Back to Ganoksin | FAQ | Contact

Gold stuck to new ingot mold


#1

Well, this is frustrating. I have a brand new ingot mold which I
sprayed with WD-40, then wiped the excess off. I preheated the mold
with my torch, but when I made my first pour, the gold stuck to the
mold. I’ve heard of this, but never had it happen. I have always
used wd-40, but was there more prep I needed to do to the new ingot
mold? Help… how do I get it off the steel?

Thanks in advance…
Laura
www.LauraGuptillJewelry.com


#2

Laura,

WD-40 is often misunderstood. People use it as a lubricant and
penetrating oil, and assume it’s oil. While it does, when just
applied, lubircate fine mechanisms to let the free up, and such, it’s
real purpose, suggested by the WD, is as a water displacing agent.
For the most part, it kerosene, I think, and it does not actually
contain much in the way of oil, or anything that would provide a
persistant lasting film on the iron. So after you sprayed your mold,
heating it pretty much removed all the WD-40. That’s way the metal
then stuck. You remove the metal by just prying and scraping it back
off. WD-40 might even help in this. But when you pour ingots,
prepare the mold with an actual oil. Motor oil, even used (good use
for it), works fine. So do other oils, such as peanut oil, etc. Heat
the mold till the oil smokes (a good bit hotter than the temp at
which WD-40 will appear to burn and smoke, since it’s much more
flammable) The other common pretreatment for a mold is to coat it
with soot. You can get that with most torch flames by turning off all
air or oxygen, so the flame is very yellow. The metal is held just
beyond the visible yellow flame, and soot is deposited. I usually do
this to a brand new mold, then add some oil to the result, and heat
it till it starts to really smoke quite a bit. Leaves a sort of
cured surface similar to a well broken in iron wok… Once initially
cured like this, the mold will only need a little more oil, every few
ingots. Machined molds, with smoother surfaces, take a lot less
preperation than rougher cast iron molds, which can initially need a
lot of soot and oil to clog up the rough pores enough so the metal
can easily seperate from it.

Peter


#3

Laura

You may find oil a better choice next time, I don’t wipe the excess
off either and allow some cooling time before trying to remove the
ingot, 10 minutes or there abouts works for me.

Try pouring some oil over the ingot and mould and use an old
screwdriver blade and hammer to free one end of the ingot, once
loosened it will ususally allow the rest to follow. Be careful to
avoid hitting the mould with the hammer, it may break.

Alan Lewis
UK


#4

Laura, try heating the mold (the outside, away from the gold you
poured). That should cause the steel to expand at a different rate
than the gold, which should then come away. Next time you use the
mold, try turning on the gas only (no oxygen) and playing the torch
over the inside of the mold instead of WD-40. That will apply a
layer of soot to the insides of the mold, which in turn helps
prevent the poured metal from sticking to it. Acetylene works better
than propane, but either will work. This isn’t the same as
preheating. You can preheat with a torch successfully, but using a
kiln after ‘sooting’ the mold works much better.

James in SoFl who has taken the awnings up, but is leaving the
plywood in place until Ivan steers clear.


#5

Hi Laura,

I have had this happen, and after finally beating the ingot out of
the mold, examined the cavity to find small imperfections sticking
out of the wall of the mold, hence grabbing the ingot and preventing
it’s easy release. I ground these away, and never had the problem
again. I also like to use a liberal coating of light oil, such as
vacuum pump oil inside the mold. It will burn nicely after pouring
and leaves a nice surface on the ingot.

If you are only casting small bar ingots, of one ounce or less,
there are very nice carbon graphite ingot molds available. Be good
about maintenance, as graphite deteriorates with use, and could
leave inclusions in your metal. For this reason I long ago abandoned
carbon graphite crucibles and stirring rods for casting in favor of
ceramics and quartz.

Mark Moretti
Alexandria, VA


#6
I have always used wd-40, but was there more prep I needed to do
to the new ingot mold? 

Hi Laura,

Can’t give any advice for removing the stuck metal, but what I do to
prep an ingot mold is to “soot” it using my oxy/acetylene torch with
the oxygen turned off. It can create a little bit of a mess, but I’ve
never had a problem with metal sticking.

