[Jewelry making - Article 01043] - Re: [Orchid] Rough surface on Sterling belt buckle casting

[LEESSILVER]

========[ Invite a Friend - http://www.ganoksin.com/invite.htm  ]========

    Casting is a mystic art. I read all the post pertaining to casting
    and always wonder how I get away with casting the things the way I
    do. I burn out 1320 degrees, melt my sterling to 1870 degrees in a
    100 ounce electro melt furnace and pour into molds at 860 degrees. I
    find if I lower the mold temp or metal melt temp my castings loose
    detail. I use scrap to new silver at a ration of 40 to 60. 


    It is difficult to determine what the problems are. My best guess is
    that it might be one or more of the following: 

    1. Old investment. It will settle and absorb moisture. This will
    cause the investment to break down and produce growth on the casting.
    Do not use very old investment and stir it up before using. 

    2. Improper mixture of water to investment. If the investment is too
    thin you will get thin parting lines that run up the casting. I
    believe this is due to bubbles that travel up the wax to the surface
    leaving parting lines. I know this because when I first started
    casting I mixed investment without weighing and measuring. When I
    got the thin parting lines I figured the investment needed to be
    thinner to allow closing of the bubble paths. Wrong. Things got
    worse. 

    3. Not mixing the investment long enough. There may be small clumps
    of incompletely mixed invest that if they land on the wax will fail
    during casting causing depressions in the casting. I pour my
    investment into the flask through a kitchen strainer after mixing it
    with an electric beater for 1.5 minutes. I always have small clumps
    trapped in the strainer. 

    4. The combination of the metal and mold temperature too hot or too
    cold. I started using scrap silver from a punching operation in my
    electro melt furnace. I would let the silver melt then add more
    silver until the crucible was full, then pour. Things went well until
    is started using casting grain. I would pour as soon as the metal was
    molten. The metal would chill as it passed over the lip of the
    crucible leaving a thin tail of silver hanging from the crucible and
    the casting missed detail. My conclusion was that the delay time of
    heating scrap allowed the crucible ring to heat up much more that it
    did when melting casting grain. The problem want away when I allowed
    the furnace to sit at melt temp for several minutes before pouring. 

    5. Improper burn out cycle. Follow the investment manufactures
    instruction. There are many errors in burn out that can cause
    failure. 

    6. Quenching the casting too soon. You will get blow outs of metal. 

    7. Improper spruing. I sprue with about three no 8 gauge wax wires
    welded together then welded to the center of the buckle at one end. I
    then add a 8 gauge sprue to both corners. I then add sprues to the
    center outside edge of the buckle. I add another 8 gauge sprue to the
    center of the buckle near the end opposite the main sprue. The pour
    is parallel to the buckle. If there is a thick spot on the buckle I
    will add a sprue to the back side of the thick section. It takes a
    lot of time to clean off sprues from the casting but that is nothing
    to the time lost if the casting fails due to not enough sprues. I
    can send a photo off line to anyone who is interested. 

    8. Use of dirty or too much scrap sterling. Its recommended to use a
    50 50 ratio. Do not use silver with solder on it. Make sure that old
    sprues are completely free form investment. 

    9. Incomplete burn out. The more wax in the burn out oven the longer
    the temperature must remain at the burn out temperature. 

    10. Not vacuuming the flask for long enough time to let air bubbles
    to leave the wax. This caused small bubbles of silver to form on the
    casting. 

    11. Metal flowing directly against a part of the design might cause
    the investment to erode. 

    12. Too much flux in the melt. 

Hope this helps,
Hope to see many of you at the Orchid dinner.
Lee Epperson.

____________________________________________________________________
T h e   O r c h i d   L i s t
Open Electronic Forum for Jewelry Manufacturing Methods and Procedures
____________________________________________________________________
Orchid FAQ:
~ http://www.ganoksin.com/orchid/faq.htm
Orchid Archives:
~ http://www.ganoksin.com/orchid/archive
Orchid Galleries:
~ http://www.ganoksin.com/orchid/gallery.htm
Invite a Friend:
~ http://www.ganoksin.com/invite.htm
____________________________________________________________________
Tips From The Jeweler's Bench - Article Archive
~ http://www.ganoksin.com/borisat/tip_sear.htm
The Jeweler's Selected Bibliography List
~ http://www.ganoksin.com/jewelry-books
Buy Orchid Jewelry:
~ http://www.ganoksin.com/shop
____________________________________________________________________
-Unsubscribe:
-Email: orchid-request AT ganoksin.com Body=unsubscribe subject=blank
____________________________________________________________________