Wax copies have bubbles in them

Discussion in 'Lost wax casting' started by Zapins, May 6, 2018.

  1. Zapins

    Zapins Silver

    Alright, any suggestions for how to avoid this? I've tried the brush on method before putting shells together and this is what I get even when I am looking for bubbles and don't see any. Brushing on takes a lot of time and doesn't seem to give results. Fixing this kind of damage takes a long time too so any suggestions for how to prevent bubbles forming between the silicone and the wax would be appreciated!

    Wax pouring temp?

    Spray to lower surface tension?

    [​IMG]2018-05-06_12-38-50 by Zapins, on Flickr
     
  2. DavidF

    DavidF Administrator Staff Member Banner Member

    Doesn't really look like bubbles ?? Have you tried heating up the mold a bit before pouring the wax, it may help :)
     
  3. Zapins

    Zapins Silver

    Nope, how would be best to heat it?
     
  4. DavidF

    DavidF Administrator Staff Member Banner Member

    My molds are much smaller than yours. I just sit mine on top of the wax injector to heat them up.
     
  5. Zapins

    Zapins Silver

    Hmm and heating them helps stop bubbles?

    I'll try heating it up somehow. Maybe 140 degrees or thereabouts. Might try it on smaller molds first.
     
  6. DavidF

    DavidF Administrator Staff Member Banner Member

    It really doesn't look like bubbles to me. Looks more like ??? Well lets just say bubble marks are round, and your defects have sharp corners like a crystallization trait. The red wax I have seems to be better for pouring into a mold over the brown (that's better sculpting) But hay, im still learning too.... :)
     
  7. Jason

    Jason Silver Banner Member

    What number of wax pull from your silicone mold is this? I pretty much always throw away the first 2 or 3 wax pulls from a new silicone mold. I do recommend washing a new mold in the kitchen sink with some pretty warm water and dish soap. Be sure it is completely dry before pouring wax into it. First brush on layer needs to be around 190-200 degrees. If this doesn't make your little marks go away, they your mold has the issue. OR you are trying to use a mold release which I don't personally recommend for wax/silicone. It's usually not necessary.
    Maybe Artospy will chime in on what your issue is. Till then, keep chasing.

    Hey David, I've only used the brown and haven't had any issues. I would like to see a closeup of the inside of this mold to better understand what's causing this.
     
  8. DavidF

    DavidF Administrator Staff Member Banner Member

    Im thinking the mold is flexing and the wax is cracking between the wax coatings or something of the sorts.
     
  9. Zapins

    Zapins Silver

    Might be flexing. That particular casting I had trouble getting the two silicone parts together so the wax may have pulled off the wall a bit and then liquid wax poured in between it and the wall on the second coat.

    I tried another pour with straight hot wax and no pre-brushing and it worked a lot better but there are still tiny little bubbles in the surface in a lot of places. It is better than the above pic but there are a lot more of them. Maybe sloshing around the mold churned air into the wax and caused this? There are a lot of details inside to agitate the wax as it flows around.

    I'm on my 3rd pour Jason. Maybe I also need better wax temperature control. I have no idea what the temp is, I just pour when I like the thickness of it. I'll see about getting pics of the inside of the mold. I don't think it has surface issues that would cause this kind of pitting.

    [​IMG]20180507_120830 by Zapins, on Flickr

    [​IMG]2018-05-07_12-13-33 by Zapins, on Flickr

    [​IMG]20180507_121001-1 by Zapins, on Flickr
     
    Last edited: May 7, 2018
  10. DavidF

    DavidF Administrator Staff Member Banner Member

    My wife just walked by and said "Yuck what is that?" :confused:
    Now those are air bubbles! You will have to take a look at your wax when its back in the pot. Im thinking some of that is entrapped air in the wax itself (at least in the upper photo). Heat the wax up hotter than what you would pour it at and let it sit for a bit to get the air bubbles to surface then let it cool back down to your pouring temp.
     
