I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

"F. George McDuffee" wrote in message
...
On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm


It's good to make a point of the fact that you have to know what you're
doing to use plaster molds for bronze temperatures, or you're in for an
explosion.

It will need a high-temperature mixture, probably containing vermiculite or
some modern ceramic replacement, and it will have to be calcined. "Bone dry"
isn't dry enough. You have to drive off some of the chemically retained
water.

Another option is green sand dusted with plumbago (graphite powder). That is
said to be capable of reproducing a person's fingerprint. I've seen some
aluminum castings done that way and they look almost like investment
castings.

--
Ed Huntress

"Ed Huntress" wrote:

It's good to make a point of the fact that you have to know what you're
doing to use plaster molds for bronze temperatures, or you're in for an
explosion.

I'm thinking plaster is like gypsum and under high heat will give up water vapor. So the
mould would have to be baked to drive it off.

My experience with bullet casting is any water combined with hot metal is catastrophic. I
was using Marvelux for flux, it has an affinity for water and I didn't preheat the spoon I
used to flux with before putting it in the pot. BANG! OUCH!

Wes

"Wes" wrote in message
...
"Ed Huntress" wrote:

It's good to make a point of the fact that you have to know what you're
doing to use plaster molds for bronze temperatures, or you're in for an
explosion.

I'm thinking plaster is like gypsum and under high heat will give up water
vapor. So the
mould would have to be baked to drive it off.

My experience with bullet casting is any water combined with hot metal is
catastrophic. I
was using Marvelux for flux, it has an affinity for water and I didn't
preheat the spoon I
used to flux with before putting it in the pot. BANG! OUCH!

Wes

Right. And when you get up to bronze-casting temperatures, the problem is
*much* more dangerous.

I have a big collection of literature from US Gypsum on casting plasters,
which I haven't consulted for, oh, maybe 20 years g, and it's buried deep
in my research material somewhere, but I think there's enough information
around the Web to put the story together. Using plaster (which is gypsum) to
cast aluminum is one thing -- although you still have to calcine it for
that. For bronze, you have to cook it a lot more, at a higher temperature,
and you need to have heat-resistant additives in it. Vermiculite (expanded
mica) is a traditional one. I don't recall how much you're supposed to use.

Since the OP is talking about an open mold, the one thing you don't have to
worry about here is venting. That's another big issue when you use plaster
for casting molds.

Personally, I'd first try sand with a dusting of graphite powder. If you
dust it just right, it fills in the texture of the sand and gives you a
really smooth finish. You can sprinkle it in from an old stocking or a piece
of pantyhose. Don't let your wife see it...

--
Ed Huntress

On Fri, 31 Oct 2008 22:59:53 -0600, the infamous F. George McDuffee
scrawled the following:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

Good discourse.

Some of the sculpture there is really interesting, Unk. But what's
with those painter "artists"? My gawd, man. Does that **** really
SELL? I guess they produce the equivalent (or worse) of Rap in
painting. This reminds me why I don't support the National Endowment
for the Arts.

Oliveira paintings, Staprans, Moses, Frohsin, any paint/poetry by
freakin' Rodefer: Ptui! I feel like washing my eyes out.

--
Everything I did in my life that was worthwhile I caught hell for.
-- Earl Warren

On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason
the molds are seasoned in the furnace, Tim, as you found out.

--
Everything I did in my life that was worthwhile I caught hell for.
-- Earl Warren

"Larry Jaques" wrote in message
...
On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason
the molds are seasoned in the furnace, Tim, as you found out.

It's not just "seasoning." First you have to dry out the free water. Then
you have to drive off a percentage of the chemically retained water. That's
called "calcining." For casting zinc or aluminum, it doesn't take much. For
casting brass or bronze, it's critical, and requires more heat.

It's not something to do by guess and by gosh. Those things can explode in a
serious way. Furthermore, ordinary Plaster of Paris will not do for casting
brass or bronze. You need special high-temperature casting plaster.

--
Ed Huntress

Ed Huntress wrote:

"Larry Jaques" wrote in message
...
On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason
the molds are seasoned in the furnace, Tim, as you found out.

