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
  #76  
Old 04-08-2007, 09:56 AM
GlennT's Avatar
GlennT GlennT is offline
Level 10 user
 
Join Date: Aug 2006
Location: Minneapolis
Posts: 4,213
Re: Bronze Clay?

Thanks Burkhard for taking the time to so clearly explain the process. It allowed the "left brain" and "right brain" to catch up with each other long enough to get it!
Reply With Quote
  #77  
Old 04-09-2007, 01:23 PM
le granfred's Avatar
le granfred le granfred is offline
Level 3 user
 
Join Date: Mar 2007
Location: Chindrieux France
Posts: 33
Re: Bronze Clay?

Yes, the idea itself is good.
But the process is not that good, and a well known technology could be operated to make the most of it. At least, this is my opinion. Think it over, it is rather easy I think. To be tried.
Reply With Quote
  #78  
Old 04-09-2007, 08:21 PM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Thanks Glenn, glad it made sense. The thing that really interests me about the technology is the potential freedom to create one-off bronze scultures without having to go through a mold-making stage. The potential time saving is also a big plus for me - I've set up my own backyard foundry for pouring bronzes, but am finding the amount of time it takes from sculpture, to silicon mold, to wax, to investment burn-out, to casting, to chasing.... to final bronze to be excrutiatingly slow for someone with my lack of patience.

le granfred - not sure I follow you - are you saying that the overall process could be simplified? I am hoping that this is true, but with these types of technologies sometimes it is easy to get a "result" but very difficult to get consistent, reliable, professional results. Hope I'm wrong. If you have ideas (or have tried things) please share - the "well known technology" you mention - are you thinking microwaves?
__________________
Burkhard
Reply With Quote
  #79  
Old 04-10-2007, 01:02 AM
le granfred's Avatar
le granfred le granfred is offline
Level 3 user
 
Join Date: Mar 2007
Location: Chindrieux France
Posts: 33
Re: Bronze Clay?

Hello

I am wondering if the whole bronze clay work could not be fused in the middle of a coil. That would look very much like induction melting and instead of the melting pot containing bronze, you would have your wax mixture made sculpture.
see what I mean ?

more on this process here
Reply With Quote
  #80  
Old 04-10-2007, 05:03 AM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Hi le granfred
I have no personal experience with induction furnaces, so really have no idea whether it could work. Worth having a look in the literature though - I'll do a quick search tomorrow to see if anyone has published anything on sintering in induction furnaces.

Three potential problems: I don't know whether the temp control is good enough for the sintering to work rather than just melting the whole bronze. Also my understanding is that induction furnaces work by setting up a current in the metal to be molten - no idea whether the wax/bronze is electrically conductive enough for this to work. Also, I've heard that induction furnaces are very expensive to build or buy and probably way out of my budget.

But then again, as I said - I don't know what I'm talking about with regard to induction furnaces - it's always easy to come up with reasons why something won't work, only to be shown by someone who actually tried it that it can work.
__________________
Burkhard
Reply With Quote
  #81  
Old 04-10-2007, 02:03 PM
DanielUCM DanielUCM is offline
Level 4 user
 
Join Date: Jul 2006
Posts: 63
Re: Bronze Clay?

Nice to hear from you Mark and thanks for that detailed run-through of the process, Burkhard! Particularly for supplying a reason for why two owens might be used. That one has really been bugging me since I haven't found any reasons for it in the various sinter-related articles I have read so far. You also did a good job in explaining details about the functioning of the kiln for those of us without the relevant academic training. Have you thought about what kind of a kiln/furnace could be used for this? Sounds like it would be possible to manage without an industrial type sintering owen.

Regards
/Daniel
Reply With Quote
  #82  
Old 04-10-2007, 08:58 PM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Hi Daniel - my current plan is to build a steel container with lid and gas lines that I can place inside my old pottery kiln. No way that I can afford a proper gas-tight furnace at this stage. Major danger that I worry about is decomposition gas leaking into the kiln and going boom if the container is not sealed properly. A gas fired kiln would probably be safer, but I'm not sure whether it's possible to get the accurate temp control that's required.

