Felt and Hammer Making

Back before the Great Depression of 1930, felt and hammer making in the United States was arguably at its zenith.  I think most of us are familiar with, or at least seen and/or heard, that type of vintage hammer.  If you have serviced early twentieth century pianos, you no doubt have come across hammers that I speak of; ones that feel soft, yet have the power of a much harder feeling hammer, and we wonder how such a hammer could have that kind of power and dynamic range and yet feel so soft.  I don’t care who makes hammers presently, none of them, in my opinion, stack up to those vintage hammers of yore. 

One of those hammer makers from by-gone days was the piano hammer division of the American Felt Company which by the 1920’s had factories in NY, Chicago, and Boston.  As an aside, the old NY American Felt Co. building which was located on 114^th East 13^th Street, NY, has now been turned into condos!  They are selling the units starting at $900,000.  What a deal!  The building has 12 floors and 41 units (google AMERICAN FELT 114 EAST 13TH STREET NY - Demsker Realty to see for yourself!).

J.G. Childs, then foreman of the felt factory in Chicago, delivered an address on felt and hammer making at the Chicago chapter meeting (a.k.a. Divisional meeting) of the National Association of Piano Tuners in November, 1924.  The following is the account of that address as found in the Tuners Journal of January 1925:

“For a great many years prior to the latter part of the 19^th century practically all hammer felt used in this country was imported, although there was a certain amount of manufacturing done here with the idea of making entirely satisfactory merchandise.  This culminated in first prize being given at the Vienna Exposition in 1873 to American made felt and later, in 1878, felt from this country received the grand prize in Paris.  This naturally brought more attention to the felt made here, with the result that large orders were placed and felt became more generally known throughout our country.  As it became better known it was universally accepted, for the realization came to piano manufacturers that felt was being made in this country that was unsurpassed by any in the world.

“It is interesting to know of the care and the numerous details that are necessary in the selection of the wool, the making of the felt and all of the steps to the final covering of the hammers for the factory.

“First of all, wool for this purpose is selected from all sections of the world, coming from Australia, South America, Cape Colony, and parts of the United States.  But of all the wool from these various sources only from five to ten percent of it can be used for the making of hammer felt – the cream only – as hammer felt requires long staple, strong, healthy stock and no other will do.

“I have mentioned ‘healthy’.  This is a much more important item than one would think, but, after all, wool is an animal fiber and its quality depends not only upon breeding but upon the condition of the animal.  If a sheep is sick during the period of wool growth or if a heavy drought occurs, it will naturally interfere with the growth of the wool during that period of growth.  This wool, of course, will break in the section represented by that growth and cannot be used for the work required of it.  In addition to this, the wool must be resilient.  It must have a proper number of kinks to the inch. It must be of the proper diameter, as wool that is too coarse will not make the fine hammer felt required nor can we use wool that is too fine as it will be too readily cut through by the strings of the piano.  In order to insure these conditions being met, each batch of wool is thoroughly tested in the laboratory to see that it meets the specifications.

“This selected wool is next thoroughly scoured with warm water and the finest of soap.  It is run through several washings to eliminate all the grease, sand and dirt, and later it is subjected to hand-picking to remove the burrs and tar specks so the finished product will be white and clean.

“It then goes through the felt mill where it is first run through the ‘picker’.  This mixes the several varieties which go to make up a good blend and starts the process of combing out the fibers so they may be laid with the run of the sheet.  This process of combing and mixing is carried further by means of cards, which is in reality a multiple combing process.  As the wool emerges from the card it is in the form of a thin film, which is deposited upon a moving belt.  On this belt the wool is built up, starting at the bass side of the sheet and gradually increasing the width of the lay-out until the entire sheet, approximately sixty inches in width, has been deposited on the belt.  In doing this, it can readily be seen that the bass end has been made much thicker and has been tapered off to a thin treble.

