I frequently do soapstone casting for pewter, normally I do a fair
number of repeats, so I’m just using a bulk melt, and dipping out
what I need. For a one off, the easy way to get an estimate is to
use modeling clay in the mold to get a volume model to do a water
displacement measure on.
You carve a place for a big button and err on the side of too much
metal. Just go for it. What do you have to lose? $10 of silver, a
couple hours and a few $s worth of tufa. I’m always amazed how we
don’t go fly a kite anymore, we go take a kite flying workshop! Just
use protective gloves, face shield, dark glasses and I use a leather
apron.
Judy, I am looking for help with the silent auction fund raiser at
the dinner. I have done tufa casting. I worked out the volume of the
mold in round terms, added a percent for the button and an extra
pinch or two. You can fill the mold to overflow with out problems.
Put the mold into a steel pan with 2 inch sides or so the metal has a
safe place to go. Stop by my store while you in Tucson. Sam
You carve a place for a big button and err on the side of too much
metal. Just go for it. What do you have to lose? $10 of silver,
a couple hours and a few $s worth of tufa. I'm always amazed how we
don't go fly a kite anymore, we go take a kite flying workshop!
Just use protective gloves, face shield, dark glasses and I use a
leather apron.
Hi: I"ve done a lot of cuttlbone casting over the years, but would
like to know more about casting in tuffa. Is it basically the same as
using cuttlebone? Where do you get it?
Tufa doesn’t have the accentuated texture of cuttlebone, instead
being slightly pebbled. It carves as easily as cuttle, perhaps a
little easier, and certainly doesn’t smell as nasty when casting.
Blocks of casting investment can be substituted for tufa, with a
resulting finer texture (almost smooth). There is an online technical
article from Lapidary Journal on tufa casting at http://www.lapidaryjournal.com/jj/jun00jj.cfm
I buy mine from IJS or Thunderbird out of Gallup, NM. You can also
check with local quarries. If they don’t have it, sometimes they can
point you to another nearby source. Ditto for rockhound clubs–just
specify tufa, not tuff. Tuff is too hard and grainy.
The Practical Metalsmith by Tim McCreight has lots of great tips for
all kinds of casting including tuffa and cuttle fish. Great book.
As far as measuring the amount of metal for cuttle fish casting - I
just eyeball it and add a little more. If I use too much I just end
up with a large button.
Hello All, this is a follow up on the difference between tuff and
tufa. I found a reference, (Lyell, 1853), that describes tuff as a
volcanic ash, but gives TWO varieties for tufa-- a calcareous tufa
and a volcanic tufa. Volcanic tufa is an Italian name for tuff and is
the variety used for tufa casting jewelry. Calcareous tufa is not
suitable for our purposes. Hope this helps. Will E.Dr. E. Hanuman
Aspler
Webmaster
I think there has been a clarification on the use of the words tuff
and tuffa since Lyell’s book, at least in English. I am looking at
the “Dictionary of Geological Terms”, third edition prepared by the
American Geological Institute. In here tuff is listed as a "general
term for all consolidated pyroclastic (yes, of igneous origin) rocks,
Not to be confused with tufa. (possibly the Italians still label both
as tufa) But tufa in this dictionary is a chemical sedimentary rock
composed of calcium carbonate. In other words, the stuff found
encrusted around hot springs and such. A hard, dense variety of it
would be called travertine. Of course, the igneous (volcanic) one is
the one we want for casting. Hope this helps. Rose Alene McArthur