It's not just "seasoning." First you have to dry out the free water. Then
you have to drive off a percentage of the chemically retained water. That's
called "calcining." For casting zinc or aluminum, it doesn't take much. For
casting brass or bronze, it's critical, and requires more heat.

I learned about this the hard way. It seems that regular plaster just
falls apart once it's been heated too long and is really dehydrated.

It's not something to do by guess and by gosh. Those things can explode in a
serious way. Furthermore, ordinary Plaster of Paris will not do for casting
brass or bronze. You need special high-temperature casting plaster.

I've had a few things come out out with brass, if the mold cracking during
use is ok.

On Sat, 01 Nov 2008 06:44:40 -0700, Larry Jaques wrote:

On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason the
molds are seasoned in the furnace, Tim, as you found out.

Some were. Fortunately a 1-inch square bit of plaster doesn't do much
damage.

A quarter-ounce of solder ejecting straight up from the mold can be
exciting, though.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Sat, 01 Nov 2008 14:46:24 +0000, Cydrome Leader wrote:

Ed Huntress wrote:

"Larry Jaques" wrote in message
...
On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex ,
or even 2 part sand molds, probably just bronze poured onto a flat
cope that has an depression in it and a dam built around the
depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets
for miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason
the molds are seasoned in the furnace, Tim, as you found out.

It's not just "seasoning." First you have to dry out the free water.
Then you have to drive off a percentage of the chemically retained
water. That's called "calcining." For casting zinc or aluminum, it
doesn't take much. For casting brass or bronze, it's critical, and
requires more heat.

I learned about this the hard way. It seems that regular plaster just
falls apart once it's been heated too long and is really dehydrated.

It's not something to do by guess and by gosh. Those things can explode
in a serious way. Furthermore, ordinary Plaster of Paris will not do
for casting brass or bronze. You need special high-temperature casting
plaster.

I've had a few things come out out with brass, if the mold cracking
during use is ok.

AFAIK plaster of paris is made by roasting gypsum; adding water just lets
the dehydrated powder turn back into gypsum.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Sat, 01 Nov 2008 09:56:09 -0400, Ed Huntress wrote:

"Larry Jaques" wrote in message
...
On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex ,
or even 2 part sand molds, probably just bronze poured onto a flat
cope that has an depression in it and a dam built around the
depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason
the molds are seasoned in the furnace, Tim, as you found out.

It's not just "seasoning." First you have to dry out the free water.
Then you have to drive off a percentage of the chemically retained
water. That's called "calcining." For casting zinc or aluminum, it
doesn't take much. For casting brass or bronze, it's critical, and
requires more heat.

It's not something to do by guess and by gosh. Those things can explode
in a serious way. Furthermore, ordinary Plaster of Paris will not do for
casting brass or bronze. You need special high-temperature casting
plaster.

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

"Tim Wescott" wrote in message
news
On Sat, 01 Nov 2008 09:56:09 -0400, Ed Huntress wrote:

"Larry Jaques" wrote in message
...
On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex ,
or even 2 part sand molds, probably just bronze poured onto a flat
cope that has an depression in it and a dam built around the
depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason
the molds are seasoned in the furnace, Tim, as you found out.

It's not just "seasoning." First you have to dry out the free water.
Then you have to drive off a percentage of the chemically retained
water. That's called "calcining." For casting zinc or aluminum, it
doesn't take much. For casting brass or bronze, it's critical, and
requires more heat.

It's not something to do by guess and by gosh. Those things can explode
in a serious way. Furthermore, ordinary Plaster of Paris will not do for
casting brass or bronze. You need special high-temperature casting
plaster.

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

I had collected some info years ago, mostly from US Gypsum, that I think is
no longer available at all. In fact, around eight years ago I decided to
update what I have by calling them to see if there was anything lurking in
their archives, and one of their people sent me some more photocopies.

There also is information about it in old British MAP books, which I have.
You may want to check the listings for those Brit model books and see what's
in print. And plaster is being used today in some high-tech casting
operations. The materials must be available commercially.

