DIYbanter - low-temp melt castings basics

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Treedweller

March 8th 05 12:27 AM

low-temp melt castings basics

Hi,
I'm new to this group, but looked through over 20,000 headers and
FAQ's for info before posting this (sorry if it's an oldie that was
worn out long ago).

I'm looking to make some simple one-sided castings from tin, pewter,
zinc, or other easy metal. I've tried sand casting (distorted when I
poured in the metal) and carving a wood mold (moisture boiled out and
created air pockets).

I got recommendation to try "investment casting" with "Satin Cast" and
I've also heard of carving soapstone.

Anyone willing to save me some of my next few obvious mistakes? If I
go for soapstone, where can I get a small piece cheap? will the Satin
Cast work well (I ordered some)? Any other suggestions? I've sen
rubber mold products, but would expect it to melt when exposed to
molten metal.

Sorry to be so vague, but I'm just starting to figure this out--any
help would be appreciated.

Thanks,
Keith

Jeff Wisnia

March 8th 05 12:49 AM

Treedweller wrote:
Hi,
I'm new to this group, but looked through over 20,000 headers and
FAQ's for info before posting this (sorry if it's an oldie that was
worn out long ago).

I'm looking to make some simple one-sided castings from tin, pewter,
zinc, or other easy metal. I've tried sand casting (distorted when I
poured in the metal) and carving a wood mold (moisture boiled out and
created air pockets).

I got recommendation to try "investment casting" with "Satin Cast" and
I've also heard of carving soapstone.

Anyone willing to save me some of my next few obvious mistakes? If I
go for soapstone, where can I get a small piece cheap? will the Satin
Cast work well (I ordered some)? Any other suggestions? I've sen
rubber mold products, but would expect it to melt when exposed to
molten metal.

Sorry to be so vague, but I'm just starting to figure this out--any
help would be appreciated.

Thanks,
Keith

If the pieces are small and you want to try something really retro you
can make mold cavities in cuttlefish bone after sanding the flat side of
the pieces of bone smooth. You can carve the mold cavity or if you have
a pattern piece just squeeze or pound it into the bone.

Here's a link:

http://artisans.ombra.net/tecniche/CUTTLEBONE.htm

I had an old timer jeweler show this to me when I was a kid. He
demonstrated the technique by casting a pair of silver ear rings.

It might just satisfy your needs, and the cuttlefish bone IS still
available:

http://alpha-supply.com/catalog/page...=cat&catid=248

Or, try your local pet shop. IIRC parrots and similar birds like to chew
on it.

HTH,

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

Treedweller

March 8th 05 02:39 AM

On Mon, 07 Mar 2005 19:49:04 -0500, Jeff Wisnia
wrote:
If the pieces are small and you want to try something really retro you
can make mold cavities in cuttlefish bone after sanding the flat side of
the pieces of bone smooth. You can carve the mold cavity or if you have
a pattern piece just squeeze or pound it into the bone.

Here's a link:

http://artisans.ombra.net/tecniche/CUTTLEBONE.htm

I had an old timer jeweler show this to me when I was a kid. He
demonstrated the technique by casting a pair of silver ear rings.

It might just satisfy your needs, and the cuttlefish bone IS still
available:

http://alpha-supply.com/catalog/page...=cat&catid=248

Or, try your local pet shop. IIRC parrots and similar birds like to chew
on it.

HTH,

Jeff
Hmm, that's definitely low tech! Thanks for the idea--I'll check the
pet shop, but I think I need bigger pieces than I've seen in this
material. I'm thinking of medallions about 2" to 2-1/2 inches in
diameter.

k

Bob May

March 8th 05 03:24 AM

Wood will work but you indeed have the problem with the tree sap. That can
be cured by putting the mold in an oven and cooking it for a while to get
the moisture out of the wood.
Another is to use plaster or pour stone. This also needs to have the
moisture cooked out of it before usage or you will have shattered molds.
Note that plaster will degrade with high temps as the water is driven out of
the chemical bond with the plaster itself.

