Posts tagged felting
Today’s topic is piano dampers. When your finger depresses a key on the piano, the string vibrates allowing us to hear the wonderful tone of the piano. But what happens when we lift that same key? The key returns to its upright position and the tone stops resonating. Why? The piano mechanism called the dampers simply press felt blocks on the vibrating strings to terminate the singing tone.
To understand a bit more about dampers, we brought in Marc Venet from world renowned felt maker Laoureux in France!
But before we delve into piano dampers, we need to take a brief look at the piano strings. On any modern piano there are usually 3 sets of strings: tri-chord, bi-chord and mono-chord. The prefixes of tri- bi- and mono- give away the fact that there are notes on the piano that contain 3, 2 and 1 string. This is significant because as we’ll soon hear, damping 3 strings at a time is very different than damping 1 string. The largest strings on the piano are the bass strings. They are copper-wound strings and produce the lowest notes of the piano where you can actually see the vibration of the string. Conversly, as you move higher in the piano, the frequency of the waveform gets faster and we can’t see the vibration. Piano strings can be called “sinusoidal” from where we get the root “sine” wave. The purpose of the damper then is to stop the wave and subsequently, the sound. The damping techniques and felt types are really different to mute different thicknesses of strings and their varying degrees of energy.
Without further adieu, and knowing a bit more of the background of dampers, let’s talk to Marc Venet from Laoureux.
Glen Barkman: The history of Laoureux, it’s been going a long time and is one of the largest piano felt makers in the world. Can you tell us a brief history of the company and how you got involved?
Marc Venet: Laoureux was founded in 1923 by Mr. Laoureux and after 3 generations of Laoureux’ leading the company until 1976, it wasn’t doing well financially. It was purchased by SCAPA group who bought the company in order to build a conglomerate in European felt business (Naish felts, Royal Georges felt, Laoureux, etc.)
My father was hired at this time in order to restore the profitability of the company Laoureux, which he succeeded to do above their expectations and quite possibly be the reason why Laoureux is now the only felt maker from this group that survived and producing today. The choice he made was to concentrate on high quality, hand made felts and avoid mass market felts like those found in the automotive industry, for example, which have bigger profits, yes but also involve big risks and large turnovers. It was a good choice. My father finally bought the company in 1988 and I joined the company in 1998.
GB: There are 3 types of strings and yet 4 types of dampers (mono,bi,tri and treble), can you tell us how each of those work?
MV: The shape and the types of dampers depend on the string they are supposed to damp.
A – The “Mono” or “One string” looks like a square with a V shape inside in order to envelop the large string on bass section of the piano.
B – The “Bi” or the “Two strings” looks like a V shape in order to get inside the space between the two strings on the tenor section of the piano.
C – The “Tri” or “Tri strings” looks the same as the “two strings” wedge shape but contains a split in the middle to act as a double wedge. These are for the lowest plain wire strings.
D – the “Flat damper” looks like a cushion of low density felt and are used for the highest notes on the piano.
For all dampers the target is to damp the sound, that means that they are in charge of absorbing the vibrations of the strings. Those vibrations are in fact frequencies like sinusoid signals (pictured above). The bass notes have low frequencies which mean long and spaced sinusoidal waves, and on the contrary, the treble or high notes have high frequencies which mean shorts but repeated sinusoidal waves.
Of course, for playing the piano, it is interesting to have more or less the same time to dampen the sounds when you release the keys, wherever you play on the keyboard (bass, tenor, or treble) and yet the frequencies and subsequent energies are quite different. For achieving that, we use different dampers with different properties adapted for the frequency of the sound. On the treble section, frequencies increase drastically when you play more to the extreme treble section. So for this section, even if there are 3 strings for each note, we have to change the method of damping from the double wedge to the flat block dampers.
GB: Is there a certain density of felt that is ideal for piano dampers?
MV: Yes of course there are optimal densities for dampers. And there are also certain densities depending on the placement inside the piano (density for bass and for treble felt are different). Ideally the density should be as low as possible. You could find on the market bass dampers with densities from 0.23 up to 0.35 and for treble dampers ranging from 0.14 up to 0.25. Physically, density is weight over volume (D = W/V). For the felt manufacturer the challenge is to make low density felt because it has superior damping properties however it is much, much more difficult to produce. In order to be able to cut them with a high degree of precision (1/10 a millimetre) the felt should be perfectly consistent otherwise it is impossible to cut. The challenge is also for piano technicians, it is much easier to work with “hard” dampers when you do not have the correct know-how and experience. A soft felt is difficult to make on several levels: First, achieving the felting process for low density is very difficult, because if you are under the good “felting point” (felting being the intertwining of fibres), the middle of the felt will remain as only wool if it is not felted. And if you are over the optimal felting point you are too hard on the surfaces and soft in the center and thus, the felt is not consistent.
