LWax-casting-msg - 9/8/14

Lost wax casting of metals.

NOTE: See also the files: casting-msg, cast-cutlefsh-msg, Cast-Wax-Seal-art, Beg-Pwtr-Cast-art, Int-Pwtr-Cast-art, pewter-msg, Workng-Beswax-art, beeswax-msg.

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This file is a collection of various messages having a common theme that I have collected from my reading of the various computer networks. Some messages date back to 1989, some may be as recent as yesterday.

This file is part of a collection of files called Stefan's Florilegium. These files are available on the Internet at: http://www.florilegium.org

I have done a limited amount of editing. Messages having to do with separate topics were sometimes split into different files and sometimes extraneous information was removed. For instance, the message IDs were removed to save space and remove clutter.

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Thank you,
    Mark S. Harris                  AKA:  THLord Stefan li Rous
                                          Stefan at florilegium.org
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Date: Wed, 14 Oct 1998 20:42:02 EDT
From: <BastetKat at aol.com>
To: sca-arts at raven.cc.ukans.edu
Subject: Re: Hot-Striking coins [SCA]

     What you are describing is casting, and the method your friends are using
will not be very successful. Hot-striking would be heating the metal up to an
annealing temperature (see my letter on circlets), not melted, and then put it
in the die. There is really no advantage to this over cold die casting (unless
you are working with much harder metals than bronze).

     There are several ways to cast metal. Similar to what your friends are
doing is charcoal block casting, where the design is carved into a block of
charcoal. The metal is place directly into the recess and hit with a torch
until melted. Then a second charcoal brick is set (not slammed, unless you
WANT molten metal in your lap) down on the first. This mold is good for 3-4
1-sided castings.

     Another method uses two charcoal blocks, with a front and back design,
wired together. You can get a two-sided casting, but the limitations are
considerable. As your friends have discovered, as soon as the heat source is
removed, the metal immediately begins to solidify. Therefore, only very short
or small castings can be done this way, and the opening needs to be fairly
big. It will help if you heat the mold up as hot as it can take (depends on
what it is made of).

     Another method is sand-casting, which will also produce a single sided
casting. The amount of detail you can get with sand casting is limited,
however.

     I'm pretty sure that in period coins were simply die-struck on cold
metal, as you have described. However, lost-wax casting could be used to
make multiple two-sided coins at once. If you are more concerned with mass
production over historic authenticity, than this might be the way to go.
Unfortunately, it requires some specialized equipment. If you have an Arts &
Crafts center where you live (are there any Universities?), you might want
to check them out.

     Basically, the process of lost wax casting (which dates back to the
Bronze ages) is this: a model is carved in wax, then a plaster mold is made
over the wax. Then, the wax is burned out of the mold. Finally, molten metal
is forced into the vacant spaces created by the burned-out wax. I repeat:
forced. It is not possible to simply pour it down the hole for the same
reasons the two-part charcoal block is limited. Usually centrifugal force is
used, or a vacuum (vacuum is inferior).

     I will be happy to answer any specific questions, but it will be much
easier if you can find some local person who has prior experience to stand
over your shoulder. I can describe techniques to you, but cannot show you how
to do it (like what color the metals turn as they are melting, etc.). Also, to
do it well, you'll need a lot of fairly expensive equipment.

Judith


Date: Fri, 03 Aug 2001 14:50:26 -0400
From: James Koch <alchem at en.com>
Newsgroups: rec.org.sca
Subject: Re: Lost Wax / Plaster casting query
Organization: EriNet Online Communications - Dayton, OH

Jonathan Blackbow wrote:
> Just to show you a good example of functional fixedness, I assumed that if
> you were doing anything with plaster, you were carving the design out of it.
> 
> 1.  If I have a medallion model and want to make a plaster cast of it to
> cast pewter into,
>     a.  How do I make a back, i.e., two part mold?  what do I use after I
> cast the front half to keep the plaster back half from sticking to the
> plaster front half?    Will Silicone release work?
>     b.  if my original is made out of super sculpey, how do I get it out of
> the plaster mold?  Will silicone release work on that too?
>     c.  How good is the detail on plaster casts?
>     d.  How many pewter critters will I get out of one plaster mold before
> the plaster loses all its detail and I have to make another one?
> 
> Any answers or info will be appreciated - I'm trying to find a cheaper /
> quicker alternative to Ditto 2.
> 
> Jonathan Blackbow

