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Casting with cuttle fish


#1

Dear all, I have just started casting sterling silver in cuttle fish
and was wondering whether any of you could offer advice on how to
improve my results.

I work in sterling silver and tend not to cast volumes larger than
5cc, my only heat source is a sievert propane gas torch with a medium
sized burner head, which seems to liquefy the metal without too much
trouble and has the added benefit of warming up my work shop. I throw
in some flux (tenacity) when the metal goes red and again when it
becomes molten. I then try and get the temperature up before pouring.

I make the moulds by dressing two pieces of cuttle fish (I divide
them into thirds) with sandpaper to get a flat surface and then press
the form into the fattest piece of bone, scraping out excess material
if the form is too big to do this in one go. I then carve in a sprue
and score some small vent lines from the inside of the mould before
clamping the two together and pouring the molten silver.

What I have found is that the end results differ quite a bit and I
would like to improve on what I have done. Also, could reusing
previously melted silver (e.g. recycling the sprues) and a build up
of glass in the crucible (I assume coming from the flux) be in part
to blame and is there a way around these?

Thanks
Chris


#2

Chris,

It sounds like you are doing most of the right things. I would
suggest that if you want to improve the looks of the final product,
you can dust the impressions with graphite dust (the same stuff used
to lubricate locks…don’t get the graphite with oil stuff though).
Then re-press the model to compact the graphite into the cuttle bone.
You can also make up a misture of borax, alcohol and sodium silicate
(aka waterglass and egg keep). Paint that in the impressions and let
it dry then paint it again. That will provide a nice smooth surface.
One other way is to use a candle and ‘smoke’ the impressions and
then repress the model again. The soot helps smooth it as well.
Some people enjoy the surface created by the bone however so it
depends on your own desires.

Re the ‘glass’ it is the flux that does it. It would help if you
stir the molten metal with a piece of wood dowel or carbon (graphite
rod) just before the pour. That clears the metal of impurities, moves
the flux to the side and absorbs excess 02 as well. Your pour needs
to be very smooth. There are ways of carbing a crucible out of a
charcoal block and wiring it to the bone so that when the metal is
molten, simply tip the whole thing verticle and the metal will run
directly into the mold. Be sure top make the gate large to
accommodate the metal. You can use old silver if it is properly
cleansed before melting it and dropping it into cold water to create
’casting grain’. It is quite a process of heating and placing it
into very hot pickle or acid, heating again, etc. If you are sure
the sprues are clean of all investment, melt them down drop into cool
water then put into hot pickle for 30 min or so. Then use 50/50 old
and new silver in your casting melts. This should give very nice
castings.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut1


#3

Chris, when I lived in Western Australia I loved cuttlefish casting.
I could get a bucketfull of good big pieces by taking a pleasant walk
along the beach. Now I’m in the UK, like you, I found it was rather
expensive to buy, compared to investment materials. Do you have a
cheap supply? I do find it very useful in some circumstances. Whilst
in Australia I ran short jewellery courses for the local arts and
crafts group and the final session was casting with cuttlefish, so
everyone got to use up all the bits of scrap arising from their
earlier sessions. So, a few thoughts:

You don’t say just how the end results differ, but the real trick is
to get the temperature high enough, and keep it high while pouring.
The metal should appear to spin in the crucible, and it helps to keep
the flame on the metal whilst pouring. Make the sprue and funnel
quite large, in fact as large as you can, so that the metal gets in
very quickly.

Stand the mould upright on a metal tray with dry sand in it. This
inspires confidence when pouring, so that you can do it quickly and
smoothly.

Lightly soot the inside of the mould as the final step before
assembling it for pouring.

Dont’t expect to get more than one casting from a mould. Sometimes
you can get more, but don’t expect it.

Recycling sprue material is fine. The usual rule of thumb is to
have at least 50 percent new metal in the melt.

You can use bits of scrap sheet an wire, but casting grain is
cheaper to buy, and is specifically formulated for casting.

I achieved interesting results when casting pendants by lightly
brushing parts of the mould, after pressing and removing the pattern,
so as to bring out the grain structure of the cuttlefish. Works well
on backgrounds, leave highlight areas smooth of course.

Good luck, and have fun.
Kevin (NW England, UK)


#4

Hello Kevin, You asked about a cheap source for cuttlebone. Here in
the US, some farm supply stores sell it in bulk to pet bird breeders.
I know you’re in the UK, but look for someone who breeds budgies and
ask where they get the cuttlebone. Hope this helps, Judy in Kansas

Judy M. Willingham, R.S.
Biological and Agricultural Engineering
237 Seaton Hall
Kansas State University
Manhattan KS 66506
(785) 532-2936


#5

I’ve lost the original post, but I believe someone in the UK was
looking for bulk sources for cuttlebone? Finally, a way I can help
someone on this list! Over my 20+ years of birdkeeping, I’ve found
several sources. These places sell it in either 1 pound or 5 pound
boxes. The UK source has a 11kg case available, plus smaller boxes as
well. If you have a choice of sizes, always get the large one–the
small ones may be too small to use for casting.

http://www.cuttleboneplus.com/cuttlebones.html (US company)
http://www.hermanbros-seed.com/pg1.htm (scroll down to cuttlebones; US 

company)
http://www.manor-farm-granaries.co.uk/newcataloguetop.html#millet (millet
&
cuttlefish are under the same heading; located in the U.K.)

–Kathy Johnson
Feathered Gems Aviary
"Caring For Your New Bird"
http://www.ddc.com/~kjohnson/birdcare.htm
Feathered Gems Jewelry
http://www.featheredgems.com


#6

Kathy, I was one of the two UK folk discusing cuttlefish. Thanks so
much for the lead on supplies, I’ve just taken a look and this
promises to be a better deal than I’ve found previously.

http://www.manor-farm-granaries.co.uk/newcataloguetop.html#millet
(millet & cuttlefish are under the same heading; located in the U.K.)

Kevin (NW England, UK)