Sandra asked about method for simple room temperature casting other
than cuttlebone.
I have a friend who teaches metal working who has the students pour
blocks made of regular casting investment that are allowed to cure.
The top surface of the block is then carved to receive the molten
silver.
Tim McCreight’s “The Complete Metalsmith” discussed using charcoal
blocks in a similar manner on page 84.
Chunk Kiesling
Chunk: I think I should repeat here that the investment should be
totally DRY if you do this, any moisture will cause the molten metal
to explode in your face! Dave
For gravity casting I recommend the delft method of sand casting. The
sand it particularly fine and clumps well. The castimgs in silver gold
copper alloys are super. There are many limitations of shape, but hey
it’s only a two-part mold.
Bri
B r i a n � A d a m
E y e g l a s s e s
a n d O t h e r J e w e l l e r y
Arrow Lane Arrowtown NEW ZEALAND
mobile 025 200 1236
Chunk: I think I should repeat here that the investment should be totally DRY if you do this, any moisture will cause the molten metal to explode in your face!
Hi,
Just my $.02 worth but you can put the investment into your burnout
furnace or your kitchen oven at home for about a half an hour at 300
degrees F. The water boils off at 212 deg. F. This technique is
also useful in using your casting investment as soldering investment
to hold parts in position for soldering.
Skip
Skip and others,
I would not pour hot metal into investment that has been “burned out"
in an oven at 300 F for 1/2 hour!! There is too much potential of
"chemical water” still being in the investnment material in quantities
high enough to cause metal to blow all over the place. The physical
water would possibly be gone in 1/2 hour (dependng on how thick the
item is) but the chemical water will still be there. This water will
not drive off until the teme is up near 900 F. This chemical water
can cause just as bid an explosion and the physical water so I would
recomment care here. Just my 2c, worth what it cost ya! John Dach
Thanks John. I generally use 1000 deg F on my burnout furnace. I
have done it the other way but have additionally heated up the
investment very slowly with the torch first. Skip
I just leave the investment in my oven while I’m cooking, or on top
of the gas-fired frig for a few weeks. I usually do up a big block at
a time, then just cut it into smaller blocks for use when I need it.
Investment is finer grained than tufa and turns out better castings. K.P. in WY
Katherine, how do you keep the investment “artificial tufa” dust from
getting all over everything? From my experiance investment is pretty
nasty stuff. Geo.
Katherine, how do you keep the investment "artificial tufa" dust from getting all over everything? From my experiance investment is pretty nasty stuff.
Are you talking about when you’re casting it, or as you’re working
it?
Before casting, you stabilize it with a sodium silicate solution.
This gives you a hard shell which prevents it from flaking or
deteriorating. It also means you’re not going to do any additional
carving on it. It allows you to do multiple casting without
significant deterioration of the mold.
When working in it, it’s not necessary to use power tools. Working
with hand tools keeps the dust relatively contained in a small area. I
happen to do my carvings sitting at the kitchen table with a
wastebasket nearby, usually while I’m watching TV with the family,
talking, or doing the homeschooling bit. The dust can be cleaned up
from the smooth surfaces of the table and floor with just a wet paper
towel. I don’t generally blow the dust off of the carving, but instead
knock it out against the side of the wastebasket. For my final check,
I’ll use a very soft sable brush to get out most of the dust, brushing
away from me or anyone else, of course. Just before using the sodium
silicate solution to stabilize the mold, I take it outside and give it
a good dusting with some canned air I use for dusting the computer.
We have pretty much constant wind where I live, so getting upwind
isn’t a big problem.
My other blocks which I haven’t yet carved, but which are thoroughly
dry, I store in plastic bags on top of my compartmented drawers. I
don’t have to worry about the dust from the investment floating
around, and I don’t have to worry about household dust getting on the
blocks. I’m not the best housekeeper in the world, after all.
I hope this addresses your concerns about contamination and exposure
to silicosis. You’re smart to have concerns about the safety of
working the material. Tufa and cuttle bone are every bit as hazardous,
as well as a plethora of things we work with every day in our line of
work. Like anything else, being aware of the hazards is the first step
in prevention. Reasonable precautions takes care of the rest.
With sincere regards,
K.P.
Thankyou Katherine, for the about your technique. For me
all the dust at all the stages of investment use from pouring to
washup causes a problem as I have residual breathing obstruction from
having had respiratory tract cancer a number of years ago. I do all
my plaster work and investment work outside with a facial filter mask
for that reason. Your tip about using sodium silicate solution was a
really good one. Looking at John Burgess’ handy dandy name guide that is water glass.
Geo.