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Injection wax


I just got a wax injector finally (never thought I’d want
one…) and want to thank whoever it was that recommended
getting a portable air storage tank fillable at a gas station
instead of an expensive compressor. I did and it works great. I
do have a question about injection waxes though and it concerns
what happens when you put the wax in and heat it up and don’t
use much. When you reheat does the wax become brittle? I paid a
guy to shoot some waxes for me and they were fine but extremely
brittle. A bit suspiscious about that. Anyway, also I got that
Ditto Clear stuff because I have an expensive wax I want to make
a mold of (its basically flat bas-relief item) and also get some
experience cutting the molds apart while being able to see the
item. Does anyone regularly make molds of their waxes and if so
do you have any tips about doing that? Thanks again…Dave

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Hi Dave, maybe I just missed something, but I didn’t see a
reference to casting the wax first. The molds I make have to be
heated to set. That would melt your good wax, and all would be
lost. Hope this helps a little. Joyce


hi dave, it’s best just ot leave the wax pot on. cooling and
melting the wax several times can certainly deteriate the
’memory’ of waxes. some injection waxes are more susceptible than
others. i’m sure you are using an injection wax, right? other
carving, build-up, sprue etc. waxes are not designed to be the
same after being melted and cooled even once. shooting wax is
pretty easy, why did you hire some one? i’ve never used rtv mold
mediums but have some samples sitting in a drawer. be extra
careful with that scalpel next to the molded wax.

best regards,
geo fox


Dear Dave,

If you are making molds of waxes, I think you ought to try our
new CASTALDO LiquaCast RTV liquid rubber. Better, faster,
cheaper, stronger, etc etc.

Send me your shipping address and we’ll send you a free sample

You’ll like it. Ask anyone!

	michael Knight

F.E. Knight, Inc., 120 Constitution Blvd., Franklin, MA 02038 |
508/520-1666 |


Hi Dave welcome to the world of hot wax and air pressure. Ain’t
it great.

I’ve made RTV molds of about 60-80 waxes – all small – over
the past several months. I have had good success with this,
generally. The two point that I’d like to make to you is that, if
you are doing more than a handful, you may have to try several
different RTV rubbers before you get one that has the appropriate
rigidity for your application. One of the compounds which I
tried was from Rio Grande, their Ditto 3D. I found this very
soft and squishy upon curing. It is so soft that I don’t like
using it for injection waxes. This is because I have to squeeze
the mold halves togehter with some force to prevent the injection
wax from squirting out the sides or – worse – out the back end,
toward me. (I’ve tried dropping my air pressure and adjusting the
temp., but it seems that for my pieces and the wax I’m using I
must stick with the pressure and temp.) The second point is that
wax shrinkage may be an issue that you’ll have to deal with. When
your original wax was made it shrunk, perhaps 1 or 2 per cent.
Now, when you make a second-generation wax that, too, will
shrink 1 or 2 per cent. The cummulative effect of this is that
your final wax has shrunk 2 or 4 per cent from the original. This
may or may not be a concern for you, but only you can just this.
If, however, the waxes involved shrink more than this amount, you
can increase the shrinkage problem by whatever cummulative
shrinkages you have.

I’m sorry, I can’t offer any tips on the brittle wax. Perhaps it
getting old, was stored in the open a long time or got heated way
too hot. (just speculation…)

Let us know how the Ditto Clear works for you. I’d like to know.
Jeff Booth


Hello Dave, I have been doing lost wax casting for a long
time… what i can offer as advice is as follows. If you are
looking for an injection wax that does not become brittle after
injection, you should try " plasto wax" I have bought this from .It is called plasto wax. It may also
be available at other suppliers such as Guesswein co. you do not
need to worry about the wax going bad in the pot… normally ,
my pots are turned on and i allow the wax temp to stabilize…
this takes a while and is important when you try to get
consistent waxes. I do not turn off my wax pots for this reason
… it takes a while to stabilize the temp. the electicity used
to keep a pot on all the time is negligible. There are many
different types of wax on the market… some of the best are
made by the Kerr company and available from most suppliers.
Brittle waxes are usually used in large heavy pieces such as belt
buckles and not on Dainty rings. An advantage of Brittle wax is
that it usually can easily be carved with wax burrs without to
much clogging of the burr. Use a steel file brush to remove the
wax from the burr periodically. Wax temp is important as well, so
follow the recommended temperatures of the wax you are using.
Realize that wax pots are not state of the art and that the
temperature controls on them are cheap bymetalic controllers
that are not accurate.Use a thermometer ( preferrably stainless
steel) type. Mold Making. I have not had to make a self curing
Silicone mold in many years… I usually just cast my customers
carved models . I do take extreme caution when casting other
peoples carved waxes… i use the best investment, weighed on
digital scales. even my water mix is weighed on a digital scale.
For wax models, i use the 38/100 investment ratio for strength.
Also when i cast models it is done in small flasks ( no more
than 4 pieces) and is Vacuum cast. The castings that i get are
absolutely clean and free of porosity… ( i use a digital oven)
and my flask temps are adjusted according to the thickness and
weight of the item being cast.