I saved all of this stuff because my intention is to write a pamphlet or
short book about it. Gathering it and summarizing it will be a very big job,
or I'd volunteer to send copies of what I have. Before I do so I will
contact current suppliers to see what updates are available.

I should mention, though, that I have several such projects hanging around
for a rainy day, and they may never see the light, because the market for
this kind of info is so small that it may not be worth it to do it right. I
always have three times as many projects in the hopper than I can possibly
complete. It's just a characteristic of my type of work.

US Gypsum (now USG) is, I think, out of that business. But you may find they
would dig into their archives for you, if you luck upon the right person.
It's usually somewhat frustrating work. That's how I make a living. d8-)

--
Ed Huntress

On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:


Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

Google on investment casting. Jewellers do this routinely with high
melting point metals like gold, silver and even platinum.

The stuff to use is investment casting plaster.
http://www.gp.com/build/product.aspx?pid=5901

It can be found at jewellers' supply places. Once the mold is made,
it needs to be "burned out" or calcined at about 1200F long enough to
"burn out" the wax and also to drive off excess moisture.

With ally you'll probably need quite a tall sprue to get enough
pressure to get molten metal into the smaller internal features -- or,
use a centrifugal approach.

"Don Foreman" wrote in message
news
On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:


Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

Google on investment casting. Jewellers do this routinely with high
melting point metals like gold, silver and even platinum.

The stuff to use is investment casting plaster.
http://www.gp.com/build/product.aspx?pid=5901

It can be found at jewellers' supply places. Once the mold is made,
it needs to be "burned out" or calcined at about 1200F long enough to
"burn out" the wax and also to drive off excess moisture.

With ally you'll probably need quite a tall sprue to get enough
pressure to get molten metal into the smaller internal features -- or,
use a centrifugal approach.

Just be aware that investment molds typically have much less of a venting
problem than cast plaster molds do, because they're a lot thinner. I should
say "gas porosity" rather than venting, actually.

--
Ed Huntress

On Nov 1, 10:52*am, "Ed Huntress" wrote:
"Don Foreman" wrote in message

news




On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:

Do you know of any references on how to do it right? *I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

Google on investment casting. *Jewellers do this routinely with high
melting point metals like gold, silver and even platinum.

The stuff to use is investment casting plaster.
http://www.gp.com/build/product.aspx?pid=5901

It can be found at jewellers' *supply places. *Once the mold is made,
it needs to be "burned out" or calcined at about 1200F long enough to
"burn out" the wax and also to drive off excess moisture.

With ally you'll probably need quite a tall sprue to get enough
pressure to get molten metal into the smaller internal features -- or,
use a centrifugal approach.

Just be aware that investment molds typically have much less of a venting
problem than cast plaster molds do, because they're a lot thinner. I should
say "gas porosity" rather than venting, actually.

--
Ed Huntress- Hide quoted text -

- Show quoted text -

So, back to sand , green sand... I've heard that a lot but never
seriously looked into it. Is
it mixed w/oil , but with extra fine grain, or what?.

I eschewed lost wax investment casting because I don't have the gear
anymore and don't
want to pay someone else for these molds, and plaster sounds like just
an extra bit too
much trouble . Oil sand I can do down and dirty .

googling green sand for now...

D

"Dar" wrote in message
...
On Nov 1, 10:52 am, "Ed Huntress" wrote:
"Don Foreman" wrote in message

news




On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

Google on investment casting. Jewellers do this routinely with high
melting point metals like gold, silver and even platinum.

The stuff to use is investment casting plaster.
http://www.gp.com/build/product.aspx?pid=5901

It can be found at jewellers' supply places. Once the mold is made,
it needs to be "burned out" or calcined at about 1200F long enough to
"burn out" the wax and also to drive off excess moisture.

With ally you'll probably need quite a tall sprue to get enough
pressure to get molten metal into the smaller internal features -- or,
use a centrifugal approach.

Just be aware that investment molds typically have much less of a venting
problem than cast plaster molds do, because they're a lot thinner. I
should
say "gas porosity" rather than venting, actually.

