A box of wax foxes

Discussion in 'Investment casting Ceramic shell method' started by Jason, Mar 16, 2018.

  1. Jason

    Jason Silver Banner Member

    So, Mr Fritz Hoppe made a cool fox he calls the Fibonacci Fox. I think he had someone try to cast these and something didn't work out. I offered to give it a whirl. This will be my first hollow piece. The plan is to cast these dudes upside down with a fat sprue right in the center in the hole on the bottom. I'm thinking of running a few vents from the inside of the edge and up to the pouring cup. I'll cast some plates for the bottoms and weld them on after the sprues are cut off. Any thoughts are always appreciated. I have zero desire to externally sprue to cut down on finishing work on the outside. These will be closed up completely, so we really dont give a foxes ass what it looks like inside. :D

    Here they are!


    The under side.



  2. Peter did this bronze bowl in the photo using a sand mould intended for aluminium and which works fine for aluminium. The bronze version in the picture, while it was sound, you could see where the bronze flow split up and met again (tiny creases in the finish from oxide layers) in the walls of the bowl which is cast upside down. I was speculating that if the mould is still facing down but angled 45 degrees up and away from the sprue (at lowest point), it would fill uniformly from the lowest point to the highest point without the metal flow having to split and meet again.

    Again, I'm only speculating about how it will flow

    Last edited: Mar 16, 2018
  3. Tobho Mott

    Tobho Mott Silver Banner Member

    They look simple enough to fill, but then I'm not a wax guy... What happened? Did he show or tell you how the foundry he already tried managed to mess these guys up? Looking forward to seeing how this plays out.

    The fact the pros failed, plus Mark's post above, makes me think it might be an idea to mold and cast one of them first, just in case something goes wrong that could be corrected by just angling the sprue a little differently on the 2nd one or what have you.

    The little hands are pretty cool too. Pretty small though, you might need to build a vacuum assist rig like David's!

    Speaking of whom, we haven't heard so much as a peep from Dave here in a couple months now that I can recall... hopefully all's well.

  4. DavidF

    DavidF Administrator Staff Member Banner Member

    Im good, just doing a production run that has my time tied up.

    I think you would be better off spruing onto the rim with the foxes on an angle so the slurry can drain out after dipping.
  5. Artopsy

    Artopsy Copper

    yep, im with david. piece of cake for a man of your calibre! straight onto the rim, no need to place the sprues inside. Will you hang your shells from a hook to dry or stand them on the pour cup? If hanging then a simple bottom feed, J gate type set up will work fine. If standing then a top feed with a couple of sprues to the rim. I am also curious why the foundry couldnt do them.
  6. Jason

    Jason Silver Banner Member

    I think the guy that tried the first one might have been at a school learning how to do this. I would think in an educational setting failure wouldn't happen. I heard the ears didn't fill I think. I'm
    not worried, ceramic shell is pretty idiot proof for a clown like me.

    Good to see you David.. don't be a stranger.

    I will hang these upside down from the cup in my typical manner you guys have seen. So that it's main sprue is inside attached right under his head and then 3 or 4 vents around the rim. Fritz first asked for them to be solid. Told him not a chance unfortunately, so any extra uncut sprues inside this thing is welcomed from the artists standpoint. We even joked about filling the foxes with lead before welding on the bottom. A 2lb chunk of lead hidden inside would be funny. You know there will be SOME Easter egg hidden within these just because I can.
    Last edited: Mar 18, 2018
  7. Jason

    Jason Silver Banner Member

    Any thoughts on this design? I'm going to be welding a bottom on these things. So, I'm thinking the bronze goes down the main sprue, fills the fox and the air is expelled through the 2 vents back up to the cup. One of the vents is placed at the highest point on the rim. What sayeth the peanut gallery? I'll hold off on spruing the 2nd one for now. The fox is offset on an angle from the pouring cup so it will balance during dewax..... (I hope) ;) Thanks for double checking my work. I do not have the mold and these must work first time. :eek:

    I'm debating adding another rim vent on the 3rd side..

    20180321_004243.jpg 20180321_004254.jpg
    20180321_004301.jpg 20180321_004319.jpg
  8. Artopsy

    Artopsy Copper

    That looks fine, my only concern is that if you have the fox tilting up then you may have a slight air pocket in the bottom of the tail where theres a high point (it might not be, it just looks like it from the photos). Likelyhood is the gases/air would leave through the permeable shell but i would probably belt and braces with a small runner from the tail to the vent if the tail is raised a bit. I know you dont want to do any runners to the surface of the sculpt so thats up to you.

    As for the vent on the third side, you could just put a small bridge from the lip to the main sprue if you think its necessary.
    You certainly wont have any problems filling it, they are VERY sturdy sprues!
  9. Jason

    Jason Silver Banner Member

    Thanks I appreciate the feedback. I'll add a small bridge on the third side and roll the dice. Hope dewax wont be an issue. Will probably add a couple more half yellow tubes to the rim/ main sprue and drill them after the shell coats.
  10. Jason

    Jason Silver Banner Member

    Made some changes to the sprue system on the foxes. I added some half thickness sprues to the edge. I started to have nightmares about dewax and they involved an exploding chicken and a fox.

    20180327_174826.jpg 20180327_174813.jpg

    This is the bottoms to the fox. Should be a no brainer.