Ideally you would also want good temperature control on the kiln with the ability to program the temperature profile. This would make life a lot simpler as I suspect that one has to ramp up to 300-400C, then soak at that temp for a while (hour?), then ramp to sintering temp, 840C, and again hold for a while (again an hour or two?). Unfortunately all I have is a crude on/off control on my kiln and a pyrometer so I would have to nurse the firing manually.
__________________
Burkhard
Reply With Quote
  #83  
Old 04-11-2007, 01:53 PM
SPRINGFIELD SPRINGFIELD is offline
Level 10 user
 
Join Date: Jul 2006
Location: BURBANK CALIFORNIA
Posts: 731
Re: Bronze Clay?

I found this thread very exciting. I have also been experimenting with metal casting but my experience is very little. So I'm hoping that some of the more experienced can offer some pointers about my latest experiments.
I have also been trying to come up with a easy way to make metal sculptures and have tried what I believe is a original approache. One day I was thinking about how concrete is made. The sand is what makes the concrete strong the actual cement is just the binder. Without the sand cement is pritty week and has no abrasion resistance. So what if you took steel or bronze powder and bound it with powdered solder. The steel would add strength and the solder would bind it. Also because the solder melts at a low temperature you can have a steel or bronze strong sculpture at temperatures in the 450 f range. Considering how inexpensive steel is the most expensive part would be the solder which you may not need much of. I tried a small experiment with some steel filings and some solder filings mixed with some soldering flux and the result was a very hard strong glob of what looked to be steel. Attempts at larger mixtures didn't work so good. I think the problem is oxidation. Sure would like to here some comments from experienced foundrymen etc.
Reply With Quote
  #84  
Old 04-12-2007, 01:04 AM
DanielUCM DanielUCM is offline
Level 4 user
 
Join Date: Jul 2006
Posts: 63
Re: Bronze Clay?

Burkhard- That sounds like a clever way to go to start with the process. Are there some suitable steel-containers available that can be converted or would you have to construct your own? I guess one problem then would be to get it air-tight.
Springfield- You might want to check out liquid-phase sintering (spelling?) which I mentioned in an earlier post.

/Daniel
Reply With Quote
  #85  
Old 04-12-2007, 03:50 AM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Daniel - my first thought was very low tech - a steel saucepan Cast iron would be better (less spalling) but difficult to get in Sydney at the moment.

Maybe a thin layer of bat wash or even plaster around the rim to provide a slightly better seal. Drill a hole in the lid for the tubing (either welded on or use tube fittings) and cross your fingers. I'm hoping that with the densely packed wicking powder there wouldn't be a lot of space for air in the can anyway and one may be able to get away with this setup. It's worth a try before going to more expensive options.

I just got my bronze powder and wax and made some test ingots. Highest loading I could get was 33g bronze powder and 3.5g wax (higher quantities of the bronze (64% wt/wt) resulted in a more powdery feeling solid, but still very hard and could be suitable for carving). Behaviour of this stuff is very similar to a corn starch and water mixture i.e. when agitated quickly it is a stiff paste but is fluid when allowed to settle slowly and vibrated. A vacuum oven and vibration table would definately be useful for getting air out of the mix and getting good quality mold castings. (Alternatively an ultrasound baths may be useful for densification/deaeration of the hot wax/bronze mixture into the molds.) If the gods (or at least a reasonable percentage of them) are willing I hope to do a test firing over the weekend.

Springfield - I have no expertise in this, but the liquid phase sintering process that Daniel mentioned might give you some pointers. In terms of the amount of solder - when mixing two powders you need at least 16 % (by volume I think) to reach the percolation threshold (i.e. the point where the solder, in this case, can form at least one meandering but complete path from one end of the material to the other). Btw, it's also possible to buy tin powder and maybe mix this with the steel or bronze? I suspect that the main problem will still be oxidation (same as for the sintered bronze process) as well as dimensional stability - in the case of solder, if you're actually melting one component then this would make the whole structure fairly fragile while the solder is in its molten state. Sorry - rambling, I actually have no idea!
__________________
Burkhard
Reply With Quote
  #86  
Old 04-12-2007, 11:38 AM
SPRINGFIELD SPRINGFIELD is offline
Level 10 user
 
Join Date: Jul 2006
Location: BURBANK CALIFORNIA
Posts: 731
Re: Bronze Clay?