--
Ed Huntress- Hide quoted text -

- Show quoted text -

So, back to sand , green sand... I've heard that a lot but never
seriously looked into it. Is
it mixed w/oil , but with extra fine grain, or what?.

First, green sand is not mixed with oil. It's mixed with clay and water. It
is based on sharp, fine-grained sand, but your Googling should give you a
better idea than we could in a short message.

Regarding the oil, there are two types of molding sand that use oil. One is
the very popular Petrobond, which most users say is easier to use than green
sand. It's a combination of sand, motor oil and a processed clay that is
"organophilic," which means it absorbs oil rather than water.

Just to avoid confusion, this is NOT the same thing as the old-style
core-molding mixes that used linseed oil as a binder. Those materials had to
be baked before use, and the point of their formulation was to stand up
better to crushing forces that occur when a casting cools around a core.
There also are baked-sand molds as well as cores, but, today, they don't use
linseed. I'm not sure if they ever did.

I eschewed lost wax investment casting because I don't have the gear
anymore and don't
want to pay someone else for these molds, and plaster sounds like just
an extra bit too
much trouble . Oil sand I can do down and dirty .

It's supposed to be really nice for hobby-scale operations.

googling green sand for now...

D

On Nov 1, 12:20*pm, "Ed Huntress" wrote:
"Dar" wrote in message

...
On Nov 1, 10:52 am, "Ed Huntress" wrote:





"Don Foreman" wrote in message

news

On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

Google on investment casting. Jewellers do this routinely with high
melting point metals like gold, silver and even platinum.

The stuff to use is investment casting plaster.
http://www.gp.com/build/product.aspx?pid=5901

It can be found at jewellers' supply places. Once the mold is made,
it needs to be "burned out" or calcined at about 1200F long enough to
"burn out" the wax and also to drive off excess moisture.

With ally you'll probably need quite a tall sprue to get enough
pressure to get molten metal into the smaller internal features -- or,
use a centrifugal approach.

Just be aware that investment molds typically have much less of a venting
problem than cast plaster molds do, because they're a lot thinner. I
should
say "gas porosity" rather than venting, actually.

--
Ed Huntress- Hide quoted text -

- Show quoted text -
So, back to sand , green sand... *I've heard that a lot but never
seriously looked into it. Is
it mixed w/oil *, but with extra fine grain, or what?.

First, green sand is not mixed with oil. It's mixed with clay and water. It
is based on sharp, fine-grained sand, but your Googling should give you a
better idea than we could in a short message.

Regarding the oil, there are two types of molding sand that use oil. One is
the very popular Petrobond, which most users say is easier to use than green
sand. It's a combination of sand, motor oil and a processed clay that is
"organophilic," which means it absorbs oil rather than water.

Just to avoid confusion, this is NOT the same thing as the old-style
core-molding mixes that used linseed oil as a binder. Those materials had to
be baked before use, and the point of their formulation was to stand up
better to crushing forces that occur when a casting cools around a core.
There also are baked-sand molds as well as cores, but, today, they don't use
linseed. I'm not sure if they ever did.

I eschewed lost wax investment casting because I don't have the gear
anymore and don't
want to pay someone else for these molds, and plaster sounds like just
an extra bit too
much trouble . Oil sand I can do down and dirty *.

It's supposed to be really nice for hobby-scale operations.

googling green sand for now...

D- Hide quoted text -

- Show quoted text -

Interestingly, I found a green sand , Diamond Green Sand , and the
guy there said
I could mix a particular one, formulated for detail, with oil or
water . Now, to find
a place that will sell less than a truckload, lol !

D

"Dar" wrote in message
...
On Nov 1, 12:20 pm, "Ed Huntress" wrote:
"Dar" wrote in message

...
On Nov 1, 10:52 am, "Ed Huntress" wrote:





"Don Foreman" wrote in message

news

On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:

Do you know of any references on how to do it right? I've got a
project
in mind (that probably needs to wait 10 years) that could be done
quite
well with plaster cast aluminum, I think.

Google on investment casting. Jewellers do this routinely with high
melting point metals like gold, silver and even platinum.

