Sculpture Community - Sculpture.net  

Go Back  Sculpture Community - Sculpture.net > Sculpture Roundtable Discussions > New Technologies
User Name
Password
Home Sculpture Community Photo Gallery ISC Sculpture.org Register FAQ Members List Search New posts Mark Forums Read

Reply
 
Thread Tools Display Modes
  #1  
Old 06-25-2005, 11:30 PM
GaryR52 GaryR52 is offline
Level 10 user
 
Join Date: Jun 2005
Location: Seattle
Posts: 673
Bronze Clay?

I discovered a product called Silver Clay (http://www.silver-clay.com/), for jewelers, which is composed of 99.9% pure silver in powdered form, suspended in a clay-like binder. You model it like clay, then fire it at a low temperature in a kiln and the binder vaporizes, leaving only the silver. The object shrinks by 30%, so you plan your piece larger than you want the final piece to be.

I was thinking it would be a great idea if they made a bronze version of this for sculptors. You could model a sculpture, fire it like clay and have a finished bronze, ready for a patina, thus bypassing the process and expense of mold-making and casting. However, they don't make a bronze version of the product, so I'm wondering if I could make my own by mixing powdered bronze with a clay-like binder of some kind, or perhaps with a microcrystalline wax. If wax is used, the wax would burn out, leaving the fused bronze. Of course, it would have to be very well mixed so the bronze wouldn't be full of holes after the wax burns out. Any thoughts?

Gary
Reply With Quote
  #2  
Old 06-30-2005, 06:16 PM
Arrow Arrow is offline
Level 8 user
 
Join Date: Jun 2005
Posts: 218
Re: Bronze Clay?

I was thinking about this too. I was thinking about a mold filled with bronze powder and binder that could be microwaved too fusing temps. Had this idea since I saw this site. http://home.c2i.net/metaphor/mvpage.html

I believe the key to the metalclay is the size and purity of of the metal particles. The average person wouldn't have anyway to grind the metal into the micro sizes. Bronze would have a higher fusing temp and mixture of different types of metals that would complicate the process.

Sinstered bronze gears and parts are possible, but they undergo a high pressure molding process before they enter a furnace for fusing.
Reply With Quote
  #3  
Old 06-30-2005, 11:03 PM
GaryR52 GaryR52 is offline
Level 10 user
 
Join Date: Jun 2005
Location: Seattle
Posts: 673
Re: Bronze Clay?

Thanks for that link, Arrow! Great idea. I've been wondering what to do with the old microwave I've got sitting out in my garage unused. Now I know.

Well, I know from my research that metal clay or silver clay, as it's sometimes called, is 99.9% fine silver after firing and the gold is 24K, so, yes, they are very pure. You're right that the means to atomize bronze is beyond the capability of the average person, but that's not necessary, anyway, as atomized bronze powder is readily available. The issue of the metal content is moot, as well, since, once the wax burns out and the bronze is sintered together, you've got pure bronze that is exactly the same bronze as before, only fused. The process of firing it won't change its fundamental composition, just its state. It goes from a powder to a solid.

I'm not sure you're right about that high pressure part, either. I know that rapid metal printing can produce bronze parts (and other metals, as well, including steel) without any pressure applied at any point in the process. Also, in rapid metal printing, there is no furnace used. The metal is laser sintered. But, that's probably a different process than the one you had in mind. It does use atomized metal, though.

I'm really intrigued and excited about the prospect of using a microwave for this. I hadn't even considered it as a possibility. The 1000 C temp quoted in the article (1830 F) is perfect for use with metal clay, which needs to be fired at 1650 F (for PMC+) for 10 minutes, or 1830 F for two hours for the Gold PMC. Since silicon bronze melts at 1780 F, this would be perfect for bronze, as well. Good thing I have a spare microwave, as I'd hate to have any burnt out wax residue all over the inside of the one I cook my meals in.

P.S.: well after reading the article, I'm a little disappointed to learn that the temps attained were the result of using an investment casting mold material that contains graphite and molochite. Obtaining either shouldn't be expensive or difficult, but I was hoping to be able to use the microwave for metal clay, as well as for trying my bronze clay idea. Maybe if I made a box with a ceramic/graphite/molochite shell into which I could place the metal clay object...but, then I wouldn't be able to keep an eye on it. Hmmm....

Gary

Last edited by GaryR52 : 06-30-2005 at 11:40 PM.
Reply With Quote
  #4  
Old 07-01-2005, 01:21 AM
Arrow Arrow is offline
Level 8 user
 
Join Date: Jun 2005
Posts: 218
Re: Bronze Clay?

I love fact that David Reid can reach in with his bare hands too invert the investment and molten metal.

