Back to Ganoksin | FAQ | Contact

Models for lost wax


#1

I need some advice on creating models for rubber molds for rings and
pendants for the lost wax casting jewelery. There are a couple of
differing opinions at work. I hold with a highly polished finish and
excessive attention to model details whilst retaining a thickness
sufficient to go through the emery and tumbling and polishing
process. The other opinion is that the model does not need to be
polished, details can be delineated during the wax cleaning process,
yada, yada, yada. What is the general consensus here.
Can anyone help?


#2

If you are producing multiple copies of the same item the idea is to
cut to a minimum the ammount of cleaning up in either the wax or the
finished casting

Producing masters for casting gives you that extra bit of time to
get it as near perfect as you can knowing that you may be producing
that item many times over.

You also have to bear in mind that through the process of lost wax
casting and polishing there is going to be some loss of detail (as
well as shrinkage!!) so the crisper the original was to start with
the better.

I prefer to finish my masters by giving them a light mat surface in
a magnetic polisher which I find helps the wax adhere to the rubber
mold - rather than a high polish where I’ve found the wax shrinks
back more, especially on flat surfaces

Mike
In cold & frosty Northumberland


#3

Mr. Robinson, As a profession moldmaker and caster I do have a
definite opinion(s) on the degree of finish on your master model. If
you are going to use a vulcanized rubber a high polish can give you
really nice waxes under the best conditions. However you can still
experience wax flow lines sometimes. I use natural rubber as my first
choice for long term and production molds. They simply hold up
longer. With the use of a natural rubber, a 600 grit finish will
actually improve the properties of wax injection to break up the
action of surface tension. Has anyone else experienced this?..John,
@John_A_Henkel J.A.Henkel.Co.,Inc.Moldmaking.Casting.Finishing


#4

I like my models to be a perfect as possible with a high polish
finish. I find that I then get waxes with a high polish from my
silicon rubber molds and the castings require less cleanup. I have
even gotten an occasional casting that had a shiny surface. Extra
thickness is a must in the model to allow for shrinkage from wax and
metal and to allow for material removal during finishing. A high
polish on the model also leaves less clean up in the waxes. My 2
cents Frank Goss


#5

Hi CJ, Both of you are correct. However, how much do you want to add
to the expense of each part? The better the model to begin with, the
less expensive the final parts are to produce. Fixing every single
wax takes time. Time is money. If the model is made right and the
wax is injected right the wax should need very little or no clean-up.
Which reduces your cost to produce them. Which in turn increases your
profits. We’re all in business to make profits right?

This is true as long as the people shooting the waxes are skilled.
If however you have hired someone off the street and they don’t know
how to shoot them it may be less expensive to have a skilled wax
cleaner. If you spend an hour finishing the model and have someone
who can’t/shouldn’t be injecting and the waxes need to be cleaned
anyway then it doesn’t pay to have you finish the model so well. Why
pay to do the same thing twice?

Ken Kotoski
MPG Repair
www.mpgrepair.com
1-877-262-2185


#6
The other opinion is that the model does not need to be polished,
details can be delineated during the wax >cleaning process, 

I have a real hard time working with people that turn out molds of
unready work. It results in unnecessary work. A properly prepared
mold requires very little and quite possibly no “wax cleanup”. Why
set yourself up to do the same work over and over again for no pay?


#7

C.J.,

The other opinion is that the model does not need to be polished,
details can be delineated during the wax cleaning process,

This statement may be true in some instances, but a skilled model
maker will know enough to simply NOT polish off details… Trust me
when I say, the more work you do in cleaning up any wax model ,
whether it be hand carved or a wax from a mold, the less time you
will spend cleaning your castings… If you have a wax with a bunch
of file marks on it and you cast it like that, you will pull your
hair out trying to get the file marks out of the cast piece… I have
been making wax models for about 10 years now so I have some
experience, For those who will tell you not to clean up the wax
model, well they must like the extra work and the possibility of
taking the “detail” off while they sand and rubber wheel their cast
pieces. I usually don’t chime in on too many subjects but this
subject I couldn’t let go… that’s my 2 cents… Marc Williams
www.marccogold.com


#8

My opinion is that its a whole lot easier to '“finish” wax than
metal.