The stuff to use is investment casting plaster.
http://www.gp.com/build/product.aspx?pid=5901

It can be found at jewellers' supply places. Once the mold is made,
it needs to be "burned out" or calcined at about 1200F long enough to
"burn out" the wax and also to drive off excess moisture.

With ally you'll probably need quite a tall sprue to get enough
pressure to get molten metal into the smaller internal features -- or,
use a centrifugal approach.

Just be aware that investment molds typically have much less of a
venting
problem than cast plaster molds do, because they're a lot thinner. I
should
say "gas porosity" rather than venting, actually.

--
Ed Huntress- Hide quoted text -

- Show quoted text -
So, back to sand , green sand... I've heard that a lot but never
seriously looked into it. Is
it mixed w/oil , but with extra fine grain, or what?.

First, green sand is not mixed with oil. It's mixed with clay and water.
It
is based on sharp, fine-grained sand, but your Googling should give you a
better idea than we could in a short message.

Regarding the oil, there are two types of molding sand that use oil. One
is
the very popular Petrobond, which most users say is easier to use than
green
sand. It's a combination of sand, motor oil and a processed clay that is
"organophilic," which means it absorbs oil rather than water.

Just to avoid confusion, this is NOT the same thing as the old-style
core-molding mixes that used linseed oil as a binder. Those materials had
to
be baked before use, and the point of their formulation was to stand up
better to crushing forces that occur when a casting cools around a core.
There also are baked-sand molds as well as cores, but, today, they don't
use
linseed. I'm not sure if they ever did.

I eschewed lost wax investment casting because I don't have the gear
anymore and don't
want to pay someone else for these molds, and plaster sounds like just
an extra bit too
much trouble . Oil sand I can do down and dirty .

It's supposed to be really nice for hobby-scale operations.

googling green sand for now...

D- Hide quoted text -

- Show quoted text -

Interestingly, I found a green sand , Diamond Green Sand , and the
guy there said
I could mix a particular one, formulated for detail, with oil or
water . Now, to find
a place that will sell less than a truckload, lol !

Ha! Just so they don't tell you it's also good for patching sidewalks. g

Petrobond, which I've never bought but which is praised here regularly by
several metalcasters, is available in small quantities. Good luck with it.

--
Ed Huntress

On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.
=================
One of the slickest things I have see for low volume use is lost
foam with "plaster" investment. Make the model out of styrafoam,
cost with plaster, possibly support the plaster mold in a flask
with sand, and pour. Styrafoam will flash off [don't breath the
very thick black smoke that will be generated -- will make a mess
if you do this indoors as the soot will coat whatever the smoke
comes in contact with]

As other posters have noted this is not "patching plaster" but
investment or refactory plaster. Any water or even dampness is a
NONO. FWIW -- you can make a concrete floor "explode" if you
dump a ladel/crucible of hot metal on it.

do a google search on "investment casting" or "plaster casting"
Several home/hobby news groups and websites active.

also google on "home metal foundry"

You can "paint" the styrafoam to seal the pores for even finer
finish.

http://www.theworkshop.ca/casting/fo...oamcasting.htm
http://www.metalcastingzone.com/lost...asting-videos/
http://www.prlog.org/10078409-castin...-released.html
http://www.prlog.org/10074778-metal-...ting-zone.html

If you use sand I suggest oil sand and not green [water damp]
sand. Petrobond is the buzzword for oil molding sand.

take a look at the casting books from Lindsay's books.
http://lindsaybks.com/prod/sub/foundry.html
Be reminded that Lindsey specalizes in reprints, so while the
information you get will be valid, it may not be up todate.
Chastain's books are all very good.

On Sat, 1 Nov 2008 11:59:24 -0700 (PDT), Dar
wrote:

On Nov 1, 12:20*pm, "Ed Huntress" wrote:
"Dar" wrote in message

...
On Nov 1, 10:52 am, "Ed Huntress" wrote:





"Don Foreman" wrote in message

news

On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

Google on investment casting. Jewellers do this routinely with high
melting point metals like gold, silver and even platinum.

The stuff to use is investment casting plaster.
http://www.gp.com/build/product.aspx?pid=5901

It can be found at jewellers' supply places. Once the mold is made,
it needs to be "burned out" or calcined at about 1200F long enough to
"burn out" the wax and also to drive off excess moisture.

