Updated 3/28/2002 By Daniel Ballard
We have learned that is a mistake to
scrape off the very top of the flask. This closes up pores in the plaster,
reducing the flow of gases from the flask ahead of the metal. Also, we
have learned not to let the flask sit for hours before it is put into
the oven. This can cause severe cracking.
All
the dangerous details on how to produce those elusive, great platinum castings
you've always longed for. Follow all instructions to a "T".and make certain
all your equipment performs swimmingly.
*For 1 flask (i.e. plastic type 3 1/4" x
2 3/4" o.d.)
1. 360 grams weighed from bulk box
(all powder should be room temperature-70-75F. Liquid at 60-65F.)
A.) Place liquid in small plastic cake
mixing bowl. (Do not use black rubber) Add powder to liquid. Wet powder thoroughly
with stir stick. About 10 sec.
· 23 mls. Per 90 grams for
bulk only. (Full strength solution) (92-93 mls for 360 grams).
B.) Use portable cake mixer with beaters
(about $12.00) and mix wetted investment for 60 seconds at high speed, beating
the mix vigorously with arm action. (Helps to make slurry more viscous)
C.) Tape a collar around top of bowl (if
needed) and place under vacuum and boil for 30 seconds after investment
rises and falls. (pound tble with fists.)
Note:
(Your vacuum equipment should
reach at least 29.5" of vacuum and should do so quickly. If
vacuum takes too long to reach boil, try a smaller bell jar. (9" or
so) Or your vacuum may be too weak. See tech sheet)
D.) Put high tape collar 3" around
top of flask.pour investment down sides of flask quickly and place
under vacuum. After start of boil, time for a two (2.5) minute span
or more under vacuum. Agitate vacuum table with fists constantly.
E.) Investment will start to
thicken under vacuum-resembling the "mud pots" at Yellowstone Park.
Test fluidity by running your finger across bottom of bowl. Release
vacuum slowly at 2 to 3 minutes and pound table with fists to settle
the already thickening mix into the flask. Set aside undisturbed for
45 minutes total.
F.) Note: Flask should "glaze over"
(lose its water on top) within about 3 minutes after set aside. Within 15 minutes,
the top will develop a "mottled" look. Leave flask alone for another 15
or 20 minutes. Plastic should feel just warm-not hot. Pull the bottom,
push the flask out of plastic breaking off the rim. Scrape smooth only
on corners, do not scrape top of flask.
G.) The flask will steam noticeably,--reaching
120F. (If using a steel flask, use flask liner material and follow set times
above.) Do not set the flask aside for any great length of time, such as
all day or night. Proceed when the flask is ready.
H.) Place flask in cold oven to start. Then,
immediately set the oven for 1250F. (If using a small electric kiln this
rise should take about 45 minutes.) After reaching 1250 F., start timing
for a two hour burnout. (More is not harmful...least can be 1 1/2 hours)
(If time is not a factor, start with a cold oven and raise slowly to 1250
Fahrenheit. This helps eliminate cracks in the flask). You may also use any
overnight program for casting.
I.) At 2 hour mark, pull flask from oven
and place on bench-set an egg timer for 30 minutes. (Walk away) At the 30
minute mark, flask temperature will be between 500F. and 600F. Or...you can
turn off the oven and let it settle at 500F for at least an hour. Take from
oven directly and cast. (If a large crack should appear, place the flask
crack-side down in your cradle. Call Doc.)
J.) At the 28 minute mark-place flask in
cradle using only gloves. Crucible is loaded with platinum and pulled back
from the flask on the arm of the machine. (Keep crucible away from
flask during melting-pushing it up to the flask right before you throw it.)
Don't dwell on the melt after the crucible joins the flask. No more than
1 second and then throw it. You should modify your machine to have a full
cradle for the flask. Call Doc.
K.) Melt is started at 30 minute
mark. 35 dwt. of platinum will melt within a minute or so. (Always
use the larger Wesgo crucible) Take 5 or 10 seconds to super heat metal-i.e.
until a white "halo"
appears around the entire pool of metal.a definite white ring. At that
time, push the cradle/crucible up the arm to meet the flask. Immediately let
the arm go. Don't wait-have the metal ready before you push the crucible
up.
L.) Let casted flask sit for 10 minutes.
Break out (both flask and flask less) by whacking out with a hammer. Remove
further investment by hammering the button hard-rest of plaster crumbles.
(If casting stones-let sit until flask is cold.)
M.) Remove with best available investment
remover. Strong lye works well. Hydrflouric acid is too dangerous for most
of us to use.
WAX PREP
Waxes should always be set
up for "indirect
contact" with the molten metal. On top of the cone in the base-put a cross
bar of 6 gauge wax wire attached with hot wax across the flask and setup
waxes directly on the wire itself.
*Note: Waxes
can be dipped in any regular wax dip. Doc prescribes any colored jewelry
dip solution (red, blue,etc.) ---I put two capfuls of it into 1 quart of
isopropyl alcohol in a small tub for dipping. (ranch or bleu cheese not recommended..)
Shake off and allow to air dry.
Approximate plat weights
2 medium bands on full crossbar=30-35 dwts.
1 medium band on ½ crossbar=20-25
dwts.
6-8 medium bands on double crossbar-65-75
dwts.
Note: Solution
can not be frozen. If you get solution that is cloudy-or has crystals in
it-discard and call Doc immediately.
Note: Small
cracks will appear in investment. This is normal.
There have
been a few reports of broken flasks with the investment on one of the
newest fastest electronic platinum casting machines. If your equipment
is a lot more violent in acceleration than your usual upright spring
wound machine, adjust accordingly. Either slow the acceleration some
or use the longer slower burnout ramp to reduce cracking.
This is a picture from Golden
Sun in Arizona.
It shows just how nice an as cast platinum surface can be!
1-800-999-7528
Daniel@preciousmetalswest.com
We used
to sell EZ-Clean and Crystal Hammer, to remove platinum investments.
Unfortunately our sources of these materials are no longer working
out for us. So that you have a list of alternatives we have posted
the following information. Whatever
you choose, be sure to use properly and safely.
Platinum
Investment Removers
Sodium
Hydroxide Powder-"Drano"
MSDS
data http://www.jtbaker.com/msds/englishhtml/s4034.htm
Ammonium
Biflouride
MSDS
data http://www.emedco.com/emed2/resource/msds/msds_view.asp?pd=ba&pf=brxyx
Ammonium
Bisulfite
Hydrofluoric
Acid
Medical
information-Note this is an extremely dangerous material in the event of
any accident, spill or exposure.
Daniel@preciousmetalswest.com
©2007
Keith Weinstein Inc.
