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Bronze Casting - Ceramic Shell with Core Technique

Materials, products, processes, suggestions and tips involving how sculpture is made.

Bronze Casting - Ceramic Shell with Core Technique

Postby mantrid » Sun Jun 26, 2011 2:20 am

Thought Id share some pics of my latest casting (bronze). The pics show the wax after the primary slurry coat. Tried to keep it in one piece but this babe has long legs and had to cut one off and attach to the side to reduce the height so it woulf fit my furnace, also the metal would have less distance to travel. I also always fill from bottom up now as I was getting problems filling from the top.

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Will post more pics of the bronze when done. Should be ready to pour on the weekend. Im really looking forward to it as this is my most complex shape to date. Sorry about poor quality pics, only have the camera on the mobile at the moment.
mantrid
 
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Re: Bronze Casting - Ceramic Shell with Core Technique

Postby mantrid » Sun Jun 26, 2011 2:21 am

Heres some pics I should have added earlier of the wax just prior to cleaning up and applying ceramic shell. Image quality is poor as using camera on phone.

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mantrid
 
Posts: 45
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Re: Bronze Casting - Ceramic Shell with Core Technique

Postby mantrid » Sun Jun 26, 2011 2:24 am

Heres the finished shell ready to burn out and pour. Its thicker than I normally do but I dont want it to crack after all the time its taken.

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A dry day at last! Did a pour this evening as soon as I got in. Heres the pics. Again apologies for the poor pics. (Can anyone recommend a good compact digital with good zoom)

Shell just after pouring Looks like a leak but its just a small spill into one of the recesses of the shell. The poor quality pic doesnt show this well.
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Just a little left over, not a bad guess.
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Crucible back in the furnace to cool down. This crucible took half hour to melt it was 3/4 full. This I put down to the big space above the crucible. You will see that I designed this furnace with the burner hole up high. This allows me to slip more fire bricks in the bottom to reduce the internal volume to save gas when heating a smaller crucible. Unfortunately I couldnt do this today as the shell wouldnt have fitted in at the same time.

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As mentioned in previous post I predicted these fire bricks would shrink and slip without support. The pic shows its started already. Will have to make those refractory slabs on the weekend.
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Shell being removed. I'm so impatient I just cant wait till its cooled down
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More shell chipped off and it looks good. Just a few blemishes where the inside surface of the shell cracked and some bronze seeped in leaving very fine ridges (flashing is the term they use). These will be easy to knock of with a chisel.
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Interesting that the pouring cup area filled and solidified, but the bronze shrunk away massively underneath it leaving a large cavern. I put this down to the fact that this piece was cast solid and was quite thick so there was much shrinkage within the shell pulling the bronze down and creating the space.
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mantrid
 
Posts: 45
Joined: Thu Jun 23, 2011 1:45 am

Re: Bronze Casting - Ceramic Shell with Core Technique

Postby mantrid » Sun Jun 26, 2011 2:25 am

Next stage was desprueing welding on leg, sandblasting. You will notice at this stage of sandblasting the surface is quite matt due to the aluminium oxide abrassive used. I finish with a final blasting with glass beads this pleens the surface giving it a nice shine.
Pics below
This one was cast solid. I had to do a bit of heating on the hand to open it up a bit to fit the stainless steel bar (which will look good when polished up)
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Did another a short time after which was hollow. I made up a core of plaster, sand and molocite flour (that I normally use as a slurry for the ceramic shell) although it is usually just the sand and plaster. The waxes are hollow so its just a matter of pouring it in with some pins through the wax that secures the the core to the shell on the outside for when the wax has been removed.

Looked promising initially but after cleaning off the shell the defects started to show. Although I think I know where I went wrong tips and advice are welcome.

Over all view with leg TIGed on.
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Larger view of TIG weld
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Close up of back. Shell must have broken away inside so allowing bronze to fill the reccess. This can be fixed by resculpting with burrs in a dremel type tool.
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Similar thing on back of hand and arm. Back of hair I think wax was too thin leaving too narrow a space and bronze didnt fill it.
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Bronze didnt fill these spots either. Dont know why as of the edge of the bronze here didnt look particularily thin
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Thin area on shin. This will be a challenge to fill with bronze without damaging the detail. Any advice?
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More holes on the knee and upper leg. I attempted to use TIG to melt some bronze in here. The sand blasting removed the core so I back filled with sand to give a base so the molten bronze wouldnt fall through. Unfortunately I run out of Argon as I'm using those tiny rip off disposables. I melted this hole larger than it was originally as I had the TIG up highish to melt the 'filler rod'. Which is actually very thick as I am using the sprues that I cut off. Note; need to get some proper filler rod. The leg has melted back to thicker bronze now so when I get some more argon I will be able to flatten and merge that blob with the surrounding metal.
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There is alot of work to do on this one and I'm not sure whether to scrap it and start again. If it didnt take so long to get to this stage it would be in the pot by now.

Will post pics of the good one when it has had the patination applied.
mantrid
 
Posts: 45
Joined: Thu Jun 23, 2011 1:45 am

Re: Bronze Casting - Ceramic Shell with Core Technique

Postby mantrid » Sun Jun 26, 2011 2:27 am

Patination applied still need to do base and cap for the pole. Thought a simple flat cylinder for the base and a sphere for the top of the pole.

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Last edited by mantrid on Sun Jun 26, 2011 2:34 am, edited 2 times in total.
mantrid
 
Posts: 45
Joined: Thu Jun 23, 2011 1:45 am

Re: Bronze Casting - Ceramic Shell with Core Technique

Postby mantrid » Sun Jun 26, 2011 2:28 am

Started the base and spherical cap for the top of the pole today. The base is a simple flat cylinder, hollow with 3 lugs? for either sticking on felt feet or to drill into and inserting threaded rods to allow the attachment of an additional stone plinth if required. There is also a cylindrical extension in the centre continuous with the riser/pouring cup. This will be to screw the bottom of the pole into. I have included 3 spheres even though I only need one. Im assuming something will go wrong so hopefully one of the 3 will be ok. I have also put them in different positions to see which works best.

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Finally finished the base and pole for this piece. Stainless steel still needs a final polish. I redone the patination particularily the hair as it was too bright. It would have darkened over time but what bothered me with it was it was too uniform in colour. it needed more contrast between the shadows and highlights.


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mantrid
 
Posts: 45
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Re: Bronze Casting - Ceramic Shell with Core Technique

Postby mantrid » Sun Jun 26, 2011 2:34 am

And an animation of the finished piece here

Pole Dancer
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Re: Bronze Casting - Ceramic Shell with Core Technique

Postby minlanire » Wed Jan 27, 2016 6:19 am

It is a very good thing I never knew before.
สูตรบาคาร่า
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