Thanks Burkhard and DanielUCM for your info. You guys sure have a lot of info and experience. Sounds like I better get some more experience using traditional methods for a while. I experiment so much I never get anything finished. Right now I'm experimenting with making shell molds using different materials for the shell.
I looked up Liquid Phase Sintering on the internet and got lots of info. I hope to give it another try in the future. I noticed that E-Bay has a lot of Vacume Ovens for sale and some are pritty inexpensive. Thanks again fore all the advice.
Reply With Quote
  #87  
Old 04-13-2007, 07:36 AM
sgriff sgriff is offline
Level 1 user
 
Join Date: Apr 2006
Location: ky
Posts: 4
Re: Bronze Clay?

Hey Burk... as i was reading your info on the texture of the bronze/binder mixture you are experimenting with i reviewed the info that mark gave in his on of his first posts..about adding Empoline...maybe this enhances the texture and workability of the "clay". I couldnt find it online but i did find info on ceramic additives/plasticizers that burn out.
I have 2 skutt kilns sleeping in my studio..i think this process has given them new legs..
Reply With Quote
  #88  
Old 04-13-2007, 08:52 AM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Hi sgriff - yeah, I was starting to wonder what the heck empoline was as well. Also haven't been able to find any info on it at all. Mark said that it's only there at 2%, which indicates that it must have a real function, (else at such low conc why bother including it). Does anyone have any ideas what empoline is/could be? (may not be the correct spelling)

With regard to other additives/plasticisers - remember, in principle in this process they have to melt, wick into the surrounding alumina powder and then they have to decompose rather than burn out (no oxygen), so polymer additives may not work - don't know. Wonder whether the stuff they put into Sculpey (I think it's dibutyl or dioctyl phthalate) would work. The phthalate volatilises at 130C and could be removed without decomposition. Of course any frogs in the area would probably start to grow 5 legs and two heads, but this doesn't seem to worry Sculpey users.
__________________
Burkhard
Reply With Quote
  #89  
Old 04-13-2007, 02:18 PM
DanielUCM DanielUCM is offline
Level 4 user
 
Join Date: Jul 2006
Posts: 63
Re: Bronze Clay?

I can just second to that - I haven't found any info on the epoline or empoline, last time I searched was however at least six months ago. There is some other binder I've read about, but it might just be inappropriate for our purposes, I'll see if I find the name of it.

It will be great to hear how your tests work out Burkhard! I've been saving to invest in some more advanced equipment than what I currently make do with, and if your low-cost method works - excellent. Unfortunately I'll leave Sweden for a few days soon, so I hope I get to know about your results before I leave I will upload a picture of the result of one of my extremely low-tech experiments, just for fun, so you know the baseline of what you must accomplish!

Springfield, I think its great that you experiment a lot, but as you say it is good to get a somewhat solid base in some established method first - if nothing else it makes it easier to read through more advanced articles.

Has anyone picked up on Marks suggestion and e-mailed the researcher he suggest that we contact? Maybe he can give some pointers on the E(m)poline if we would really get stuck?
Reply With Quote
  #90  
Old 04-16-2007, 01:12 AM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

For those interested – my first experiments in trying to recreate, at home, the sintered bronze process described by Mark Pilato. As is usual with this type of experiment it worked just well enough to make me want to continue – no champagne to celebrate yet (but worthy of a couple of beers).

Usual caveat: Because I do not know who may read this, the following is provided for information only. I do not suggest that anything I describe here is safe or should be attempted by anyone who does not have the appropriate training. Please see safety warnings on my previous post. If you injure yourself or others, don’t blame me – you have been warned.

