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Ditto Clear


#1

Someone requested I post my experiences with Rio’s Ditto Clear
RTV mold compound. I’m new to mold making and wanted to make a
mold of an expensive wax and save it. Well, Ditto Clear takes two
days to harden which is kind of a bummer. The other annoying
thing about this stuff is after removing from the frame all four
corners and the sprue opening hadn’t hardened completely and were
sticky. I’m pretty sure I used enough catalyst as the rest of
the mold and most importantly the inside was hardened. I put it
under a lamp to warm it for several hours but the sticky part
never hardened. I cut the four corners off. I did a test on a
commercial wax and to try my hand at cutting a mold open, I did
fair at that and seeing the item inside was helpful. Anyway, it
looks like it will accomplish what I want it to do and am making
the mold for the real wax tonite so will you know if it does the
same sticky thing. Dave

Kickass Websites for the Corporate World http://www.kickassdesign.com
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#2

Dave, I have been casting carved wax models for a number of high
quality jewelry stores for the past 20 years… so far, i have
never lost a casting… and the castings are clean and porosity
free. I take a lot of extra precautions in the casting process.

I use the best investment , mixed for strength. all my
investment and water is weighed on digital scales…models are
individually cast in their own miniature flasks. all oven
temperatures are digitally controlled and the items to be cast
are done so at a temperature specific to the item, even if it
means waiting an extra hour or 2 for the item to achieve the
correct flask temp. I have found that it often costs more in time
and materials to make an rtv mold than to cast the wax directly.
If you follow some of the above parameters, you could cast ti
yourself. If you wish, I would be happy to cast your carved waxes
for you… Daniel Grandi http://www.racecarjewelry.com
sales@racecarjewelry.com


#3

Hi: appreciate the offer but I already made the mold, this is my
first time and did a mediocre job of cutting the mold open but at
least the wax is undamaged. Only reason for doing this is that I
paid a wax carver $175 to carve a figurative piece for me and
afraid I’d remember that when casting and sneeze in the melt or
something and blow it. I’ve never really blown a casting but just
paranoid about this one. I wonder if you cast in silver much? I
have a continual problem with pits just below the surface and
have tried just about everything you could name except the de-ox
silver so far. Is it necessery to shake the flask sprue down to
dislodge any ash? Someone suggested that might be the problem?
MOst of my pieces are thick so fortunately can polish away the
pits but this is pretty frustrating. I’m spruing more
intelligently than I used to and that has helped some. I bought
some wax web and not sure if its really doing anything. Also I’m
having a problem with getting a good wax from my mold. I have 3
rubber molds I bought and have gotten successful waxes from
those, and my first RTV mold of a commercial wax ring was able to
get good waxes from those, but all those pieces ares rounded with
little detail. The piece I’m trying to do now is basically a flat
heavy bas-relief piece with a face very detailed carved in it.
I’m using Rio’s Magnajet wax and getting air pockets where the
wax won’t fill. I tried some belt buckle wax which fills mostly
with occasional air pockets but the detail is way too soft and
not useable. Do I need to cut an air vent you think? Do these
vents go outside the mold? Whats a good way to cut these if
needed? I have an awful lot of books but mold making and wax
injecting is barely covered in any of them…any info would be
appreciated, thanks…Dave

Kickass Websites for the Corporate World http://www.kickassdesign.com
Crystalguy Jewelry http://www.opendoor.com/stephensdesign/crystalguy.html
Recumbent Cyclist’s Advocacy Group
http://www.opendoor.com/stephensdesign/bent/rcag.html


#4

Another RTV you might try is GI-300 from Silicones Inc. in High
Point NC. You can make two or three or however many parts mold
according to the way it is set up. For a two part mold, place
the object to be molded in a cardboardbox slightly elevated on a
piece of clay or even an old piece of hardened silicone. Pour
the silicone to the level that will separate easily when removing
from the hardened mold. Once that level is hard (about 3 hours
in a warm room) brush a solution made of a dab of vaseline and a
large squirt of lighter fluid on the hardened mold. then pour
another layer and let harden. Mold will separate without cutting
and will be quite firm for shooting waxes. This material is also
tough enough so that you can pour pewter directly into the mold
without destroying the mold. Just another suggestion if you
aren’t satisfied with the Rio stuff. I found the Rio stuff
rather uncooperative.


#5

Sorry…it’s me again. Forgot to say the silicone stuff needs
to be vacuumed after mixing and before pouring. Then again, it
should be vacuumed after pouring. I’m sure you are thoroughly
confused now, that’s my usual state of mind. Have a lovely day!


#6

Venting your mold will probably help with the bubble problem. Be
very conservative with the cuts. Start off shallow and don’t cut
all the way to the outside of the mold. If you are having trouble
with a particular area not filling then cut to the outside. Too
many vents are usually worse than none so be careful. Also check
the temperature of the wax pot; it sounds as if it may be too
hot. Good Luck, Robert


#7
   Forgot to say the silicone stuff needs to be vacuumed after
mixing and before pouring.  Then again, it should be vacuumed
after pouring.  I'm sure you are thoroughly confused now,
that's my usual state of mind.  

