Hi Fleur
I don't change the water during curing. After curing if I figure the lime might be a problem I soak my stuff for a couple three days changing the water every day.
Curing stuff indoors is easy.
Buy one or two of those cheap plastic containers sold for storing stuff. I like the see thru kind. Put water in the bottom, toss in your ball and cover it with a big cloth or towel. That will suck water from the bottom keeping you ball wet.

{{gwi:73514}}

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.

Fleur de Z5, translated: Flower of Idaho ;-)

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 first of all for not saying "Take two asperin and call me in the morning" to my poorly worded title.

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?

Hi Jazz
The downside of plastic bags is the tufa tends to chew holes in them and then they leak.
I use bags as well but I bought a few of those boot trays and set the bags in those.
This can work very well if you use cloth (or paper) in your bag and have it sticking out the bottom through a hole.
You can then fill the boot tray with water and it will get sucked inside.
You can also use the boot tray without a bag. Just cover you work with a towel and let it suck water up over your work. Add water to the tray as it evaporates.
This can also be great if your work area is very dry in winter. You are curing your stuff and humidifying at the same time.
The downside is if you forget to keep the boot tray full of water your piece could dry out and not get a proper cure.

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.:(

Jazzbone, you should go to Washington they way you turn a phrase :)

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.

Hi Fleur
Tufa is mostly hurry up and wait. I work hard for a few minutes and take a break. I just shook up two five gallon buckets of dry recipe and my arms feel like shaky noodles.
My back is killing me but at this very minute I'm in a comfortable chair wire brushing three pieces.
I have 4 computers on my network, one here in my shop, one in my kitchen, and one in my office and a wireless laptop that I use on the road and in bed.:)
Every time I take a break from anything there is a keyboard beside me, although this one is on it's last legs. Shop dust eats them up pretty fast.:)
Three of them also have TV cards so as I'm posting this I'm also watching the news in a small window in the corner of this screen.
I have 25 working computers in all including the first one I got in 1980.:)
And every piece of software known to mankind. About 7000 Cds and DVDs worth.
You might say I like to get really involved in my hobbies.:)

Hi Fleur
About my work.
I hardly took any pictures at all this spring and summer.
I've never been very interested in taking pictures for myself because I'm rarely happy with the look of the end result.
My work is not that spectacular to see in a photograph.
How many half balls and bowls of different colors does anyone want to see. Or stepping stones. I can make black and white stepping stones with pigment and sand blasting materials that glisten like metalic paint in the sun but they don't photograph well at all. My cryogenic perlite pieces are pretty ordinary to look at. Only when you lift them and find how little they weight is anyone really impressed. The only one I photographed was my first, a pink ball I made into a planter.
Folks are astounded when I tell them my stuff is all unpainted concrete and hypertufa. Most think it's a type of plastic or painted clay.:)
I'm not that artistic. I work mostly to show exposed aggregate and pigment colored concrete in all it's simple glory. No paint, no stain.
If you want art and inspiration hang out on Dena's picture site, or L&Ls. That's where you will find artistic inspiration.
That said I have started photographing my latest projects as tutorials.
1) My lantern of balls. It will look rather intimidating to some but it's really nothing more than a stack of balls with holes cut in them with cookie cutters. Very simple stuff anyone with the ball molds could do.
But it is my vanity piece for this fall so I want it to look nice.

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:)

Jazzbone, why do you need to go through the process to remove the laitance if you intend to paint the piece? I haven't noticed any difference (when I paint them) between the leaves I rinsed a lot and the leaves I rinsed never or the leaves I cured underwater or the ones I cured in a bag. Since I just started doing this a few months ago, I am hoping I haven't made the paint finish less able to last by not removing the laitance from the concrete. Any advice?
Laura

Hi Laura
I can't speak to leaves but removing the laitance was a must when painting or coating new cement floors or the paint would last.

Oops that should read the paint would NOT last.
Not removing the laitance is akin to painting over dust or so I was told.

tufaenough - I wonder if there's a way to remove the laitance months after a piece is finished and dry. I haven't been casting long enough to need the information and have been good about curing but it would be good to know.

Hi Fleur
I wish I could help but I really don't know the best way to remove it for our type of projects. Especially when you are trying to keep a super smooth finish.
We used chemicals and scrubbers on big floors before the coatings were applied but that was years ago.
In my Crete projects it's not an issue because they are all exposed aggregate. I scrub the hell out of everything I make.:)

I think Tuffenough is right. A good brushing and rinsing to remove loose particles is fine for painting. When folks use muriatic (hydrochloric) acid for etching concrete before painting I am not sure if the intent is to neutralize the alkalinity of the surface or to "eat away" a very fine layer of the surface to create a good bonding surface for the paint. I suspect it is the latter; its like a micro fine scratch coat for the paint. We usually hear about this being done on floors and patios where the surface has been troweled until it is slick and there is a lot of wear-n-tear on the finished product. For our purposes just brush off the loose stuff and rinse out the crevices, make sure it is DRY, then paint.

Whew,
You all are using some interesting words....Laitance.
I was thinking Efflouresence would be more of a problem then Laitance. Laitance can be caused by more of a slurry of material that can sort of flake off the surface, and can be brushed clear. It can actually take a wire brush if the cementous material has had a chance to bond much.
Efflourensence however is the salts in the mix coming to the surface and creating a little more difficulty in painting or staining. This can actually be exaserbated by soaking your piece initially in a tub of water, rushing the salts to the surface rather than them slowly being 'cured out', hydrated out through the application of spritizing your piece with water. The mix definitely needs water to hydrate enhancing its cure.
Dena
Here is a link to some extra concrete terms, Laitance is not one I had heard of, only experienced.

Here is a link that might be useful: concrete and cement terms