The question I wanted to answer with the current trial was whether it’s possible to create an oxygen-reduced atmosphere in which to fire the bronze/wax mixture that would enable sintering without severe bronze oxidation occurring. Main interest for me is also whether it’s possible to do this using stuff that’s readily available to most sculptors, or whether this really is a technology that needs to be done using fairly expensive industrial scale technology (kilns, temp controllers, nitrogen lines etc).

I prepared seven samples, to play with the bronze/wax ratios etc:

Sample A: 3.5 g microcrystalline wax + 54 g bronze powder (94% w/w, 64% v/v). When hot, very dry looking, powdery mixture, pressed into mould while hot. When cold was firm solid but powdery.
Sample B: 3.5 g microcrystalline wax + 30 g bronze powder (90% w/w, 50% v/v). When hot was a very viscous paste, behaved similar to cornstarch/water. Bronze settles in mould with vibration and a 2mm layer of wax formed on surface.
Sample C: 3.5 g microcrystalline wax + 40 g bronze powder (92% w/w, 57% v/v). When hot, dry powdery mixture similar to A.
Sample D: 3.5 g microcrystalline wax + 34 g bronze powder (91% w/w, 53% v/v). Similar to sample B except only very thin layer of wax left on top of mould.
Sample E: 3.5 g jewellery wax + 33 g bronze powder (90.4% w/w, 52% v/v). Settles in mould similar to sample D.
Sample F: 3.5 g jewellery wax + 3g tin powder + 30 g bronze powder.
Sample H: Same as sample E.

Samples cast as round buttons ~ 3cm diameter, 1 cm height.

My steel container + kiln was prepared as follows:

A hole was drilled into the lid of a stainless steel cook pot (not aluminium, anodised aluminium, or stainless with aluminium base!) and ¼ inch stainless steel tubing was attached using Swagelock fittings. The tube was long enough to protrude out of the spy-hole at the side of the kiln. No nitrogen inlet was provided for this experiment.

A layer of fine TiO2 powder (used rather than alumina simply because it was on-hand) was packed into the pot, the samples were placed on top and the pot was then filled with further TiO2 powder until the pot was nearly full (about 3/4 inch head space left). The powder was tamped down with the end of a piece of wood. The lid was placed on the pot and the rim was sealed with a small amount of plaster of paris mixture (this later cracked severely while firing, but still held the lid firmly in place – although probably not air-tight). Pot was assembled into kiln, the pyrometer ended up sitting just above the lid of the pot.

(As a control, sample H was packed in the TiO2 powder in an open steel dish i.e. exposed directly to the kiln atmosphere.)

A small LPG gas torch was placed so that the end of the stainless steel tubing protruding from the kiln sat in the middle of the flame of the gas torch (this served a dual function, firstly it ensured that any decomposition gas generated from the wax would be safely burned off, and secondly it ensured that no oxygen could back diffuse into the tubing and into the pot).

Kiln was started and heating rate adjusted manually by controlling the on/off time. Initial heating at 70% on rate raised the temp to ~ 570C within 80 minutes, when a small flame appeared from the end of the steel tube. Heating rate was reduced to 55% for a further 60 minutes until there was no more flame coming from the steel tube (temp had risen slowly to 634C during this time). Note the flame was extremely sooty even when the gas torch was turned on full with an oxidising atmosphere – danger of inhalation of toxic materials, including carbon monoxide poisoning. Good ventilation essential. Heating was increased until temp reached 850C and by adjusting the on/off time the temp was maintained between 843 and 850C for a further 120 minutes. Kiln was shut down, lid lifted soon after to rapidly cool everything. After 20 min the gas torch was also extinguished.

Results:
Only partially worked – most samples not fully sintered. I think the main problem was that I measured temp at top of pot, not inside or bottom. I found that in my kiln there was a largish temp gradient between top and bottom of kiln of ~ 80C, hence the temp inside probably never got to the 840C required.

