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Guestimating wax to silver weight


#1

Hello:

Is there a fairly accurate method to guestimate how much a model
made from green wax might weight in silver? The wax model weights
about 2.5 grams…

DeDe


#2

Check this out.

http://www.dendritics.com/scales/wax-calc.asp

Hope this helps.
Barbra V.


#3

DeDe, the specific gravity of wax is about 1.0, the specific gravity
of sterling silver is 10.36…

Multiply the weight of wax to SG. of silver and you get the weight
in silver.

wax-2.5g x 10.36 = 25.9g

Best Wishes!
Ken Sanders
http://www.sandersjewelry.com


#4

To calculate the weight of a wax model to it’s weight in sterling,
multiply by 10.5. Your example would weigh 26.25grams.

JinK


#5

Hi DeDemetal,

In my jewelry design class, I was taught the following formula for
calculating the required amount of sterling silver (ss) casting
grain: weight of the wax model (in grams) multiplied by 14 plus 5
equals weight (in grams) of ss casting grain.

I was taught that the “14” value represents the silver casting
itself and the “5” value represents the button/sprue.

Based on this formula, a wax model weighing 2.5 gm x 14 = 35 + 5 =
40 gm required ss casting grain

I used this formula with both blue (softer) and green (firmer) wax
models for more than 10 castings for class projects. My results were
completely satisfactory, as were those of all my classmates who
weighed/calculated correctly. I always added a few casting grains
"for good measure" and am still recycling my buttons/sprues into
cuttlefish castings.

HTH, and happy, successful casting!
MAC


#6

Dede, Multiply the weight of the wax model by 10.4 (relative weight
in sterling). That gives the weight of the piece in silver. Many
folks also multiply the result by 1.25 to provide extra silver for
the button (the extra silver that appears above the sprue after
casting) to allow the casting to draw extra metal as it cools. This
often involks disagreements amongst caster…some say it is not
necessary, others say it is essential. To be safe when starting out,
add in the extra!

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut2


#7

DeDe,

In silver it should weigh approximately 10 X the wax weight, 25
grams.

Joel

Joel Schwalb Studio
@Joel_Schwalb
www.schwalbstudio.com


#8
  Is there a fairly accurate method to guestimate how much a model
made from green wax might weight in silver?  The wax model weights
about 2.5 grams.. 

If you have a scale: multiply the weight of the wax by the specific
gravity (density) of the desired metal, in this case 10.5.

If you don’t have a scale you can use the water displacement method.
Put water in a tall skinny cylinder. Mark the top of the water level
on the glass with a sharpie or china marker. Submerge the wax under
the water, and mark the new, higher level on the cylinder. Remove
the wax, make sure the water level is up to the first mark on the
cylinder. Add metal until the water reaches the upper mark.
Warning!! If you use this method for calculating your weight, make
sure you dry the metal thoroughly or your casting will be porous.
Don’t forget to add some metal for the sprue. Tyler Teague wrote some
excellent articles for AJM Magazine on proper sprue angle and
buttons.

Have a great day!
Kate Wolf in Portland Maine
http://www.wolfwax.com
http://www.wolftools.biz
http://www.katewolfdesigns.com


#9

Dede,

Multiplying the weight of the wax by 11 gives you the approx. weight
in sterling. (i.e., your model in sterling should weigh 27.5 g)

As far as I know, all the waxes use pretty much the same weight
calculation.

Karen Goeller
@Karen_Goeller


#10

DeDe,

What you are looking for are the specific gravities of the metals
that you wish to replace the wax with.

Wax has more or less a specific gravity (sg) of 1. Simply multiply
the weight of your sprued wax by the sg of the metal you wish to
replace it with.

Sterling’s sg is 10.4. That is, the object that you made in wax (sg
of 1) will be 10.4 times as heavy in sterling. So if your wax weighs
2 grams, it will weigh 20.8 in sterling. You must also add some
weight for the button, about a 1/3 to 1/2 of the sprued sterling
object, about 7- 10 grams. Total weight in silver for casting
(including button and sprues): 30 grams or so.

If you wish to only know the weight of the ring, then just weigh the
unsprued wax.

Some more specific gravities: 14k= 13.5 18k = 15.6 brass/bronze
= 9 Once you know the wax weight, it’s, simple to figure out the
weights it will be in whatever metal you wish.

When I cast organics such as bark or plant matter or plastic such as
HO figures, etc., I assume that they will have a similar sg as wax:1.