Good microwave furnace pic.
http://www.popsci.com/popsci/how2/ar...023030,00.html

I wonder how much silicon carbide bricks cost.
Reply With Quote
  #5  
Old 07-01-2005, 02:45 AM
GaryR52 GaryR52 is offline
Level 10 user
 
Join Date: Jun 2005
Location: Seattle
Posts: 673
Re: Bronze Clay?

Well, according to this (http://www.unibrite.com/PL_dENTAL.htm), you can buy 50 lbs of silicon carbide for $87.40 (the black variety. The green costs much more, for some reason). I also found this, but no prices: http://www.alphamaterials.com/silicon_carbide.htm. Silicon carbide bricks are sold as kiln furniture, so they're fairly common.

Gary
Reply With Quote
  #6  
Old 07-01-2005, 04:11 PM
Araich's Avatar
Araich Araich is offline
Moderator
 
Join Date: Apr 2003
Location: Sydney, Australia
Posts: 990
Re: Bronze Clay?

That is really clever, using silicon carbide. I'd tried many years ago to make use of a microwave but couldn't work out how to build up such high temperatures.

How well does the inside of the microwave cope with that heat I wonder?
__________________
'some australian sculpture...'
Reply With Quote
  #7  
Old 07-01-2005, 08:17 PM
GaryR52 GaryR52 is offline
Level 10 user
 
Join Date: Jun 2005
Location: Seattle
Posts: 673
Re: Bronze Clay?

I wonder the same, Araich. Meanwhile, I emailed someone at the PMC Guild and he said he didn't think it was a good idea to try it at all. I figured he'd say so, since he began by saying they are reluctant to tell anyone they can do this because they don't want to be held liable for the consequences if someone burns down their kitchen trying it.

I would imagine that, since the silicon carbide absorbs the heat, it would be mostly contained by the bricks. But then, even so, it has to radiate that heat to somewhere, also.

Gary
Reply With Quote
  #8  
Old 07-03-2005, 07:58 PM
Arrow Arrow is offline
Level 8 user
 
Join Date: Jun 2005
Posts: 218
Re: Bronze Clay?

More microwaved metal info.

http://www.sciencedaily.com/releases...0622055733.htm

"Powder metals do absorb microwave radiation and can be heated and sintered, using microwaves... Because microwave sintering takes less time and lower energy levels, it is cost effective... We obtained essentially fully dense bodies with substantially improved mechanical properties compared to identical bodies sintered in the conventional manner"

Now I'm on the hunt for the right binder formula. I wonder how long before we will see the first Microwave powered fine arts foundries
Reply With Quote
  #9  
Old 03-29-2007, 12:06 PM
mark pilato mark pilato is offline
Level 8 user
 
Join Date: Jun 2006
Location: new york
Posts: 223
Re: Bronze Clay?

Hi all, its been along time since i posted on this topic, but I have some good news, I tracked down Rand German the man him self. He is excited in working with artists again on this, and he asked me to share his e-mail with you. so e-mail him tell him why you want it and see how you can be apart of this exciting process. Good luck, Rands E-mail german@cavs.msstate.edu
and all the best,
Mark

Last edited by mark pilato : 03-29-2007 at 02:24 PM.
Reply With Quote
  #10  
Old 03-29-2007, 02:28 PM
mark pilato mark pilato is offline
Level 8 user
 
Join Date: Jun 2006
Location: new york
Posts: 223
Re: Bronze Clay?

I changed the e-mail in the last post so make sure you got the right one.
all the best,
Mark
Randall M. German
CAVS Chair Professor of Mechanical Engineering
Director, Center for Advanced Vehicular Systems
Mississippi State University
P. O. Box 5405
Mississippi State, MS 39762-5404

email german@cavs.msstate.edu

Last edited by mark pilato : 03-29-2007 at 04:23 PM.
Reply With Quote
  #11  
Old 06-02-2007, 05:57 PM
mahmoud haggag's Avatar
mahmoud haggag mahmoud haggag is offline
Level 3 user
 
Join Date: Jun 2007
Location: EGYPT
Posts: 27
Re: What is the composition of & Importance

undefined
Reply With Quote
  #12  
Old 06-03-2007, 01:16 AM
jphariot jphariot is offline
Level 3 user
 
Join Date: Jun 2007
Location: Los Angeles
Posts: 43
Re: Bronze Clay?

