<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 5.50.4522.1800" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV> Hammer maker’s ignorance.   I’ve been making hammers since 1980 but what I don’t know = about felt making could fill a large volume. What I do know may interest some of you so = here it is.   Felt is made of wool, so far so good. There are a number of wools = that could and have been used for piano hammer making. Wool is used because, = presumably it is a medium that can be packed into a mass that is both hard and = resilient at one and the same time. I suspect that the grid like character of felted = wool as well as its ‘scratchy’ feel have more than a little to do = with its potential for tone producing. Wool, like wine, is affected by the amounts of rainfall = and therefore by the nutrients in the grasses eaten by the sheep, so that = wool has what wine lovers call ‘vintages’ (woolages?). These factors = used to be important in matching wool varieties for the blends of hammer felt sheets back = when pianos were – at least in my opinion – better, on the whole, than = they are today.   Hammer felt sheets are constructed in two ways: felting and pressing, = both methods are used but in different proportions to one another, depending = on the hammer maker’s requirements and on the abilities of the felt = maker.   Felting is the process of working the wool fibers by mechanical = fingers so that they interlock to form a felted mass that is three dimentional; the = fibers are oriented in every direction imaginable.   Pressing is just that, pressing the fibers to cause them to interlock = having laid them out, more or less, in a given direction. The resulting mat is = thin (about .0625" or so). The number of thin mats required to make up a = given weight of hammer felt sheets is tacked together and the felt sheet is layered. = Since the entire hammer felt sheet tapers from bass to treble and the = thickness of each thin mat is constant, it follows that each mat is tapered to end = somewhere along the bass/treble axis to permit the whole sheet to maintain its = overall taper.   The relative merits of tone producing capacities of the two types of = felt: layered (pressed) felt versus three dimentional (felted) felt can be = easily deduced from the amounts of voicing required for each both during = installation and repeat voicings due to tonal stability or its absence later, during = the life span of the hammers.   It seems clear that layered felt hammers can barely perform without = massive infusions of hardener to enable the first stage of tone production = – the impact, occasioning the inescapable need for a great deal of needling to tonally = adjust the second stage of tone production – the rebound.   My personal dislike and distrust of this system emanates from the = implied loss of control for the technician. Can you make a hammer made from = layered felt work? Of course you can but you’re never in control. When you = juice a hammer you never know how much the tone will change until the thinners have dried = and listening becomes possible. Since, having juiced the hammers, you now = need to needle the excessive brightness out you’ve lost control over the = tonal stability of the hammers. This is so because the tone produced by the hammers = you’ve spent so much time and effort voicing is the result not so much of the makeup = of the felt and the pressing of the hammers but of your actions – juicing = and needling.   From my experience working with the materials I work with – = felt, wood, steel and copper wires – I know that the more control I have over these = materials during a given process – the better, the more predictable the = tonal results over time. I endeavor to pass on maximum control to the technicians using my = products so they, in turn, can more easily obtain the desired tonal results.   I shall discuss three d (felted) felt next time.   Thanks for reading this,   Ari Isaac. </DIV></BODY></HTML>