Take care, Andy Cooperman


#11

I just want to thank everyone for their wonderful replys to my
question.

All the best!

DeDe
dedemetal


#12
    Warning!! If you use this method for calculating your weight,
make sure you dry the metal thoroughly or your casting will be
porous. 

Don’t you think that the water will boil off when the metal reaches
212 F? I don’t see how it would be possible for the metal to reach
anything close to melting temperature while there is still liquid
water present cooling the metal.

Bruce D. Holmgrain
http://www.goldwerx.com
@Red_Rodder
JA Certified Master Bench Jeweler / CAD/CAM Solutions


#13
       Warning!! If you use this method for calculating your

weight, make sure you dry the metal thoroughly or your casting will
be porous.

  Don't you think that the water will boil off when the metal
reaches 212 F? I don't see how it would be possible for the metal
to reach anything close to melting temperature while there is still
liquid water present cooling the metal. 

Uh, oh! Now I’m worried that I’m passing on one of those insidious
jewelers myths (Now that would be a great thread!). I was taught to
dry the damp shot (with a hairdryer),then put it in a metal pan on
top of the kiln during burn out, to make sure it was wicked dry- or
we’d have gas porosity.

Now, I’m off to do my homework (that involves calling a couple of
buddies- too much fun!). I’ll get back to you!

Have a great day!

-Kate Wolf in Portland Maine
http://www.katewolfdesigns.com
http://www.wolftools.biz
http://www.wolfwax.com


#14

I have to second the opinion that nothing happens if the shot is a
bit wet when you put it into the crucible. I’ve used torch and on
other occasions forced air furnace to melt shot that came straight
out of the shotting tank, only mostly drained.

We made shot and poured it onto a towel to soak up most of the
moisture. Weighed out the quantity we needed and put it into the
crucible. We never dumped the damp shot directly into a hot crucible.
I make sure my shot is dry before I put it into the electromelt…I
have some superstition about the carbon crucible soaking up water and
maybe weakening the crucible. No evidence to support my action, I’m
just always careful that my metal is dry when I put it into the
carbon crucible.

The water just evaporates when hit with heat. It’s completely gone
before the metal begins to look hot.

Now putting wet metal into molten metal is another matter. :slight_smile: Can
you say, ‘steam explosion’, spraying hot metal around the casting
arena? ! ! ! Voice of experience here. I was not careful about drying
old sprues after they came out of the tumbler from cleaning. There
wasn’t much moisture on them, but there was enough to spray several
grams of silver around. I’m glad that I was at the far end of a pair
of crucible tongs, not leaning over the Hoover melting furnace. I was
lucky and only got a few holes burnt in the sleeves of my shirt.

Chuck in Asheville


#15
  Don't you think that the water will boil off when the metal
reaches 212 F? I don't see how it would be possible for the metal
to reach anything close to melting temperature while there is still
liquid water present cooling the metal. 

Ok, consulted my casting guru- Tyler Teague, this is what he said:

  "-in a way you did pass along a myth but in another way, there
  is merit. Let me explain.  If you are casting with wet grain,
  of course the water will evaporate when the metal temperature
  reaches 212F in the absences of excessive pressure.  The
  vaporization temperature of water increases as pressure
  increases.  In the typical casting machine, this only happens
  when you have water trapped inside of some popcorn shaped shot.
   What would then likely happen is that you would eventually
  have a loud pop and some splattering of molten metal out of the
  melting crucible.  However, the liberated oxygen from the
  evaporated water can cause reactive elements in an alloy to
  form oxides such as cupric, silicon or zinc oxide during the
  melting process. 

  Oxides can cause harm in several ways but here are two that
  can increase porosity.  Scenario one, oxides prevent the
  metallic portions of an alloy from bonding, similar to the way
  that solder will not flow on an oxide.  If your model already
  has stress from a less than perfect design, then grain
  boundaries with oxides are weaker than the metal around it and
  it is at the point of the oxide that the structure will break
  first and appear as "porosity". 

  Scenario two, oxides in a molten metal stream can form
  blockages that prevent proper metal flow in a casting.  Imagine
  the trash that you see under a bridge after a heavy rain.  Any
  time you get turbulent metal flow or a restriction in
  directional solidification due to oxide trash in the stream you
  have a opportunity for "porosity".  So, you should definitely
  use dry shot but mainly so as not to pop something into your
  eye. 