Hello Burkhard,
I am really impressed with the amount of research you have done here.
I was doing a google search for Bronze Clay and lucky me. I have been researching this on the side for about 3 years now. I am impressed with Marks process, and especially his work. But when you described the Gasses emitted during the wax burn out, I got a little nervous. But I would still prefer that to investment casting hell.
Let me mention that I have been investment casting on and off for about 5 years and hate every bit of it.But now I have no choice, because I have some projects that require it. So I have been looking at the PMC for about 4 years.
Wondered about using it for Bronze and other alloys, but realized that they would oxidize unless placed in an inert atmosphere.
I have a question: Would it work to place an electric kiln into a vacuum chamber? Wouldnt that make it inert? If I have to use Nitrogen then I will. But I would like to get a clearer picture of how that works?
So to continue, I was a bit nervous with the gasses emmited and wondered why not just use the same binder as the PMC?
Then I read your discovery of the Bentonite formula. Sounds good. I think I have used Bentonite as a sand casting binder??
At any rate, how is the process going now? I was planning to start my experiments by late summer-early fall, but I am really getting so tired of investment casting that I think I am going to push it to a sooner date.
I am working on building a resin casting machine, and I am developing my own alloys, so I am really into helping you all here in working on this.
I am wondering if Mark is very commited to the Wax-Bronze Powder system, or if he is interested in helping with some other methods? I am just trying to find an efficient, consistant, and safe system to sinter Bronze and other alloys.
I currently cast a lot of pewter into silicon. Love the undercuts and freedom. But the choice of alloys is really limited. Its left me with the dreaded investment casting.
Thanks again, and please let me know where your at with the Bentonite Formula?
Thanks Again,
John Hariot

Last edited by jphariot : 06-03-2007 at 06:31 PM. Reason: wrong word
Reply With Quote
  #13  
Old 06-04-2007, 03:20 AM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

John - thanks, last summer I got as far as setting up a small foundry and learning how to do small lost wax pieces and also very quickly got tired of the amount of work and effort required.

In terms of vacuum chamber - in principle yes you could set up the furnace inside a vac chamber, I think I have seen reports where this is done. However, you'd need an impressively large vac chamber to stick a whole kiln inside. You'd also need to provide access for power and control wiring and I'm guessing a very good quality oil pump. Alternatively sticking a vac chamber inside the kiln could be done, but now you need to make sure that the chamber is vac tight at 900C and isn't going to implode at these temps. Also if using a vac pump remember you'll need very good gas traps else the soot produced will quickly gum up the vac pump. If you have access to such equipment it's possible, but not worth considering to do at "home" because it would be much simpler to just connect a gas line to the chamber and flood the chamber with an inert gas. I haven't gotten around to taking pics of my current setup yet - it's our end of financial year coming up and I'm up to my ears in project planning, budgets and other $%#* stuff.

I just finished a "quick and dirty" experiment that shows that carbon dioxide gas can also be used as the inert gas. This is useful because the easiest (and probably cheapest) source of gas cylinder/inert gas combo for me are CO2 gas cylinders from the guys who supply the beer home brew crowd (apparently used to charge kegs of home brew). Maybe I can kill two birds with one stone.

Yes, you probably did use bentonite as a sand casting binder. Should also be available at most pottery supply shops as it's used in clay and glaze formulation.

I've now fired the bronze powder/bentonite (95:5 weight/weight) mix three times, all more or less successfully. My current firing regime is to load the pieces inside a can packed in TiO2 (for support) inside a 14l stockpot, place lid (lid has steel gas line attached that is connected to gas cylinder) on top, place three heavy steel weights ontop of lid (to give a reasonable seal), turn on gas. I then ramp up the heat to 900C, which takes me two hours, then hold at 900C for 1.5 hours, turn the kiln off, and allow to cool under inert gas. So far I've not been very patient, so after 30 minutes I open the pot up (wearing welding gloves, face shield and using raku tongs) and take out the bronze pieces and quench in water to see the results. I probably should let things cool down far more, the bronzes are still red hot at that stage.

Couple of things I've noticed with the bronze clay:

One - with the pieces I've done so far it looks like the very top of the surface (top 0.1 mm?) of the fired bronze clay is quite porous and pitted (using a magnifying glass) and in order to get a good finish I need to run a buffing/sanding wheel over the surface. This is not really a major problem except for very fine detail. Don't know whether this is intrinsic to the bronze clay, the firing temp inside my pot, or the size distribution of my bronze powder.

Two - my larger hand formed pieces develop cracks in them either on drying or during the firing. This may be due to bits of bronze clay not bonding when I add them together in the "wet" stage. I've tried adding some paper pulp to the bronze powder/bentonite mix (approx 1-5 g paper/100 g bronze powder/bentonite) in order to make a "bronze paper clay" and this fired as well as the ordinary bronze clay. I think it may be better to sculpt with (not as "brittle"), and I'm hoping that just like ordinary paper clay that it will allow the joining of wet clay pieces more successfully.