Margaret: do you have a contact number or know one of the
catalog places that carry that stuff? Yes, I WAS wondering if you
had to vacuum it also. The ditto stuff is a real pain to get
bubbles out of, took me 2 hours to mix and ended up vacuuming for
quite awhile to get bubbles off the model. Don’t plan on making
molds of waxes much in the future bvt then again I might if I can
get something thats quick and works well…Dave

Kickass Websites for the Corporate World http://www.kickassdesign.com
Crystalguy Jewelry http://www.opendoor.com/stephensdesign/crystalguy.html
Recumbent Cyclist’s Advocacy Group
http://www.opendoor.com/stephensdesign/bent/rcag.html


#8
   Venting your mold will probably help with the bubble
problem. Be very conservative with the cuts. Start off shallow
and don't cut all the way to the outside of the mold. If you
are having trouble with a particular area not filling then cut
to the outside. Too many vents are usually worse than none so
be careful. Also check the temperature of the wax pot; it
sounds as if it may be too hot. 

Robert and all: Rio supplies this horribly toxic mold release
spray in the Ditto kit and it doesn’t work worth a damn. I talked
to a local jewelry guy here who works at a manufacturing place
and he suggested using talc; I have some parting powder from an
old sandcasting kit and it made an incredible difference. I made
sure the wax temp was right on this time but the powder allows
air to escape and now I’m getting perfect waxes except for the
usual bubbles sometimes. I don’t know why Rio includes this spray
in the kit if it doesn’t work…Dave

Kickass Websites for the Corporate World http://www.kickassdesign.com
Crystalguy Jewelry http://www.opendoor.com/stephensdesign/crystalguy.html
Recumbent Cyclist’s Advocacy Group
http://www.opendoor.com/stephensdesign/bent/rcag.html


#9

Off the top of my head, I haven’t got the number but the company
name is Silicones Inc. High Point, N.C. I use the formula GI300.
They have other formulas but for molding everything from wax to
metal, I find it a very forgiving material. It also is very
detailed. If you want more info, contact me off Orchid. Good
Luck!


#10

I’ve yet to find an RTV silicone rubber that doesn’t improve
with vacuuming. I’m most familier with the Dow Corning E-RTV.
For that, the process is as follows: Immediatly after mixing the
required amount of catalyst with the resin (do this in a greatly
oversized container. A large coffee can works nicely for the
amount of rubber needed for 3-4 molds. In essence, the can is
only about 1/4 full of rubber at most. Less is better. Now
vacuum, watching closely. The rubber will rise up and try to
overflow the can. Just before it does overflow, release the
vacuum valve, letting air into the bell jar. the rubber
collapses. Close the valve again. Just as it is about to
overflow, open the valve. Continue this for about 7 full minutes.
by the time you’re done with that, the rubber will still be
rising way up, but not quite as far, perhaps. It may still seem
like there must be a lot of air, but it will be almost gone, at
least in terms of bubbles big enough to see and interfer with
your waxes. Now pour the mold. The mold frame should also be
high enough to allow at least twice the volume that will actually
be required. Vacuum the poured molds (pour only enough to
barely cover the model) in the same manner as above, for another
five minutes. Be careful that the rubber does not start to seem
any thicker than when you first mixed it. Though it takes quite
a while to actually cure, it starts to begin to thicken in less
than 15 minutes, and you need to be done with the vacuuming and
pouring and revacuuming by that time. By the time you’ve
repeatedly vacuumed and released the vacuum on the poured mold,
you may have had a bit of overflow. that’s OK. Now top up the
mold to the level above the model that is desired, set aside and
rest assured that when you go to cut this mold, you will find no
traces of imbedded bubbles in the rubber. Other RTV rubbers may
require more or less vacuuming, but one key I’ve noticed is that
they seldom give you good instructions on how to do it. Took
some time and experimenting to figure out that it needed to be
risen and collapsed repeatedly, and for about 7 minutes, to get
the required results. (courtesy of AU enterprises and Linus
Drogs, who did that experimenting. I just took note of his
results, and relay them as I recall them. Hopefully I’ve
remembered them right.

By the way, an aside: Not all RTV rubbers are silicone. I
bought a black RTV rubber from Swest (forget the exact name)
It’s a polysulfone or some such name, if I recall. Looks and
handles like a slightly thick rubber similar to E-RTV, except
that it gave no bubbles with just a plain pour, no vacuum.
However, and this is important, It adhered strongly to the model,
which was gold plated over base metal. The instructions mention
casually that it will stick to copper based materials, but I
didn’t take it seriously enough. I was unable to seperate the
rubber from the model without (literally) shredding the mold.
The last of the rubber took vigorous abrasion and solvents to
remove from the model. Clearly a waste of time and money for no
useable mold. The instructions mention the need for a seperating
agent, but don’t say what. I’d assume that a thinned coating of
vaseline will work, but frankly, I’m not likely to use that crap
again. In addition to being a total waste for that mold, it is
no cheaper than the Dow product, and the finished rubber is so
soft that it’s almost laughable in terms of trying to keep mold
dimensions stable while injecting. I’d be willing to guess this
rubber was originally intended to be used in other ways, like
maybe a surface skin mold of a wax or plaster original, the
rubber skin then reinforced with another plaster outer mold, for
pouring was or plaster into. ie, a sculpture molding rubber,
instead of a jewelry molding one.

Peter Rowe


#11

Dave,

Had the same problem with silver casting… Found that if I did
the following the problem just went away!

– Insure that u are using very clean silver … and the pour is
clean…

– Insure the silver is heated to the proper temp … i was
pouring at to low a temp… Watch the ‘bowl’ of the pouring
container for a ‘Red line’ … all the way around the bowl . . I
’‘dump pour’’ immediately… I am doing vacuum casting.

Seems work for me and also got rid of the porosity and gray
sliver problem seem to work … info from an “old, great,
bench dude”

Jim