The job consists of making felt the same from top to bottom. This is not easy. It takes much more time, involving more hands-on processes and also involves a lot of waste. That is why it is more expensive than denser felt. Ironically, you pay more even if there is less wool inside because it is much softer but contains greater damping properties.
GB: In the cullinary world, it’s kind of like baking the cake right? Too hot and you burn the outside, too cold an oven and the center doesn’t get cooked. Interesting. Speaking of damping properties, what makes for great dampers? And can you take us through the manufacturing process a little?
MV: Wool is the first and natural technical fiber with a “form memory”. The felt pressed against the strings absorbs string vibration. If you leave the felt released, the impression will erase. This is what makes great dampers. The softer the felt, the better the form memory. Making great felt requires technical know-how but also great raw materials. Normally felt is graded by 2 criteria: the quality of the wool used and the density. We buy the wool taking into consideration the length of the fibers (told in millimetres), diameter of the fibers (told in microns), and ability to felt more or less (the curving of the fibers). Of course the thinner and the longest fibers are much more expensive than the shortest and the biggest fibers.
A – Wool opening and Blending: we make a blend of wool with different single lots in order to have something always the same. With blended wine for example, you assemble different qualities with more or less the same proportions to create consistency. If we were using only one type of wool for each production, we would have different results from one production run to another and so good blending allows consistency in production.
B – Carding: the blend goes into the carding lines in order to create wool layers. With our machines we can adjust the weight by square meters of the layers, and also the fiber direction (crossed or not).
C – Composition: It is a hand made process consisting of assembling and cutting several wool layers depending on the final result we want to achieve. In short, we know the final dimension and density we want. We will use the right weight of wool at the right dimension taking in consideration the shrinking coefficient we will apply.
D – Felting: The transformation between wool to textile. It is a natural process (no chemicals involved) where the fibers are matted together via friction.
E – Fulling: Once we transformed the wool layers to felt, we have to shrink it to it’s final dimension in order to give it it’s right density. This is again a hand-made process, one piece at a time. Dimensions of the felt should be controlled because we need to keep consistency in the shrinking. The right density is obtained when the felt is at the right dimension, not before, not after.
F – Drying. The previous process of felting and fulling require moisture and so the felt must be dried.
G – Pressing: Here we calibrate the thickness of the felt, for example 10.2 mm thick. We use hot presses to achieve this.
H – Finishing: Depending the product we make it goes to the dedicated workshop in order to be cut or assembled to its finished purpose.
GB: Aside from piano felt, what other applications do you make felt for?
MV: There are many many different applications for felt. Felt is used for its natural properties of absorbing, transferring and sealing. Some industrial fields using felts: writing instruments, railway, automotive, nuclear, tools, bakery, design and of course, piano making.
Glen Barkman: Wow that was a fantastic glimpse inside the world of felt making by Laoureux. They are located in Normandy, France and operate in 7,000 m2 facility (about 75,000 ft2 factory). A special thanks to Marc for his expertise and continued dedication in providing the world with quality felt.
Is he a spy? No. Is he famous? No. But this one man’s company has single-handedly infiltrated most of the major names of pianos in the world. 200,000 pianos per year to be exact! Who is he? Jack Brand. Haven’t heard of him? I hadn’t either until the interview with Del Fandrich a few months back. After some preliminary investigating, I found out that Jack Brand owns a company in Canada called Brand Felt. So what does this have to do with pianos? Jack Brand, third generation felt maker along with his father, Klaus Brand, re-established the German Weickert/Wurzen production facility, the oldest, most respected felt maker of piano felt in the world. I queried Jack a few months ago about his interest in shedding some light on the felt making process and he agreed to do this interview. I’m so excited to share his words. I’ve only scratched the surface and already I’m finding that felt making is more about art and intuition than formula; that you could spend a lifetime studying how hammer felt affects piano tone so drastically. Established in 1783, Weickert is over 230 years old! The trade secrets, production notes, and piano technician feedback have been handed down so that this closely guarded secret of felt making lives on. But don’t take my word for it… let’s hear it from Jack.