Jonathan,
Quite a bit depends on the original you are attempting to copy.  You may
have to experiment and determine what works best for you.

a)  Simply press the original into the wet plaster in such a way as to
eliminate bubbles.  You may have to daub the piece with wet plaster to
fill depressions.  Make sure the mold surface is as smooth and level as
possible.  Once the front half is made, cover it with cellophane or a
heavy coating of some other parting compound such as wax, Thompson's
Water Seal & etc...  I am not familiar with silicone release, but if
plaster will not stick to it, then it ought to work.  Then pour on the
backing plaster.  The original must have no undercuts.  Otherwise it
will break the mold when you try to remove it. If the original does have
undercuts you will do well to use a vinyl molding compound obtainable
from craft supply companies.  This is a powder which when mixed in water
forms a rubber like mold.  You can then pour casting wax into the rubber
mold and make multiple copies.  The rubber mold can be stored for a few
weeks but will eventually oxidize and crack. The wax copies can have
sprues and vents attached and can then be immersed in plaster.  No
parting of the mold is necessary since the wax will be fired out in a
kiln.  Plaster molds have to be fired whether wax is used or not to
totally eliminate water.  This must be done slowly and for several
hours.  Otherwise the mold will explode from steam pressure when the
metal is poured.  A lost wax mold will produce only one item.  You might
get several from a two part mold depending on the complexity of the
design.  However, plaster molds are not rugged.

b)  You ought to be able to pry the original out of the wax without any
release, but using silicone can't hurt.

c)  Plaster casts give incredibly good detail.  Better than the unaided
eye can see.  I once lost wax cast a gold ring.  The wax original had
fingerprints on it's sides since I expected to have to sand and buff the
surface anyway.  Once cast, to my surprise, the fingerprints were
perfectly visible in the gold!

d)  As stated above, you might only get one two or three casts out of a
plaster mold before it flakes to the point that detail is lost.  For
more rugged molds I recommend cuttlefish bone, soap stone, wood or
metal.  I once cast about 30 pewter Celtic crosses in a basswood mold. 
I have gotten inlimited casts out of a copper mold.  With copper though
making the original is time consuming and you get bad casts until the
mold gets hot enough.  The mold will have to be fitted with handles like
a bullet mold, or you will have to wear gloves to manipulate it.

Jim Koch (Gladius The Alchemist)


From: Hjordis Olvirsdottir <julesong at eons.com>
Newsgroups: rec.org.sca
Subject: Re: Lost Wax / Plaster casting query
Date: Fri, 03 Aug 2001 13:10:27 -0700
Organization: Eskimo North www.eskimo.com (800) 246-6874

This won't answer your question, exactly, but...

There's a really good bronze casting set of webpages at
http://hem.spray.se/anders.sberg/index.htm

--Hjordis


From: EKMetalsmiths at yahoogroups.com
Subject: [EKMetalsmiths] Digest Number 1705
Date: January 19, 2014 8:48:48 AM CST
To: EKMetalsmiths at yahoogroups.com

<<< What mold material and investment would you use for lost wax casting of silver?
Irene >>>

Wax comes in many different temps. and hardnesses . For investment in a
sling casing or stgeam casting I would use casting plaster from US Gyspm.
You can find it in most pottery supply houses. I got 50 mlbs for about 12
dollars a couple of years ago.

Dan in Auburn

Posted by: "Charles Anderson" charlesian2000
Hello Irene,

The mould material for the wax models I would recommend a cold cast RTV, 
a vulcaniser would be no good as your wax model would melt away.

Kerr satin cast is a nice product, and you get very good results.

As for me :-

If I am to cast items myself (usually ingots sheet and larger bronze 
items) I will use Delft clay, close to investment casting can be 
achieved, faster and more efficiently. You can even do lost foam 
casting with exceptional results... if you use the right polystyrene.

If it's a wax carving I'll take it to a professional casting house, 
because they can cast our pieces far cheaper than we can.

Kindest regards Charles from Oz


Date" Sat Jan 18, 2014 9:01 pm (PST) . 
Posted by: "irene purificato" ipurificato
Thanks, I took a class in lost wax casting for glass.  He used a silicone for the first casting so you could make as many wax castings of a 3D model that you wanted.  Then invested around the wax with an investment labeled for Glass.  Then we cast in the kiln.