  11. Zapins

    Zapins Silver

    Haha yeah it does look weird up close.

    I had the wax smoking before letting it cool down a bit to pour, and didn't see bubbles in the pot. I think they may have developed after sloshing around over the textured inner surface of the mold (see above). Not sure how to really reduce the bubbles if this is the case. Maybe just more gentle shloshing? But then the wax may cool too quickly and not coat evenly.

    There must be some easy way to do this!
     
  12. DavidF

    DavidF Administrator Staff Member Banner Member

    Ive been thinking about a "wax sprayer" LOL But its just a thought, For now heat up the mold and try pouring the wax thru a piece of pipe directed at the bottom of the mold so it fills from the bottom up without splashing on the sides. However you do it its going to be tough, the feathers are just a bunch of air entrapment's waiting to happen. :oops:
    Hmm unless you ???
     
  13. Jason

    Jason Silver Banner Member

    41910384532_c39fc778b2_c.jpg

    Yup.. now those are bubbles! You were pouring too cold. You got better results with hotter wax. Now you are starting to "season" the rebound. Now do it 3 more times. My rebound 25 will start to turn colors a little after a few hot pours. That's when it will start turning out good copies. I don't preheat my silicone. The buildup of heat from the wax was enough for me.
    3buck meat thermometer from wally world will help you out with temp control.

    Looking at your closeup of the mold, nothing personal man, but I see a lot of shit in there on those feathers. (caused by bits of missing wax on the original) They will cause the negative space on the wax. You might just have to do a bunch of wax chasing. Rebound 25 captures AMAZING detail. It will show your every fault and detail. Both good and bad!
     
    Last edited: May 7, 2018
  14. Zapins

    Zapins Silver

    I'll see what I can rustle up with the thermometer.

    Interesting with the change of color I haven't seen that with the other rubber I use for block molds. Maybe it is just different material.

    One thing I noticed with the rebound is that it seems to tear a lot easier than the block molded stuff. It does stretch but I'm losing small thin detailed sections with each pour when I remove the wax. I wonder how many copies it can make without damaging the mold too much.

    Also, I wonder if 1/8" thick walls would cast reliably in bronze? Would be a good cost saver if i could do that instead of 1/4" thick walls.
     
  15. Jason

    Jason Silver Banner Member

    There.. I painted you a pretty picture.
    1/8" ???? I don't have the stones to try that. How about you shoot for 3/16 instead? And where the hell is Artospy? He's the master at this stuff. After you get a good copy, you can always thicken it up after it's pulled from the mold. Just paint on a thin layer of wax. Hold it up to the light and look through it, chop some out and check your thickness if need be. That's what I'm having to do with my lantern frames.
     
  16. Zapins

    Zapins Silver

    Haha yeah I see the nails. I'd say only on the weekend but its already monday.

    I've been pouring thin sheets of wax and attaching them inside the shells to thicken it up to the req dimensions. Yeah 3/16 would probably work better. The feathers stick off father than that so it will be variably thick in most places.

    There are of course some defects in the mold but still a lot of bubbles under the surface of the wax too. It is weird because the bubbles are all in a line across the bird's chest. Not sure exactly how that happened. Maybe its where the wax settled while it cooled and trapped the air?
     
  17. Jason

    Jason Silver Banner Member

    That's quite possible. There is lots of cracks and crevices on that thing that's for sure. Crank the heat way up around 200 on that first coat. Artospy told me once heat the wax until it almost smokes and shut the heat off. Pour, slosh dump. Wait 2-3mins and pour again with the same pot of wax, wait again and repeat.
     
  18. Zapins

    Zapins Silver

    Yeah hotter first layer seemed to work better than colder brushing on layers.

    Where is art anyway?
     
  19. Jason

    Jason Silver Banner Member

    Last time I saw him here, he mentioned something about moving shop I think. If he goes missing like Mantrid did, I'm quitting the bronze biz.
     

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