angular needle like structure with a very high hardness.

 

While martensitic steel is extremely hard, it is also extremely brittle and will break or chip with the slightest shock. Furthermore, internal stresses remain in the material from the sudden high temperature quenching and these will also tend to lead to fatigue failure. Tempering relieves these stresses and causes a partial decomposition of the martensite into other crystalline forms called ferrite & cementite. The amount of this partial phase change is controlled by the tempering temperature. The tempered steel is not as hard as pure martensite, but is much tougher.

 

So to produce material suitable for reeds the steel is first heated to cherry red and is then cooled very quickly in an oil bath. This gives a very hard but brittle material. In this state it would be almost impossible to file with normal tools and would have a very short life due to it’s brittleness.

 

The material is then heated slowly up to a tempering temperature somewhere between 450 and 600 deg C. As the steel is heated some of the martensite changes to ferrite and cementite and the hardness decreases but the material gets tougher. At any given temperature in this process, the particular crystalline nature and its degree of toughness/hardness, can be permanently fixed in place by rapid cooling in a quenching bath.

 

As the temperature rises, the surface of the steel undergoes some spectacular temperature specific colour changes. These are due to the formation of different complex oxides of iron which fortuitously are different in colour.

Starting at around 400 deg a straw colour appears which changes through light and dark brown, browny purple, light and dark purple and eventually at around 575 – 600 deg the familiar ‘blueing’ often seen on the underside of reeds.

 

In order to allow proper heat distribution and the dissipation of internal stresses, the material is held at the required temperature for a period of hours before being quenched to ‘lock’ the required crystalline structure in place

It follows that at this higher temperature, more of the Martensite is converted and the blue reed material is significantly softer than straw colour material. It will also be significantly softer and easier to work.

 

This would also tally with Paul’s comment that early Crabb and Jeffries reeds have a straw like colour….. they are notoriously hard and hence difficult to file.

 

What the exact relationships are between brittleness, hardness and ‘springiness’ or indeed how these might relate to the sound produced by a reed I cannot say.

 

Hardening and softening of brass can also be carried out by heat treatment. I am somewhat less sure of the details of the processes but, for what it is worth, here goes….

 

When brass is heated to a particular yellowy/orange colour (best viewed in semi darkness) and then allowed to cool slowly, the brass will harden significantly. ( the exact opposite to steel you may note)

If the brass is heated to this temperature but is cooled rapidly, it will anneal or ‘soften’ the material.

 

The process is repeatedly used during the process of making brass instruments and the like since, as brass is hammered, it becomes harder and, you’ve guessed it, more brittle. If work were not stopped periodically to anneal the brass by heat treatment, the brass would split under the hammer.

 

I have also heard that, sometimes, completed instruments ( Not Concertinas !!! ) are also cryogenically treated at very low temperatures to relieve and distribute the internal material stresses built up in the forming processes. This is said to give a much rounder and fuller tone to the instrument. How this works I have no idea.

 

If you wish to try hardening reed sized pieces of brass remember their surface area is high in comparison to their mass and they will tend to cool rapidly…. The exact opposite to what you want to achieve.

One tip is to preheat a block of steel to a similar temperature, place the heated reed on the block and cover it with some form of heatproof insulation. Rockwool mat or similar) This should allow for the desired slow cooling.

 

If you have made it to the bottom of this post and not dozed off, I am both flattered and impressed.

 

Regards

 

Dave

Edited December 1, 2003 by Dave Prebble

[JimLucas]

I have also heard that, sometimes, completed instruments ( Not Concertinas !!!  ) are also cryogenically treated at very low temperatures to relieve and distribute the internal material stresses built up in the forming processes. This is said to give a much rounder and fuller tone to the instrument. How this works I have no idea.

I read an article just this past week claiming that it "works" by the placebo effect. Specifically, it said that a rigorous experiment had just conclusively demonstrated that there was no measurable difference after such freezing, but that "if people believe it will sound different, they will 'hear' a different sound." Unfortunately, I can't remember where I saw the article, and a search hasn't succeeded. Maybe it was in one of the newspapers I saw while I was in England. I remember the article as being in English, not Danish.

 

...heatproof insulation. Rockwool mat or similar

"Rock wool"? Isn't that another name for asbestos?

[Dave Prebble]

Hi Jim,

 

Likewise, I can't remember where I came across it either......must be some sort of brain / age embrittlement process affecting our temper

 

I must admit that it seemed perhaps a little unlikely to me as I would have thought that the lower the temperature reached, the less the likelihood or even possibility of any phase changes in the material taking place. I did wonder, however, if it could be in some way a product of the contraction and subsequent expansion in the metal as it went through significant changes in temperature.

