Can someone compare torch melting of sterling or gold to using a
melting furnace. What are the pros and cons of one method over the
other? I am considering a Rio catalog # 704-072.
Thanks,
Martin Buchholtz
Hi Martin,
I have never used a torch to melted metal for casting. I have always
used an Electro-Melt Furnace. I guess I am somewhat prejudice.
I strongly recommend using an Electro-Melt automatic melt furnace
for the following reasons:
-
You can control the temperature of the metal more accurately than
you can with a torch. The temperature reading on the controller may
not be the exact temperature of the metal but once the controller
temperature is set each melt will be a consistent temperature even
if it is not at the temperature shown on the gage. If you have a
problem with metal temperature you can correct the controller to
provide a metal that will cast properly. -
The flask temperature at pour will be a consistent temperature
because the time from removing the flask from the oven until you
pour will be consistent.
It is much easier to have a consistent temperature of both the flask
and metal at pour when using an electric furnace.
-
You can fill the furnace to its maximum capacity of metal and make
several pours with in 5 minutes of each pour until you use all the
melt metal. The 5 minute delay between pours is mandatory to allow
the ring of the crucible to reheat between pours. If the crucible
ring is not reheated after a pour before the next pour the ring will
chill the metal as it is poured. -
The controller will maintain the temperature of the metal as long
as it is powered. This allows you a little more freedom between
pours. -
Pouring Metal from the Electro-Melt furnace is like pouring your
morning cup of coffee.
disadvantages:
-
It takes about an hour or more to melt the first batch of metal to
pour temperature in the 30 oz 120 volt Electo-Melt Furnace. It takes
about 20 minutes to heat succeeding batches of metal. -
The graphite cruicible is expensive and will have to be replaced
after about 20 to 30 reheats.
704-072 furnace
I do not recommend the 704-072 melt furnace as it is designed. It
is cheaper than the Electo-Melt furnace but I believe it is much more
dangerous. You will have to remove a very hot crucible with maybe 800
grams of molten metal from the furnace using long handle tongs.
Because the tongs are long it will be difficult to place the
crucible in the proper place to pour the metal and hold it there as
the metal is poured into a small flask. Controlling the crucible as
it is rotated to pour the metal will be difficult. The groove for the
tongs will disappear as the crucible is used making it useless. I
would guess that the grooved crucible will not last as long as the
Electro-Melt crucible.
If the 704-072 furnace had a handle like the Electo-Melt and a way to
hold the lid open with the same hand that is holding the handle it
would be a much better buy.
That’s my two cents.
Lee Epperson
Hi
I have looked at this issue at length, fill us in on some details of
your options-
Electric Furnace? That would be resistance or perhaps induction. Blow
Furnace? Natural gas makes w great reducing atmosphere and carbon
crucibles handle any oxygen that the silver absorbed.
Torch?
What gas have you been using?
A torch can be inconsistent, but on the other hand is so flexible on
gas mix and heat.
Daniel Ballard
www.pmwest.us
800-999-7528
Martin
If you are spin casting, using the torch makes sense, especially
since the melt can be covered buy the flame till you cast. Keeping
the melt covered by the flame will prevent oxygen from entering the
metal.
The electro melt style is very good for vacuum casting. The carbon
in the graphite crucible pulls oxygen from the melt and air which
would otherwise ALL enter the metal. The main problem with the
electro melt style is that you must top pour through the air into
your flask. Top pouring is not as good as bottom pouring, the method
used in spin-casters and most casting machines. In bottom pouring
all the dross and other floating junk enters the flask last and ends
up in the button and not in the flask. In top pouring the dross mixes
in as the metal pours. In addition the top pouring design must be
poured from a higher position, meaning that the metal must pass
through more air before it enters the flask. You can actually see a
surface film form on the metal as you pour. An electric melter with a
funnel spout pouring lid would overcome those problems. With an
electric melter you can pour at exact temperatures. Using a torch you
must guess when the temp is right. Some people weigh out every cast.
We fill the crucible to the top and then add dry metal after every
cast. The largest cast we have made with the 30 oz is 830 grams
silver, using a worn crucible. The 30 oz size is a pain for adding
sprues because the larger pieces don’t always move to the bottom of
the crucible as they melt. They often get stuck, even when mixed
50/50 with new grain. Pushing the unmelted pieces down doesn’t seem
safe or wise. If you do more than a few flasks of silver at a time I
would recommend one of the larger models.
Marty