The Contenti co. sells a white 2 part silicone rubber that

takes 16 hours to cure. this rubber has certain advantages over
other silicones in that it is possible to pour white metal (
pure tin) directly into the rubber mold without damage to the
mold… you must vent the mold properly and use some talcum
powder on the surface. The tin is easily workeable and can be
made into an absolutely perfect model that can then be molded in
conventional rubber. this is really good for larger items. Clear
Ditto rubber is also good for limited wax injection. If you
have never cut a rubber mold before , i would not try it on an
expensive wax … it takes a little experince to cut molds. do a
simple pieces first. good luck, Dan



Very interested in the storage tank idea! Have a Vigor manual,
push down, injector … would like to have update with an
automatic injector … do you have ANY idea as to how to attach
the tank to the vigor manual, small, injector… the injector is
in all of the tool books… set the mold on the injector, push
down and its done… but sometimes the injection is bad… figure
the auto with tank would be much better???



Jim, Those push down wax pots are really not designed for
injecting into rubber molds… the original design was used to
inject wax slurry (nearly melted wax) into an aluminium or metal
mold. the idea is to press down on the handle while the metal
mold is firmly held in place on the nozzle… in this manner it
is possible to inject wax into a metal mold as high as 300 lbs/"
which would fill any metal mold… especially if you attached the
top of the plunger to a non-rotating drill press to get extra
leverage. what you need is a air operated waxpot… if you don’t
want to have to buy air tanks and such, the Kerr co. made/ makes a
wax pot with a pump attached to the wax chamber. kerr does not
sell direct, but this kind of pot may be available from The
Contenti Co. the Guesswein co. or possibly Rio Grand. The web
address for the contenti co is ask for
john or Arthur… they would know what i’m talking about. if
they don’t have it, they can get it . Elaine at the Guesswein co
is also a very good person to check with.

If you want to put it together yourself, with no tank… buy an
air operated wax pot from any supplier, buy a foot operated air
pump from any bycicle store… go to a good hardware store to
get the hose and hosebarbs and clamps to connect it all. i
usually put a one way check valve in the hose since many pumps
don’t have one ( without one, the air will leak back out through
the pump). after all this, you are done! If you have any
questions, please contact me. ( i used to design and build
jewelry equip.) Now, i do casting and finished products for
designers. Dan Grandi


Hey Jim: I’m no expert but I used the quick connect connectors
you can get in the same department you find the air storage tank.
The problem with the manual pump injector and the storage tank
idea is the better injectors have an air regulator on the air
line input…this keeps the pressure in the injector at a steady
pressure where you set it. I’m sure you could go to a welding
supply place and tell them what you want to do and it would be a
simple matter of of threading one of the quick connect nipples
into the wax tank on top (actually the regulator would be first
then the connector on top of that. You wouldn’t really need a
quick connect thing just a regulator but not sure if its a
special type or not. This is my first injector by the

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Hi Gang,

Regulators for reducing/controlling the pressure in air lines
are not the same as the regulators for oxy/acet. The air pressure
regulators are much less expensive. They’re usually made of
industrial grade plastics & can’t be used for oxy/gas service.
Most any industrial supply & some of the import tool stores like
Harbor Freight sell them.

They usually have several models to choose from; some come with
a filter & gauge, some with a gauge, some with a filter & some
without either. The cheapo’s sell for about $7.00 but for a few
$'s more you can get one with a gauge. The filter isn’t really to
important if you live in a drier climate &/or drain the moisture
from your

air compressor tank with regularity. If you use the compressor
for spray painting or sand/glass/abrasive blasting, the filter
may be a worthwhile purchase, it traps moisture & other
particulates. The filters can be removed for cleaning. You only
buy it once, so buy it right! It only costs a little more to go
first class; you go just as far, just not as often.



Jim: you know I might have been wrong about your hand pump
injection wax thing. I don’t think those have an airtight sealing
top on the pot, the seal is in the handpump itself I think, you
might want to check this before you waste time and money on your
pot. I found a good Grobet injection wax pot for $240 online and
glad I didn’t get the handpump type which I was warned

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I’ve used Rio Aqua wax for years without problems. For difficult
molds the suggestion to be careful not to hold the plates is right
on. In those situations I find it often helps to use a mold clamp
instead of hand holding. The Rio clamp works well since you can vary
the holding pressure.

Hal Holzer