With ally you'll probably need quite a tall sprue to get enough
pressure to get molten metal into the smaller internal features -- or,
use a centrifugal approach.

Just be aware that investment molds typically have much less of a venting
problem than cast plaster molds do, because they're a lot thinner. I
should
say "gas porosity" rather than venting, actually.

--
Ed Huntress- Hide quoted text -

- Show quoted text -
So, back to sand , green sand... *I've heard that a lot but never
seriously looked into it. Is
it mixed w/oil *, but with extra fine grain, or what?.

First, green sand is not mixed with oil. It's mixed with clay and water. It
is based on sharp, fine-grained sand, but your Googling should give you a
better idea than we could in a short message.

Regarding the oil, there are two types of molding sand that use oil. One is
the very popular Petrobond, which most users say is easier to use than green
sand. It's a combination of sand, motor oil and a processed clay that is
"organophilic," which means it absorbs oil rather than water.

Just to avoid confusion, this is NOT the same thing as the old-style
core-molding mixes that used linseed oil as a binder. Those materials had to
be baked before use, and the point of their formulation was to stand up
better to crushing forces that occur when a casting cools around a core.
There also are baked-sand molds as well as cores, but, today, they don't use
linseed. I'm not sure if they ever did.

I eschewed lost wax investment casting because I don't have the gear
anymore and don't
want to pay someone else for these molds, and plaster sounds like just
an extra bit too
much trouble . Oil sand I can do down and dirty *.

It's supposed to be really nice for hobby-scale operations.

googling green sand for now...

D- Hide quoted text -

- Show quoted text -

Interestingly, I found a green sand , Diamond Green Sand , and the
guy there said
I could mix a particular one, formulated for detail, with oil or
water . Now, to find
a place that will sell less than a truckload, lol !

D

http://www.budgetcastingsupply.com/
will sell you as little as 25 lb of Petrobond.

On Sat, 1 Nov 2008 09:56:09 -0400, the infamous "Ed Huntress"
scrawled the following:


"Larry Jaques" wrote in message
.. .
On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason
the molds are seasoned in the furnace, Tim, as you found out.

It's not just "seasoning." First you have to dry out the free water. Then
you have to drive off a percentage of the chemically retained water. That's
called "calcining." For casting zinc or aluminum, it doesn't take much. For
casting brass or bronze, it's critical, and requires more heat.

It's not something to do by guess and by gosh. Those things can explode in a
serious way. Furthermore, ordinary Plaster of Paris will not do for casting
brass or bronze. You need special high-temperature casting plaster.

Yeah. The last book on that was a few years ago, Langland's _From Clay
to Bronze_. It convinced me that bronze sculpting was too much work.


--
Everything I did in my life that was worthwhile I caught hell for.
-- Earl Warren

On Sat, 01 Nov 2008 11:07:44 -0500, the infamous Tim Wescott
scrawled the following:

On Sat, 01 Nov 2008 09:56:09 -0400, Ed Huntress wrote:

"Larry Jaques" wrote in message
...
On Sat, 01 Nov 2008 01:23:16 -0500, the infamous Tim Wescott
scrawled the following:

On Fri, 31 Oct 2008 22:59:53 -0600, F. George McDuffee wrote:

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex ,
or even 2 part sand molds, probably just bronze poured onto a flat
cope that has an depression in it and a dam built around the
depression .

thanks

DS
I would consider plaster molds for best detail

see
http://www.modernsculpture.com/bronze.htm

I've only ever used plaster molds (a long time ago, molding bullets for
miniature cannon out of solder. It's a wonder I'm still alive).

Were they still wet and exploded on you? There's a very good reason
the molds are seasoned in the furnace, Tim, as you found out.

It's not just "seasoning." First you have to dry out the free water.
Then you have to drive off a percentage of the chemically retained
water. That's called "calcining." For casting zinc or aluminum, it
doesn't take much. For casting brass or bronze, it's critical, and
requires more heat.

