Ecsaine and B-72 Resin

I’d like to mention to this group two synthetic materials I’ve been testing which may be of use in harpsichord building. Ecsaine can be described as “synthetic buckskin.” It has been used in pianos for several decades as a buckskin substitute. It is stable and of consistent quality, and is extremely wear-resistant. It can be obtained in four thicknesses (.075, .073, .055, and .032”) from Pianotek Supply company in Michigan USA. Acryloid B-72 is an acrylic ester resin which is soluble in all types of alcohol. It is used in art conservation and has recently been introduced to piano technology for voicing hammers. I’ve been exploring the use of these materials to make harpsichord and lautenwerke plectra, stiffening the ecsaine in B-72 solution and using Titebond glue to laminate the ecsaine sheets to desired thicknesses and textures. My happiest result has been laminating soft .073” ecsaine on top of stiffened .073” ecsaine to make plectra for a small Sperrhake harpsichord which I restrung as a 1 X 8’ lautenwerke. The photo shows Sperrhake jacks with the rather stubby cut plectra. I have been able to voice these to give two distinct dynamics approaching the quality of a lute or harp plucked by the fingertip. I also had success in making stiffer plectra using three layers of stiffened ecsaine with the thin black on top. These I used for several months in a wire strung 1 x 8’ instrument. The B-72 resin is also useful as a glue size to affix the plectra in the Sperrhake jack tongues, easily reversed with alcohol. Thicker B-72 can substitute for burnt shellac. B-72 is available from TALAS conservation supply house in New York City.

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This is marvellous Ed. I am all for things like this. The only question I’d have is what about the longevity of the plectra. Good?

Very interesting. I have been considering using ecsaine for various projects myself. Next up is topping over worn down 19th century square piano hammers. Finding consistent leather has always been a problem.

The lamination method definitely has historical precedent. I am however puzzled as to why you would choose to use B72 when it would seem some other material would work that does not require nasty solvents?

B-72 Is somewhat soluble in alcohol, but mostly intended for use with acetone. It takes a fairly long time to get it to dissolve in alcohol. There are other alcohol soluble substances such as the traditional shellac, hide glue or a fish glue that would work as a stiffening agent and be quite easily reversible.

Interesting.
A little over a year ago I investigated using a polymer for plectrum-leather replacement. Because there is Delrin today, maybe a synthetic leather replacement was a possibility.

As part of an extended Navy-research program I had encountered a very tough Polyurea rubber (two-phase), having a fairly high modulus (stiff), that seemed very promising. It was a prime candidate for shielding ship hulls from explosive attacks (remember the 2000 Destroyer US Cole attack in Yemen?).

With that history on the material I subjected it to a durability test like Martin Spaink had done on the British Oak-tanned leather by Baker, where he gave up testing further, after about half a million cycles (e.g. see his Jackrail message of September 18, 2020, attached below). The Polyurea material clearly showed wear (but still a smooth contact area) under 8x magnification, when I gave up after 200,000 cycles. In any other way it sounded and felt indistinguishable from the Beef hide leather I used to get from Hendrik Broekman (Hubbard Harsichords); I now use Baker leather.

I did not have the whole register outfitted with the Polyurea, and have been made aware (through The Jackrail) that isolated (different) plectra do not sound like having the whole register outfitted with it. That was something I did not know when I had to decide (around 1975) whether to go with Delrin (or Celcon) vs avian material. Thus, I visited the Smithsonian’s harpsichord collection, in which some of the instruments had both feather and Delrin mixed: I could not discern any difference. So I ended up with Delrin choice, because of the wear consideration.

To close this long story: Any information on the durability of these materials?