“Right at this point is where we can make up the sheet with a heavier tenor or with any other special instructions that the customer may desire.  The lay-out made here will naturally be reflected in the finished hammer.  The batt, as it is then called, is run underneath hardener rollers – which, by means of vibrated motion helped by heat and moisture, interlock the wool fibers and harden this soft, downy batt into a firm piece of hammer felt.  However, this hardening process has really affected only one side, so this sheet is taken off and put onto a rehardener – which hardens the other side.

“The sheet, which has during this period been, approximately, thirty feet long, is then cut up into smaller sheets, approximately five feet square, and is put through the process known as fulling.  This is, in reality, a shrinking process – which locks the fibers more closely and shrinks the whole sheet.  It is accomplished by large hammers suspended from a crossbeam, which thump away at this felt until it has been reduced to a sheet approximately three feet square.

“This process is helped very materially by warm water and a clear soap solution – and is carried on for over half a day.  At the end of this time the sheets are taken out, washed free of the soap and the water extracted.  Then attention must be given to the treble end.  This generally must be very brilliant and to obtain this brilliance, the trebles must be re-fulled by hand in order that they may have the special touch which the customer may desire.  Following this, the sheets are pressed out to remove any heavy wrinkles, sanded, trimmed to an even size, inspected, and they are then ready for the hammer shop.

“The hammer shop, the Boston Piano Supply Company, on receipt of the hammer felt, again inspects it to see that it meets the specifications outlined by the customer.  The sheets are then laid aside and held for the respective customers, as they represent, as nearly as it is humanly possible to control felt, the touch requested.

“When an order is received the sheets are taken to the cutting bench, where they are stripped by hand in long cuts, running from the bass to the treble, and inspected again.  These strips go to the covering department, where the wooden moldings are first set into the press and covered with the under felt.  Upon this the strip of top felt is then stretched and held in place for the number of hours required for the glue to set properly.  It is desirable to leave the hammers in the molds no longer than is necessary, just long enough to complete properly this stretching process, to eliminate the outer skin which other processes would leave upon the completed hammer.  It is our ambition to deliver a hammer which requires very little tone regulation, and this is always in our thoughts, as we realize it is a great assistance to the manufacturer.

“The hammers are then taken from the molds and the rough edges of the hammer felt trimmed off.  The amount of felt trimmed off the edge is carefully gauged in the endeavor to leave the same amount of felt on each side of the hammer so that it will be properly balanced.  After this, the whole strip is sanded off and the hammers are cut apart.  The hammers then go in trays to the wiring machines and from that point are bored to the scale, pitch (angles), and size of boring the customer specifies.  There is one more inspection made before the hammers are finally packed, then the package is marked with the customer’s scale number and sent out.

“You will readily realize that through these many processes there are opportunities for variation; that the least thing in the start of the felt through the mill will have its effect upon the finished hammer in the hands of the tone regulator.  It is therefore our aim to watch the details of felt manufacturing with the utmost care, in order that a uniform product may be attained.

“The very nature of wool itself makes it difficult to hold to the absolute accuracy of touch that some people may demand and, for that reason, many questions have been asked about tone regulating.  I can only say to you that this is a subject on which I will not attempt to talk, but that you, as tone regulators, know that you cannot pick a hammer to pieces and produce a soft mushy hammer and still get satisfactory results.  You, of course, must needle hammers – but when you do so, for the good of the hammer do as little needling as you can.  Every time you stick a needle into that hammer you are bound to cut some of the fibers and that loosens the tension which prolongs the life of the hammer to quite an extent.”

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Addendum: One of the detrimental effects the gluing process has on hammers made today, is the enormous amount of heat the glue requires to set up.  This is done in order to cut down on production time.  Instead of hours in the caul as the glue hardens, it now takes mere minutes. But now because of the amount of heat they use, it affects the felt negatively in that it loses resiliency.  The hammer maker gains in that it shortens production time, but quality suffers.