[I'm going to try to go back to the bronze wax soon to see if I also see the surface pitting there, but it really does produce a whole lot more soot and noxious gases than the bronze clay. (At one stage I lifted the lid of my kiln up during the firing of a bronze wax. My steel pot lid must have leaked quite badly because the inside of the kiln was full of flammable gas which gave a quite exciting whoompa as the air hit the gas and ignited in a ball of flame. Luckily I was wearing face shield and long sleeved welding gloves so no harm done. Very pretty really). Also, I've not yet managed to figure out a 100% effective way of burning all the soot that comes out of the gas outlet line when using the bronze wax, even sticking a propane torch on the outlet was not totally effective.]

In terms of why not use the same binder as used in PMC ? Good question - simply because I've been totally unsuccessful with this so far - I'd love to know why. It could be due to a whole bunch of reasons to do with the way I fired the pieces, or with the fact that the particular binders I used where slightly different and decomposed leaving too much residue behind or something else. This does not mean it won't work, I just haven't hit on the right combo. Too many things to try, alas, not enough time.
__________________
Burkhard
Reply With Quote
  #14  
Old 06-04-2007, 05:39 AM
enitharmon enitharmon is offline
Level 2 user
 
Join Date: Apr 2007
Location: England
Posts: 20
Re: Bronze Clay?

I have been reading the progress here for months now, quite inspiring. Always exciting when things go boom! Motivated me to read patents and articles. Burkhard, good to see Aussie initiative! the patent for the bentonite mix suggested using an organic substance for greater viscosity...sugar was mentioned. Did you try that? Experience with ceramics, joining pieces to avoid cracks...if you cross hatch and slip the join, blend the join and the seal the sculpture in a plastic bag leaving it for a few days to redistribute the moisture across the join has been successful..might work with the bentonite mix. An article looking at the oxidation, weathering and porosity of the sintered bronze written by Dr German sounds promising too and shows [microscopic] images of the process.
Reply With Quote
  #15  
Old 06-04-2007, 07:49 AM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Hi enitharmon - thanks for the encouragement to all the people who posted in this thread. Hopefully slowly but surely some more people will have results (positive and negative) to share.

I haven't tried the sugar additive (I thought he used that to increase the amount of microorganism in order to increase slipperyness. I'll have to reread the patent. I sort of assumed this was just one of those throw away lines used in patents as I don't think it was actually listed as one of the patent claims, but you're right - worth a quick experiment).

With regard to the joining of pieces of bronze clay - I sort of tried cross-hatching (although not as well as I could have), adding bronze clay "slip" to the parts before joining, and also left the small figure in a plastic bag for a couple of days to equilibrate the moisture, followed by slow evaporation in the plastic bag with only a few holes, before removing the bag etc. No joy. Cracks still formed. However, this may still be just a matter of technique. Read in another article that in order to avoid cracking of ceramic greenware, they did the initial drying of their green body at 90% humidity for 24 hours when most of the shrinkage occured, followed by normal drying.
__________________
Burkhard
Reply With Quote
  #16  
Old 06-07-2007, 05:01 AM
enitharmon enitharmon is offline
Level 2 user
 
Join Date: Apr 2007
Location: England
Posts: 20
Re: Bronze Clay?

Hmm if the bronze paper clay works whole areas of possibility are opened, modelling, shaping, carving, embossing. Inspired again Burkhard!
Was in situ strength maintained? Firing paper in ceramics causes problems but you say it worked with the metal, do you think it increased the porosity? Burnishing prior to firing ceramics is an old technique to compact the particles, I wonder if this might apply to the metal clay and reduce porosity.
Did you use a variety of particle sizes for the bronze powder somewhere I think I read a ratio of 7:1 small to large gave greater sintering strength and reduced porosity, same article said the firing cycle for the wax bronze was 24 hrs which would imply a longer cooling period. Is the proportion of crystalline wax to parafin critical?
Could anyone help with where to get metal powder in the UK coz I think its time for the burning boom! stuff here too.

Last edited by enitharmon : 06-07-2007 at 05:32 AM.
Reply With Quote
  #17  
Old 06-07-2007, 09:54 AM
Harryman Harryman is offline
Level 6 user
 
Join Date: Feb 2007
Location: Colorado
Posts: 103
Re: Bronze Clay?

Any thoughts on forming the clay over a core that could burn out? Less mass of clay would mean less shrinkage, maybe less cracks. Or is this stuff too friable to hold up in a thinner layer?
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


Sculpture Community, Sculpture.net
International Sculpture Center, Sculpture.org
vBulletin, Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Russ RuBert