--
Why isn't there an Ozone Hole at the NORTH Pole?

[email protected]

March 8th 05 03:50 AM

Go to Home Depot and get some casting plaster. You will need to heat
it to drive the moisture out. Not just the non-bound water, but also
the water that caused the plaster to set. This makes it weak. So you
might try putting the piece on top of some waxed paper , then brushing
plaster on it so you don't have air bubbles on the surface of your
piece. Then put some chicken wire over the plaster and add more
plaster. Let all that set. Then turn over and remove your pattern.
Heat to about 400 degrees F ( I am guessing at the temp ) and then puor
the metal while the mold is still hot.

You might also try buying some silicon rubber caulking compound while
you are at Home Depot. It ought to work for one or two pieces. They
make silicon rubber that is more heat resistant, but I am not sure
where you would find it.

Dan

Ecnerwal

March 8th 05 03:57 AM

Art supply store should have the soapstone. A flea market might also
(bed-warming stones, used griddles), as might a kitchen supply store
(griddles, but not cheap). Ideally, find a broken soapstone stove in a
junkyard.

Toss your wood mold in an oven for a while, or just do a few pours in it
and remelt them to get the surface moisture out.

There may be a problem with your sand-casting technique or sand mix if
it's "distorting when you pour in the metal"

--
Cats, Coffee, Chocolate...vices to live by

jackK

March 8th 05 05:12 AM

Tim Williams

March 8th 05 06:36 AM

"Treedweller" wrote in message
...
I'm looking to make some simple one-sided castings from tin, pewter,
zinc, or other easy metal. I've tried sand casting (distorted when I
poured in the metal) and carving a wood mold (moisture boiled out and
created air pockets).

Silicone molds may be suitable for this, although a bit much for just
one-sided castings.

Plaster, cast around a greased pattern and baked in the oven (at 500°F for
an hour or three) will hold up to all white metals. Better still, if your
mold fails, you can grind it up and viola, Plaster of Paris ready to use
again!

Wood will only work for solder (basically pewter), the cellulose and etc.
decomposes (burns) much above 400 or 500°F, releasing gas.

What was wrong with your sand casting? Sand, properly bonded and tempered,
will do anything from mercury (heh, well, if you cooled your mold with dry
ice first) to steel and beyond. If it can be melted and poured, chances are
it's been put in a sand mold of some sort at some time.

Greensand can be made very simply from sand with a little clay and water to
make it sticky, if you don't know how it should feel it will take a lot of
adjustment to get the right mixture but it's the simplest, easiest to use,
and oldest (i.e. ancient) route.

Anyone willing to save me some of my next few obvious mistakes? If I
go for soapstone, where can I get a small piece cheap? will the Satin
Cast work well (I ordered some)? Any other suggestions? I've sen
rubber mold products, but would expect it to melt when exposed to
molten metal.

Silicones are available which withstand up to 800°F, these are a bit
expensive; a cooler-rated one can be used, although you get shorter life out
of it.

Tim

--
"California is the breakfast state: fruits, nuts and flakes."
Website: http://webpages.charter.net/dawill/tmoranwms

Treedweller

March 8th 05 06:56 AM

On Mon, 07 Mar 2005 18:27:31 -0600, Treedweller
wrote:

Hi,
I'm new to this group, but looked through over 20,000 headers and
FAQ's for info before posting this (sorry if it's an oldie that was
worn out long ago).

I'm looking to make some simple one-sided castings from tin, pewter,
zinc, or other easy metal. I've tried sand casting (distorted when I
poured in the metal) and carving a wood mold (moisture boiled out and
created air pockets).

I got recommendation to try "investment casting" with "Satin Cast" and
I've also heard of carving soapstone.

Anyone willing to save me some of my next few obvious mistakes? If I
go for soapstone, where can I get a small piece cheap? will the Satin
Cast work well (I ordered some)? Any other suggestions? I've sen
rubber mold products, but would expect it to melt when exposed to
molten metal.

