In one method, I have the impression that to cure a leaf, you must keep it moist or submerged for 3 days or so, changing the water daily to leach out the lime. Then leave it submerged for weeks or a month to finish curing. What happens if you don't change the water?

Another method that has been suggested is to put the leaf in a sealed plastic bag with water for a period to keep the leaf moist by condensation. I guess what I'm asking is, how does this method remove the lime? Must the water here be changed daily or often? Must the lime be removed to cure the concrete?

Finally, if I decide to crete indoors over winter and choose to do a ball or sphere, how can I cure that. I'd hate to quit this fun activity just because of colder weather.

All suggestions will be welcome. I'd like some concrete answers. (Pun intended.)

Or if you need to cure a bunch of stuff get yourself a small chest freezer that is broken ( they are free). You can stack a lot of stuff in there. Pour water in the bottom and start stacking.
The top of the freezer makes a great tufa work bench as well.

All you need to do is keep the piece from drying out as the concrete goes through its cure process. It takes concrete 28 days to reach its full cure and it will do this whether it is in water, plastic bags, or air. It is the dramatic loss of moisture from the surface which creates a moisture gradient and results in stresses due to hydraulic forces trying equilibrate that causes cracks or fractures. (Could I have said that in a more confusing way?) Just keep the surface moist to prevent drying during the first week or two. A lot depends on the shape and mass of the piece. Angles and corners are where stresses tend to concentrate. A solid sphere or ball would not likely crack if it was allowed to cure in air provided there was not an extreme draft.

As for removing lime, what you are really wanting to do is get rid of the laitance. Laitance is a thin film of cement and sand fines which come to the surface of fresh, wet concrete and are not adhered or bonded. When fresh, concrete has a pH as high as 13-14. As it cures the pH should go down to around 9-10 which is still very alkaline. When folks leach out the "lime" from their work they are actually getting rid of the laitance. This is only necessary if you plan to use the piece in such a way that living organisms that are pH sensitive come in contact with moisture from it or if you plan to paint it.

Hypertufa, with peat moss entrained, will have a lot of cementitious material that will come loose because of tiny bits of peat moss at the surface breaking and the rough surface has much more area for laitance. You usually do not put tufa pieces in a water bath unless they are very, very well set; a covering of plastic or regular misting is the method of choice for tufa.

As for indoors, I would think a humid environment inside of a plastic bag would serve well to cure anything.

Thanks too for the advice. I currently have two leaves in one of those shallower containers in a little used bathtub. Easy to get to water supply and handy drain.

I have some of the taller containers too and if the spheres or balls fit in those, I'll be home free.

When do you find time to tufa? You're always Johnny on the spot to tufa and crete questions. Also, you find interesting links to places of interest on the web. You remind me of the first responders of Katrina and Rita. Good on you. Do you have an album of your work on the web anywhere?

I use all these methods, and like them all.
The storage containers.
The bags.
The boot trays.
And the little non working freezer.

I'm also complete out of room, and my back is killing me these last few days of moving stuff around getting ready for winter.:(

Fleur, to put it simply: moisture causes a chemical reaction in the concrete which causes it to harden: if you stick your items in a trash bag, tie it shut and leave it alone (after the initial 24-48 hour cure after which you have messed around with the surface)("messed aroung" being a technical term) for 28 days or so, the trapped moisture will facilitate the cure. It it's during the warm months, throw them in the shade under a tree (you don't want them in extreme heat which the summer sun will create in that closed plastice bag); if it's cold, put 'em in the cellar where they won't freeze and let them cure away to their little hearts' content.

It's my understanding that removing the lime from containers is important if you are anticipating putting lime-sensative plants in there, so that their sensibilities won't be assaulted by the presence of the lime.

2)I'm duplicating the square tufa container on the Hypertufa home page as well. I'm doing it as tutorial because I think the methods used to make it are overly complicated and I would like to show folks how to duplicate that container with 6 square feet of reusable blue styrofoam (3 bucks worth)and a sharp knife. No wood, no sand, no mold release, no voids, no building, etc.

3) Bricks. There has been a lot of interest in making fancy bricks.

4) A tutorial on my simple stepping stones. I know people will laugh at my simple tulip design but the technique is a good one and those with more artistic talent could have great fun with this. The beauty is the color in my stones will never wear off and the exposed aggregate makes them great for non slip.

Fleur I'm far more interested in the process than the end result.
Once my work is curing I'm ready to move on so I doubt I'll ever set up a website to display my work:)