thickener for epoxy

I have used all kinds of thickeners for epoxy: I have used Cabosil, fine sawdust, flour, lime, etc, but today I used the best yet: Fumed Silica from Raka.  It mixes easily into a paste that is both thick (won't run) and thin (is easily manipulated).  It is an absolute joy to work with - I highly recommend it.
 
Chuck Leinweber
http://www.duckworksmagazine.com