Sample A: bronze powder, no structure. Not sintered at all. 100% powder
Sample B: Looked solid, but attacking with screwdriver revealed the outside was 2 mm sintered, nice bronze coloured looking metal, can be filed, polished, kept its shape (including the sample letter scratched into the surface). Inside – still lots of unsintered powder. ~70% powder
Sample C: some sintering i.e. hard outside crust. ~ 90% powder
Sample D: Looked solid, as per sample B, but only about a 1mm sintered outside layer, the rest still powder. ~80% powder.
Sample E: powder, no sintered structure, ~100% powder
Sample F: Very thin layer of sintered skin, ~ 97% powder
Sample H: (this was the one exposed to kiln atmosphere) outside was a ~1mm thick skin of what looked like black copper oxide (+ tin oxide?). This could be pealed off reasonably easily (although it was quite hard and had retained good imprint of the letter scratched into it). Inside was red copper coloured hard, metallic material. I suspect the tin had oxidised severely and left the chunk of copper behind.

Preliminary Conclusions:
1) Major problem seemed to be that the bronze powder did not sinter completely.
- probably pyrometer readings were low compared to the actual temp inside the pot.
- probably need to soak the pot at sintering temp for longer.
- could be a major problem if the kiln temp is not uniform within the kiln i.e. the top of a sculpture could get fried whereas the bottom is not sintered properly.
2) The bronze/wax mixture if fired in air oxidises heavily to the point where its not useable even when packed in a wicking powder such as TiO2 (sample H).
3) The present system seems OK with regard to producing a non-oxidising atmosphere inside the pot, but this needs to be confirmed (i.e. is it good enough for the longer sinter times and higher temps that I might need to fully sinter the pieces).

Less important findings:
4) For some reason not all waxes are equal i.e. jewellery wax (the type used to make small rings etc for lost wax casting) did not yield significant sintering. May need to increase temp further? Or may be a function of wax. Why? - don’t really have the foggiest idea. Maybe the jewellery wax expands too much prior to melting, moving the bronze particles too far apart for easy sintering.
5) Also, for some reason the sample with the lowest amount of bronze powder (sample B) gave the best sintered sample. I would have expected the sample with the highest bronze loading (sample A) to be the best sintered, however this was just dust. Why? – again not the foggiest, but may have something to do with the packing of the bronze powder in the mould prior to the wax cooling?
6) Addition of 10% extra tin powder didn’t do anything exciting at this stage.
7) Not having an electronic temp controller that one can program is a nuisance, but nursing the kiln to manually adjust the temp is do-able.

Next steps:
=> repeat experiment but with increased temp and soak times to see if the problem really is to do with the sintering temp not being reached.
=> have another beer.
__________________
Burkhard
Reply With Quote
  #91  
Old 04-16-2007, 10:18 AM
GlennT's Avatar
GlennT GlennT is offline
Level 10 user
 
Join Date: Aug 2006
Location: Minneapolis
Posts: 4,213
Re: Bronze Clay?

Some further analysis;

The level of intoxication produced by the beer divided by the square root of confusion plus or minus the ponder and muse factor may hinder the sinter in the ratio of (94% xy ) ( 760g key lime pie R squared ) where x = the nosy neighbor next door and y = studio vermin in rural locations.

Hope that helps
Reply With Quote
  #92  
Old 04-16-2007, 05:02 PM
mark pilato mark pilato is offline
Level 8 user
 
Join Date: Jun 2006
Location: new york
Posts: 223
Re: Bronze Clay?

hi Burhard call me, I think i can help you get over some of the humps.
607-326-3508
all the best,
Mark
Reply With Quote
  #93  
Old 04-16-2007, 08:10 PM
RWJR RWJR is offline
Level 9 user
 
Join Date: Jul 2006
Location: Breaux Bridge, louisiana
Posts: 264
Re: Bronze Clay?

looks like these guys have it figured out http://www.powdermetallurgyco.com
Reply With Quote
  #94  
Old 04-16-2007, 08:14 PM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Hi Glenn - I like it! I think the equation may also be applicable to the rest of my confused life. Yeah, I know, I do tend to get overly analytical and detailed when I'm in technology-nerd mode One of the reasons I love sculpting - totally different parts of the brain used.

