Well, I cast my first item this weekend in my self-taught path
towards fame and fortune, er, well at least towards self satisfaction.
I did a ring in silver, which turned out pretty cool. I didn’t think
that it would come out as well as it did, especially given some of
the issues I had (the mold fell out of the casting machine while I was
melting the silver, torch was not hot enough so I had to heat three
times, etc).
I was following some instructions from Tim McCreight’s book, and
threw a pinch of borax in at first red and when the metal became
molten.
The problem that I had I discovered after polishing… the metal was
a bit pitted here and there. I had expected some knobs from bubbles
(no vacuum machine), and received them, and cleaned them up OK, but
the pits were unexpected.
Were these some chips perhaps off the mold when it fell the couple of
inches to the tray of the casting machine? Would a late and too heavy
fluxing with borax cause crystals to find their way into the mold? Is
it some other known and obvious cause?
Thanks in advance!
Darcy , whenever I am in doubt I gently shake the flask with the
opening down to try to evacuate any flakes of investment that may have
been loosened by such accidents . A friend of mine always uses a
vacume on his flasks . Many happy returns on your journey , David
Darcy, Welcome to the wonderful world of casting! It is a joy (and a
pain sometimes) yet the finished product can be a treasure for all.
You mentioned the pitting on your piece. Are the holes round, oblong
or do the holes have a somewhat defined shape? The problem you
experienced is generally a temperature (metal or flask) issue, sprue
or gate feed issue or as you said by dropping the flask, you may have
fractured the investment causing small bits to remain in the cavity
and then flowing with the metal. If you would like to contact me off
line, I might be able to help you further with this issue. You can
reach me at @Joe_Lovato. Joe Lovato
Darcy, Congratulations…The first cast is full of many emotions good
and bad. Silver is difficult to cast well and pits can be formed from
casting temperatures both in the molten metal and the flask
temperature at time of casting. There has been a great mound of
on reasons and solutions in the archives over the
years…try that first and you will be amazed at the amount of people
that have had the same trouble. I doubt that the flux addition when
metal was molted was you trouble. Stick around and your self teaching
will only get better. Ron
I had expected some knobs from bubbles > (no vacuum machine), and
received them, and cleaned them up OK, but > the pits were
unexpected.
Hi Darcy, great description of your first casting. That sounds about
right. Pits can result from improper spruing and allowing oxygen to
get in your melt, which almost certainly happened as you said you
melted 3 times. Keep your flame over the top of your crucible at all
times, using a bit more gas than you normally would. The flame should
look orange and feathery. This is called a reducing flame. I like to
use a carbon rod to introduce the borax into the melt, so I don’t have
to pull my torch at all. As soon as your melt pulls up into a ball,
go ahead and cast. Overheating the metal can cause pits and all kinds
of trouble. You’re on the way. Now if you do it like I did, you may
have consistently decent castings in just a few short years (grin).
Mike
If the edges of the pits are sharp and the “pit” is angular, it is
potential they were flecks of investment, BUT if so there should be
corresponding “bulges” on the casting/sprue/vent (if any) system. If
the positive metal areas are not apparent on the metal parts, did
some investment break off around the top of the can and fall into the
pour hole??? If the “pits” and round, inward “bubbles” this is more
likely a flux problem or oxidation from the repeated heats on the
metal. If there is reddish, brownish glass like stuff in the pits,
this is flux. Did you take the flux off of the surface of the melt
right before pouring it (use a quartz, graphite or if necessary a
steel rod to get the flux off of the surface). Also stirring the
metal a bit just before pouring (with the rods previously mentioned)
is often practiced by many casters. Pouring the metal through the
torch flame is another good idea.
Also, a successful first casting, even with a few pits is a great
start. Practice, practice, practice.
John Dach
MidLife Crisis Enterprises
Cynthia Thomas Designs
Cynthia’s sculptures are at: http://www.mlce.net
Darcy wrote: Well, I cast my first item this weekend…
Congrats, Darcy! I’m not as much a casting expert as I know some
other Orchidians are, but I’d say there’s a good chance the metal may
have been overheated. It’s most desirable to have a smooth transition
of crucible to casting machine, one easy melt, and let 'er rip! Of
course, any loose debris in the mold will cause problems, but I don’t
think borax would be this issue. You’d really have to go overboard
with the borax.
I’m assuming in this case you’re working with a centrifugal casting
machine. It’s a little intimidating to try it with a hot flask, but
you might want to consider wiring it into the casting machine with
binding wire - a simple “X” over the flask and under the cradle. This
should help keep the flask secure, and it won’t lose too much heat.
Then start your melt with a good sized torch - with oxygen if
possible. I throw a good pinch of borax (Matt’s Casting Flux) on at
the beginning of the melt, and a bit more when it’s good and watery,
and ready to cast. As soon as the molten metal is “rolling” easily, I
cast.
I can’t describe the physics or chemistry of overheating or
repeatedly heating the metal, but I’m pretty certain it will absorb a
great deal of oxygen from the air and probably change the physical
characteristics of the cast metal to some degree. I wouldn’t be
surprised if porosity and brittleness were the result.
