You could try making the base first and inserting a coupla' short pieces of rebar where the neck will be. Let that harden well, then build up the container portion on top of the embedded rebar. Bending the ends over into an "L" shape on each end also helps secure them. Just a thought...anybody else?...

Hi Serene,

I was ging to suggest using 2 plumbing flanges with a short piece of galv. pipe between them to get you started, then do as tango suggested and add the container portion on top.

Let us know how you make out, it sounds like a great project!

~GardenChicken

Hi Serene, (replace the last e with an a and you have my name lol)

Anyway, what about getting some thin plastic and form it into a 'cone shape'(invision the cones animals wear so they don't scratch their ears :) cover that with hardware mesh then cover with your mix. I have been wanting to do a large urn shaped piece and this is the method that I plan on using. of course you can tweak it here and there and add support like stiffer wire up the sides if needed as you build it. Hope that helps :)
Anela

Serene I would build it in two pieces Urn/Base.
That way if you break one you can replace it.
Also you can avoid most of the problems with slump by going two piece.
How were you planning to mold the urn?

Thanks for all the ideas but now I have more questions. I'm not very strong so can't bend rebar, I'm watching my budget so I can't buys all the stuff to bend rebar or cut it. So I was wondering if I could take GardenChicken's suggestion of using plumbers flanges and pipes but instead use PVC pipes?
Would this work the same as metal?

tufaenough: I though about taping a ball to a cardboard carpet tube to use as a form for the urn. I would form the tufa around this. I could take another cardboard tube to form the stem. I haven't figured out what to use for the base.

Serene

Do you have your basic urn shape that you could show us? A website you can point at and say "Something like that".

Sue

I made some urns a few years ago, bought a plastic urn from HD, you can take the base off and cast them separately .I oiled it inside and used plastic sheet too. Put the tufa inside, came out easily, looks very nice, antique.For the top part, inserted a plastic flower pot in the tufa, I removed it later. Wasn't easy!

Andrea

Serene, you could use pvc (schedule 40 or 80, NOT DWV) as your framework. You'd just need to use larger diameters to get the strength you require. You could probably find scrap pieces at a plumbing shop in the size needed too. No need to buy a length of whole pipe unless you are sure you'll use it for other projects. Good luck.