I would avoid using a water welder to do any type of fusing. The
flame area is generally too small to evenly heat the object to
be granulated. In my experience with granulation, pieces to be
granulated (or fused) needed to be brought close the melting
temperature by placement in a kiln or upon a small "beehive"
type fusing kiln. The torch, with a soft reducing type flame,
would bring the objects up to the final, fusing, temperature. I
have never seen a water torch capable of generating anything
other than a sharp, hot, pointed flame, one that would only heat
a very small area . Unless you want an unhappy client, I’d
steer them clear of a water torch for this type of work.
Just my $.02, Eben