I have no idea why you would think it would be me or MrDibble. Perhaps you didn’t understand why MrDibble replaced Teapot with Amphora in that context.
Lost wax casting moulds are single use - the parts of the mould outside the cast object are broken away in the case of clay moulds, and dissolved/rubbed away in the case of plaster moulds for lower-temperature metals.
The mould for the dodecahedron could have started with a solid dodecahedral core of dried clay, onto which the wax is built, or the exact form of the dodecahedron, including the holes and the central void could be made of wax, then coated in clay - the middle bit of the wax mould could just be filled by pushing pieces of soft clay into place with the fingers - it’s not even necessary for the ‘core’ of the mould to be perfectly solid - it just needs to coat the inside of the wax form adequately.
There are many puzzles. The knobs on the corners are good for standing the thing up in any orientation, but they could also be good for lashing or tying to with cord or leather thong.
The holes are usually different sizes on opposing faces, except when they aren’t.
One thing that I think maybe supports the idea of this being part of some game, is that the small circle-and-dot markings on some of them are very similar to the circle-and-dot markings of dice and other gaming pieces and boards from around the same period - but that might only be a reflection of the relative simplicity of making such a marking.
Roman dice:
Roman gaming pieces:
NB: if it was a game, I don’t think the game involved throwing or rolling the dodecahedron - they don’t seem to be built for that
Circle+dot symbols are also common religious/metaphysical symbols from the time, including in Neoplatonism (the Monad) and Egyptian polytheism (Sun symbol). As a symbol, concentric circles goes way, way back. And functionally, they are, of course, very easy to make consistently with very simple tools.
I’m not saying that it is impossible that MrDibble is a cover for PZ Myers, but I would be quite surprised (and impressed).
We turn out to be talking about the same process, just that you think positive wax mold plates were made instead of negative clay plates that I imagined, and you understand the need to assemble it in that manner. I think I have gone wrong because I think to much like an industrialist. The craftsmen and artisans of that time wouldn’t be interested in developing a process to produce them more easily in quantity, they’d want to be preserving their exclusive ability to produce such items and maximize their return on each one. The items in available pictures aren’t all that intricate on their faces, but again, we are extrapolating from minimal evidence. i’m getting a headache trying to type this, want to find out more. Someday will rebuild my foundry and try making a simpler geometric figure for fun. I do need to know more about the molding materials available at the time. I was thinking only of clay but they had good volcanic ash cements to use, possibily a finer grain pourable mold material. I’m sure they knew much more about clay molding than I do, my experience is limited to sand casting.
I don’t think the plates were assembled on a solid core, though. There would have been no need to.
Clay would suffice. The Romans were very familiar with using clay slip for ceramics work, the same would work here, with coarser/firmer clay, grog or sand added for strength and temper after the detail is captured.
You seem to be wanting to make this more complicated than it needs to be. Did you watch the Ethiopian casting videos I linked to?.
What would they use then?
I will eventually. Again, can’t see too well right now.
Don’t see the difficulty you speak of, we are describing the same process so far save for how the outer mold is constructed.
Nothing. The wax original stands on its own. No need for a core.
Seriously, just look at how Mangetout did it… here, I’ll link it again.
No, we’re not. I’m talking about direct wax casting. Build a standalone wax model with sprues, cover with slip and clay, fire (in the same fire you’re smelting the bronze in, even), cast. No cement (with associated curing time - look at how long it took Mangetout’s plaster to dehydrate), no carved core, no complications.
You can build a dodecahedron from pieces of paper with just scissors and some tape to hold the edges together. It’s pretty easy. You can “glue” sheets of wax just by melting them a bit, or dribbling a little molten wax onto the edge to plan to join, and it will hold the angle. I haven’t seen Mangetout’s attempt, but i believe i could build one of those out of wax with fairly simple tools. Note that I’ve done similar stuff with foam board, a knife, and ordinary glue. An interior object to place it on would get in the way, more than it would help, i think.
A thin, heated blade run along the joint is the best way to do the melting. Mangetout had the right idea with beveling the edges of his pentagons, but then did “soldering” with more wax, with blowtorch or just painting on melted wax.
Just running a hot knife along the joint would work better, I know from experience.
I bevel the foam to get the joints to meet properly. A hot knife doesn’t work great for foam. 
Anyway, fundamentally, i agree with you that building one of those out of wax is totally feasible. If there were craftsmen who made anything approximately that size with lost wax casting, making the wax model would not have been unduly challenging.
Hot wire, on the other hand…
If a solid core wasn’t used there would be inconsistencies in the outcome. Maybe we only see the ones that turn out well, but there’s no need to try to keep a dodecahedron together in it’s shape and then fill it with material when you could use a solid core.
Some do. I made one myself by welding a knife blade onto a soldering gun tip. But as said above, a hot wire works much better.
I don’t see why. The shape is rigid. If you get the pentagons right they just assemble. It’s probably easier to make twelve same-sized pentagons than to shape a regular dodecahedron out of clay.
And i think the solid core would get in the way.
I’d heard of Russell’s Teapot before but I didn’t make the connection until it was pointed out to me.
Just to note if you were planning to produce more than one of these things, you could make a few moulds to mass-produce the components - a lead mould for the pentagon and another one for the ‘knob’ - if you cast hot wax into a cold lead mould, it would set almost immediately, so you could really crank out the basic wax components, then cut the holes and assemble them etc.
Edit: that is:
- Cast wax into reusable moulds to make pentagons, knobs and sprues as components
- Pierce and decorate the pentagons
- Assemble pentagons and knobs into a wax form, attach sprues
- Coat in clay, leave to dry
- Fire (and burn out the wax)
- Cast bronze into the void in the clay form
Why?
What “fill it with material”? You can leave the centre hollow and the casting would still work.
Sure. But from what I’ve read, we’ve never found any two of these things that are the same, which seems to rule out mass production.