Italian Job Gold Bar Project

Shonuff

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Started work on my next gold bar replica project. I made a mold of an original gold bar prop I have from the movie and made some resin duplicates, as well as some wax ones for later. My first attempt at a legit metal version I'm attempting with sandcasting off of the resin positive. The result is not quite there, and wire-wheeling off the surface textures can lead to removing some of the crisper detail I was able to get in the top's designs. The lower portions defects are most likely caused by either impurities in the aluminum, or issues of initial splashdown when pouring. I can remove that by creating a void for the initial pour to hit that then steps down into the bar's negative. Next I'll try my hand at lost wax casting using plaster investment, and if that fails will move on to ceramic slurry/shell.

Eventually once I get a solid method developed, I'll get these polished up and gold plated. Also messing around with different metals. Having one weigh close to what a gold version would actually be gives the prop a wonderful feeling of heft and authenticity, and makes for a superb doorstop.


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Shonuff

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I changed the mold setup, adding a trench and a gate to try and remove some of the surface irregularities I got from Round 1. The final result turned out much better. For Round 3 I will ditch the open mold and go for a fully enclosed sand-cast mold.

Initial Pour into new gating setup
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Initial Demold
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Sand Removed and cooled down
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Round 1 vs Round 2
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Treeman

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There is degassing step while it is molten. I am not sure of the specifics, just the procedure to get a smoother final bar.
 

Shonuff

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There is degassing step while it is molten. I am not sure of the specifics, just the procedure to get a smoother final bar.
Thanks Treeman. I can use Sodium Bicarbonate (baking soda) to degas it, need to make a custom tool to keep it under the metal long enough to process out all the excess hydrogen. Also I've seen people use Lite Salt as a flux to help decrease the metals surface tension and lower its viscosity. I'll use both additional steps this next go around.
 

Shonuff

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Nice work!
I would love to buy a resin cast shell from your mold if you are selling?
Hi Coinprop. Thanks for the interest, but if I end up selling productions from this project it will only be a finished metal version. I might branch out and offer buyers their choice of metal for the casting but I will not be selling any non-metal variants unfortunately
 

Shonuff

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Little update on this project. I did a casting tonight using copper. I'm still getting a ton of defects and divits within the sand cast, I'm going to move on to alternative casting methods and see if I can get better results. The weight on this thing feels awesome tho
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Mach

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Copper is prone to absorb oxygen and have surface defects. Everdur bronze alloy is easiest to cast assuming you're going to plate anyway. Starting with clean virgin metal is key. On casting technique, you can get a decent surface finish using a rammed, closed petrobond mold but investment followed by ceramic shell gives the best finish. You might check out thehomefoundry.org. Very talented folks who are always willing to help.
 

lmgill

Sr Member
You can also make your bar in pewter. This has a low enough meting point that it can be cast in high temp silicone.
Another option is to fabricate the "bar" in sheet copper with silver solder (Not low temp plumbers solder). Then fill it with pewter.
 

Shonuff

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You can also make your bar in pewter. This has a low enough meting point that it can be cast in high temp silicone.
Another option is to fabricate the "bar" in sheet copper with silver solder (Not low temp plumbers solder). Then fill it with pewter.
I'll give pewter and silicone a try, but end goal is to get a casting method down that will allow me to recycle down cheaper metals and convert to a safe full of gold plated bars :) Aluminum will most likely be the go to metal for this project, as it as a relatively low melting temp and is easy to find and recycle down scrap.
 

lmgill

Sr Member
I'll give pewter and silicone a try, but end goal is to get a casting method down that will allow me to recycle down cheaper metals and convert to a safe full of gold plated bars :) Aluminum will most likely be the go to metal for this project, as it as a relatively low melting temp and is easy to find and recycle down scrap.
If you plan on making the bars gold colored, electroplating aluminum is tricky. Aluminum oxidizes so quickly that most platers will not plate it.
 

Shonuff

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If you plan on making the bars gold colored, electroplating aluminum is tricky. Aluminum oxidizes so quickly that most platers will not plate it.
because of the size of the piece, my plating kit isn't robust enough to take care of the bars. Luckily i found a plating company near me that can handle that step and plating Aluminum is within the services they provide.
 

The Terminator

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Very nice! I have always wanted a couple of gold bars. Shame they are so expensive, for some reason :p hehe
Might I suggest "Nordic gold", a Swedish copper alloy: 89% copper, 5% aluminium, 5% zinc, and 1% tin.


What are the dimensions of the original you have, in millimeters?
 

lmgill

Sr Member
Another thing occurred to me, you could electro-form the bars in your current silicone mold, making a copper shell, then fill that shell. Electroforming is/ was a common way to make copies of artifacts for museums.
 

Shonuff

Active Member
RPF PREMIUM MEMBER
Another thing occurred to me, you could electro-form the bars in your current silicone mold, making a copper shell, then fill that shell. Electroforming is/ was a common way to make copies of artifacts for museums.
I was not aware of this technique. I'll dive in and see how it all works. Thanks Imgill!
 

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