For the creation of such vases take liter plastic bottle of soda (you can take and more volume). From the bottle cut off the top and bottom (I did first holes with a knife, then cut with scissors).
Plain clay soaked in hot water for 5 minutes, when it is tender, take out and rolled out with a rolling pin, (workplace covered with polyethylene film).
Bottles inserted into the rolled out clay.
Few waited for clay to cool completely.
Now pour in a bottle of gypsum, but not completely, you need to leave a little space.
Then I use just such a bunch of wooden skewers for kebabs.
I wrap it with cling film and tape is still on top.
We put a bunch in the middle of the bottle, if kept bad, we can hold a minute or two, until the plaster is well grab
Somewhere in half an hour, when the plaster is already hard, cut with a knife and scotch tape. And I start to pull out the side skewers one. First pulled out difficult, then it is easy. With scotch tape is also deleted.
Pull out the vase from clay, the top or the bottom (where there is not a place drenched plaster) make a small incision with a knife and carefully remove the bottle with a plaster.
It looks like the inner part.
These are the vases produced in the end.
After drying, the plaster top and bottom of the leveling large sandpaper, cover the bowl with white glue for greater strength
on the vases can make decoupage, decorate salty dough, plastic, or simply paint (acrylic paint plaster better) as you wish.
To answer questions about billing.
grooves on painted vases made in the usual pencil on wet plaster painted first, then walked a few times pressing the lines (sharper than a pencil, the thinner lines are obtained). Gypsum, which is used is called alabaster, he remained almost dry gray and shaky, so it was pretty easy to do. The second batch drained already from another plaster on it to cut grooves was harder (immediately solidified), and better not to use a pencil, and which is a sharp metal tool, think fit cutters on wood, you can still try to cut on a dry plaster, just before it better-sanding sandpaper surface.