It's not something to do by guess and by gosh. Those things can explode
in a serious way. Furthermore, ordinary Plaster of Paris will not do for
casting brass or bronze. You need special high-temperature casting
plaster.

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

www.amazon.com search the book section on "bronze casting", Tim.

--
Everything I did in my life that was worthwhile I caught hell for.
-- Earl Warren

"Tim Wescott" wrote in message
news
Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

Tim Mc Creight's book Practical Casting is pretty detailed and
comprehensive. ISBN 0-9615984-0-9.
Also this is one of my favourite web sites
http://www.backyardmetalcasting.com/index.html

--
Michael Koblic,
Campbell River, BC

F. George McDuffee wrote:
One of the slickest things I have see for low volume use is lost
foam with "plaster" investment. Make the model out of styrafoam,
cost with plaster, possibly support the plaster mold in a flask
with sand, and pour. ...

You don't even need to coat with plaster. Make a model in foam, cover
with sand & pour. There is a particular foam to use & I don't think
it's Styrofoam - one of the insulation foams. One would think that the
foam would melt & the sand collapse before the metal could fill, but it
doesn't. IIRC, you don't get the same detail in the casting as you do
with green sand.

Bob

On Nov 1, 7:11*pm, "Michael Koblic" wrote:
"Tim Wescott" wrote in message

news
Do you know of any references on how to do it right? *I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.

Tim Mc Creight's book Practical Casting is pretty detailed and
comprehensive. ISBN 0-9615984-0-9.
Also this is one of my favourite web siteshttp://www.backyardmetalcasting..com/index.html

--
Michael Koblic,
Campbell River, BC

Sheesh, Tim McCreight is everywhere (at least in the jewelry -book-
writing arena. I helped with a tiny artcle in
Metalsmith mag by him about my specialty way back around '92
somewhere, and have seen the name on lots of books I never read .

Yeah, I almost ordred some Petrobond from Budget but thought I'd
research a little more , mostly because I
was curious about green sand and if it came finer grit than 'normal'
oil sand .

What I'm going to be making are bronze conforming mold sets , matching
male & female repousse forming
molds for copper jewelry parts. I've made this sort of thing with
nylon female dies and steel or bronze punches , or plastic steel
sets, but we need something tougher than the nylon, or plastic steel,
or zinc, but at the same time a solution much less expensive that
conventional grapghite electrode edm-made die parts. The client
claims to want hundreds of mold sets and says they have to be cheap. I
already have the inexpensive flat part blanking die technology
going, so these molds will take pre-cut flat blanks and shape them in
a press. That's the way I decided to go , over another way: forming
the parts with the same kind of mold , but starting with a larger
piece of sheet and basically drawing the shape in the middle, leaving
a flat flange around the draw, and trimming in a modified cheapo (oh
but very skillfully made, lol !) blanking die. The advantage being the
cheaper faster blanking stage of the former scenario. Lots of
potential bugaboos with the guys down in mexico stamping designs into
the flat parts , then forming them in the bronze molds . But it all
juuust miiiight work out

eventually ...

blog off

Dar
http://www.sheltech.net

Don Foreman wrote:
On Sat, 1 Nov 2008 11:59:24 -0700 (PDT), Dar
wrote:

On Nov 1, 12:20 pm, "Ed Huntress" wrote:
"Dar" wrote in message

...
On Nov 1, 10:52 am, "Ed Huntress" wrote:





"Don Foreman" wrote in message
news On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:
Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.
Google on investment casting. Jewellers do this routinely with high
melting point metals like gold, silver and even platinum.
The stuff to use is investment casting plaster.
http://www.gp.com/build/product.aspx?pid=5901
It can be found at jewellers' supply places. Once the mold is made,
it needs to be "burned out" or calcined at about 1200F long enough to
"burn out" the wax and also to drive off excess moisture.
With ally you'll probably need quite a tall sprue to get enough
pressure to get molten metal into the smaller internal features -- or,
use a centrifugal approach.
Just be aware that investment molds typically have much less of a venting
problem than cast plaster molds do, because they're a lot thinner. I
should
say "gas porosity" rather than venting, actually.
--
Ed Huntress- Hide quoted text -
- Show quoted text -
So, back to sand , green sand... I've heard that a lot but never
seriously looked into it. Is
it mixed w/oil , but with extra fine grain, or what?.
First, green sand is not mixed with oil. It's mixed with clay and water. It
is based on sharp, fine-grained sand, but your Googling should give you a
better idea than we could in a short message.

