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Piranha Jawbone Mold?

Hello! I have a piranha jawbone that I’d love to have a mold made of so I can eventually sandcast or even melt silver to fill the mold. I was wondering if you had any recommendations as I would not want to lose the original, but not sure what the best options are due to the delicacy of jawbones vs manmade material? Any insight would be appreciated. I even thought perhaps a 3d scanner/printer might be doable without destroying it…thanks again for any help.

@seth-ganoksin-admin is there a way to filter the Search option so you can specify years? Everytime I use the Search function I get very random years and uneable to change that (perhaps because I access the site from my phone and not desktop?).

Your best bet is a clear silicone mold. Then shoot wax copies and then lost wax casting of the wax. I don’t know how delicate this thing is. It might be a tough wax to get out of the mold without breaking it.

An RTV somewhat soft silicon mold material would most likely to the trick, then use a relatively “rubbery” injection wax (not a hard, “crispy” wax) at least for the first tries at what wax to use (there are MANY, MANY formulations with all sorts of different properties).

When making the mold, a cut mold could be made (fastest cheapest and quickest) or make a 2 part mold via using a separation barrier between the 2 mold parts (or 3 parts if a 3rd section is needed to get easier wax removal). Then cast the wax(s) in what ever metal you choose. 3D printing might be an alternative but I do not have any idea of the cost. The mold as described above would be somewhere between $30-40 to $100, wax injections (once the wax type was decided upon) a couple of dollars each. Then the cost of investment and casting and of course the cost of the metal to be used in the casting(s). Without seeing the actual bone, I would imagine the bone structure is very thin in some areas and thee areas may need slight build up or thickening to ultimately get good waxes, some trial and error might be called for unless you can find someone with experience and knowledge in casting items with “large area” thin parameters, not a common situation in most jewelry. This is not an impossible job by any stroke, but it may need a bit of finessing to get good, usable and long-lived jewelry.

I doubt sand casting would work but then again I do not do small sand castings. Generally sand cast items are not real small, real thin or complex forms. Really fine detail/smooth surfaces common in jewelry are not usually or easily possible in sand casting just due to the processes and materials used in such work.

Hope this helps a bit.


John Dach


I have not done my own casting in decades now but in school I remember all sorts of experiments we did.
My hunch is that the best results would be reached by sacrificing the fish jaw for the first metal model. After finishing the casting, a good rubber mold could be made for reproductions.

The fish jaw can be replaced.

A quick search pulled up this discussion on other forums:

Just random thought, since this is not my specialty.

I do disagree with you as the RTV rubbers available today make molding something like this (not metal or crushable with high pressure) easy to do. The heat vulcanized rubber molds that were and still are common in the jewelry trade, do need (usually) a metal model but with the RTV’s this is no longer NEEDED. Also VERY HIGH detail is available with silicon RTV, more so than with heat vulcanized molds or other RTV rubbers. Folks as Castalgo (Sp) Mold materials may have some other thoughts, but you know have mine (for what it is worth).

John Dach


I agree with John; RTV would be the way to go. Bone and teeth burn out poorly at best, since they are largely composed of refractory minerals. The tips of the teeth will likely catch air unless they’re vented, but this can be done in the cutting-out process. A metal piranha jaw would make an interesting object, but I question how functional a piece of jewelry it will be. In my experience, sharp objects only get sharper when they’re cast in metal, and this thing could be uncomfortable at best and a real hazard at worst for those wearing it or innocent bystanders who accidentally come into contact with it. It would be good to consider how to avoid this when designing a piece of jewelry that features this mandible - maybe have the teeth sunk into something else, so they aren’t exposed and dangerous.

Andrew Werby

Unless the jawbone has dried out for years, DO NOT DO A VULCANIZED MOLD. Way back when I was learning to make molds, I had an organic piece that was still a little soft from a bit of moisture. What was it? It was a small bone. Well long story short it exploded in the press and shot parts of it out into the classroom. No one was hit or hurt. I got yelled at long and loud. I doubt anyone who was there or any who took that class after me ever heard the end of it or vulcanized a questionable maybe still not dried out bone or any other organic seemingly hard material. Good luck, I would go the RTV route myself.


Thank you for replying and sorry I haven’t been able to get online to respond. What I meant by delicate is that it’s not man-made so there is only so much pressure that can be applied before breakage. For what it’s worth, I think it has been dried out for roughly 5yrs or so. I included a couple pics just so you can visualize what I’m talking about. I have never made a mold before so I will do some research on the RTV route!

As we have all suggested this can be done with a silicone rubber mold that does not require heat or pressure. There are many on here that can make the mold for you. I charge $150 to make one of these molds. With it you can make 1000s of wax models if you have a wax injector. Or you can send it to somebody like RaceCar jewelry where they can give you a price for the mold waxes and casting in the metal of your choice.

I think what you will find is that making the mold is easy, cutting it on the other hand won’t be. Accurate, well thought-out cutting is the key to successful mold making. I think John’s recommendation to contract a professional with lots of experience to do the job is very sage. Otherwise, you will probably end up with an unusable mold and a destroyed jawbone. Cutting a good, usable working mold of a plain band is challenging as a first attempt, that jawbone will present a real challenge to any mold-maker regardless of their experience, especially if the desire is to keep it intact.