[Jewelry making - Article 00608] - [Orchid] Casting procedures

[Michael R. Mathews Sr.]

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    Hello All: I have been trying to come up with the best method of
    investing, Burn out and Casting over the last several years and I
    think I got it now so I thought I would share it with Ya'll. I
    consistently invest as per the advice of Eddie Bell at Rio Grande
    (http://www.riogrande.com/) thru and article in the summer 2003
    edition of "Bench magazine"(http://www.bwsimon.com/bench/). I almost
    exclusively cast hard green carving wax models using 2.5X2 inch
    flasks. I use R&R (http://www.ransom-randolph.com/index.html) SJ-27
    investment with a 38 ml. to 100 gr. mixing ratio. I use room
    temperature distilled water and weigh out the investment carefully
    every time to ensure consistency. I do however stray from common
    practice by adding the water to the investment for mixing but I have
    found that this keeps the dust down more than the other way around. I
    have been consistently getting a 13 minute gloss off on this 100 lb.
    keg of investment so I mix for 6 minutes,vacuum for 1.5 minutes,pour
    and vacuum for 1.5 minutes and then let the flasks sit on the
    investing table for 1 hour before numbering the flasks and putting
    them in the over to sit overnight until my programmable thermominder
    starts the burnout cycle. Using this investing process has eliminated
    water marks on my castings and reduced my clean up time and wasted
    metal. I am using an Ashurst Designs model 4 kilnminder programmed to
    start the cycle at 5:30 am for a cast time of 4:30 pm. A total of 11
    hours consisting of  300 F in 20 minutes with a 1.5 hour dwell. 400 F
    in 20 minutes with a 1.5 hour dwell. 1250 F in 3 hours with a 2.5
    hour dwell. 1000 F in 1 hour with at least a 1 hour dwell until I
    cast.If you are using larger flasks the set time of the investment
    will take longer of course and the dwell time before casting will be
    longer. I added the extra 400 F dwell in the burnout on the advise
    of JACMBJ Shannon Calloway, Instructor at the Texas Institute of
    Jewelry Technology, Paris Texas because I cast hard carving wax
    almost exclusively. Other advise from Shannon was to never invest
    injected models and carving wax models in the same flask as the
    difference in expansion in the two can damage the mold. I reduced the
    maximum temperature of my cycle from 1350 F to 1250 F on the
    suggestion of research presented to the Santa Fe Symposium that 1350
    F is too hot as brought to my attention by James Binion of this
    forum. 

    I preheat my crucible until it glows red, I then pull my flask out
    of the oven and set it on my vacuum caster. I add the metal to the
    crucible and melt with a bushy flame. I stir in flux, if required, by
    dipping the heated quartz stir rod in the flux and adding it to the
    melt without removing the flame from the melt. This reduces the
    amount of Oxygen that can be absorbed by the melt by removing the
    flame to add flux. Once the metal is completely melted with no more
    solids I count to 10 and turn on the caster and pour while holding
    the flame on the melt the entire time. I run the vacuum until the
    sprue button solidifies and then remove the flask and set it aside
    until the sprue stops glowing red and then quench immediately as
    recommended by Hoover and Strong (http://www.hooverandstrong.com/)
    for metals other than rose golds. I hope this helps someone out there
    with water mark problems as I was having. Michael R. Mathews Sr.   
    Victoria,Texas    Usa JACMBJ   www.geocities.com/waxcarver 



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