 

I added this snippet to my post as a point of interest others might care to follow up just for the fun of it. Certainly can't think of any makers who have cryogenic facilities tucked away in the back room!

 

It did occur to me after making my last posting that I ought to have added that there are wide variations in the composition of the many types of 'carbon steel' available today each formulated to give properties suited to specialist applications, including I have little doubt, corrosion resistance. Each of these steel grades will have it's own special hardening and tempering regime to produce a range of different hardness/stiffness/brittleness properties.

 

Due to this range in types of steel, though the principles I set out will apply in general, direct comparison between temper colours of reeds should only be considered as a 'rule of thumb' guide. Laboratory hardness testing would be the only way to truly assess the properties present in particular reeds

 

Regard

 

Dave

 

Sorry Jim, I forgot

Rockwool is simply glass fibre wool similar to that used in loft insulation.

Since fibre sizes are in the same order as those found in asbestos, do wear a dust mask and gloves and treat with some respect

Dave

Edited December 1, 2003 by Dave Prebble

[Richard Morse]

...heatproof insulation. Rockwool mat or similar

"Rock wool"?  Isn't that another name for asbestos?

Rock wool is insulation made from furnace slag (from basaltic rock and recycled steel mill waste) which is steam expanded/blown into a spinning chamber, which pulls the lave into fibers (much like cotton candy). The fibers are then packed together into a mat, cut into batts, or fiberized into loose fill....

 

Rockwool contains no asbestos. Slag wool is similar but contains no basaltic rock. Fiberglass is made from glass.

[Ken_Coles]

The cryogenic treatment does have some current faddishness among trumpet and horn players I know of. Sort of like the fad for very heavy trumpet mouthpieces. It may make a tiny difference, but the accomplished players I respect the most consider this sort of thing a detail and put more value on practice, etc. That hasn't prevented a small industry from appearing.

 

Squeeze, and blow, on.

[Sandy Winters]

****Reed "feet"... I Mean "tongues", you know, what goes inside the "shoes

 

I put my foot in my mouth on many occasions (in fact it is a favorite activity) but I've not considered putting my tongue in my shoe. Perhaps if the shoe was cyrogenically treated first. :-)

[ttonon]

Dave,

 

I believe the hardening and tempering temperatures you state are correct numerically, though they should be expressed in degrees F, not degrees C.

 

Another comment is that the apparent color of thin films is not descriptive of the material itself and more likely due to the interference of light waves bouncing off the front and rear surfaces of the films. This is true for any film with thickness on the order of the wavelength of the impinging radiation. This color is not well related to the color of the bulk material (large amounts of it). Although I haven't read much about the films on heated metal, I believe these concepts mean that the blue color represents a certain combination of tempering time and temperature; i.e., those conditions that grow a film of the thickness range that presents a blue color. Other tempering conditions will produce film thicknesses suitable for yellow, and so on. Many people in the thin film industry accurately judge the thickness of deposited film by their color, and I believe the correlation between thickness and color is independent of the film material, provided that the material is reasonably transmissive. Another point is that the thickness/color relationship is periodic, since the perceived color depends upon interference; thus, films with thicknesses of even multiples of the wavelength in question will produce the same color. A thickness limit is reached where the film material becomes too absorbent, attenuating the light in its second pass through the material, after rebounding from the back interface. At some point, the film material's bulk properties take over.

 

Best regards,

Tom

[Dave Prebble]

Hi Tom,

 

Thank you indeed for pointing out my error. It stuck out like a lighthouse on a dark night the second I read your post.

 

All temperatures should have read Deg F (not C)

 

It is 30 years since I covered this stuff at college and I am afraid I shall never be fully comfortable around metrication and Centigrade!

 

Having read your notes I shall do a little follow up reading about thin film oxides.

I have been meaning to find out a little more about coloured aluminium surface treatments for a possible future project so this may tie in nicely.

 

Regards and thanks again

 

Dave

[d.elliott]

Well chaps,

 

a very nice series of explanations, in lay terms, of quite complex phenomina.

 

The heat treatment, inclusive of tempering adjusts what is known as the 'condition' of the steel. In the British Standards (I am thinking of the BS970 range of engineering steels) the various conditions are specified and are denoted by a letter code, 'T' condition or 'W' condition, followed by a table of mechanical properties. I am tempted to get some reed steels hardness checked, note the tempering colour and look at the implications against say various high carbon spring steels. Not that I can identify particular compositions this way, but I might be able to spot some modern alternatives, and the hardness data might be useful.

 

Dave