Materials Metal Anyone?

What's your deadline?

Insane? Maybe. I think there was a person that did cast a doll in metal.

I'd recommend aluminum, since it's the lightest, cheapest and easiest to modify. (Since you will need to drill and cut off sprues.) Bronze would be expensive and heavy, and iron would be impossibly heavy. I had a friend cast her own version of Thor's Hammer in iron, and that small thing was really heavy.

If I were you, I wouldn't start out making a BJD. Personally, I'd go about it like some of the old fashioned porcelain dolls, with just the head, shoulders/top of bust, lower arms/hands and feet. I think that would look really neat with the metal and a cloth body. Plus then you would have more time to perfectly define those parts with less stress.

Oh great, now I have an idea for a vintage looking doll. XD

 

What lead to my interest in BJD actually came first from stop motion armatures. You can make various joints with metal bars and balls. So I don't think making a metal BJD is far fetched. Even making one similar to stop motion armature but with more meat to it... er metal to it to flesh it out. I am not sure what kind of metal they use so that might be worth researching if this is something you want to try.

 

Metal BJDs

Here is one:

Iron Maiden BJD

That BJD was made with Lost Wax Ceramic Shell process.
I have liked it since I first saw it here.

What is the best metal from the choices of aluminum, bronze, and iron?
That is a subjective opinion.
All three metals can be cast in Ceramic Shell molds.
Aluminum and bronze can be cast in plaster-sand Luto molds.
Both Ceramic Shell and Luto molds are Lost Wax (Cire Perdue) casting processes.
In the past, I have used both processes with cored wax patterns to produce
bronze and aluminum castings in a small art-bronze foundry in my home studio.
Making a metal BJD should be very doable in a university situation where you have so many resources!

Personally, if I were going to make a metal BJD, I would go for bronze.
Bronze melts and pours at a much higher temperature than aluminum, but much lower than iron.
Bronze weighs more than aluminum, but less than iron.
Bronze can accept an incredible range of chemical patination for colouring the surface.

You can follow a traditional bronze sculpture casting process,
slightly modified for making a BJD (thanks to Martha Armstrong-Hand (1920-2004) ):

Make full-size working drawings with at least a front and side views, shrinkage included.
Make a wire armature, using the full-size working drawings.
You can sculpt your original doll in oil-clay over a wire armature attached to a modeling stand.
Remove the completed oil-clay sculpt from the modeling stand and cut it apart at the head, torso, and limbs.
Make waste molds of the head, torso, and limbs using plaster or moulage.
Cast carving wax into the waste molds. Cast carving wax balls for joints.
Design the ball joints, and weld the carving wax balls to the limbs.
Test-string the carving wax BJD with round elastic doll cord.
Refine the carving doll parts until finished as well as you want them to be.
Use the carving wax doll parts as patterns to make RTV silicone rubber molds for casting sculpture wax.
Attach gates, runners, sprues, and pouring cup to sculpture wax.
All the gating is done according to what kind of refractory mold you are going to use!
If you are going to use a Ceramic Shell mold, then the gating will be done one way.
For a Luto mold, the gating will be done another way.
Likewise for coring.
Make the refractory molds around your doll parts.
Burn out the wax in a kiln (for Luto molds), or a flash furnace (for Ceramic Shell molds).
Melt and pour your molds using the proper method.
De-mold the cooled castings.
Remove the gating system, and cores.
Fill in core-pin holes, chase the imperfections, (gate stubs, etc.).
Clean the castings.
Apply patinas.
Wax.
ETA: Assemble doll with metal springs, s-hooks, swivels, & bars, to tension.
ETA: Insert eyes, wig, clothe, shoe, and accessorize. (Or a nude metal doll.)
Display.


PS: this is just off the top of my head, sitting in front of my PC.
All errors and omissions are mine.

 

That is actually a great suggestion, Renzi!!!

A leather body might work better for a metal BJD?
Old dolls also had leather bodies (kid leather)?

Refer to my post, above....
Go ahead and model the complete doll over a wire armature on a modeling stand.
Remove it from the modeling stand, and cut at the head, torso, legs and arms.
Make your waste molds from the oil-clay sculpt and cast the parts in carving wax.
Use the Head, Lower Arms and hands, and Lower legs and feet.
Go ahead and cast those five parts.
Instead of ball joints, make grooves in the top of the lower arms and lower legs
in order to tie the leather parts to the metal parts. Add a neck and shoulder plate
to the head. The shoulder plate should have some holes for tying it to the leather
body.