Hi Mark - thanks for your generous offer, however, I'm sitting in Sydney Australia so email may be simpler (I think you're 15 hours behind time-wise? I'll have to check). If you have the time to post any comments, suggestions, glaring errors etc about what I've done so far that would be cool (I know you're busy). I think the way you described the process in your earlier posts really got a lot of people exited (just look at the number of hits this thread keeps getting!).
__________________
Burkhard
Reply With Quote
  #95  
Old 04-16-2007, 09:06 PM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Hi RWJR, yes, this is the sort of "industry standard" process that's actually been around for quite a long time. Sintered bronze parts are often used as self-lubricating parts because the porous bronze can be impregnated with oil. BUT the processes used in industry usually involve high-pressure compaction of the powder into steel moulds prior to sintering. There is quite a large industry using sintered metal powders to produce all sorts of objects - it's especially interesting for producing objects from metals that have very high melting points. However, these methods aren't really applicable for sculpture in general unless you want to mass produce your work.
__________________
Burkhard
Reply With Quote
  #96  
Old 04-16-2007, 10:37 PM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

The following is pretty much an excercise in learning how to post picture on this forum - obviously too much time on my hands. Hope it works, if this keeps going I may just get my act together enough (scary) to post some pics of my sculptures as well.

The first picture is inside of the kiln with my high tech cooking pot showing steel tube exiting kiln. Pic 2 showing outside of kiln, pyrometer and gas burner positioned at exit of steel tube. Pic 3 amount of flame produced at mouth of steel tube from decomposition gas from the wax. Pic 4 same thing but with burner back in place. Pic 5 shows 3 samples: left, sample B, the sintered piece that pretty much worked; middle, the way most pieces looked i.e. not cooked all the way through but with a sintered skin; right, is the piece (sample H) that was sintered just in air showing lots of black oxide and copper red inside.

__________________
Burkhard
Reply With Quote
  #97  
Old 04-17-2007, 12:44 AM
Burkhard Burkhard is offline
Level 3 user
 
Join Date: Apr 2007
Location: Sydney, Australia
Posts: 49
Re: Bronze Clay?

Aha, the mysterious epolene

Epolene: The toughness, opacity, and gloss in high-quality candles has traditionally been determined by the quality of wax used. The high-melting-point petroleum waxes that provide these desirable features have become scarce as the market for high-quality candles has grown. This has generated a need for additives for low-melting-point waxes that will impart the desirable features normally associated with the more expensive, higher-melting-point products. Eastman Chemical Company offers polyethylene waxes that can fill this need, including Epolene N-34, Epolene N-10, Epolene N-11, Epolene C-15, and Epolene C-10

http://www.quimisor.com.mx/tecnicas/...0Additives.htm
__________________
Burkhard
Reply With Quote
  #98  
Old 04-18-2007, 12:40 PM
DanielUCM DanielUCM is offline
Level 4 user
 
Join Date: Jul 2006
Posts: 63
Re: Bronze Clay?

Burkhard, thank you for your thorough reporting! Encouraging that you managed to avoid oxidation with that accessable solution.

For those interested I have here attached a picture from an experiment (well mayby not experiments in the strict sense of the word..) that I did around August last year. I did two samples using bronze powder of a 89/11% mix of Cu and Sn. With a "fraktion" (I believe that's the word my supplier used, can't recall what term is commonly used in English) of <0,045. I used two different forms of mikrovax/microwax supplied by a Swedish company. I unfortunately didn't have time to record my endevour in any serious manner since I had some eight other samples (not relevant to discuss right now) that I wanted to process during the same time-period over a weekend (the owen I use is not located where I live most of the time so I seldom have time to use it). I just did a couple of blobs of the mix based on the two different forms of wax, the texture was more smooth than powdery, if that's some indicator of the ratio I used an open container so I naturally got the problem with oxidation.
Why I tell you guys this is because I did the sintering at a higher temperature than you Burkhard, most likely over 850 celsius (judging by the colour of the stainless steel container I would like to think it was about 900 celsius), and got a solid core. I baked it for some 1,5 hours at that temperature. The attached piece is about 50*40 mm with a thickness (around the place of where I have filed away some of the outer layer) of about 3 mm. The core of solid bronze is around 1,5 mm thick. Note that the so called core does have a surface riddled with tiny holes. It seems like the aluminum oxide powder and the outer layer of bronze powder protected the inner parts enough for them to sinter. The piece is hard enough that it cannot be broken with the hands (the other piece I was able to bend though). I used a gas-powered owen.
Next time I do this I'll try to keep better records (and use better equipment), but at the point of the test I just wanted to get started.

