Angelika: 
Most of the mothproofing agents have been removed from the market because
they contained "labile halogens"--usually chlorinated organic compounds. You
are no longer obtain them or use them legally in the United States; they are
probably illegal in Germany too. I thought that Bayer had a product 11%
pyrethrin for mothproofing but on their website
www.textileauxiliaries.bayer.com it is not listed--I'll check my files.
It may have been pulled off the market too. Pyrethrins are quickly degraded
by sunlight but inside pianos, etc. it would not be a problem. For flutists
or others, pyrethrins can produce allergies (their natural product source is
a painted chrysanthemum I believe). For a short history of Mothproofing
agents, I wrote "Mothproofing Museum Textiles" for the ICOM-CC 7th Triennial
Meeting. It may be that your keyboard instruments were already mothproofed.
The insect must eat the treated felt to be poisoned, so the insect will
still damage the felt. The difference is that the insect will not eat very
much. If you or anyone else would like a copy of my old paper, I would be
happy to send it out. 
Mary 

>>> [log in to unmask] 08/13/03 01:39AM >>>
Dear colleagues,
I joined the discussion list only a couple of days ago - this is my first
trial to present a problem and hopefully find out about ways to solve it.
This museum has a large collection of historical keyboard instruments. All
of them contain various types of wool felt. The pieces of felt have
different shapes, many are very tiny and they are mostly glued to the wooden
parts of the instruments. Many of them seem to be very attractiv to moths.
Does anybody know a chemical substance which can be used to mothproof these
wooly bits "in situ" ? 
The instruments are on display, some are frequently tuned and played on.
Thank you very much for your suggestions. 
 
Angelika Riley
 
Textilrestaurierung
Museum für Kunst und  Gewerbe
Steintorplatz
D-20099 Hamburg
Germany
Tel: 040/428 54 27 53
Fax: 040/427 92 92 35