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Bronze casting help


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I let it dry for a day in a sunny spot, then slowly heat in an oven, start on low+- 30 min, then if there is no radical change in colour, raise it to med. Same. Then to high, soak a while to make sure mousture is gone, if you weigh it every now and then, it'll stop loosing wheight when dry... 'Scuse spelling, walking my dogs anf don't have specs with me! Darn this getting old!

To become old and wise... You first have to survive being young and foolish! ;) Ikisu.blogsot.com. Email; milesikisu@gmail.com mobile: +27784653651

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Great tip, thanks! I can only imagine how many timed I would have had to do this without any help!

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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Always a pleasure!

To become old and wise... You first have to survive being young and foolish! ;) Ikisu.blogsot.com. Email; milesikisu@gmail.com mobile: +27784653651

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Here it is ladies and gents, 4th time's a charm (the other one of the two molds bottomed out). I had my doubts because the top filled so fast, but she's solid! 1 down, 3 to go!

image.jpg

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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Nice one!

To become old and wise... You first have to survive being young and foolish! ;) Ikisu.blogsot.com. Email; milesikisu@gmail.com mobile: +27784653651

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Quick update-

After initial investigation, I discovered that the cast was not quite as good as I first thought. Heating the investment too quickly during burnout proved that the inside void was actually deformed by the quick release of trapped water. As a result, one side of the fitting was a little deformed. I would have just brought everything down to the new high spot, but that would have done too much to the handle junction. So, here's rounds five and six, more carefully cured molds and melting the bronze in my smaller, more precise forge. Fingers crossed!

 

John

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Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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Success for real this time, full casting but the geometry will take some cleaning to get just right. All in all, happy that I am finally done with the first casting (only took five, sixth wasn't needed). Thanks again everyone for the help, and soon I'll have the other three pieces cast and cleaned up for this long, long standing project.

 

John

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Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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I notice possible oxide inclusions in the cast. Did you de-oxydize the metal? A piece of charcoal floating on the surface should be enough. Also, I'd recommend attaching the sprue to a part that won't be visible. At the attachment you have a good chance of there being shrinkage holes at the connection, due to the large thickness transition. So when you cut off the sprue, there may be holes visible right there.

Jeroen Zuiderwijk

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I think that is the plaster that didn't wash off when I broke it out of the flask. After doing a little cleaning of the surface, it looks a lot better. I will definitely put a little charcoal in next time though. Thanks for the recommendations, that'll help a lot for the next three. I was a little worried about the sprue problem, but fortunately it worked out alright with this one. Even with pouring the wax copies, there was a little of that problem from the shrinkage as it cooled. Probably should have taken that as a sign!

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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For firing, I put it in a toaster oven for a few hours to liquefy the wax, pour as much out as possible, then bring it slowly up to around 1800 over the course of an hour, letting it cool a bit, then keep it next to the back of the forge (like in the picture two up) until I'm ready to pour.

 

Also, I used a little flux to help with deoxidization, would that help at all? It coated the surface of the bronze to keep the direct blast of the propane off it, but I'm not sure how much that helps. I'll definitely also be using charcoal next time though.

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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I think that is the plaster that didn't wash off when I broke it out of the flask.

 

What I refer to is the wrinkles right from the midrib. The photo is not detailed enough that I can say for certain, but if you get wrinkles included in the cast, either the metal was too cool (like f.e. by a cooled down skin on top of the crucible) or there are oxides cast in. When that happens, you get parts where the metal has not fused solid in the casting. You get things that can look f.e. like this: http://1501bc.com/bronzes/rapier_30_maart_2003_b.jpg

Jeroen Zuiderwijk

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For firing, I put it in a toaster oven for a few hours to liquefy the wax, pour as much out as possible, then bring it slowly up to around 1800 over the course of an hour, letting it cool a bit, then keep it next to the back of the forge (like in the picture two up) until I'm ready to pour.

 

Also, I used a little flux to help with deoxidization, would that help at all? It coated the surface of the bronze to keep the direct blast of the propane off it, but I'm not sure how much that helps. I'll definitely also be using charcoal next time though.

 

The firing sounds right, I didn't read if you heated it up far enough to remove the chemically bonded water. I'd fire it a bit longer though just to be sure all the wax is burned off, as it will soak into the plaster (no experience with plaster myself, but it does that in clay moulds).

 

Flux is more a shield. It's not necessary for bronze, unless it's a very dirty metal and you need to flux to bond the dirt together. For oxygen, just a piece of charcoal will soak up all oxygen from the metal, leaving a nice clean metal inside the crucible. You can even add it just moments before casting, and you'll see the charcoal soak up the oxides in seconds.

Jeroen Zuiderwijk

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That makes more sense, thanks. I think there was a little of that, but fortunately it all ground off. I just assumed that it was from the mold, but I suppose that is not the case.

