At 16:48 -0700 13/10/07, David Love wrote: >Can anyone comment about different grades of felt generally, Wurzen felt >specifically. Does a higher grade mean more processing necessarily? If so, >does it also mean less lanolin left in the felt, less elasticity for in the >fibers or anything else that might be considered a detriment? It seems to >me that higher grade may not necessarily produce a more resilient hammer >(felt), or better tone. Any comments? This is a vast topic, and I'm always amazed at the great variety of different hammers on the pianos I deal with (mainly 100 years old or so) that produce good results. Some are apparently very dense and firmly felted and others (eg. Bechstein) are superficially quite soft and fluffy. Both produce good results and last well. All that really matters in a hammer is the characteristics of the felt between the apex of the moulding and the nose of the hammer, but to achieve the proper characteristics of this part requires special skill on the part of the hammer-maker and a good choice of felt. Owing to the way the rhomboid felt strip is forced wound the moulding, the outer surface of the hammer is under great tension and as the felt approaches the moulding the tension graduates to great compression, so that there is a cylindrical area round the apex of the moulding that is under greater and greater compression towards the centre. The reason, so I understand, for impregnating the "wings" of the felt strip, as on the old Steinways etc. was to lock the fibres so that when the felt is forced round the moulding greater tension is produced at the nose of the hammer, since the fibres cannot pull round. If the quality and length of the fibres is wrong, then the felt can pull apart and release the necessary tension, relieving the compression further in. Most hammers, of course, are not impregnated and the gradual transition from felt under tension to felt under compression is achieved nevertheless, and the shape to which the "rhomb" is cut is probably most important. It's also important that a good cement be used and a lot of modern hammers are greatly inferior to the old ones owing to the use of inferior glue. I wish that Dolge had expanded the section on piano hammers his book When he recounts that at his factory two expert gluers could cover 240 sets of hammers in a ten hour shift on one machine, one gets some idea of the scale of things in those days, compared to which piano-making today is a cottage industry! I read a lot on this list about doping hammers. Why should it be necessary to dope any hammer that is properly made from the proper felt in the first place? JD
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