Bronze Hands Lost Wax Project

Discussion in 'Lost wax casting' started by Sillytrain, Dec 3, 2019.

  1. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    They are not.

    Vacuum is needed on small castings to overcome surface tension and the viscous nature of molten metals. Vacuum will potentially produce more detail and less defects but it isn't needed on larger castings. Flasks are convenient for small objects but larger block investments are often not contained in flasks. One of the bronze art casters here, Rasper, uses imbedded chicken wire as reinforcement for his castings and also uses common plaster with plaster/sand/ludo in the outer layers for investment. Vacuum is no more needed for block investment than it is for ceramic shell. Aside from curing, get the mold temperature, metal temperature, feed, and venting system right and you'll get there.

    Best,
    Kelly
     
  2. Jason

    Jason Gold

    not spin casting. that's not vacuum
     
  3. Jason

    Jason Gold

    and ya dont pull a vacuum on plaster, sand and cat poop. he's using ultrvest and clearly doesnt understand how it works.

    edited.. I'm driving today. sorry

    No reason to use ultravest if you arent going to pull a vacuum. A rig can be made for no money. David our fearless leader shows this very method on his YT channel. Look up thehomefoundry on YT. You'll see him in the driveway sucking on a piece of pipe.
     
    Last edited: Feb 7, 2020
    Tobho Mott likes this.
  4. Sillytrain

    Sillytrain Silver

    When you say “no reason to use ultravest” if I’m not pulling with a vacuum... do you have a recommendation for a different/cheaper investment medium that isn’t engineered for vacuum casting?
     
  5. Jason

    Jason Gold

    yeah.. plaster, cat poop, straw, broken bits of old investment.

    It's what the masters did. It works, but not as good as proper investment.
    Trust me. You want no part of doing this one the old school way.
     
    Last edited: Feb 8, 2020
  6. Sillytrain

    Sillytrain Silver

    Still alive and kickin', guys. I bought a kiln for $100. Gonna try to hook up a PID for it to make my block mold curing process go more smoothly. My last dewaxing attempt was sketchy at best. My suspended wax hand somehow drifted too close to one of the sides of the block mold, So before I dewaxed it I strapped a metal plate to the side where the dime sized hole showed up. I knew it wouldn't be a perfect cast but I wanted the experience of trying another pour especially to test if i needed to do additional spruing on the finger tips. My ramshackled multi high-temp hot air gun setup got it cured but caused cracks cause of non-uniform curing. The kiln will fix that problem next time. Surprisingly, even with the cracks, the pour actually went pretty well. i chalk it up to the metal bands i put around the block to help hold it together. one of my hot air guns died, so I couldn't get the block mold up to the right temp to receive the molten bronze properly. so two of the longest fingers have some of the tips missing (probably because the bronze started to solidify before it could reach the end. But the other fingers filled out with no problems.

    A question I have for the group is how do you properly remove any of the black charring on the surface of the cast after it's over. i tried a brass wire brush but the black seems pretty stubborn. any tips for removing it or preventing it in the first place?
    Attached is a picture of the results of the first cast that had the block mold fail in the middle of the pour, and the solid hand from the second cast.
    I'm so close to victory i can taste it!
     

    Attached Files:

  7. Jason

    Jason Gold

    What black charring? I get very little if any. After I cut everything off, I bead blast my bronze to see what needs additional work. From there its chasing time. I use diamond tools on a dremel, sanding drums and some gnarly little carbide burrs as necessary. Oh, and a tig welder running on dc.

    I need a close up of your as cast surface finish. Something looks off. Without seeing it first hand, I'm betting your melting too lean of a mixture and screwing your bronze up. I did that when I first started.
     
  8. Zapins

    Zapins Gold

    You're pouring too hot. Its too fluid and penetrates the shell and burns it so it sticks.
     
    Jason likes this.
  9. Sillytrain

    Sillytrain Silver

    Thanks zap! That makes a lot of sense. So is it impossible to remove what’s sticking when that happens?
    Also any idea what the optimal pouring temp for everdur is?
     
  10. Jason

    Jason Gold

    probably not without a LOT of hard work standing and grinding.

    Everdur gets poured between 1800 and 2100F. Cooler for thicker stuff and hotter when you need it to flow through small channels.
     
  11. Zapins

    Zapins Gold

    It's difficult to remove. Sand blasting can do it but often the surface texture is left rough. It's better to redo it at the right temp. It will solve a lot of the defects you got too not just the surface issues.

    Temperature control is done using a thermocouple and a volt meter. There is a thread somewhere on how to make one for about 50 bucks. Buy one of these and a cheap harbor freight 5 buck volt meter then shove it inside a bent pipe and you've got a thermocouple. http://mifco.com/shop/thermocouple-for-ht-furnaces/12-thermocouple/

    Then you use an online chart to convert the bolts to temperature.