Wolfgang

EdS Ed Sutton
June 29

I’d like to mention to this group two synthetic materials I’ve been testing which may be of use in harpsichord building. Ecsaine can be described as “synthetic buckskin.” It has been used in pianos for several decades as a buckskin substitute. It is stable and of consistent quality, and is extremely wear-resistant. It can be obtained in four thicknesses (.075, .073, .055, and .032”) from Pianotek Supply company in Michigan USA. Acryloid B-72 is an acrylic ester resin which is soluble in all types of alcohol. It is used in art conservation and has recently been introduced to piano technology for voicing hammers. I’ve been exploring the use of these materials to make harpsichord and lautenwerke plectra, stiffening the ecsaine in B-72 solution and using Titebond glue to laminate the ecsaine sheets to desired thicknesses and textures. My happiest result has been laminating soft .073” ecsaine on top of stiffened .073” ecsaine to make plectra for a small Sperrhake harpsichord which I restrung as a 1 X 8’ lautenwerke. The photo shows Sperrhake jacks with the rather stubby cut plectra. I have been able to voice these to give two distinct dynamics approaching the quality of a lute or harp plucked by the fingertip. I also had success in making stiffer plectra using three layers of stiffened ecsaine with the thin black on top. These I used for several months in a wire strung 1 x 8’ instrument. The B-72 resin is also useful as a glue size to affix the plectra in the Sperrhake jack tongues, easily reversed with alcohol. Thicker B-72 can substitute for burnt shellac. B-72 is available from TALAS conservation supply house in New York City.


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Wolfgang G. Knauss
Theodore von Karman Professor of
Aeronautics and Applied Mechanics, emeritus
California Institute of Technology
Pasadena CA 91001

626 395 4524 Phone — Office
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I wish I could answer based on extended, controlled testing.
Bruce Clark, engineer for Mason & Hamlin Pianos, said they tested ecsaine in piano action parts, and after about one million strikes they could not discern wear. They own the Piano Disc player company, so they are well set up for such testing.
B-72 used adding stiffness piano hammers that are a little too soft seems to penetrate the felt well and, when dissolved in alcohol (not acetone) it sets within the felt, does not draw to the surface as the alcohol evaporates. There are reports in conservation literature that acetone tends to draw resins to the surface as it evaporates. B-72 in alcohol doesn’t produce “crispy” sounding hammers and seems more flexible than plexiglas and shellac when used to “voice up” piano hammers. Ken Eschete uses it a lot in piano conservation and published an article about it in the Piano Technicians Journal about two years ago.
Personally, I lack the instruments and playing skills to do definitive testing. Last summer I played triple laminated ecsaine plectra, all layers hardened, in an experimental wire strung instrument for about two and a half months. Irregularities in those jacks made voicing difficult, but I can’t blame the plectra. if someone wants to replace, say, the leather plectra of a revival instrument, stiffened ecsaine may be worth a try.
A few years ago I restrung a single manual Sperrhake with flourocarbon strings. I removed the original 4’ bridge and just strung it 1 x 8’ and put in new jacks with delrin plectra. This made a pleasing simple instrument, but I wanted something gentler and quieter. I was able to make a register of scavenged Sperrhake jacks, replacing the old leather with plectra of laminated ecsaine, stiffened on the bottom, soft on the top. The result has been very pleasing. Register movement is limited by capstans, so I can switch from a mp to p with a movement of the register lever. The movement is very small. If I could find a way to make a quick capstan adjustment, I could probably get a third dynamic.
Besides sounding lovely, it has enabled me to do early morning playing without waking the house. I have about six weeks of regular light playing and it hasn’t deteriorated. That is the extent of what I can offer at this time.
I’ll reply to Anne in another post.

Anne-
If you can tolerate it’s non-organic, non-historic nature, you may find ecsaine a useful hammer cover, and Pianotek sells small amounts at a reasonable price.
I don’t find alcohol a particularly noxious solvent. B-72 in alcohol smell sa lot like shellac. It dissolves in everclear, 99% isopropyl and shellac thinner (denatured methanol).
My impression is B-72 is a lot like shellac, but more flexible and water repellent.
I don’t recommend using acetone. (See Ken Eschete’s article.)
…More in my response to Fred Sturm.

Fred-
As I recall you disagreed with Ken Eschete’s and Dan Levitan’s recommendations of B-72 in PTG circles, but have you ever used it?
Ken, Dan and I successfully dissolve B-72 in alcohol by putting it in a jar, stirring every few hours and letting it sit over night. If you want instant solution, use acetone, but Ken specifically recommends not using acetone for reasons I mentioned in my reply to Andrew Bernard, and besides, acetone smells awful.
Ken measures exact proportions. Dan and I stir and let sit. B-72 sludge drops out, leaving what we assume is a saturated, un-agitated solution. This becomes a base which we can decant and “cut” to desired strengths.
For my lautenwerke plectra, I dipped strips of ecsaine in this base solution, squeegeed them between my fingers, and hung them up to dry.
For piano hammer voicing I dip a little strip of tissue in the cut solution and let it dry for 10 minutes, suspended. Then by bending and feeling I can discern that it is not too stiff for what I want in the piano.