Irene


To: EKMetalsmiths at yahoogroups.com
Polystyrene for casting was [supplies, lost wax casting]
Thu Jan 23, 2014 2:04 am (PST) . 
Posted by: "Charles Anderson" charlesian2000 Hi Liam,

> Okay, now you have me curious – what polystyrene would you recommend?
> -Liam

So that others won't be lost (tee hee), I'll be verbose.

Lost foam casting has been around since the 1960's, and to this day it's 
used in industry to make many things very quickly (even Ferrari engine 
blocks).

The idea is you take a foam model, it can have undercuts and voids 
whatever. Then you put the foam model into loose sand. Make a sprue 
and pour in molten aluminium, the polystyrene turns to gas as soon as 
the molten metal hits it. Let cool and voila you have an aluminium 
model replacing your foam model.

If you want to make metal items in say bronze, silver or gold, you will 
need a denser moulding material other than sand. You can use bonded 
casting sand, but I recommend Delft clay, it produces a finer result.

You can use normal white packing polystyrene, but I've found that the 
white architectural variety is better, it's almost as hard as pine, 
close celled, hard to compress. It can be shaped and sanded.

What ever you do steer clear of that pink and green insulation foam you 
find in a hardware store, it has a fire retardant in it.

So long story short "white closed celled architectural polystyrene".

Kindest regards Charles from Oz


To: EKMetalsmiths at yahoogroups.com
Re: Polystyrene for casting was [supplies, lost wax casting]
Sat Jan 25, 2014 4:25 pm (PST) . 
Posted by: "Charles Anderson"

On 26/01/2014 00:50, Mark Feldmann wrote:
>> So long story short "white closed celled architectural polystyrene".
> Hey there, Charles-
> Do you know if that's what we call it over here in the States?
>
> Yvan Wolvesbane

You may call it styrofoam, but polystyrene should get some bells ringing.

A very interesting thing you can do is if you make sword pommels you can 
make them to size in polystyrene first, fit it to your sword, see if it 
looks good, adjust if needed, cast it with the void and you'll have a 
close fit to the tang.

Regard Charles from Oz


To: EKMetalsmiths at yahoogroups.com
Subject: Re: lost wax casting
Date: Sun May 4, 2014 2:21 pm (PDT) . 
Posted by: "Dan Brewer"

On Sun, May 4, 2014 at 9:36 AM, irene purificato <ipurificato at yahoo.com>wrote:
> I am trying lost wax casting.
>
> Is there a way of telling when you have steamed all the wax out of the
> mold?
>
> Irene

You will need to bring the mold up to a temp that is at least 100 deg
hotter than you wax melt point and hod it for an hour or so. If you can do
this in an oven it would be best. This way you are assured that all the
wax is melted out. Idealy you would bring the mold up to ablot 1500 degree
for two hours and hold . Pour metal in the mold with mold temp about 250 to
400 deg.
Dan in Auburn


To: EKMetalsmiths at yahoogroups.com
Subject: Re: lost wax casting
Date: Sun May 4, 2014 3:43 pm (PDT) . 
Posted by: "A. Fisher" sustre2

Assuming a "plaster" mold-

it's best to cook the mold at a temp just above the melting point of the 
wax (maybe 50-100F) and have the mold upside-down initially, with a 
tray underneath for the excess wax to drain into. Then, when most of the 
wax has melted and flowed out of the mold, turn it right-side-up and 
heat to whatever temp is needed to cast your metal.

Burning out ALL the wax creates a lot of fumes and takes lots of extra 
time. Better to drain most of the wax, and then only have to burn out 
the remnants.

-Amanda
www.afmetalsmith.com


To: EKMetalsmiths at yahoogroups.com
Subject: Re: lost wax casting
Date: Mon May 5, 2014 11:24 am (PDT) . 
Posted by: "Dan Brewer" danqualman

On Mon, May 5, 2014 at 8:56 AM, Daniel Kretchmar <dan at irontreeworks.com>wrote:
> What are you making the molds out of? I made mine out of plaster and the
> mold crumbled on me yesterday.....Any suggestions would be appreciated.

Make a visit to your local pottery supply house. They have a producet made
by US Gsypsum called casting plaster.

Questions about your setup. Do you have a kiln or a place to fire your
mold?

I use casting plaster.