  Now about that water displacement method.  Just weigh the wax
  and multiply by the specific density of the metal that they are
  casting." 

Phew! Thanks Tyler!
Have a great day, you all!

Kate Wolf in Portland Maine

http://www.katewolfdesigns.com
http://www.wolftools.biz
http://www.wolfwax.com


#16

This same phenomena occurs when we pour molten metal into a cold
cast iron ingot mold. That only happened once to me and I learned a
costly lesson not to mention burns on my arms. I now heat the ingot
molds to be sure no moisture is present. I also use WD 40 in the
mold.

Per damp or wet shot, I always buy 24kt shot or bits to make my 18kt
gold alloy. The only time I had a problem with shot is when the mfg
accidentally traped water inside or air inside when you will get a
pop through no fault of your own.

Robert


#17

Hi Gang,

I’ve never melted any wet or damp casting grain, so what I’m about
to say maybe incorrect.

It seems to me that what most folks have said, that the
dampness/water would evaporate long before casting temp is reached
is true. However, if you live in an area that has a lot of minerals
in the water, some of the minerals may stay behind & affect the
resulting casting. It’s probably best to error on the side of
safety & cast with clean, dry casting grain/material.

Dave


#18

If a sprue is wet when you put it in the crucible, when you torch
melt the metal, you liberate the oxygen (H2O) and the metal can
absorb it. My experience is when I use a wet sprue, when the metal is
molten, it looks like bubbling mud, rather than a smooth shiny
surface.

Richard Hart


#19
          "-in a way you did pass along a myth but in another way,
there is merit. Let me explain.  If you are casting with wet grain,
of course the water will evaporate when the metal temperature
reaches 212F in the absences of excessive pressure.  The
vaporization temperature of water increases as pressure increases. 
In the typical casting machine, this only happens when you have
water trapped inside of some popcorn shaped shot. What would then
likely happen is that you would eventually have a loud pop and some
splattering of molten metal out of the melting crucible. 

My experience with trapped moisture is that it cannot be dried with
a hairdryer, paper towels, or even by warming on top of the oven.
This is moisture that has been sealed into a hollow in the shot. In
my experience, it always pops before the metal has formed a pool.

          However, the liberated oxygen from the evaporated water
can cause reactive elements in an alloy to form oxides such as
cupric, silicon or zinc oxide during the melting process. 

Here again, the oxygen is bound to the hydrogen. It is not really
free. There is a continual stream of water coming from the tip of
your torch. Why would you think that water in the shot differs from
the water streaming from your torch?

          Oxides can cause harm in several ways but here are two
that can increase porosity.  Scenario one, oxides prevent the
metallic portions of an alloy from bonding, similar to the way that
solder will not flow on an oxide.  If your model already has stress
from a less than perfect design, then grain boundaries with oxides
are weaker than the metal around it and it is at the point of the
oxide that the structure will breakor 

For sure, oxides are the damnation of every jeweler. That is why
most of us use flux. It helps to dissolve oxides and helps to coat
the metal to further protect it.

          Scenario two, oxides in a molten metal stream can form
blockages that prevent proper metal flow in a casting.  Imagine the
trash that you see under a bridge after a heavy rain.  Any time you
get turbulent metal flow or a restriction in directional
solidification due to oxide trash in the stream you have a
opportunity for "porosity". 

All true.

          So, you should definitely use dry shot but mainly so as
not to pop something into your eye. 

As pointed out above, even dry shot can pop. That is a good reason
to wear some type of eye protection.

Bruce D. Holmgrain
http://www.goldwerx.com
@Red_Rodder
JA Certified Master Bench Jeweler / CAD/CAM Solutions


#20
    It seems to me that what most folks have said, that the
dampness/water would evaporate long before casting temp is reached
is true. However, if you live in an area that has a lot of
minerals in the water, some of the minerals may  stay behind &
affect the resulting casting. It's probably  best to error on the
side of safety & cast with clean, dry casting grain/material. 

Possibly a good point, but personally, I’d find it very hard to
believe that one would introduce an appreciably amount of foreign
matter in this way. Perhaps by boiling down several gallons of water
with the grain immersed, one could produce enough minerals to make a
difference. Perhaps the minerals would even improve the casting. Eh?

Bruce D. Holmgrain
http://www.goldwerx.com
@Red_Rodder
JA Certified Master Bench Jeweler / CAD/CAM Solutions