My first experience along these lines was casting a ring with an
open geometric design. In preparing the wax for casting, I did a
good job on most of the ring, but forgot to remove the marks left
from cutting the open work on the mold. Well, I tried every file,
emery paper cut in all sorts of shapes, etc.

Finally, I read about securing a string to the bench, loading it
with tripoli, threading the string through the openwork in the ring,
hanging on to the other end of the string, and rubbing the ring
back and forth on the string. It seemed to take forever, but it
worked and was a valuable lesson: Look at your wax from every
possible angle to make sure you find and remove anything you don’t
want in your cast ring.

My Two Cents,
Joyce


#9

I have been making wax models for over 25 years and learned early on
that the better the finish on the wax, the less work there is in
cleaning and polishing the casting. When making the wax one has to
account for the polishing of the model and treat the details
accordingly. It is always easier to correct any errors or blemishes
in the wax than in the casting. Joel Schwalb @Joel_Schwalb
www.schwalbstudio.com


#10
The other opinion is that the model does not need to be polished,
details can be delineated during the wax >cleaning process, 

Hi all, I’ve been making my living as a master modelmaker for many
years (I prefer working in wax, but I’m quite proficient in metal as
well). I approach the level of finish on a case- by- case basis. If
I am carving a wax with sweeping curvilinear forms, I will take the
piece to a high finish. If the piece has precise corners, sharp
detail I will smooth out all chatter and file marks very carefully
with my scraping tools (but I won’t polish it). There are pieces I
have carved quickly and cut detail into that I will polish over a
flame- because I want to round out the form and soften the edges.
The same thing goes for my metal models- the curvilinear form will
be polished before molding. The highly detailed piece will be hand
burnished (very tedious!) and taken to the equivalent of a 600-800
grit finish. In my workshops we discuss the level of finish. If
someone is new to the process of carving wax but proficient in metal
work- it may be best for them to take their wax model to 90 percent
completion and do the final 10 percent in metal. Over time, with
more experience that ratio will be more like 98 percent completion
in wax and 2 percent in metal. Time is money. Know what your skill
sets are, honor that and at the same time push yourself to further
your craft. This seems like a balanced approach that encourages and
promotes growth. HTH- Kate Wolf (it’s not supposed to rain in
Maine in December) http://www.katewolfdesigns.com


#11

As far as making models for lost wax mold making, I can offer the
following reasons and suggestions towards getting the best model made
for the job.

Some suggest polishing the model, others say use a 600 grit
finish… My suggestion is this… Once the model is created either
in wax and then converted to metal …or… entirely made by hand in
metal you do the following… remove all blemishes from the surface
through the use of sand paper ,fiber wheels , files or whatever you
are used to using. Then take it to a polishing wheel and polish the
entire piece on that polishing wheel until it is absolutely perfect.
Now, if you wish to use a dull surface for mold making, dull it
down . I prefer a high polished model as I can visually see any
defect in the original. Any defect in the original will be
reproduced , so this is important.

Now, by polishing the model, you may find areas on the surface of
the design that do not polish well… such as grooves or sharp edged
corners. This may require you to use other finishing equipment (by
Hand) to get the design perfect… Now, Remember this… Anything
that had to be done by hand on the outside of the model to polish it
will also have to be done by hand in the cast production pieces. Do
you want to spend a lot of time finishing areas by hand that may not
be neccessary ???

Probably not ! So what you will learn in this process is Not to
create super sharp edges or corners that are not accessible to the
polishing wheel you intend to use.If you need to create a
corner,make sure that the crease of the corner has a slight
curvature ( the word is Slight…) This way, your polishing wheel may
be able to polish that corner without having to use sand paper,
files,… etc to get into the area. . You have now successfully
reduced labor in the finishing process of your item. Imagine that
you had to do 5 minutes of hand work and you had an order for 500
pieces… You would be spending 41 hours doing hand work !!! If you
were paying a casting/ finishing shop to do this and to also polish
the design afterwards, You may have unintentionally increased your
finishing cost by $1300 depending on the shoprate used for this hand
work… Now, when you leave flaws in your model, you can understand
what it may cost you in labor if these flaws did not exist.

