Alginate Molds

I am interested in making temporary molds so that I can get a single
wax from the impression of a ring (say) without removing the stones,
then drill out the wax impression of the stones and refine the seats,
etc.,before making the actual rubber mold. I’d hate to have to make
two rubber molds. Would dental alginate be useful for this, and
could I use my wax injector on it?? Skip, this sounds like your kind
of question, you out there?? Anyone??


Roy, regarding your question:
Last weekend in bronze casting we did that, it was only a 1 piece
mold but worked fairly well. The drawback is that it doesn’t hold up
through more than about 4 waxes - it starts losing definition. And
we poured the wax in instead of injecting.

Donna in WY

Jess: Alginate is a water based impression material and as such is
subject to warping as the water evaporates from the set alginate.
What you want to do cannot be done and expect any kind of useable
result. If you pour hot wax into the alginate mold the water will
steam off and you will have a rough wax model if you have any results
at all. Your wax will probably “freeze” as soon as it contacts the
wet alginate and you are stuck with a lot of work and no useable
result. Best advice is to use one of the siloxane or rubber base
impression materials. Get with one of your dental lab guys and look
for Duralay pattern acrylic. Make your “trial pattern” from that and
then cast it to make the pattern for the vulcanized mold. Sorry
but it looks like you have to do the two step method. Skip any
additional ideas? I’ve been away from the bench too long to be “up
to date” on the latest duplicating technique. Mike

Dear Roy,

This sound like a perfect application for our new CASTALDO Quick-Sil
0% shrinkage no-vulcanize RTV putty, which cures in only 15 minutes at
room temperature. It makes long -lasting production molds , but
there’s no reason you can’t use it as a temporary mold as well.

Give me your shipping address and I’d be happy to send you a small
free sample .

Anyone else out there interested as well: Check it out on our web
site at:

Regards,Michael Knight

Roy: I messed around with alginate molds and in my article in
Lapidary Journal this month you can see one application…I don’t
think it would be a good idea for you, alginate gets bubbles in it
that are hard NOT to get. However Castaldo makes some stuff called
Quik Sil that is a two part silicone putty that cures in about 15
minutes and gets really good detail, enough to make two part molds
even. For a detailed mold thats quick to do I would use this stuff,
its easy to use and won’t hurt anything…Dave

Dear Roy Alginate can work, but may not hold up to wax injection.
There are any number of different dental impression materials which
will not shrink with passing of time as alginate does. These are more
costly, but are excellent for cold mold making. There is a group of
materials known as polysiloxanes and also polyethers which will
permit using as you descibe. They have the advantage of relatively
short cure time as compareto other RTV’s obtainable from jewelry

Hope this helps. Email me if you have any questions. @DrDule

Mike and Jess,

Mike you are right on about alginate. I have even told my clients
not to use it for the impression of the opposing dentition because of
its is so dimensionally unstable and inaccurate, besides, the mix
proportions are so critical.

Mike Knight of Castaldo has an RTV bench curing material from
Castaldo that is marvelous and is compatible with Dura-Lay (a super
product). He will send you a sample to try out. His e-mail address
is The sample is quite large. I have tried
it and my response is “Where have you been all of my life!”. It is
absolutely superb. Using this product you don’t need to vulcanize
and it is made for injecting.

Warmest Regards,


I haven’t tried injecting the wax, but I’ve poured wax on alginate
molds. They’re very good for a one-or-two shot deal, but if you want
any more pieces from the same mold, a good way to get well-defined
repeats is to have your first wax cast and then have a rubber mold
of it made. Dee

Dear Dee,

An even better way is not to use alginate molds at all.

Our CASTALDO LiquaCast and Quick-Sil mold rubbers offer two new,
quick and easy ways to make molds of carvings, waxes, flowers, objects
from nature, etc. And they produce tough, long lasting production
molds that last and last. No need to make a casting and then yet
another mold, with all the resulting shrinkage and loss of detail.

I’d be happy to send you (and anyone else interested) a free sample.
Please give me your shipping address.
Michael Knight

F.E. Knight, Inc.
120 Constitution Blvd.
Franklin, MA 02038
United States of America
Voice: 508-520-1666
Fax: 508-520-2402

Dear Michael,

I started to do a comparrison between your silicones and the Dow
corning product only to see that the sample I have from you is not
useable. Could you send me another sample of both the new products?
Please send them to Todd Hawkinson 308 Prince St Suite 238, St. Paul
MN 55101.

I’ll give you my honest feedback off line.

Best Regards,
Todd Hawkinson
Jewelry Dept.
Minneapolis Community & Technical College