    Here is a longer build thread for pyrometers
    http://www.alloyavenue.com/vb/showthread.php?10142-Pyrometers%97/page13&highlight=pyrometer%20build
     
  12. Sillytrain

    Sillytrain Silver

    Still here trucking along guys. I had an electrician buddy of mine help me build a pid controller box for my kiln temp so I can perfectly control my curing process now! I also picked up a proper vacuum chamber for degassing my investment medium.
    I started using pipe strapping bands to help put tension on my block mold and keep it from cracking during the curing process.
    I got really to a successful cast on Saturday!
    Other adjustments....
    I bought a huge roll of ceramic fiber to line my melting forge and also using scraps I'm able to hold the crucible and pour it solo instead of having to involve multiple people, so that's been an awesome development.
    I believing the pitting in my last cast was because I didn't have enough liquid bronze (see links below)... there happened to be too much dross in my crucible so the last bit of liquid bronze poured out too slowly, and the crack on the thumb was most likely cause i didn't wait long enough before demolding. I'm ordering 30 more lbs of Everdur from Lancaster at $4.30 / lb. ($20 shipping so total is about $150) so, Thanks for the tip on that vendor.
    I decided to reduce the length of my sprues down to about 4" and it worked out well. doing that saved me a significant amount of investment material and made handling the block mold much easier cause it's lighter. I'm hopeful that next round will produce the results I'm looking for.
    Another change I made was in creating my silicone mold of the hands. It takes forever to paint layers directly on my father in laws hands, so instead i used algenate and made a plaster mold, then used that to make my mold. I also switched to using the Smooth-On Dragon Skin line as it has superior durability and it holds up way better when doing multiple wax casts. My other silicone molds ended up splitting apart near the creases where the fingers meet the hand when demolding. I'm also using a demolding spray to help the wax model come out with less strain on the silicone mold.
    Still wishing i could do the ceramic dipping process cause it seems way easier but beggars can't be choosers, and that's rout seems to be a serious investment of time and cost.

    Thanks again to everyone who's helped get me up to speed making this happen.
    Here's some links to pictures and gifs of my progress, the pouring process, and result:

    https://i.imgur.com/rMBdSSq.png
    https://i.imgur.com/XfrMVCk.jpg
    https://s7.gifyu.com/images/ARcu9ur---Imgur6c096f81122d53ff.gif
    https://s7.gifyu.com/images/ezgif-7-eca4ae7bf089.gif
     
  13. Tobho Mott

    Tobho Mott Gold Banner Member

    Wow! I never saw anyone handle a hot crucible that way before.

    Jeff
     
  14. DavidF

    DavidF Administrator Staff Member Banner Member

    A Testament to the insulating properties of ceramic fiber blankets that's for sure!!!
     
    Jason likes this.
  15. Jason

    Jason Gold

    Dude, build a pouring shank. I pick up 1700 degree shells with kaowool and gloves and it's still friggen hot! I've had the occasion metal splatter pop UP when pouring.
    If that's not frightening for ya, you need to see Jeffs foot. My wife that usually stands fire guard for me during pouring had a few things to say about your method when I showed that to her.
    To put it nicely, we fear for your safety man.

    I went a little overkill on mine, but works great. If ya look around, you find lots of easy examples here that work. A simple loop on the end of a rod will work.
    pouringtool.jpeg


    You are getting really close with your hand. That one is pretty much repairable by tig welding it. If this bronze thing turns out to be your bag, you will want to take the plunge and get a machine. Tig welding bronze is actually really easy, if you were closer, I could teach you how to do it in an hour. An OA torch setup is another option, but that method sucks compared to TIG. The inverter machine market is real competitive and prices are pretty cheap. https://ahpwelds.com/catalog/tig
     
    Last edited: May 18, 2020
    The Desert Yeti likes this.
  16. Sillytrain

    Sillytrain Silver

    For sure DavidF. It's only a 1" thick ceramic fiber blanket, and with my welder gloves on, I could only feel a slight warming while pouring!
    FYI I did extensive testing before trying something this crazy.
     
  17. Sillytrain

    Sillytrain Silver

    Thanks for your feedback, Jason. I do tend to make people nervous with my unconventional approaches. I'm actually usually pretty risk averse, but I felt pretty comfortable pouring that way especially with full face protection from any potential splatter pop ups. The only exposed risk i felt was my shoes, so i was trying to be extra aware of where my feet were in relation to my pouring.
    I actually like your idea of a mounted pouring system. I actually built a 3-man pouring rig with some spare leaf-spring steel and rebar. It works ok, but I had more pouring precision using the ceramic fiber. a mounted system like yours would be marvelous to build eventually. how does it pivot to pour exactly?
    maybe until i can build a pouring shank, ill line the tops of my shoes with some of that ceramic wool. lol. heck i have enough of the stuff that i probably could make some leg & shin guards with straps or something.

    [​IMG]
     
  18. Tobho Mott

    Tobho Mott Gold Banner Member

    Maybe I should point out that when I say "wow, I never saw that before," sometimes that is just Canadian for, "holy crap, you wouldn't catch me doing that!"

    This is my foot for 2 months after one drop of molten bronze bounced off my steel toe. I had to wear slippers to work for the first week and a half or so of that because shoes hurt too much.

    Foundry Burns

    Also see the post right before that one, where Jason has embedded a video clip of what it can look like when a mold decides to Just Say No and spit the molten metal back at you. That can happen with no warning. I wouldn't want my head to be up so close directly above the sprue right then, face shield or not...

    Common sense and understanding the risks is the most important PPE, and only you can know what feels safe and comfortable for you. So I don't know if any of this will change your mind, or really if you even should change it. But when any of the bunch of pyromaniacs we've got here starts hemming and hawing about "I dunno, is that really safe?" I take it pretty seriously. It couldn't hurt to have a look. But it might save you from an unwanted hot golden shower.

    There's at least one thread here where members have posted pictures of their crucible handling tools. Maybe you will find an idea there that is safer and also suits your needs.

    I think you are getting close with that casting. Good luck with the next attempt!

    Jeff
     
  19. Sillytrain

    Sillytrain Silver

    Thanks Jeff!!
     
  20. rocco

    rocco Silver

    Two words for you guys, WELDING SPATS!

    I tend to agree with that. Generally speaking we're not really a bunch of OSHA watchdogs here so when multiple people here express their reservations about something, it's worth at least thinking about.
     
    Last edited: May 19, 2020

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