Exploding Water casting

Hi all…sending out a query here from Nova Scotia, where the fog
keeps insisting that we not see the sunshine. I had a student that
was casting Shakudo ingots into a canvas catch sheet submerged in a
bucket of water, similarly to the way it is done in Japan when
making the more exotic and oxidation-happy copper alloys. Well, as
he is pouring the metal into the water, 80 or so grams of it
momentarily pool on the canvas, spread out as three separate
globules, then retract into the center again. At this exact moment
of coalescence the last 10 grams falls from the crucible and joins
the rest on the bottom. In approximately as long as it takes to say
"uh-oh…", the water had vapourized in a white jet that erupted
from the bucket mouth, sprayed the entitre room, split the 22 gauge
galvanized steel bucket along the seams, blown out the torch, and
reduced the ingot to a fine haze of copper dust that covered the
student, the walls, the floor, and any other nearby surface.
Thankfully, the student was unhurt other than that
punched-in-the-gut feeling from the shock front of the explosion
catching him in the midsection. He was in full protective gear.
So, the question is, WHY? Was this a unique situation that will
never be duplicated? Have we grossly misunderstood and misapplied
the water casting technique revered by its Japanese practitioners?
Or is there something that we’ve missed in investigating this
near-miss? Any and all feed back would be appreciated, as I do not
want to over react, but I don’t wish to under-react either. I am
perfectly content to cast even the most copper rich alloy in a plain
steel ingot mold, and have had no appreciable effects of oxidation
from doing this, but I don’t want to restrict a technique based on
one freak occurance if it was indeed a freak…what say the
community? Thanks, Danny

I have had this happen to me twice, and been in the room when it
happened to other people two other times. Have not had the bucket
split, but have spread copper, shakudo, and/or shibuichi bits around
the area. So far I have not taken the time to experiment and figure
out the why. My guess is that it was due to either:

  1. pouring the copper to slowly into the water.

  2. having the crucible to close or to far away from the top of the
    water surface when pouring.

Either way it looked like water got encased inside the molten metal.
(Similar to the water occasionally found in streling casting grain.)
The resulting super heated water, i.e. steam pressure, overpowered
the surface tension of the rapidly cooling metal and blew up the

Danny, I don’t have an answer for you. I will be following this post
closely as I have had similar explosions with silver and bronze. I
do a Pine straw and Water casting workshop at my studio.The amounts
we pour have been on the order of 10 to 20 pennyweights at a time.
Because of the possible explosions, a full face shield and Leather
welder’s apron absolutely must be worn. I have had 4 explosions out
of some 80 pours. Far to many in any case. I have watched the
temperature of the metal, the way it hits the water, how fast it hits
the water, the temperature of the water, and still don’t have a clue
to the cause. I want to say that it is the nature of the beast but
really think it is the result of water getting englobed by the molten
metal. The explosions I have had seem to happen at the surface of the

Could the out gassing out absorbed oxygen at the instant of
solidification be an issue here? God what an erudite statement!

Bill Churlik


Was the water almost boiling? if not that may contribute to your

event. Second how deep was the water? It should be only about 5"
deep. There is a good photo sequence of this process in Steve
Midgett’s most recent book “Mokume Gane a Comprehensive Study” ISBN
0-9651650-7-8 In it they are using a wide shallow container for the
water. It is only about 6-7" deep and maybe 15" in diameter. So the
metal does not travel very far through the water to the cotton cloth
mold. The times I have done this I have used very shallow pans and
water that was in the 200 degree range.

<edit - add book details>

Mokume Gane - A Comprehensive Study
by Steve Midgett $34.95
Hardcover: 157 pages 
Publisher: Earthshine Pr; (2000) 

Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160

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