I take me wax pattern with all of the sprues attached and paint it with Jet
Dry. It is an additive for your dishwasher to break the surface tension on
the dishes. Let the jet dry dry. 

Next coat is a slurry of casting plaster. This be the consisty of pancake batter. Make sure that the entire wax master is coated. Let dry a little . Paint on another coat and shake a coat of flint sand on the wet plaster. Let dry for a little. 

Mix another batch of the casting plaster and add some sand to it. Coat the
mold. shake sand over the wet plaster. When you have about 3/8 inch of
coating reduce the water and increase the sand. 

Coat the mold until you have a coating of about an inch. Imbed a layer of chicken wire around the plaster. set to dry. You will want a flat top and a flat bottom. You can use a cardboard box with a light in it to speed your drying. Let dry for a few days under gental heat. Now if you have placed the sprues correctly you can heat the mold when it is inverted and remove most of the wax. 

This can be done by steaming or in a low oven with a catch basin. But I
reccomend an oven that you will never cook in. After you have removed the
majority of the wax you need to fire the mold. 

Bring up the temp in your kiln to about 1500 deg. Hold for 2 hours. The wax now should all be burned out. you might need to vaccume out the ash. Reheat to about 200 deg and pour your metal.

I hope this helps a little. It is the way I do it but your milage may vary.

Dan in Auburn


To: EKMetalsmiths at yahoogroups.com
Subject: Re: lost wax casting
Date: Mon May 5, 2014 12:31 pm (PDT) . 
Posted by: "irene purificato" ipurificato

Review the MSDS for both Plaster of Paris and Potter's plaster.  You will find that the Potter's is 95% plaster of Paris.

Their properties are almost the same.

Irene


To: EKMetalsmiths at yahoogroups.com
Subject: Re: lost wax casting
Date: Mon May 5, 2014 12:45 pm (PDT) . 
Posted by: "Dan Brewer" danqualman

On Mon, May 5, 2014 at 12:31 PM, irene purificato <ipurificato at yahoo.com>wrote:
> Review the MSDS for both Plaster of Paris and Potter's plaster. you will
> find that the Potter's is 95% plaster of Paris.
>
> Their properties are almost the same.
>
> Irene


Cost is another factor. Casting plaster cost me 20 dollars for 50 Lbs.
Plaster of Paris is about 10 dollars for 5 lbs.

Just as long as you fire it. Plaster of paris will retain water unless it
is fired. Bad when it comes time to cast bronze. Small volcano. Much
excitement. Remember the vents. I also cover the pouring cup with
vermiculite to insulate it as the casting cools. It seems to reduce the
shrinkage problems I have had.

Dan in Auburn


To: EKMetalsmiths at yahoogroups.com
Subject: Re: lost wax casting
Date: Mon May 5, 2014 1:39 pm (PDT) . 
Posted by: "A. Fisher" sustre2

The kind of plaster used for lost wax casting is called "Investment", 
and there are various kinds rated for various temps. Both jewelry and 
dental supply places should have it. Note that it's important to be VERY 
precise in the mixing, and a vacuum table helps remove bubbles that 
you'll otherwise have to clean up.

I think if I were casting small things out of a low-melt metal- pewter 
and the like- I'd experiment with sand and/or clay casting... but I 
don't know if they'd work for lost wax.

-Amanda Fisher


To: EKMetalsmiths at yahoogroups.com
Subject: Re: lost wax casting
Date: Tue May 6, 2014 2:44 am (PDT) . 
Posted by: "Ron Charlotte" al_thaalibi

You can use a wax model in sand, but only if it meets the normal sand 
casting model rules (no under cuts, etc).

Clay molds work just fine with wax. You still have to do burn-out. 
Investment was created to replace clay molds, when you come right down 
to it.

You don't really need a vacuum table to de-bubble. Vibration will do 
the trick, it's just not as efficient.
-- 
Ron Charlotte
Gainesville, FL
ronch2 at bellsouth.net or thaalibi at gmail.com


To: EKMetalsmiths at yahoogroups.com
Subject: Re: lost wax casting
Date: Tue May 6, 2014 5:06 am (PDT) . 
Posted by: "Charles Anderson" charlesian2000

PSA.

Investment plaster is full of silicates, these will kill you if you 
breath them in so wear a dust mask when mixing them.

Regards Charles from Oz

<the end>
Edited by Mark S. Harris	LW-casting-msg	9 of 9