Sometime in the past, either on the MMD itself or in some link,
I remember references to a solder mask or solder stop used to limit the
flow of solder when making or repairing organ pipes.  As I recall it
involved whiting and gum arabic.  Can someone tell us if this is
correct, the proportions, and details as to its use?  As to solder,
is 63/37 or 75/25 the better choice?

Any and all help will be appreciated.

Bob Oppenheim