And the epoline mystery is unravelling, nice!

/Daniel
Attached Thumbnails
Click image for larger version

Name:	Daniel_S_sinteredbronze.jpg.jpg
Views:	365
Size:	26.4 KB
ID:	5842  
Reply With Quote
  #99  
Old 04-18-2007, 02:19 PM
mark pilato mark pilato is offline
Level 8 user
 
Join Date: Jun 2006
Location: new york
Posts: 223
Re: Bronze Clay?

okay guys as far as the mix- its easy, get a crock pot turn it to about 350 pour in the wax,let melt, then pour in your bronze powder making sure the powder has a range in granule size, like a stone wall. mix it like plaster until islands form. when the batch is up to temp, 350, then vibrate the pot with a foot massager or vibrating massager. skim the wax off the surface after about two minutes, then pour mix into the mold making sure to also vibrate mold at same time. It helps to have a large pour cup because the bronze will also settle leaving a wax layer on top. If you have a vacuum furnace this works the best, put the rubber mold in and pump out the air. I bought one second hand for 50.00. after this is done wait for it to cool, clean it up, sculpt it, making nice then put it in a small steal can surrounded by aluminum oxide powder . first put about an inch of powder at bottom of can, then place piece in can, so that it has an inch of space around it. then pour in powder, after its full tap the can up and down, this helps pack the powder. If you are doing relief sculpture or small pieces all you need to do is pour about a 1/8 inch powder on a kiln shelf then place your sculptures on top and cover with the powder. Ive done about 100 small sculptures in one run this way. okay heres the next step the kiln, picture below. place cans in stainless can that is in your kiln, put lid on, turn on nitrogen bring your kiln temp up to about 350 c for your first hold until wax is burnt out then bring to second hold of about 550 c for about an hour or if you have a full kiln 3, then bring to sintering temp, hold for two hours turn off gas and kiln and let cool. you must use nitrogen or this wont work. picture bellow shows kiln with stainless can inside, I used the kilns port holes to plum in stainless pipe welding it to can, one pipe is for burn out, one pipe is for pyrometer and the other is for nitrogen. the top of the Stainless can does not have to seal, the nitrogen does the trick. you can place kiln shelves in you main can the the smaller cans can be placed on kiln shelves making sure there is 3 inches of space between. hope this helps. hope you ge it,
all the best ,
Mark
Attached Thumbnails
Click image for larger version

Name:	kiln.jpg
Views:	432
Size:	57.6 KB
ID:	5843  
Reply With Quote
  #100  
Old 04-18-2007, 03:55 PM
DanielUCM DanielUCM is offline
Level 4 user
 
Join Date: Jul 2006
Posts: 63
Re: Bronze Clay?

Thanks Mark for that additional information about the Pilato-process! So you have one larger container which is permanently inserted in your kiln and then you can just place whatever other cans you have filled in that.. And you don't have to seal the larger container. Concerning the three pipes: Do they need to be placed in some specific order to make sure that the nitrogen does its work, and that the burn out functions properly?

(Everyone who starts utilising the process for themselves according to your instructions should send you paper copies of photos of their first work using it - so you can get an archive of what the process have been used for!)

/Daniel

Sorry, I just saw that your attached picture, opens up for a bigger view with more detail on the ordering of the tubes!

Last edited by DanielUCM : 04-19-2007 at 12:28 AM. Reason: Clarification
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 - 2018, Jelsoft Enterprises Ltd.
Russ RuBert