Good luck,

Dave Sebaste
Sebaste Studio
Charlotte, NC (USA)


#7

Laura,

Peter is correct. WD-40 is a water displacing agent, not an oil. On

an old, used ingot mold, you would not have noticed that it is not
very effective in coating your ingot mold, as the mold probably has a
good amount of soot already attached to it from years of use. As you
discovered unfortunately, a new mold needs a lot more pre-treatment.
Remove as much of the stuck metal as possible before reusing the new
mold. Chip it our, or grind it out. If you are using a two-piece mold
with a polished surface, you should be able to remove this metal by
sanding.

I would like to add to his suggestions for preparing your mold

prior to pouring your ingots. I used to use motor oil, but always
hated the smokey smell. Now I use wax. Candle wax will work. So will
injection wax, and I always seem to have plenty of that around. I use
an open mold for wire ingots. If you are pouring a small ingot, just
dip a small piece of paper towel in some liquid wax, ball it up, and
push it into the wire channel. Warm the mold until the wax starts to
melt, melt your metal, and pour. The molten metal will stop when it
hits the waxed paper towel. The ingot always drops out with a shiny
finish, and the smell of burning wax is far more pleasant in the
studio that burning motor oil. I have to thank Namu Cho for this
great tip.

Namu also gave me some very small and thin ceramic crucibles from

Korea. I absolutely love these for doing small melts, as they heat up
very quickly. They are only 65mm in diameter, 20mm deep, with a wall
thickness of just 2.5mm. They are shaped like a shallow bowl. I prep
them by soaking them in water, then slowly drying them with a torch.
Coat with flux, and they’re ready to use. With a proper coating, I
can melt platinum in these. I have never seen these in any tool
supply catalog here in the States, but Otto Frei does have a similar
crucible (Pg. 210, C and D). You will need a small pair of tongs to
pick these up. Regular crucible tongs are way to big. You can make a
pair from ordinary hardware store chain nose pliers by heating the
tips and bending them slightly to match the angle of the crucible.
It is a little hard to describe the angle exactly, but if you try to
pick up one of these crucibles by its edge, you will see what I mean.

Another thing to remember is to always forge the ingot before

rolling it. Give it more than just a few “Love Taps.” Forge it. You
will get a far better result when you proceed to the rolling mill.

Douglas Zaruba
35 N. Market St.
Frederick, MD 21701
301 695-1107
@Douglas_Zaruba


#8

Laura,

Preheating the mould serves two purposes:

  1. Expels moisture from the steel so that steam is not generated
    when the molten metal makes contact on pouring. Trapped steam can
    expand in the mould cavity and expel the molten metal. This can be
    nasty.

  2. The heated mould allows the molten metal to flow into the
    mould without freezing against cold steel. The mould only needs to be
    "touch hot".

I suggest that you try bees wax as a lubricant on the mould to
prevent the metal from sticking. Just heat the mould to touch hot and
rub the bees wax on top of the mould opening and it will run down the
inside and coat the surfaces. The coating of bees wax will serve at
least three to four ingots before reapplication is necessary.

Oil is messy; it creates too much smoke when the mould is heated and
also when the molten metal is poured. You need a good fume extractor
or you end up trying to dodge the smoke vapour. You also end up with
oil on your fingers after handling the mould.

I hope this helps.
Graham Farr
Sydney, Australia.


#9

Gold stuck to new ingot mold

Thank you so much for all of your help! I will change what I use for
"oil" and will treat it with the soot also! You guys are great! I
was able to pry the gold away without damaging the mold. Thanks
again… Laura

www.LauraGuptillJewelry.com


#10

The lube I use in ingot molds for both gold and silver is Pam ( the
cooking spray ) never had an ingot stick …HTH

Ron


#11

I want to thank all of you for the responses and suggestions I
received when I got my gold stuck to my new ingot mold! I got it
off by waiting a day, and gently chipping it off with a screwdriver
and a hammer. Came off cleanly with no damage to the mold. I learned
that WD-40 is good for getting rust off of tools, but is not an oil
to protect it with. Thank you! What a COOL resource it is to have
all of you jewelers in MY workshop with me!! YAY! ;>

Laura in NH
www.LauraGuptillJewelry.com