Weickert and Wurzen are some of the oldest names (THE oldest??) for felt manufacturing in the world and yet the Weickert felt has been “re-introduced” again for hammer manufacturing, correct? Can you tell us a little history about the name and origins as well as your involvement with Weickert and Wurzen?
Wurzen is the oldest existing felt plant of wet processed felts in the World. The oldest. Basically, I was very lucky to come across this beautiful opportunity to re-introduce the old legendary Weickert Felt. All the know-how had disappeared between 1945 and 1991.The Weickert company was expropriated in 1945 by the Communist government and the family fled to the West. The last owner of the company was Alice Weickert, who was an American and had married into the Weickert family. Steinway New York was one of the largest US customers for Weickert hammer felt. I am the fourth generation of textile makers, third as felt makers in the Brand family. All previous generations lost everything due to wars and expropriations, my dad and mom started in the West with nothing after WW2. I am the first in four generations who can build on something.
In 1991 my dad asked me if I was interested in coming back to Germany to look at my grandfather’s plant which couldn’t be salvaged and also at the former Weickert felt plant.
To make a long story short, my dad and I re-privatized the old Weickert plant in 1991. We got a phone call from Renner, Germany asking us whether we could produce the old Weickert felt. We were lucky, the old production recipes were handed to me by an old former production manager of Weickert’s. We ran some materials and the hammers were sent anonymously to Steinway. The response from Steinway (who did not know who had made the felt) was:
– this felt reminds us of the old Weickert Felt
– where is this felt company?
– and we want more
The rest is history. The PTG (Piano Technician’s Guild) of Germany came to the Wurzen plant in 1992, and conducted blind tests on four different grands and the difference in tonal result was significant. After that our supply for Wurzen/Weickert hammer felt was always sold out. Capacity has steadily increased to the point where today annually 180,000 to 200,000 instruments are outfitted with Wurzen felt, about the same amount as in 1903 when ‘Weickert’ felt already had a widely recognized name in the piano world.
Your company Brandfelt.com – how did you get into this business? Did you grow up always wanting to manufacture felt?
I basically learnt felt around the breakfast and dinner table. Our living quarters were at the felt plant. My parents sent me to Canada in 1971 because they wanted me to grow up in a country where there hopefully would not be wars. A small felt plant was founded in Toronto, something to fall back on, in case everything gets lost again thru political turmoil.
Personally I am a production/product development guy who identifies with a natural product like wool felt and who got lucky to stumble upon the challenge of piano felts, which is probably the most difficult felt to make. My colleagues and I didn’t invent the Weickert hammerfelt production method, we only re-introduced it because of fortunate circumstances together with determination and real interest in the product by a whole bunch of people in our factory. At this point I also want to thank all the piano builders and hammerhead makers in the world who showed genuine interest in making a better product and let results speak for themselves.
Piano felt is a small part of our overall world sales, but it is one of the most challenging and interesting ones. We have manufacturing and converting plants in USA, Canada, Europe and Far East.
Let’s get into hammer felt making. How many basic grades of felt are there?
First of all I would say there are today about four major different manufacturing methods in the world for piano hammer felt.
1) I call it the Royal George method out of England, whose technology was purchased by a Japanese felt company in the early 90s,just as the Wurzen /Weickert hammer felt method was being reintroduced into the market place. Royal George as a felt maker does not exist anymore.
2) The VFG method which is a manufacturer out of Germany (in the former West Germany before German reunification in 1989).
3) The Japanese/Chinese method which existed before a Japanese felt company purchased the know how from Royal George, England.
4) The Weickert/Wurzen method which was developed in 1847 near Leipzig and which by 1861 was internationally recognized. By the early 1900 ‘s the J.D. Weickert Piano Forte Felt Company supplied top hammer felt for about 200,000 annually world wide.
Each of these felt methods provide different resiliency or elasticity effects in the felt, hence different results at the hammer head maker and different tones at the voicing stage (because each type of felt will react different in voicing even if hammerhead making method, voicing method and type of instrument are the same)
Each felt manufacturer offers in addition different grades. The Wurzen Felt company offers 4 different grades:
-Piano (which can also be used for grand instruments)
-Weickert Special (the latest and probably also the best in most instances, especially for grand instruments)
All these four different grades by Wurzen are being produced in accordance with the basic principles of the legendary Weickert hammerfelt manufacturing method. The difference in the above felt grades can, for example mean different wool blends and/or slightly changed processes, for example with more or less hand labour in the different stages of production. But we always follow the old Weickert method which nobody else does in the world at the moment. Basically the different grades offer different kinds of elasticities to the hammerhead maker and end user. Weickert in the olden days also carried four different grades of top hammer felt.