This way, you would only have five parts to make, mold, cast, and finish.
That is still quite a project for a sculpture class.
You would have to do a lot of work outside of class in order to finish it in time?
Think: many long nights at the University sculpture studio?


If you have sculpted a whole doll (recommended by Martha A-H -- even if
all you are going to do is a head, arms, legs doll -- as described above), and then
waste molded the whole doll, you can still use the waste molds (if made in plaster)
to cast the whole doll for making a metal BJD when you have more time?

Just some more thoughts.

 

You use the same lost wax ceramic shell process for aluminum. I don't think casting aluminum is riskier at all, it's just lighter and softer. I know many of my classmates had better results with it, but that could have been a coincidence.

Failures in metal casting are not nearly as random as some people think, it all depends on how well you make the mold/shell. Sprue placement is very, very important. If you have the sprues in the right spots, you're set. I would have a teacher or TA check to make sure that there is no spot where air could be stuck. It's just like resin in that respect, the fact that it's molten metal does not make air bubbles go away.

I had classmates who ignored this , got huge bubbles and blamed the material. They also made the shells too thin and blamed the material when they broke. Sigh. XD

To be fair, things can go wrong beyond your control sometimes. I had a teacher break my ceramic shell after the wax was melted out. She sort of glued it back together, but the bronze leaked out and required a lot of extra cleaning up/grinding. If you fall in love with a head, I'd at least make a plaster mold. Silicone molds, in my opinion, are way too expensive for a project that is worked on for a semester or less and plaster works well with the wax ones uses for metal casting.

If you are required to use bronze also, maybe you could make the shoes in that material? That way, the doll wouldn't be affected weight-wise if you wanted her to stand on her own.

 

Note: Water and wax do not mix.
So you can make multiple piece plaster molds, and saturate the molds with water before pouring wax into them. If you try to pour molten wax into dry plaster molds, the plaster will absorb the wax, and you have a fail. So remember to use water-saturated plaster molds to cast wax. Moulage is a reusable hot-melt mold material that also can be used in the same way as a water-saturated plaster mold. With a water-staurated plaster mold, or a moulage mold, you pour the wax into the mold, wait until the wax thickens to the thickness you want it to be, then pour the excess wax out of the mold, back into the wax pot. A water-saturated plaster mold can be store4d and used again by saturating it with water before you pour wax into it. The plaster itself cannot be reused. A moulage mold is not easily stored, but it can be chopped up and stored in a tightly sealed jar, then used again and again to make molds for pouring wax.

The advantage of using a water-saturated plaster mold, or a moulage mold for making your wax patterns is that both plaster and moulage are much less expensive than silicone rubber. However, if you have access to old silicone rubber molds, they can be chopped-up and placed around your pattern to make a mold. You will need some fresh silicone rubber, but not as much as you would need to fill the whole mold. This method of making a silicone rubber waste mold for casting wax is described in the book _Pop_Sculpture_, by Tim Bruckner, et al.

The differences between Ceramic Shell refractory molds nad Luto molds are:
A Ceramic Shell mold is lighter in weight, and does not take as long to flash the wax out, and calcine.
A Luto mold of the same pattern can weight up to ten times more than the same pattern in a Ceramic Shell mold. Also, the Luto mold can take up to several days to burn out the wax.
In both types of mold, you can probably gate all the pieces you want to cast in one mold, on a tree.
However, the sprueng and gating for a Ceramic Shell mold is usually much simpler than the spruing and gating for a Luto mold. That is because a Ceramic Shell mold develops a network of micro-cracks in it that allow for better escape of gases than a Luto mold. The Luto molds needs to have a good system of air vents incorporated into the gating system.

As far as aluminum and bronze go.....
Yes, aluminum is much lighter in weight, but tell me, is weight really a factor with a Metal BJD?
I would consider a Metal BJD to be a piece of Sculpture more than a toy,
so weight would not be as much of a consideration, to me.
Make your bronze patterns thin enough, and the weight won't be too bad.
(Bronze weighs 3 times more than aluminum, and ten times more than a wax pattern.) <-- dbl chk this!
Aluminum is softer, and lighter, but it requires the use of a TIG welder to make repairs.
With bronze, you can use an Oxy-Acetylene outfit to make repairs,
like they did before TIG welding was invented.
Also, with bronze, you can do all sorts of patinas.
There are whole books dedicated to applying patinas to bronze.
Also, I just like the surface quality of bronze.
As I said before, it is a subjective opinion.