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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I really appreciate all the advice, I can't imagine how many times it would take to get all the variables down. How long should I let it cure? Another half hour of longer than that? Also, would I be likely to damage the metal from having too hot a forge? I only ask because I had some porous bronze in the first cast and I'm not sure what happened.

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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I really appreciate all the advice, I can't imagine how many times it would take to get all the variables down. How long should I let it cure? Another half hour of longer than that? Also, would I be likely to damage the metal from having too hot a forge? I only ask because I had some porous bronze in the first cast and I'm not sure what happened.

 

For the firing, in principle if you cast the bronze in, and the bronze isn't bubbling or spitting, and the detail in the cast is well then it is sufficient. So you are probably ok. But for clay moulds, I know an hour is usually too short to burn off all of the wax.

 

When the metal is too hot, the surface will start bobbing. I don't know the exact consequences of that, but I've heard it will not cast as well. Also, the hotter, the faster metal will burn off, particularly the less noble metals such as tin, which can result in slag in the crucible. The porous cast, could simply have been residue wax or chemically bonded water in the mould.

Jeroen Zuiderwijk

Facebook page: https://www.facebook.com/barbarianmetalworking

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There wasn't any supluttering fortunately. The porousity however happened before the bronze ever made it into the cavity. A few large chunks of spongy bronze fell out of the crucible and clogged the sprue before it could fill entirely. That was the first time I used a graphite crucible, could that have anything to do with it? The second time it worked fine (other than having a bad mold). For the most recent one however I used a clay crucible so it could fit in the smaller forge, which I had also used before. In the dish, I had a clearer line of sight to the bronze and it never reached that degraded, aerated state. At first I thought it might have been the bits that never fully melted, but the fluid bronze poured perfectly. I'll see if I can re consolidate the sponge bronze to check if the tin burned out or if it is something else.

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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I really appreciate all the advice, I can't imagine how many times it would take to get all the variables down. How long should I let it cure? Another half hour of longer than that? Also, would I be likely to damage the metal from having too hot a forge? I only ask because I had some porous bronze in the first cast and I'm not sure what happened.

I doubt your forge is getting too hot,I have cast many pieces with an oxy-acetylene torch at temps exceeding 3000 degrees F. From your photos it looks like you need a better sprue,it should be a straight shot from the button to the piece being cast.It also appears you are not using enough metal for the casting,your button should be 2-3 times larger.

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Thanks Dan, must have missed this earlier. The button is small only because I stopped pouring when the void topped off. There is space for quite a bit more. Should I be filling that anyway? I thought it would not make a difference, but then I've thought that about a lot of things that matter :rolleyes:

 

Also, now that I have the casting cleaned up and fitted to the blade, I've been messing around with the patina quite a bit to get it looking just right. Is there anything I can do to darken it (thinking gunmetal grey or even black)? I've already gone through cycles of ferric (opposite of what I wanted to happen), potassium permanganate (takes it to a darker dull brown), and ammonia (for some green/blue highlighting). I keep thinking back to the demo Jim Kelso did at Ashokan a few years back. The patinas he can get on anything is incredible, but unfortunately my stock of chemicals is a bit limited. Any ideas on ways to really darken bronze?

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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  • 2 weeks later...

Figured I'd give another update in this thread as the project nears completion. The spacers are cast, now waiting on the investment for the pommel to cure. The patina situation is looking good. I was originally trying to do a stonewashed texture, but don't have the proper media available. So instead I went for a more rugged, pocked finish achieved by tumbling it with a bunch of small pipe fittings. After that, I brightened the high spots with a little ferric chloride, then patinated it with alternating rounds of potassium permanganate and ammonia (after coming up dry for liver of sulphur in a timely manner), then tumbled it a second time with a handful of copper airgun bbs. The effect was good, nice and dark. You can see a little of what remains of that patina on the top half of the lower guard, but I had to do a little more blending with the antler handle pieces. For consistency with the other three pieces, I am going to take it back to a polish and start over. The spacers are sound, and after realizing how precise the fit has to be to remove all the gaps, I have everything save the upper guard on tight and sanded flush. Here's a current picture of the progress. To alleviate the stark and probably ugly contrast between the patinated bronze and the white antler, I plan on aging that to fit the theme of the blade.

 

Cheers!

 

John

 

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Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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Just did a quick blog post on the casting process as I did it. Needless to say I learned a lot!

 

Lost Wax Casting

 

The blade is so close to being done. Can't wait to show it to you all!

 


John

Not all those who wander are lost. -J.R.R. Tolkien

-Shards of the Dark Age- my blog
-Nine Worlds Workshop-
-Last Apocalypse Forge-

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That's looking good, John! Once you get your casting down pat, it'll become easier...I'm waiting for the finished product with anticipation!

To become old and wise... You first have to survive being young and foolish! ;) Ikisu.blogsot.com. Email; milesikisu@gmail.com mobile: +27784653651

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