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Rchid - member's introduction (fwd)


#1

I have a question about lost wax casting. I’ve probably cast less than ten
pieces so far, all small waxes in 2 1/2 x 2 1/2 flasks casting sterling
silver. Casting single pieces at a time also. I am wondering if anyone out
there does this on a regular basis and is doing it sucessfully without
porosity problems. Sterling seems to be more prone to this than gold. Any
tips or advice on how to get porous free casts would be really helpful.
…Dave Stephens

Art Jewelry for Conscious People
http://www.opendoor.com/stephensdesign/crystalguy.html


#2

I have a question about lost wax casting. I’ve probably cast less than ten
pieces so far, all small waxes in 2 1/2 x 2 1/2 flasks casting sterling
silver. Casting single pieces at a time also. I am wondering if anyone out
there does this on a regular basis and is doing it sucessfully without
porosity problems. Sterling seems to be more prone to this than gold. Any
tips or advice on how to get porous free casts would be really helpful.
…Dave Stephens

I usually use a 2 1/2 inch flask. Today I was using a 2 inch flask.

Normally, I can get up to a half dozen rings into such a flask. Today I was
casting links for a tennis bracelet. Don’t do much sterling. In fact I don’t
sell any silver. Any silver I use is restricted to models or prototypes.
As for porosity, I still get some, but I have found that what I do
get I can remove with a burnisher. Usually a rotary burnisher running on the
flexible shaft.
A couple of things that seem to be of major importance in
preventing porosity in the first place. Flask temperature: I usually try to
cast yellow gold at about 900 degrees F. White gold a little hotter. Heavy
pieces a little cooler. Lighter pieces a little hotter. Of equal importance
is spruing. Perhaps more so. I try to use as heavy a sprue as I am willing
to cut with a jewelers saw. Some people say that it should be as heavy as
the heaviest part of the casting. Probably good advice, but I haven’t gone
this far. One thing to remember is that as the casting cools, it will
contract. If there is a heavy enough sprue, the sprue can continue to feed
metal to the casting. Another thing that I can’t prove, but I believe is so
is that turbulance will affect the quality of a casting. This means anyplace
where metal makes a particularly violent turn or is pinched through a small
sprue, there will be problems.
So in a nutshell, I look for temperature, cooling effects and
turbulence.
I’m sure a few other people can add a lot.

http://www.knight-hub.com/manmtndense/bhh3.htm
e-mail: @Bruce_Holmgrain
snail mail: POB 7072, McLean, VA 22106-7972, U.S.A.


#3

Steve(if I may!, its shorter and i’m a pooor typist!),

Have the same problem with gold, as well as silver… been told it due to
reuse and stuff or really poor casting techniques as suggested by the word
’cleanlenes’!!!
Sorry bout the words but thus far it seems to be true, the more careful I am
relative to 'stuff(more polite to myself then careless) seems to be the
problem. Also, the idea of 'bubbling the silver, that is, temp is to hot to
pour is sometimes a problem … plus 1,000 more… that’s why they call
them EXPERTS or MASTERS … and they( as appropriate!) tend to chuckle at
us’ens!!!
Da Jim … Amateur
At 03:36 PM 9/23/96 -0800, you wrote:


#4

Bruce::::
In response to your posting 96-09-23 22:12:21 EDT
Your problem with your castings is several things.
1: The flask temperature that I use is 1’000* F. when It comes out of the
oven.
2: The temp of The Sterling is By color. When the ,molten sterling gets a
mirrow look it is ready to cast.
3: In spruing small objects such as rings or small pieces I use 1/8" sprue
with a 3/16"wax ball just above the button. This takes the heat away from the
part that is castand reduces the process of purosity. If the metal is too hot
when cast you will have purosity . If the part you are casting weighs more
than the button you will have problems. I hope this will help solve some of
your problems.
4: You will have to keep experminting with these systems and finall you will
get it .
Yours bibgbrba@aol.com


#5

Dave,
I used to have the same problem with silver. I do alot of casting in both
gold (mostly) and silver. I found a great sterling silver casting grain from
United precious metals. This stuff is great. It is a deoxidizing metal and it
pours like butter and there is 75% less clean up after casting. That is to say
the castings have no hard to get off even after pickling black oxidation.
These castings come out like a dull satin finished silver. The name of the
metal is the sterling #57 casting grain. The name of the company again is
United Precious Metals. There phone number is 800-999-FINE. Call them up and
ask for some info. I use the stuf by the pound and I rarely if ever get
porosity…Try it you WILL love it.
Marc WilliamsFrom: owner-orchid@proteus.imagiware.com on behalf of Dave Stephens
Sent: Monday, September 23, 1996 7:36 PM
To: orchid@ganoksin.com
Subject: Re: rchid - member’s introduction (fwd)

I have a question about lost wax casting. I’ve probably cast less than ten
pieces so far, all small waxes in 2 1/2 x 2 1/2 flasks casting sterling
silver. Casting single pieces at a time also. I am wondering if anyone out
there does this on a regular basis and is doing it sucessfully without
porosity problems. Sterling seems to be more prone to this than gold. Any
tips or advice on how to get porous free casts would be really helpful.
…Dave Stephens

Art Jewelry for Conscious People
http://www.opendoor.com/stephensdesign/crystalguy.html

procedures


#6

Hi Dave: All those other things being true also, you might try something
which works for gravity casting and regarding spruing. This is done for
pieces much larger than jewelry, but principle the same. Your main sprue
(gate) has feeders from it which will fill your piece, diameter being at
least equal to your thickest part, gate is greater thickness than feeders.
Gate too is extended straight down beyond the model. Feeders come off
from the gate in the middle of the gate length. If your space is tight,
you can form the gate shaped like a “J” so that the gate wraps around
your model within the flask and the feeders would come off the J in
the middle. Theory being that by dropping your metal into gate first
leaves much of dross there and eliminating turbulence. Essentially metal
"fills" the piece rather than being forced into investment mold directly.
This method has gravity as impetus behind the metal rather than centrifugal
force, and used for casting bronze sculpture. But I have always used it
for spruing up my jewelry pieces with never a problem with porosity.
Hope that helps.

Susan


#7

Dave: One other thing, to watch your oxygen setting on your torch. Too
much oxygen in the flame will force more oxygen into your metal.
(You probably already knew that, but maybe someone else outh there
does not.)

Susan