What exactly is virgin wool? I presume it doesn’t refer to non-promiscuous sheep…hahaa Do piano hammers primarily use virgin wool?
Virgin wool is wool shorn from live sheep, not dead sheep (usually raised for meat production. Those wools are called skin wools which often are chemically removed). Usually live animals get shorn twice or once a year depending on the food environment and what type of length or fineness of fibre is required. These are virgin wools.
So the big question: What raw materials and process make for great piano felt? What factors affect tone?
Using the right fibres is very important and a prerequisite. The Wurzen/Weickert felt company has a long tradition of knowing what fibres are best suited and how these fibres have to be processed after they are shorn from the sheep. We have our own company specific recipes and specifications, which we consider proprietary. But the different steps in the manufacturing method are essential to provide good tone results in the end (fibre blend, mixing, carding, felting, fulling, finishing). This is where the real know how lies and which differentiates the Wurzen/Weickert felt from all other methods in the world.
In my seminar on the principles of felt making I hand out identical pairs of felt samples which represent the different stages of production, i.e. felted or fulled material but which feel quite different from one another in your hand when you squeeze, bend or just touch them. The pairs of samples are identical in fibre, dimensions and weight and still one will feel harder or stiffer than the other (or one surface feels smoother and the other rougher). Why the difference? Well it is the difference in production method. For example the one sample may have been exposed to high temperature steam whereas the other to low temperature steam affecting the moisture content in the felting and interlocking of fibres process (for fibres to interlock properly the scales on the fibres have to properly open up before they can interlock which only happens if you have the right temperature and moisture content),the right stoke and speed settings of the felting plates, plate patterns, type of transportation cloth on which the material gets felted, etc…
The point is the resiliency/elasticity of the product always changes if one changes any of the parameters in the production process. So that is the craftsmanship which one has to attain thru a lot of trials and errors. Specs of weight and dimension and which fibres alone don’t define the elasticity of hammer felt. One needs to know how these wool fibres are being processed under what parameters at each step of the production process.
The end result is a certain felt elasticity which stands for, in our case, for the Weickert method of hammer felt making. Generations of felt makers at our plant in Wurzen developed it in conjunction with and with feedback from piano builders and hammerhead makers since 1847. The Weickert method is proven and with the help of a good hammer head maker who will adjust his method to our felt, it will produce a beautiful tone. It is very important to work closely with a hammer head maker and also with the piano builder or piano technician to get optimal results. You can have great felt but without the right hammer making method you will end up with mediocre results. Vice versa a good hammerhead maker who knows his stuff and uses a mediocre piece of felt can still get a decent result but not the optimal one.
We know of many examples where the identical Wurzen felt hammer specification was made into hammers by different hammerhead makers for the same piano factory customer, one was good and the other was rejected. The conclusion is that without all three parties working closely together (felt maker, hammer maker, piano builder) you almost have no chance to get the optimal tone result.
To answer your question ‘what affects tone’ I would say it is almost endless but it helps to know what felt and which grade is on your hammer,who made the hammer and what method was used (ie hand vs Hydraulic press, prepress or not, shape of how felt is cut from sheet, what temperatures and times in presses etc…) and what design of instrument and tonal taste one wants to achieve.
The art and science behind felt making, the experimentation, the feedback from builders and technicians – it’s amazing that the Weickert “secret recipe” was not lost. Pianos around the world might have been changed forever had these production notes not have been found and handed to you.
Yes! The basic trade secrets were handed over to me by the then production manager in 1991 who in turn got it from the previous production manager who was still working during the Weickert family era. The last production adjustment to the Grand D hammerfelt spec production sheet for Steinway was initialled and dated in 1933.
Wow! That’s incredible. For those wanting to see felt making in action, here’s a video link to the Brand Felt Company in Canada. I’ve learned so much about an area of pianos I knew so little. And scratching the surface one quickly realizes how broad this speciality is. I just want to convey my thanks to Jack for taking the time to do this interview. Your insights and expertise are not only helpful but inspiring and captivating.
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