The original recipe for Hypertufa was Portland cement, sand and peat moss. The peat moss detriorates and leaves the piece with little nooks and crannies. This lets moss and lichens grow and gives more of a stone like appearance. Depending on what recipe you use the peat moss will give you a lighter weight mix as opposed to concrete.
1)the mix is not drying, it's curing. Peat moss retains moisture and will give you a slower cure than the straight mortar mix you used.
2) depending on the recipe you use and how much moisture you get the piece to retain while it's CURING you can carve for a couple of days.
3) "I still am not satisfied that the resulting stone is dry" STONE! STONE! I'm sorry I thought you were talking about hypertufa. sorry I'll go away now.
Make your mix, fill your mold,mist with water,wrap in plastic and put in shade, in 24 to 48 hours (depends on size and outdoor temps too)unmold,gently clean up, carve or wire brush, mist with water and wrap back up in plastic in the shade, depending on the temps...open plastic and mist piece with water and wrap back up in plastic for a couple more days,take out of plastic and place in water bath for a couple of days, plant!
You're off to a great start, a nice lantern would be a good next project for your patio. Take a look in the "Gallery" side of this forum, think there's some pics of planters and lanterns over there. Billie

Billie

A lantern!!!???

You don't know what you've just triggered!

Thanks for all the input. In spite of this recent failure, your input, and observations on what went wrong and what went right in this project has me feeling VERY confident :-)

This is really a lot of fun.
Do a search on this forum for lantern and you should see some nice pics and instructions. You can use several containers for molds and stack them when your pieces are cured. Billie