Lessons learned 7-04-2018 - first bronze pour

Discussion in 'General foundry chat' started by Kurtis Kiesel, Jul 5, 2018.

  1. Kurtis Kiesel

    Kurtis Kiesel Copper

    So I started at about 10:30 am. I placed my ceramic shell into the kiln leaving the vents open and turned on one burner to low. Just to ensure no moisture was in the shell. For the next hour, I re-tooled my shank to be adjustable and some other minor fiddling. At 11:30 I tossed the crucible and bronze into the kiln alongside the shell and turned the kiln up to high-high on the two elements, starting temp was 0,130c.

    Note Outdoor temp
    Temp 87F Dew 73F Humidity63 %

    It rained at the 2-3 o'clock hours in full sun the whole time, very odd weather.

    At 5:00pm kiln temps were at 1,128c.

    Temp 85F Dew72F Humidity65 %

    I set up my pouring area, ran all the steps in my mind checking to make sure all tools were nearby.
    1. check setup
    2. turn off kiln
    3. open kiln
    4. remove shell
    5. move crucible to the plinth
    6. clean off the surface of the bronze
    7. attach shank
    8. pour
    9. Any overages in ingots
    10. release shank
    11. move crucible to the kiln for slow cool.
    Step 6, cleaning off the surface of the bronze, took longer than expected and step 7, attaching to the shank, I ran into severe problems. I had testing the shank in a different orientation for the initial test and the crucible was 180* in the other direction for the actual pour. The result was 1/4 of an inch too low, I had to raise the locking mechanism on the shank, which I started to do and realized that I was taking to long, I returned the crucible to the kiln while I got it right. I had turned the kiln back on, but I did not give it the hours needed to get back up to full temperature, before trying to pour again.

    When I came back to pour it was no longer runny but thick. Moving to pour it plopped a thimble size piece of bronze into the shell, it fell like lava instead of running like metal. I knew immediately, 'this is wrong' I returned the shell and crucible to the kiln, setting it to high for 2 hours.


    Temp 87 F Dew 73F Humidity 63 %

    Kiln: 1,143c

    I then redid the 11 steps to complete the pour. I waited for the duration of time it took to say a rosary with my family, and then quenched and broke the shell. There was a larger high silica brown oxidized clump of error on the center of the piece. The shell absorbed the "plop" and it did fuse to the piece as "extra" material. I plan on grinding it away in the metal chasing processes.

    De-sprue'ing resulted in a strange geode center in the center as a bubble inside the piece and the sprue below the pouring cup. I am a little baffled. It did not affect the face of the piece.

    The piece has defects past my basic blunders, small sub-grain sized holes, possibly air from slurry I can keep this piece and hopefully make something respectably elegant with a lot of chasing.

    Current weight of piece: 4.8lbs (bathroom scale)

    Lessons learned:
    1. I probably need 2 kilns or under the advice of 'everyone': a fuel foundry and a kiln. This just reinforces all that, which I am working towards.
    2. Don't doddle, I could have saved a minute or more of time and not had the pouring problem.
    3. Shell absorbs bronze over long times in higher than melting heats (I suspected this)
    4. If this plop pour happens again; Master Jason say put the shell upside down.
    5. One corner was imperfect. The corner sprue needs to touch the back side of the corner and be trimmed square. More sprues on edges as well need to be added.
    6. I had a lot more minor defects in the casting. I want a higher bronze temperature overall next time, blow off the first layer of air bubbles when dipping the slurry, which I just brushed before.
    7. There was a geode in the main sprue off the cup. I need to post pictures and ask questions, temperature?
    8. I really have no clue what to chase metal with. Ask questions about tools:
    • What power tools can I use to buff and clean in the metal chasing that I can get at ChinaFreight?
    • I was told ss wire brush, maybe mine are ss?
    • What is with this geode?
  2. Jason

    Jason Silver Banner Member

    dammit.. I'm in the islands right now and dont see any photos. I swear every pour is a learning experience. You learned the hard way that crucibles change shape when full and hot. I think they squat and get fatter but dont quote me. Anyways. You are on point. Use the kiln to get the shells up to temp and get rolling on a proper fuel powered furnace to melt your bronze. That's how I have been doing it and all is well.

    SS brush is fine, if that's the finish you're after, but I bead blast first and work from there.

    If you want a pouring temp, I say start with the shell around 1700. I use a 5buck type k meter and a 5buck probe off Amazon. Links later for ya. I'm busy at the moment with sand, salt water and a cold Kalik beer.

    Pouring temp for the bronze varies. Thin stuff, pour pretty friggen hot. around 2100
    For thicker stuff, lower the temp. When I started I was running too hot and saw surface issues. Too cold and parts won't fill. Shell and bronze is really forgiving and ya gotta F it up pretty bad for it to not work.

    All the best man. cant wait to see your geode. lol

    Kurtis Kiesel likes this.
  3. Kurtis Kiesel

    Kurtis Kiesel Copper

    I had not posted images yet...

    Here is the shell filled.


  4. Jason

    Jason Silver Banner Member

    Got a photo of the actual piece????
  5. Kurtis Kiesel

    Kurtis Kiesel Copper

    Not yet, been assembling a sandbalster with my son. It always takes twice as long with help from a 5 year old, but the time is worth it.

    The sheep looks very ruff I don't want to post bad pics alone.
    joe yard likes this.
  6. Jason

    Jason Silver Banner Member

    We learn more from baaaaad pictures. See what I did there?:oops:
    Kurtis Kiesel likes this.
  7. oldironfarmer

    oldironfarmer Silver Banner Member

    You need to go on the lamb if you can't do any better than that.
    Kurtis Kiesel and Jason like this.
  8. Kurtis Kiesel

    Kurtis Kiesel Copper

    Wire brushed..
    IMG_20180708_152105337_HDR_crop_433x343.jpg Sand blasted:
    Detail sand blast:

    Versus detail of gypsum casting

    Attached Files:

  9. Jason

    Jason Silver Banner Member

    Thanks for posting those.. Is that quality bronze or some home brew stuff? I can't remember. It does look cold that for sure.
  10. Kurtis Kiesel

    Kurtis Kiesel Copper

    Recycled, but tested.
  11. crazybillybob

    crazybillybob Silver Banner Member

    I'm not bronze guy but if it were aluminum I would make the pour cup taller to get a little more head pressure in there to pick up the fine details. Then again I haven't played with shells either so I might be guessing out my backside on this one too.
    All in all it's good first go.

  12. DavidF

    DavidF Administrator Staff Member Banner Member

    That looks suspiciously like a red brass and not silicone bronze. Although the two look similar they cast way way differently. What was your source of the metal??
    Last edited: Jul 10, 2018
  13. Zapins

    Zapins Silver

    I think this might cast better if you feed it from the top edge instead of from the back. Direct casting things with high detail doesn't always seem to work. Or J sprue it and feed from the bottom and let it fill up from there, then add a little vent sprue to the top to let the air out. I think less turbulence that way causes better retention of details.
  14. Jason

    Jason Silver Banner Member

    It might be the lighting.. in one photo, it looks red. It should pour fine face down or on its side. The metal just looks cold to me and couldnt fill the tiny details. Melt it down and try it again. For a first attempt it's pretty good.

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