The photo shows four B-72 pellets.
They appear to have been extruded and then chopped.
The bottom pellets are how they arrive. They are about 3.2 to 3.4 mm thick in the flatter dimension.
The top pellets have been pressed in a machinist’s vise. They are now about 1.7 to 2.4 mm.
I stopped pressing because I didn’t want to injure the vise or my hand.
The pellets show no cracking or shattering.
I don’t think you’d get similar results with shellac, hide glue or plexiglas, so I believe B-72 is relatively more flexible and shatter resistant than traditional materials.
Because of this, it may be reasonable to expect long life as a stiffener in ecsaine plectra.
I have no extended laboratory proof, but felt it might be of interest to this group.
The materials are inexpensive and easy to obtain.

Dear Ed.

I understand your confidence, but let me point out a caution, which is based on my years of experience with failure and wear of and in (polymeric) solids.

I do not doubt that the durability of a leather substitute on piano hammers is real. I have often wondered that the felt on my 1921 Steinway is as good as it is (100 yeas old now; and the technician assured me there was no need to change it, though I do not know whether it was changed in the meantime as I acquredit only45 years ago). But with a piano hammer and a harpsichord plectrum there is at least one major difference: The hammer situation is an impact problem, whereas the harpsichord involves a friction/wear process.

An impact (percussion contact) involves primarily compressive stresses (forces) with internal forces at the microlevel pushing the material together; the forces that tend to separate the material locally are secondary. Thus, most of the material is being pushed together by the dominant forces, not expanded/separated.
In contrast, in the harpsichord the string slides over the plectrum end, setting up shear (and thus tensile) stress components, that work towards “scraping off” material from the surface of the plectrum. Because of the low friction of Delrin, and its relative hardness, that is no problem for a primary voicing material. However, the repeated scraping of the string over a (softish) polymer will remove material at the molecular level, and leaves the plectrum rounded from the top down and towards the tip with increasing number of plucks. That is what I confirmed visibly in my 200,000 cycle Spaink-type test.

The facit: A year of wear may be tolerable on a leather substitute, but whether you will experience or approach the longevity of Delrin is a different matter. The question should be whether the substitute is substantially more wear-resistant than leather, where the contact between the leather and the string occurs on the hardest part of the leather. I would love to hear that a polymer can outlive leather without impairing the harpsichord’s sound, because re-voicing 63 tongues with leather is a bit of a bear (I am doing that right now). On the other hand, the “wear" of a leather plectrum and a polymer one my be quite different, in that the polymer may literally wear off at the tip surface, while leather plectrum looses its stiffness (reduced plucking strength) through fatigue degradation of the fibrous structure before the tough skin on its top is markedly affected.

Wolfgang

EdS Ed Sutton
June 30

I wish I could answer based on extended, controlled testing.
Bruce Clark, engineer for Mason & Hamlin Pianos, said they tested ecsaine in piano action parts, and after about one million strikes they could not discern wear. They own the Piano Disc player company, so they are well set up for such testing.
B-72 used adding stiffness piano hammers that are a little too soft seems to penetrate the felt well and, when dissolved in alcohol (not acetone) it sets within the felt, does not draw to the surface as the alcohol evaporates. There are reports in conservation literature that acetone tends to draw resins to the surface as it evaporates. B-72 in alcohol doesn’t produce “crispy” sounding hammers and seems more flexible than plexiglas and shellac when used to “voice up” piano hammers. Ken Eschete uses it a lot in piano conservation and published an article about it in the Piano Technicians Journal about two years ago.
Personally, I lack the instruments and playing skills to do definitive testing. Last summer I played triple laminated ecsaine plectra, all layers hardened, in an experimental wire strung instrument for about two and a half months. Irregularities in those jacks made voicing difficult, but I can’t blame the plectra. if someone wants to replace, say, the leather plectra of a revival instrument, stiffened ecsaine may be worth a try.
A few years ago I restrung a single manual Sperrhake with flourocarbon strings. I removed the original 4’ bridge and just strung it 1 x 8’ and put in new jacks with delrin plectra. This made a pleasing simple instrument, but I wanted something gentler and quieter. I was able to make a register of scavenged Sperrhake jacks, replacing the old leather with plectra of laminated ecsaine, stiffened on the bottom, soft on the top. The result has been very pleasing. Register movement is limited by capstans, so I can switch from a mp to p with a movement of the register lever. The movement is very small. If I could find a way to make a quick capstan adjustment, I could probably get a third dynamic.
Besides sounding lovely, it has enabled me to do early morning playing without waking the house. I have about six weeks of regular light playing and it hasn’t deteriorated. That is the extent of what I can offer at this time.
I’ll reply to Anne in another post.