Regarding the oil, there are two types of molding sand that use oil. One is
the very popular Petrobond, which most users say is easier to use than green
sand. It's a combination of sand, motor oil and a processed clay that is
"organophilic," which means it absorbs oil rather than water.

Just to avoid confusion, this is NOT the same thing as the old-style
core-molding mixes that used linseed oil as a binder. Those materials had to
be baked before use, and the point of their formulation was to stand up
better to crushing forces that occur when a casting cools around a core.
There also are baked-sand molds as well as cores, but, today, they don't use
linseed. I'm not sure if they ever did.

I eschewed lost wax investment casting because I don't have the gear
anymore and don't
want to pay someone else for these molds, and plaster sounds like just
an extra bit too
much trouble . Oil sand I can do down and dirty .
It's supposed to be really nice for hobby-scale operations.

googling green sand for now...
D- Hide quoted text -

- Show quoted text -
Interestingly, I found a green sand , Diamond Green Sand , and the
guy there said
I could mix a particular one, formulated for detail, with oil or
water . Now, to find
a place that will sell less than a truckload, lol !

D

http://www.budgetcastingsupply.com/
will sell you as little as 25 lb of Petrobond.
I've bought from the man - nice guy. He brought it to my
company instead of shipping. Now I live back in Texas. Still have my Petrobond
in a waist high drum. I was into casting - just have to get back and
work on it more. Never had much time to do it before.

Martin

F. George McDuffee wrote:
On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.
=================
One of the slickest things I have see for low volume use is lost
foam with "plaster" investment. Make the model out of styrafoam,
cost with plaster, possibly support the plaster mold in a flask
with sand, and pour. Styrafoam will flash off [don't breath the
very thick black smoke that will be generated -- will make a mess
if you do this indoors as the soot will coat whatever the smoke
comes in contact with]

As other posters have noted this is not "patching plaster" but
investment or refactory plaster. Any water or even dampness is a
NONO. FWIW -- you can make a concrete floor "explode" if you
dump a ladel/crucible of hot metal on it.

do a google search on "investment casting" or "plaster casting"
Several home/hobby news groups and websites active.

also google on "home metal foundry"

You can "paint" the styrafoam to seal the pores for even finer
finish.

http://www.theworkshop.ca/casting/fo...oamcasting.htm
http://www.metalcastingzone.com/lost...asting-videos/
http://www.prlog.org/10078409-castin...-released.html
http://www.prlog.org/10074778-metal-...ting-zone.html

If you use sand I suggest oil sand and not green [water damp]
sand. Petrobond is the buzzword for oil molding sand.

take a look at the casting books from Lindsay's books.
http://lindsaybks.com/prod/sub/foundry.html
Be reminded that Lindsey specalizes in reprints, so while the
information you get will be valid, it may not be up todate.
Chastain's books are all very good.



Petrobond has resin within for fine smooth edges. It flows and
fills in the sides as the metal flows and fills the design.

Martin

On Fri, 31 Oct 2008 21:38:22 -0700 (PDT), Dar
wrote:

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS

Here are some photos of the Iron Guild of MA College of Art doing a
night time pour on Halloween night.

http://neme-s.org/Iron_Guild_Hallowe...iron_guild.htm

Not great photos but the best I could manage under the circumstance. I
will be adding a couple of video clips later in the day or tomorrow.

Errol Groff

I need to make a bunch of molds in sandcast bronze and would like to
know the kind of sand
to get for finest detail/smoothest finish . They won't be complex , or
even 2 part sand molds, probably just bronze poured onto a flat cope
that has an depression in it and a dam built around the depression .

thanks

DS


My recommendation is petrobond. You can
view a short video using petrobond on YouTube at
http://www.youtube.com/watch?v=NKXj5Ng3X58

Rod