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Soft modeling wax for lost wax casting


#1

I’m taking my first lost wax casting class, and have a question
about the soft modeling wax. It seems to be the ideal medium for the
projects that I have in mind, but how well does it hold up during the
investment process? I’ve made some thin, flat leaf petals for my
project but since the wax is so soft I’m worried that the shape will
be altered during vacuuming.


#2

I made a replica of a Roman scalpel out of Mold-a-wax, not a
problem.

Regards Charles A.


#3

Hi Beckie,

How soft is “soft?” I make my own soft wax and, depending on the
proportion of the ingredients, I can mold it with my fingers. The
more I touch it, the softer it gets. I take it to a professional who
"converts" it to silver. (Sorry, I don’t have the terminology in
English). I did have a little “droop” on a flower once, but I heated
the metal and was able to “undroop” it.

Ronnie in Argentina


#4

Becky,

I haven’t had any problems with soft wax holding its shape during
vacuuming of the investment. For thinner items I would use a higher
1100F to 1300F kiln temperature for the casting temperature.

Ken Moore
www.kenworx.com


#5

Hi there,

When we do projects with delicate wax or organic material–we only
vacum the investment really well. Then carefully pour into flask,
lightly/gently tap on the sides of the flask to raise any residual
airbubbles and then stop/let it set up…

I have done this for over 30 years down at the Adobe Art Center or up
at CCAC (Calif. College of the Arts) and here in the shop…Maybe you
get a few tiny bubbles but probably not…

Ciao from Oaktown,
Jo-AnnMaggiora Donivan


#6

Hi Beckie

I use Ferris Mould-A-Wax for a lot of my hand modelled patterns. The
only problem I have is if it is too warm in the studio (say over 26C)
when it stays to soft for sprueing so that my trees tend to sag.
Otherwise it is lovely for hand modelling organic forms but it is not
the best for carving where you need sharp detail. It invests and
burns out just fine.

All the best
Jen


#7

I use soft wax for a lot of my casting & it does just fine in the
investment & with vacuuming. The bigger issue is trying to sand it
without squashing it & keeping ring models round. :slight_smile:

(My prof & I just had a discussion about soft vs. hard waxes for
casting because of some sculpted wedding rings I was working on. For
me, The advantage to the soft is that I get a lot of freedom in
making the model & if I carve too much wax away, I can add more,
which is difficult with the hard wax. The downside is that I can’t
do as much finishing work on the soft wax because it isn’t strong
enough.)

Sharon


#8

Sharon,

There is no reason you can’t build up hard waxes. True you do run the
risk of burning yer fingers down to the bone. Added wax is slightly
softer until it sets for a few days, if you can notice the difference
then you are getting pretty damned good.

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand


#9

One of the biggest reasons I think soft waxes aren’t more popular for
professional quality wax models is that ideally, the completed wax
model should have a thin cross section, of less than 1 mm thick. In a
wax model the size of an average ring, say, thicker cross sections
just aren’t usually necessary, contribute to porose casting, are a
waste of precious metals, and make for an unnecessarily heavy
casting.

While soft waxes can be sculpted into many different shapes easily,
it is the “hollowing out” process of achieving that 1 mm ( or less)
thickness that becomes almost impossible with a soft wax. At this
ideal wall thickness, they just collapse in your fingers. Even
"carvable" injection waxes are difficult to bur, file, or hollow out.

Hard carving waxes carve easily, can take on fabulous detail, can be
repaired invisibly and in seconds with the same wax and a heat
controlled tool. Hollowing out hard carving waxes is done easily with
a strong light behind your work, watching the color of the was
thickness change as you bur out the wax. Carving waxes can also be
worked hot, rather a “syrupy” consistency, but when cooled, they can
be again carved as well as hollowed out unlike softer waxes.

A subtractive method of generating wax models by hand, as well as
machining, can be taken to extreme accuracy and detail, and hollowed
out to the most incredible lightness, making a sophisticated casting
with no extra weight than necessary.

Jay Whaley


#10
ideally, the completed wax model should have a thin cross section,
of less than 1 mm thick. In a wax model the size of an average
ring, say, thicker cross sections just aren't usually necessary,
contribute to porose casting, are a waste of precious metals, and
make for an unnecessarily heavy casting. 

I respectfully disagree.

Stuller’s wedding bands are between 2 to 2.5mm. They do have new
lightweight bands that are about 1.5mm. They cannot be sized because
of whatever process they use.

Over the last 20 years I have rarely made a shank less than 2mm. I
re-shank worn out shanks regularly, and I make quality rings that
will take many more years to get thin than the ones I repair. Wider
bands can be thinner than narrow, but I still would not go below 1.5
after finishing.

Particularly, platinum rings that are thin come in mashed and out of
round if they are not thick enough, and 1mm ain’t gonna do. Sterling
rings suffer the same fate.

I have an opinion, I also have experience as I have quite a large
customer base that has been with me for 10-15 years. I rarely
re-shank the rings I design and make for my customers. I have
increased my prices due to the rise in gold prices, some of my custom
rings are competitively priced with Stuller and Quality Gold.

I also do not believe thicker bands have a higher risk of porosity,
not my experience. I regularly cast 100% old gold for my customers.
The are warned of the possible consequences, I rarely have porosity,
if I do, it is with white gold which can be difficult on a good day.

Richard Hart G.G.
Denver, Co.


#11

Just out of curiosity I measured sterling rings made overseas. The
majority of 4mm and 5mm wide shanks were mostly 1.4mm to just over
2.2mm thick.

My wife does the buying and sometimes she buys sterling rings with
shanks that are about 1mm wide x 1mm thick. I know they won’t last
long, I have my standards, and she has hers…there are no
repercussions for her as I am responsible for repairs for no charge
(or refund or exchange) of merchandise purchased from our store.

Two part puzzle rings I make out of any two combinations of two
golds white yellow or red ( or both the same color) are each 1.75mm
thick and 2.5mm wide.

Richard Hart G.G.
Denver Co.


#12

Richard,

I think we are essentially on the same page here. I agree with you
that a cast ring shank should not have a 1 mm thickness. That is
insanely thin for a ring band, and could not be expected to wear
well or not distort over time. I did not consider the shank thickness
somehow in my post. My post had more to do with details of the ring
top, not the shank. While the shank of the ring band should have a
durable thickness, and 2 mm is a reasonable thickness here, I would
not bring that same 2 mm wall thickness up into the top of the ring,
if there is extra dimension there, well above or beyond the finger.
I’m having trouble defining what I’m trying to say.

Let’s say the ring’s design is fairly high off the finger. While the
back of the shank could be thicker, on the bottom of the finger,
there would be no practical reason to have a solid ring top.
Practically speaking, that top section would need to be hollowed out,
allowing for a much lighter ring, with much less metal used, and
would assure a better casting.

Allowances would need to be made in the wax model for thickness
needed in any stone setting involved, as well as structural
considerations of the cast piece.

Oh, and with the newer casting systems out there, really fine
porosity-free castings can be done with about any thickness of wax
model, but these casting machines come with a hefty price tag.

Jay Whaley