    Now this is an add on... Fritz the artist was working with a man to repair a horse statute. (I think...) Something about either a damaged
    or missing horse reigns. He mails this skinny piece of wax in a funky shape. I had to straighten it out a little and stuck it to a sprue. Not really
    holding my breath on this one. I'll try to pour it wicked hot and hope like hell it fills. The statute owner sadly just died, so it's kind of a present for
    his widow. It really should have been done with a vacuum investment setup instead of ceramic shell. But I won't know if shell could work without
    trying it. SO here it is. It's already in shell so, it is what it is and too late to change it now.

  11. Artopsy

    Artopsy Copper

    Looking good. That should all fill fine. It looks like the reigns look like they will be no problem. They wont need as many shell layers as the other stuff if you want to conserve materials. Its nominal though so no hardship if you give em an extra dip. Depending on the original metal the horse sculpture was cast in you might get a difference in colour but a good patina guy will probably be able to match it if they havent used silicon bronze. Also silicon bronze is a bit forgiving if you need to reshape it a bit to fit.
    On another point, i dont know what your deal is with the artist of the foxes but in the past i have done work for sculptors that couldnt afford to pay but would let me have a copy as payment (one of the edition or keep the artist proof). This is a win-win situation, but only if you actually like the work or you think that the artist is going to be worth something someday. Just something to consider.
  12. Jason

    Jason Silver Banner Member

    You have more faith about these reigns than I do. I decided not to hang them because you know how heavy shell can get. The next time they are inverted will be when I dump the bronze in. :p I figure they will have to shape and bend them into shape on installation. They will have to work patina themselves on the reigns. I think he wants to polish his fox himself, I don't do high polish, too much damn work.

    Good point about payment. He offered to pay and I didn't give him a price, whatever it will be, it will be 1/10 of what a foundry would charge that's for sure. And yes, keeping one for myself was definitely the plan. I'm keeping one of them. Mr sleepy fox is pretty cool and Fritz has the family, the location and the skills to take this pretty far.
    Good looking out and great advice sir!
  13. Artopsy

    Artopsy Copper

    Couldnt agree more! The time and labour involved is just not worth it to get a high polish finish for most things.
    I guess if you are keeping one of the 20 edition (or however many youre making) then you might be doing a bit of buffing yourself unless he's going to polish yours and send it back?!
    This may not be relevent for you on this job as youre not finishing them but what i tend to do if im finishing them as well as casting and im keeping one as payment is i will mark one in the wax with AP or AC (artist proof or artist copy) instead of an edition number. This will be used as the "reference" for the rest of the copies. This ensures that every one looks the same.
    It isnt so bad if you are making all 20 of the edition in one go but this rarely happens as the outlay is big to have them sitting on a shelf while they sell. You would more likely make a couple or 3 at a time and these batches could be months or years apart. This makes it difficult to remember how the first batch looked. So you make a 'master' reference that you keep hold of and use it to match all the others. It also allows the artist to sell all 20 (or however many he has named in the edition) and you get your copy too. You can get away with making 2 master references (one for the artist and one for the sculptor) but any more and it starts to look a bit suspicious. Remember, an artist lives and dies by his reputation so if its dicovered that there are more pieces that the number of the edition then it is fraud and collector types get pissed off and sometimes litigious! So dont forget to mark your copy.
  14. Jason

    Jason Silver Banner Member

    4th coat of shell. The inside of the cavity is slow drying. I'm not in any hurry.
    (Take note Zap, shove a fan up your bird or be prepared to wait an entire 24hrs between layers)
    This is around 75degrees and 45%humidity drying in my living room.


  15. Jason

    Jason Silver Banner Member

    Uh oh... Something is not right. I did the typical flash fire dewax on a fox and saw lots of cracks. So I went and looked at the second one that had not been fired and it was cracked before I put any heat on it. These things have been sitting in the air undisturbed for a week. WTF is going on here?


    Ya gotta look close to see the crack running around the fox, but its there. I'll give this one a few more dips and try to rescue the other one after she cools.
  16. Jason

    Jason Silver Banner Member

    For your viewing pleasure..... I'm being told we don't really know what this wax actually is, except it is some kind of 20year old microcrystalline. I did notice when attaching stuff to it, it was a little difficult. So we are thinking the foxes weren't made using actual low expanding wax. WHOOPS!

  17. DavidF

    DavidF Administrator Staff Member Banner Member

    wrap the shell with some thin wire and give it a few more coats.......

    Flash firing didn't work so well with the pla plastic either. I got alot of cracks when i did.
    Slow firing I had no problems...
  18. Jason

    Jason Silver Banner Member

    Thanks David... I'm recoating now and hope to be able to save these two pieces. Funny how I did the bottom plates for the foxes out of all my
    own wax and no problem. :rolleyes: I really think the wax he used wasn't up to the task. What really flips my lid is I had cracking before I even fired the
    2nd one! Might be time to explore that hot water dewax method again. Who would think melting wax could be such a pain in the ass?:mad:
    Last edited: Apr 17, 2018
  19. Zapins

    Zapins Silver

    Make a mold of the foxes and then pour in casting wax.

    Also, might not be the problem that you have but the shell instructions are pretty specific about drying temperature. If I remember right it was between 70-77F for best results. I always thought that was awfully narrow, but perhaps that has something to do with it?
  20. Artopsy

    Artopsy Copper

    Was the temperature consistent throughout the coating process and was the slurry stored in the same environment?
    If im hot boxing i store the slurry and sands at the same temp as the waxes. If you take a hotter wax and dip it into colder slurry (or vice-versa) then the shell can be weaked by contracting (or expanding) repeatedly over the course of several layers. As has already been mentioned, different waxes expand at different rates and it could be that the wax used was not ideal for the job.

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