That question is not as easy to answer as you might think. On the surface, we can look at the actual time it takes me to paint any given stone. That part is simple enough, and readily measurable.
But that's a very simplistic answer, because there's much more to it than just painting.
How do you "count" the time it takes to find the stone, among the thousands out there on the beach?
How do you "count" the time that goes into working out the design in my head, before it is actually put on the stone?
How do you count the time that gets added on when I "mess up somewhere" and end up having to send a stone back to the beach because I draw a line or design element in the wrong place?
In addition, Alchemy Stones are a collaborative effort between my wife and myself-- for each stone, she creates a marvelous custom made and completely hand sewn pouch that's as much part of the stone as... well, the stone itself. How do you "count" the time that goes into the making of each bag?
In short, there's no easy answer to "how long does it take." It takes precisely "as long as it needs to."