Sorry to be so vague, but I'm just starting to figure this out--any
help would be appreciated.

Thanks,
Keith
Good ideas from lots of people--thanks.

To answer a few questions, the sand probably didn't work because of my
technique, as was suggested (I was pouring directly into the mold,
when I should have probably made a trough to let the metal run into
the mold instead of splashing down). But since I was pressing a clay
model into the sand and it broke on the first try (the disk had cupped
because of uneven drying), I was looking for something a bit more
sustainable in terms of mass production. Maybe I'll carve a model
from wood and use it to press into the sand for another go.

The wood mold did get better after I dried it in the oven, and
repetition was showing improvement, but also the wood was burning more
each time, so again mass production was not looking promising.

I saw a piece of soapstone at one art supply (out of many visited) but
only a very large hunk, and more than I was hoping to spend (as
always, I should probably just get real and face the fact that I'll
have to spend to get good results).

It was suggested to me that plain plaster would not cut it--maybe I
should have tried it, hell it's cheap.

Another question soapstone:
Just how easy is it to work this stuff? If I buy the big chunk, can I
chisel off nice, clean faces, or can I cut it with a saw (hacksaw or
other)? I'd like to have at least one flat side, preferably two, to
make it easy to have a level mold to pour into. I realize the point
is that this stuf is soft and easy to carve, but how soft is soft when
we're talking stone? I'm used to wood, but haven't tried the hard
stuff.

Thanks again, and please keep the advice coming--if nothing else, it's
making me feel less foolish for my early failures.

k

jackK

March 8th 05 08:17 AM

David Billington

March 8th 05 09:45 AM

For casting pewter I have used Dow Corning Silastic 3120 with BC
catalyst with good success.

Treedweller wrote:

Hi,
I'm new to this group, but looked through over 20,000 headers and
FAQ's for info before posting this (sorry if it's an oldie that was
worn out long ago).

I'm looking to make some simple one-sided castings from tin, pewter,
zinc, or other easy metal. I've tried sand casting (distorted when I
poured in the metal) and carving a wood mold (moisture boiled out and
created air pockets).

I got recommendation to try "investment casting" with "Satin Cast" and
I've also heard of carving soapstone.

Anyone willing to save me some of my next few obvious mistakes? If I
go for soapstone, where can I get a small piece cheap? will the Satin
Cast work well (I ordered some)? Any other suggestions? I've sen
rubber mold products, but would expect it to melt when exposed to
molten metal.

Sorry to be so vague, but I'm just starting to figure this out--any
help would be appreciated.

Thanks,
Keith

Rick Cook

March 8th 05 10:09 AM

Karl Vorwerk

March 8th 05 10:52 AM

I used to cast pewter in 2 part silicone also. Works well.
Ney smelting and refining in NY used to have the best prices for pewter.
Karl

"David Billington" wrote in message
.. .
For casting pewter I have used Dow Corning Silastic 3120 with BC catalyst
with good success.

Treedweller wrote:

Hi,
I'm new to this group, but looked through over 20,000 headers and
FAQ's for info before posting this (sorry if it's an oldie that was
worn out long ago).

I'm looking to make some simple one-sided castings from tin, pewter,
zinc, or other easy metal. I've tried sand casting (distorted when I
poured in the metal) and carving a wood mold (moisture boiled out and
created air pockets).

I got recommendation to try "investment casting" with "Satin Cast" and
I've also heard of carving soapstone.
Anyone willing to save me some of my next few obvious mistakes? If I
go for soapstone, where can I get a small piece cheap? will the Satin
Cast work well (I ordered some)? Any other suggestions? I've sen
rubber mold products, but would expect it to melt when exposed to
molten metal.

Sorry to be so vague, but I'm just starting to figure this out--any
help would be appreciated.