If you leave a line , a pit or a rough area or depression where
there should not be one, you will pay dearly in time and effort
removing this flaw at a later time… I can think of a lot of things
I could do with 41 hours of free time !!! This is why I prefer to see
perfected, polished models over dull ones… too many times in the
past we have received dull models and then to find out after casting
300 pieces that there is a slight pit or mark in the model that was
not visible. If we receive a highly polished model from a customer
and there is a pit or defect in it, this is not a problem as we are
aware of the defect and we can remove this mark or pit in the
rubber mold through various methods and eliminate the extra labor
that would go into removing it. This , will now save you money on the
finishing end.

A highly polished model used with a silicone vulcanized mold will
produce a highly polished wax which will result in a smoother
casting. It is possible that you may get a swirl mark in some waxes,
but this is easily eliminated if one knows how to do so … Other time
savers that can be used in model work… texture the inside of the
design where it is not critical to be seen… like the inside of a
ring or the back of a pendant… this will help in finishing with
vibratory machines, magnetic pin polishers and tubs as this area
will look bight and finished after going through mechanical
finishing… then, you can concentrate on hand finishing /polishing
the visible areas . Daniel Grandi

We do casting, finishing in gold,silver, bronze and pewter for
people in the trade as well as model work, mold making, cnc/cad/cam,
soldering etc. contact off list at : sales@racecarjewelry.com


#12

Another letter ( short ) from Jewelry Bootcamp. Several things which
will help cleaning up your waxes before sprueing them for casting is
use of several simple techniques. First use a panty stick ( a section
of panty hose which is stretched over a thin section of wood - for
example a paint stirring stick ) just as you would use a sanding
stick. Second wax can be burnished with smooth dental probes ( just
dip the point into cold water ) and or scraped lightly. The first
process removes a minimum amount of material and the second removes
little, if any.

Another area of vital interest is where and how you intend to sprue
your model. I will not get too deeply into this area, but I will
mention that a sprue on a small , hard to hold item , can be used to
hold the item while detailing is done and before the sprue is
removed. I have just finished the third semester at T I J T at Paris
Texas. During the summer we learned casting and repair work. This
semester we spent setting stones in the rings which we had cast
during the summer. This gave me an overall view which I consider
invaluable. What may look like a short cut today may not be one
tomorrow. This has shown me the necessity of having someone with
an overall view of the entire process overlooking and coordinating
work. My next semester will be spent in precious metals class . ( N0
MORE SILICON BRONZE OR BRASS ) . This is wonderful, the down side is
that I will be expected to pay for any gold losses or wastage which I
am responsible for . This gold loss payments average $ 100 per person
per semester. The better work I can do on my waxes and castings, the
less gold I will need to grind,file, sand or buff off. This is my
beer money I am saving !!! I am including the address below for
anyone who is interested. there are compressed and accelerated
programs available, and other short courses which can be tailored to
fit the individuals needs. Please note that I am a student, and a
satisfied one at this school, but I am still just a student . Please
call the individual below for more She has been of great
assistance to me… And as for the Faculty I can only say -
WORLD CLASS .

tshannon@paris.cc.tx.us TIJT@paris.cc.tx.us Admission
Information 1-800-232-5804

I will make a short note in passing. I am a medically retired
pensioner. My pension will be supplemented by Social Security.
Social Security is being mucked around with and may not be as good in
the future as we were told it would be in our youth. I am learning
another skilled trade which I can continue to work at as long as my
eyesight and hands hold out. First a skilled Tradesman, later an
Artisan, and perhaps at last an Artist. This current recession is not
my first one to have weathered. With these thoughts in mind, I am not
as apprehensive of the future as I might be otherwise. I am very
thankful for the and guidance which I have received on
this ( the Orchid ) site. I am comforted by the friends which I have
made here as well.

Thank You all very much.

ROBB - Retired Old Baby Boomer


#13

I’m not a wax working maven by any means, but for me, the degree of
finish depends to a large extent on the type of wax. If it is a
carving from hard wax, I’ll finish to a fine luster because I can. I
find constructions made of soft wax, sheet wax, etc. to be very
maddening to try and finish to a fine degree, so I’ll do what I can,
and refine the finish after casting.

My $.02,
Dave