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In Reply To

andro Andrew Bernard
June 30

This is marvellous Ed. I am all for things like this. The only question I’d have is what about the longevity of the plectra. Good?


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Wolfgang G. Knauss
Theodore von Karman Professor of
Aeronautics and Applied Mechanics, emeritus
California Institute of Technology
Pasadena CA 91001

626 395 4524 Phone — Office
626 798 3793 Phone — Home
626 797 0405 Fax — Home

Wolfgang-
The stresses applied to ecsaine in piano actions are several.
On the knuckle there is a strong hammering stress, followed by drag in two directions. This contact is usually lubricated by dry lubricant.
On the backcheck there is a dragging force between the ecsaine and the wood hammer tail, not lubricated and intended to “jam” under the force of the hammer leaving the string.
What I find of interest is that ecsaine is available in several thicknesses and that its stiffness can be modified by sizing with different strengths of B-72 resin, and that layers of ecsaine can be laminated to produce different thicknesses, stiffnesses and surface textures. I’ve made so many varieties that I’ve lost track of what’s what, and so am limiting my report to one simple combination of soft ecsaine on top of stiffened ecsaine. This produces something which may be similar to peau de buffle. In any case, it gives the gentle effect I want on my lautenwerke.
Stiffer laminations give an effect similar to hard leather, but for that effect I’d rather use delrin.
I think I’ve made my limited claim that it’s worth investigating clear, and I look forward to possible reports from people who are better able to test, criticize and evaluate the materials.
Here’s a link to a short article about Ken Eschete which makes brief mention of his use of B-72 resin about half way through the article.< https://www.spokesman.com/stories/2021/jun/27/spokane-piano-restorer-touches-keys-of-history-fro/?fbclid=IwAR3rR9KPJgAPuYUymPM68vTaM7qs-9dNKgp6S88lYZiLCt8Cny4BG9DhG2o>

Thank you, Ed. It is clear that I am not a piano technician, knowledgeable of the details of all the piano action that you mention. Obviously I had only the hammer tip surface in mind. But it is good to know that polymers exist that can simulate leather and possibly with great durability.
Wolfgang

EdS Ed Sutton
July 2

Wolfgang-
The stresses applied to ecsaine in piano actions are several.
On the knuckle there is a strong hammering stress, followed by drag in two directions. This contact is usually lubricated by dry lubricant.
On the backcheck there is a dragging force between the ecsaine and the wood hammer tail, not lubricated and intended to “jam” under the force of the hammer leaving the string.
What I find of interest is that ecsaine is available in several thicknesses and that its stiffness can be modified by sizing with different strengths of B-72 resin, and that layers of ecsaine can be laminated to produce different thicknesses, stiffnesses and surface textures. I’ve made so many varieties that I’ve lost track of what’s what, and so am limiting my report to one simple combination of soft ecsaine on top of stiffened ecsaine. This produces something which may be similar to peau de buffle. In any case, it gives the gentle effect I want on my lautenwerke.
Stiffer laminations give an effect similar to hard leather, but for that effect I’d rather use delrin.
I think I’ve made my limited claim that it’s worth investigating clear, and I look forward to possible reports from people who are better able to test, criticize and evaluate the materials.
Here’s a link to a short article about Ken Eschete which makes brief mention of his use of B-72 resin about half way through the article.< https://www.spokesman.com/stories/2021/jun/27/spokane-piano-restorer-touches-keys-of-history-fro/?fbclid=IwAR3rR9KPJgAPuYUymPM68vTaM7qs-9dNKgp6S88lYZiLCt8Cny4BG9DhG2o>


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Wolfgang G. Knauss
Theodore von Karman Professor of
Aeronautics and Applied Mechanics, emeritus
California Institute of Technology
Pasadena CA 91001

626 395 4524 Phone — Office
626 798 3793 Phone — Home
626 797 0405 Fax — Home