Try it again, and best of luck! Each new journey starts with a first
step!
Dave
Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com mailto:dave@sebaste.com
http://www.CarolinaArtisans.com http://www.CarolinaArtisans.com
Darcy, I’ve been there! You will get much good advice from the
knowledgeable people on Orchid. If you want to talk with another
self-taught gal about casting, write me off line. Readwow@home.com.
First off what type of torch did you use, what form was your silver
in (all scrap, all grain?other?). Then the spruing is so important,
and the surface of the object in wax. I don’t think the borax caused
the problem. We all get the little pits from time to time and there
are many reasons. Often you can narrow them down and prevent most of
them. None the less, wasn’t it great
fun!!! Annette
Well, I had my second casting yesterday. The ring came out
perfectly… too bad the wax model had problems :-)… I’m going to
do my third tomorrow, with a good model and my new tiny bit of
experience so I have high hopes!
There certainly is something magical about doing this…
Thanks,
Hi Darcy, Congratulations on your first casting ! On My website, I
have an area called “workshop” If you go into the workshop and go
through the pictures and explanations, you will find some interesting
ideas on how to set up a simple ,easy, torch stand so that you can
have both hands free to get your flasks from the oven.There are also
pictures of a vacuum flask liner that you insert into your flask
before investing and this will increase the amount of vacuum that can
be drawn through the flask helping to eliminate gas , allowing you to
cast at lower temperatures and getting a much better fill than with
wax webs or plastic liners.It also has a built in Guard that extends
2 inches beyond the top of the flask to prevent the investment from
boiling out of the flask.This is a patented device that is available
from www.contenti.com and from www.Gueswein.com The pictures are of
my old workshop built into the basement of my house before we moved
to our 4000 sqft plant in Cranston RI. There are alot of good ideas
at the site that show how to set up very inexpensive benches,
ovens/hoods ,soldering benches and exhausts simply and cheaply using
house hold items. Hope this helps. Daniel Grandi
http:www.racecarjewelry.com We do casting and finished products
for designers and people in the trade in gold, silver, bronze and
pewter.
Hi Darcy, great description of your first casting. That sounds
about right. Pits can result from improper spruing and allowing
oxygen to get in your melt, which almost certainly happened as you
said you melted 3 times. Keep your flame over the top of your
crucible at all times, using a bit more gas than you normally would.
The flame should look orange and feathery. This is called a
reducing flame. I like to
I have a question about that… whenever I use a reducing flame, I
have trouble getting the temperature up. The silver just seems to get
red and nothing beyond that. On both attempts I bailed after a bit and
went with a hotter more oxygen rich flame. The first was pitted, but
the second was perfect in the end. I’m thinking that it was small
chips of investment from when the mold dropped.
use a carbon rod to introduce the borax into the melt, so I
don't have to pull my torch at all. As soon as your melt pulls up
into a ball,
I will do this next time… I’ve been tossing it in with the flame
still on, creates a bit of a cloud but kinda works :-).
go ahead and cast. Overheating the metal can cause pits and
all kinds of trouble. You're on the way. Now if you do it like I
did, you may have consistently decent castings in just a few short
years (grin). Mike
It’s great to have this as a resource for questions.
Thanks for your help,
Dear Darcy:
Casting is so exciting and so addictive! I love the instant
gratification! I am currently taking my second class in Lost Wax
Casting. There are several things that have been made very clear.
First is to be sure to spend as much time as you need to finish the
original wax pattern so that it is eye clean and as close to perfect
as possible before you invest it. This will assure you a minimum of
repairs or clean up details fixing the areas that were not quite right
after it has been cast. It is much easier to work the wax then the
cast metal form. Another, is that using a vacuum to de-air the
investment and then again de-air the flask after it has been filled
with the investment, are extremely important steps in the process.
Also, the location and execution of forming the joint where the sprue
is attached to the wax pattern (your wax original) is also very
important so as to assure the proper flow of the molten metal.
Gradually build-up the wax to form a cone from the sprue to the wax
pattern. Be sure to use a properly prepared crucible. First,
preheat your crucible with the torch before you add your metal. Pay
attention to pre-heating the hole at the back of the crucible. Place
the metal into the pre-heated crucible. After heating for a minute
or so, add a pinch or two of borax flux, stir and heat until the
molten metal forms into a shiny ball. We use a quartz stirring rod to
mix the metal and flux as it melts. We also use a torch with a
mixture of oxygen and propane to heat the metal in the crucible.
Always use separate crucibles for each different type of metal. They
do not mix well. Be sure to move quickly from the time your remove
the torch from the molten metal to the time you release the casting
machine lever, as the metal will begin to cool as soon as you remove
the torch. Always, let the spinning flask come to a full stop before
removing the flask from the casting machine. Place the flask aside to
cool for a few minutes before plunging the flask into water to
quickly cool the casting. Never, Ever, place white gold into water to
flash cool your flask. It changes the properties of the metal and
becomes very brittle. Remove the casting from the flask and Voila, you
have instant Gratification! I just love It! I hope this information
proves helpful!
Don’t give up, just keep asking questions! Good Luck!