The well known flute maker Robert Bigio has for some years been making a plastic-Delrin- stopper and a crown of African blackwood as a replacement for the usual cork assembly in the head of the flute. This combination in the experience of somebody playing the instrument, gives an improved response and tone compared with the cork assembly which it replaces: it has become quite popular.
In 2002 I embarked on an experimental program which entailed the replacement of the Delrin stopper by stoppers made from a number of non-ferrous metals to his design, and found that these produced marked changes to the performance of the head piece some of which were musically valuable. The results of these experiments were embodied in an article I contributed to the March 2003 issue of "Pan" which is the the journal of the British Flute Society. (Click on "Pan" to see a copy). In particular I reported that a zirconium stopper produced the best results on the flute I was then using for my experiments. Since then zirconium stoppers have become quite popular and it is fair to say that the reception by buyers generally has been favourable to enthusiastic. The response is better than for the usual cork assembly and the tone more robust than that afforded by Delrin. ( I maintain that the the tone of the metal or Delrin stopper is more flexible than that of the cork assembly)
Since this article appeared I have added a few more metals to the original selection and have also experimented with replacing the blackwood crown with crowns made of various metals. These too cause changes, in some cases beneficial, to the performance of the head although they are not so pronounced as those effected by using metal stoppers.
It has also become quite clear to me that although zirconium stoppers improve most metal flutes there are other metals which when tried out may give even better results. To those interested I recommend that it is worth the the trouble to try out a selection of metals before making a choice. I am available for demonstrations.
The influence of metal stoppers and crowns on the playing characteristics of the head is worthy of a trial by all serious flute players.
