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Thread: porosity

  1. #1
    Join Date
    Mar 2006
    Location
    Waikerie SA
    Posts
    39

    Default porosity

    I have been making bells using traditional loam mould for some time I have made around 20 bells all with relative success. The last batch looked fantastic when cast but on fettling I discovered they are all riddled with porosity. Does anyone have any suggestions what I may have done wrong this time?
    Here is some pic of how I do the process https://www.stonevahestate.com/bells/

    bells6.jpgIMG_20211012_115150.jpg

  2. #2
    Join Date
    Apr 2018
    Location
    Drouin Vic
    Posts
    633

    Default

    Hi Vin, I was hoping someone with far more experience than me might reply to your post but having been doing some limited research in preparation for a little bit of yellow metal casting, it seems likely that the porosity is due to an oxidising condition in the melting process, i.e. a lean burn, resulting in gas absorption into the molten metal that is then released after pouring. Did you de-oxidise the molten metal before pouring?
    It would be great if you could post a thread describing how you did the swept molds, even if you used the same photos as your link but with some description attached.

  3. #3
    Join Date
    Mar 2006
    Location
    Waikerie SA
    Posts
    39

    Default Thank

    Thanks Pete, the melting has not changed, same fuel, same furnace, same pouring. I do think the problem has to be mould related, unfortunately I continually make small changes making the moulds which has definitely improved the surfaces and out comes till this batch. I feel that just maybe the pug that I seal the cope and mantle with was a little damper than normal. The other thing I have changed was an increase in the amount of horse hair and whether this allows the damp pug to wick moisture up into the mould causing the problem.
    I will post how the process is done in a day or two, just busy at the minute!

  4. #4
    Join Date
    Mar 2006
    Location
    Waikerie SA
    Posts
    39

    Default

    Quote Originally Posted by Pete O View Post
    Hi Vin, I was hoping someone with far more experience than me might reply to your post but having been doing some limited research in preparation for a little bit of yellow metal casting, it seems likely that the porosity is due to an oxidising condition in the melting process, i.e. a lean burn, resulting in gas absorption into the molten metal that is then released after pouring. Did you de-oxidise the molten metal before pouring?
    It would be great if you could post a thread describing how you did the swept molds, even if you used the same photos as your link but with some description attached.
    Hi all, I think now that the problem was moisture and maybe some hydrated lime that I added to the fire clay, live and learn. The next batch was good so I it seems i am back on track. For those interested I have just put up a new website about my bells Vinsbells

  5. #5
    Join Date
    May 2012
    Location
    Dandenong
    Posts
    76

    Default

    Thanks for all the details you've put up, very interesting!

  6. #6
    Join Date
    Mar 2006
    Location
    Waikerie SA
    Posts
    39

    Default Just an update

    I have finished the bell project some time ago and thought a few may be interested in it. Over a two year period I built a mobile carillon from scratch to finish without any plans. you can find more info related to the project here Vinsbells

    The video is of the carillons first outing and in this clip my wife is playing and has had very little practice.

  7. #7
    Join Date
    Dec 2009
    Location
    Sydney
    Posts
    327

    Default

    How cool is that!
    Looking forward to seeing you at Lost Trades Fair, or Ironfest, or some kind of machinery rally...
    regs
    AOC
    'Waratah' spring hammer by Hands & Scott c.1911- 20, 'Duffy, Todd & Williams' spring hammer c.1920, Premo lathe- 1953, Premo filing machine.

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