Thanks,
Keith

Bugs	March 8th 05 02:10 PM

Contact a dental supply house and buy some investment for casting. It
mixes up like Plaster of Paris, but will stand very high temps. The
rubber material, wax also works, is mainly to make a master mold to
pour the investment into. This is what is used to cast gold crowns and
dental bridges. It isn't all that expensive, although I haven't bought
any for over 20 years.
Bugs

[email protected]

March 8th 05 06:04 PM

Bob May

March 8th 05 09:54 PM

For sandcasting, you don't put the piece into the sand but rather put the
sand into the mold with the piece on the bottom. Then pack the sand well
and you should be set.
Splashing the metal in does tend to destroy the mold rather rapidly as the
metal is rather heavy and erodes where it hits. If you have to splash, use
a thin stream and don't allow a large drop of the metal.

--
Why isn't there an Ozone Hole at the NORTH Pole?

[email protected]

March 9th 05 03:42 AM

Plain plaster will work! You can buy casting plaster at Home Depot in
25 lb bags.

Soapstone is easy to work, but dulls tools fairly rapidly. The local
highschool art classes use wood working tools to do scuptures out of
soapstone. Not as well known is the fact that you can use soapstone
powder somewhat like powdered metal. Mold it and compress it, then
sinter it. It is how the better vacuum tube sockets were made.

Dan

Bob Engelhardt

March 9th 05 02:51 PM

wrote:

... you can use soapstone
powder somewhat like powdered metal. Mold it and compress it, then
sinter it. ...

Hey, that's cool. How much pressure to compress and how much heat to
sinter, would you think? In other words, do you think it's something
that an HSM could do?

Bob

[email protected]

March 9th 05 04:20 PM

I do think it is something that can be done at home. The details are
in " Procedures in Experimental Physics " by Strong. Available as a
reprint for Linsay. I will look it up and post. You can also turn
solid soapstone into Steatite in a pottery kiln. Experiments at the
highschool did not work well. The piece did change, but fractured along
an impurity line. I did not see the actual experiment.

Dan
Bob Engelhardt wrote:
wrote:

... you can use soapstone
powder somewhat like powdered metal. Mold it and compress it, then
sinter it. ...

Hey, that's cool. How much pressure to compress and how much heat to

sinter, would you think? In other words, do you think it's something

that an HSM could do?

Bob

Treedweller

March 10th 05 11:44 PM

On 8 Mar 2005 19:42:24 -0800, wrote:

Plain plaster will work! You can buy casting plaster at Home Depot in
25 lb bags.

Soapstone is easy to work, but dulls tools fairly rapidly. The local
highschool art classes use wood working tools to do scuptures out of
soapstone. Not as well known is the fact that you can use soapstone
powder somewhat like powdered metal. Mold it and compress it, then
sinter it. It is how the better vacuum tube sockets were made.

Dan
Good to know, Thanks!

I got my plaster today, so I'll give it a try and if it doesn't turn
out well I'll go buy the big hunk o' soapstone.

k

[email protected]

March 11th 05 01:46 AM

I did look it up and found the temperatures higher than I remembered.
Solid soapstone had two temperatures. First it said 1300 C. Then it
said 1100 C for 24 or 48 hours. About 1 % shrinkage for the solid.
Need to go slow thru 500 degrees to 800 degrees to let the bound water
leave.

Compacted........ No pressure given. About 8% shrinkage. And the temp
was 1100 C. Maybe I ought to check the last figure again.

Dan

wrote:
I do think it is something that can be done at home. The details are
in " Procedures in Experimental Physics " by Strong. Available as a
reprint for Linsay. I will look it up and post. You can also turn
solid soapstone into Steatite in a pottery kiln. Experiments at the
highschool did not work well. The piece did change, but fractured
along
an impurity line. I did not see the actual experiment.

Dan
Bob Engelhardt wrote:
wrote:

... you can use soapstone
powder somewhat like powdered metal. Mold it and compress it,
then
sinter it. ...

Hey, that's cool. How much pressure to compress and how much heat
to

sinter, would you think? In other words, do you think it's
something

that an HSM could do?

Bob

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