New to spruing

Discussion in 'Lost wax casting' started by LJLundgren, Jul 25, 2020.

  1. LJLundgren

    LJLundgren Copper

    Hello. I’m very new to casting. I’ve casted a handful of things all with lost wax investment casting. Right now I need help with spruing.
    I’m making a little base for a bear sculpture but the only way I can support it is by holding it up with a wire. It needs to be vertical in order to fit in my flask. Just wondering if there is a better way? Any advice or tips are welcome. upload_2020-7-25_16-28-5.jpeg
     

    Attached Files:

  2. Jason

    Jason Gold

    Welcome aboard dude! I would run one fat sprue to the base of the cavity and then run a few smaller ones from the edge back to either the cup or on the main.
    Look at how I sprued the fox. This method works good for hollow cavities like your piece here.



    20180321_004301.jpg
     
    LJLundgren likes this.
  3. Jason

    Jason Gold

  4. LJLundgren

    LJLundgren Copper

    That looks like a simple way to do it. The problem I’m running into is that if I have it flat like that it won’t fit into my flask. It’s too long. That’s why I tried suspending it with a wire more vertical. If I pour the investment in it the way it is now, the wire will be in there for good. I don’t know if that’s a problem. I don’t think I’ve seen people use wires. It seems like they always get the wax to hold itself up.
    Maybe it’s just my stupid homemade sprues.

    If I remember correctly you used a slurry to do the fox, I’d like to try some slurry sometime but right now all I have is investment.
    Why do people use a slurry vs investment?
     
  5. Jason

    Jason Gold

    Suspending that wire in there could be a problem for you. It is very likely it will float around and end up where you dont want it without some really careful planning. You cannot have it stuck anywhere in your final part or it will be there forever. In addition, you must leave it extending outside the wax a couple of places where it will get a foot hold in your investment. If it's only in the wax, no telling where it will go once the wax is removed. Following me??

    Solid investment is king. It offers the highest resolution, that's why jewelers use this stuff for tiny tiny work. With that said, Ceramic shell uses slurry to capture the detail and the silicas add the necessary strength to hold back the molten metal until it solidifies. Ceramic shell is cheaper than block investment that you are using. It is a slower process and takes 2-3 days to build up the layers of shell instead of your current investment of pour, harden, melt wax, heat and pour metal. Dont discount ceramic shell, I often find my finger prints in my finished bronze pieces that transferred over from the wax work and the slurry picked it up!

    They both have their uses and it's often an economical/size and shape decision deciding which method to use.;)
     
  6. LJLundgren

    LJLundgren Copper

    Got it. Thanks. I’ll have to rethink it then. Might be easier to just get a bigger piece of pipe to use as a flask for now.
     
  7. Zapins

    Zapins Silver

    Whats the other side look like? Kind of hard to judge what we are seeing from that pic. Is that solid? How thick?
     
  8. LJLundgren

    LJLundgren Copper

    it’s a rock base for a little bear I sculpted. This is what I’m going for.
     
  9. LJLundgren

    LJLundgren Copper

    upload_2020-7-26_18-59-9.jpeg
     

    Attached Files:

  10. Zapins

    Zapins Silver

    Is it hollow or solid? If its hollow then one ~1" sprue should do it. If its going to cast as a solid rock then you'll need a very thick sprue almost same diameter as rock and about as long as the rock to ensure no cavities.

    Approx 1/4" to 1/3" thick walls are good to aim for if its hollow.
     
  11. LJLundgren

    LJLundgren Copper

    Hmm. Ok. It is hollow so I’ll try a 1” spru. I have some plaster molds of different sized dowels. I’ve been using them to make my own sprues I do have a 1” that I can make. I’ll give that a try.
     
  12. Zapins

    Zapins Silver

    Sounds good! Looking forwards to seeing it done!
     
  13. Jason

    Jason Gold

    That's a realistic looking rock! Did you pull a silicone of something?
     
  14. LJLundgren

    LJLundgren Copper

    I used some crumbled up paper wrapped in tape. Shaped it to fit the bear. Then I put plaster over it And dabbed it with a sponge so it would have the texture of rock. Then made a rubber mold.
     
    Jason likes this.
  15. Jason

    Jason Gold

    Good technique. It's very convincing. Remember, to work towards having your wax thickness right around 1/4" thick. Any bozo can cast fat bronze, quality pieces are cast as thin as possible.;) It's something I have to continually remind myself to do. Sometimes I even go on an excavating expedition on a completed wax. I'll get in there and dig out the fat sections.
     
  16. Petee716

    Petee716 Silver Banner Member

    You've done some impressive sculpting. What is the bear made of?

    Pete
     
  17. Jason

    Jason Gold

    sil bronze
     
  18. LJLundgren

    LJLundgren Copper

    I sculpted it out of super sculpey clay. Then went through the process of lost wax casting it into silicon bronze. I might try to cast the base in brass because I have a lot of scrap brass and I’m not sure the color difference will matter much when they are both patina-ed. A bear isn’t the same color as a rock anyway. But I’ll have to see how it looks. Don’t know if it’s common to mix metals or not.
     
  19. Jason

    Jason Gold

    Give it to the junk man. Don't melt different metals in the same crucible. EVER! Bronze is cheap, use that.
     
    OMM likes this.
  20. LJLundgren

    LJLundgren Copper

    What’s you favorite type and source for bronze?
     

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