Back to Ganoksin | FAQ | Contact

Vaccum castings and Fire scales


#1

Hi Lee, If you would please let me know how to eleminate firescale

               Michael Spears
               11350 C.R. 67.1
               Trinidad, CO  81082

Thanks in advance, Michael


#2

I just got some deox silver for casting which i was told would
eliminate fire scale from castings. Have not triied it yet I have
both a Neycraft Centrafuge, and a Vacuum caster. A friend said
she had trouble with brittle castings when she used deox. Any one
else having that problem? I got my silver from AAA Refining which
is in Portland, Oregon, and am wondering if I should have gotten
regular casting grain instead of deox. Thanks for your help. Alma


#3

Alma, make sure you allow 20 minutes for cool down. One of the
biggest mistakes a lot of people make is quenching too quickly. Be
patient with all cast pieces, de-ox or not.

Best, Doug Perry


#4

One thing that I have found to help is to put a piece of charcoal
briquette on top of the button a soon as it solidifies & leave it
there until quenching the flask. Use a traditional briquette, not a
quick lighting type. You could use a piece of broken charcoal block
as well. Primitive, but cheap.

All the best!


#5
One thing that I have found to help is to put a piece of charcoal
briquette on top of the button a soon as it solidifies & leave it
there until quenching the flask.

I usually torch the button sans oxygen. This covers the flask with
methane and CO. I don’t know how helpful it in fact is, but it
doesn’t seem to hurt.


#6

My casters have stopped using de-ox because the castings were so
brittle that they were snapping when they were cleaning off the
investment. Now had to go back to silver/zinc mixture, Christine.


#7

Christine, does the brittleness with the deox silver occur only
with vacuum casting, or does it also occur with centrifugal
casting??? Several Orchidians have suggested that one wait for 20
minutes before quenching and thereby avoid any brittle castings.
Have your casters tried this? I have yet to use my deox silver but
will be be sure to follow all the recommended proceedures—slow
quenching etc. Hope I don’t have a problem as I just got a fairly
big batch of deox silver. Hate to have to trade it in at a loss
for the regular stuff. Alma


#8

Christine, Make sure that you are casting at the proper temperature.
I believe it’s about 1950=B0 F, but check w/ your supplier of de-ox or
with Hoover and Strong. It is about 200=B0 F higher than sterling. And
also make sure you let it cool for about 20 minutes after casting
before quenching. If you do those two things, you should eliminate
the brittleness problem. We had the same problems with de-ox when we
first started working with it. Also, as with all metals, make sure
everything is properly sprued. Hope that helps!

JoAnna Kelleher, Director of Operations
Pearl Exotics Trading Company
www.pearlexotics.com


#9
    Several   Orchidians have suggested that one wait for 20
minutes before quenching and thereby avoid any brittle castings. 

I was told that waiting too long before quenching would make it much
harder to get the investment off the castings. We tend to quench 5-10
minutes after casting, but we sit our hot flasks on a large piece of
steel I-beam that acts as a heat sink, so maybe they cool faster than
other folks’ flasks. How cool can a flask get and still “explode” the
investment out into the water when it’s dunked?

Kathy Johnson
Feathered Gems Jewelry
http://www.featheredgems.com


#10

I had an incredibly complex 14K 9 pointed star break apart in my
pocket from using commercial alloys. I use copper and silver only for
my gold alloy and have not had problems since. I consider commercial
alloys, just that…commercial…, and will continue using my own
alloys. I do not seem to have a firescale problem with castings with
silver. Jay


#11

I’d bet that waiting 20 minutes is a rule that’s intended for medium
to large flasks. A two inch flask compared to a 4 inch flask is
quite different. You can always soak your castings in vinegar if
you find you’ve waited too long. It softens the investment.

We quench after 20 minutes. The investment boils away merrily and
isn’t difficult to remove. We’ve had no problems related to
brittleness. Someone mentioned 1950F as the casting temperature for
deox sterling. The parameters may vary with suppliers, but if we
cast that hot, we’d have problems. We have great results between
1850-1870.

If anyone out there does subsequent soldering on castings, you’ve
got to try deox silver. You can take a more slapdash approach to
your soldering without having to pay for it when it comes to
polishing. I’ve noticed many comments about careless fluxing and
firescale.

Dana Carlson


#12

Hi Dana and List, Your absolutely correct…1950 oF is definitely way
to hot for DeOx silver… around 1850oF is correct for most of
them…

there are varieties that are cast colder… As I have mentioned in
previous posts, there are about 30 different deox silvers on the
market and they are not the same… some are designed for different
purposes…so it is really important to check with your metal
supplier and get all the info on the alloy… including quench time,
temp. and also if you are torch casting for centrifuge, torch
casting for Vaccuum or if you are using a machine that is high
frequency , medium frequency or low frequency melting…these
machines are available as vaccuum casters and centrifugal casters.

As I have mentioned as well as Dana and a few others, quench time
can be a critical factor… we use 20 minutes for larger flasks and
they break out perfect… anywhere from 10 to 15 minutes maximum fro
small flasks…

We also use a highpressure water blaster to remove the excess
investment from the cast trees and vinegar mixed with water in an
ultrasonic to remove small residues… then we pickle the tree so
that it is perfectly white… if it does not go perfectly white,
your pickle may be weak or it may have gone bad…

If you over heat or cast with too hot a flask or overheat when
soldering, you will have problems when you polish large smooth
highgloss areas. Best wishes to all. Daniel Grandi

We do casting,finishing,cnc model work hand made models ,
enamelling,soldering ,fusion and a lot of other processes for
designers , jewelers and people in the trade. Please contact :
sales@racecarjewelry.com

We are an Orchid advertiser , Please support orchid by advertising
with orchid for the services you offer as we do. This will help
Hanuman a great deal and it will also improve your business.


#13
   Make sure that you are casting at the proper temperature. It is
about 200=B0 F higher than sterling. And also make sure you let it
cool for about 20 minutes after casting before quenching. If you do
those two things, you should eliminate the brittleness problem. 

hello Joanne, thanks for the advice.I am not casting myself, I am
using a casting company which is very reputable, and has been
experimenting a lot with different " de ox’s". The last batch before
they decided to give up on de ox totally were actually snapping as
they came out of the investment, and those that didn’t snap in two
had cracks through them. I’ll be passing on all the advice from
Orchid to them, Thanks, Christine


#14

My casters only use vacuum casting,( they are a large casting
firm),and I haven’t asked them yet about the waiting time, but as
they have been trying for several months to get this right , they
probably have tried most things. I’ll ask them when I pick up my
next batch, thanks, Christine