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Thread: Homemade Bronze clay FAILURE! Any ideas what I'm doing wrong?

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  1. #1
    Join Date
    Jan 2017
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    21

    Question Homemade Bronze clay FAILURE! Any ideas what I'm doing wrong?

    Good Morning!

    I'm new to metal clay, and experimenting.

    I tied to make my own bronze clay, and it was a dismal failure. I'm hoping the people here can help me figure out why!

    Ingredients (I live in Germany, so sorry for the German language pages :
    Bronzepulver, atomized
    Grain size: 44 microns (325 mesh) irregular
    Melting point: 1083 ° C
    https://www.amazon.de/gp/product/B01...?ie=UTF8&psc=1

    Methylcellulose
    100% pure methyl cellulose E464 Nutritional information: Suitable for vegans and vegetarians, GMO-free, suitable for halal food.
    https://www.amazon.de/gp/product/B01...?ie=UTF8&psc=1

    Recipe:
    ~3 parts bronze powder (3 'scoops')
    ~1 part methylcellulose (1 scoop)
    - Distilled water to powdery clay
    - Massaged with olive oil until workable consistency

    Molding clay. :
    - Made a number of my usual 'test coins'…a small disk about the size and thickness of a quarter…imprinted with a simple pattern.
    - Dried at ~100°F for about 6 hours. Then left sitting overnight at room temp.

    Firing and results:
    I fired the clay with three attempts. Each coin separately.

    1. First coin.
    Fired using the same technique for store-bought PMC3 bronze clay.
    - Large butane torch
    (https://www.amazon.de/gp/product/B00...?ie=UTF8&psc=1)
    - 8 minute timer.
    - Burned off binder for ~1 min
    - Sintered at nice, cherry red glow for 7 mins.
    - Immediately cooled in water (dropped in room temp water)
    - Results: See image one. Coin crumbled like ash No discernable metal sintered.

    2. Second coin.
    Fired using significantly higher heat.
    - Large butane torch
    - 8 minute timer.
    - Burned off binder for ~1 min
    - Sintered at bright orange glow for 7 mins.
    - Immediately cooled in water (dropped in room temp water)
    - Results: See image two. Most of coin disintegrated during sintering. INTERESTING NOTE: Little balls of molten bronze bubbled to surface. Edges of coin appear to have sintered.

    3. Third coin.
    Fired using significantly lower heat.
    - Small butane torch (https://www.amazon.de/Melting-Brazin...c+butane+torch)
    - 8 minute timer.
    - Burned off binder for ~1 min
    - Sintered below any observable heat glow for 7 mins.
    - Immediately cooled in water (dropped in room temp water)
    - Results: See image three. Basically, the same as one. Coin breaks in half easily (easier than breaking the dried clay before hand )

    SOOOOOOOOOO!
    ANY IDEAS WHAT I'M DOING WRONG? WHAT I CAN CHANGE?

    Thanks!
    Attached Thumbnails Attached Thumbnails Try1.jpg   Try2.jpg   Try3.jpg  

  2. #2
    Join Date
    Jul 2009
    Location
    Romsey
    Posts
    4,877

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    I have to say from the outset - I've not tried this and don't work with clay, but kudos for giving it a go.

    My immediate thought is that your butane torch may not be putting out quite enough heat for sintering - the instructions I've seen for torch firing home-made clays say to look for a shimmer. Can you surround the test pieces with firebricks to slow down the heat loss? Also, is there any mileage in oven-drying the pieces to drive off any remaining water?

    There's a number of recipes & ideas here - http://www.metalclayacademy.com/meta...etal-clay.html
    Most of them seem to be kiln-firing for 1 hour for the binder, 2 hours to sinter. I've no real expectation that the DIY clays will respond the same as commercial ones.

  3. #3
    Join Date
    Jan 2017
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    21

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    The torch can get up to about 800°C and, on the second test coin, I think it was too hot. The torch at 7 mins is the firing method I use for the commercial metal clays.

    I am curious however, if the solution for non-commercial metal clays is; lower temp for longer. Maybe in a kiln.

  4. #4
    Join Date
    Mar 2011
    Location
    Manchester UK
    Posts
    694

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    I was interested so I had a look on youtube the guy also has some other videos on mixing etc

    Last edited by josef1; 03-03-2017 at 01:20 PM.

  5. #5
    Join Date
    Jan 2017
    Posts
    21

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    Thats awesome. Actually, that's where I got my recipe (Actually https://www.youtube.com/watch?v=rXfrOrz2cB8)

    He's using a kiln and I'm using a torch. I'm very curious why the PMC3 commercial bronze is very easily torch-able, and this isn't.

    Although, watching that link again, I looked up my Bronze powder and it is recommended for cold casting (although I can't get the metal content on it).

    I've ordered some different powder from another manufacturer (who does list the content). Maybe it will be better?

    I'll keep the thread posted

  6. #6
    Join Date
    Jul 2009
    Location
    Romsey
    Posts
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    If it's for cold casting, is it definitely bronze and not a coloured aluminium powder?

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