Any image is appropriate, as long as is of something remotely connected to 'tufa. And folks familiar with graphics software are always welcome. Now I know I can direct questions to you :-)

It looks like the diameter of your ball will be about 2"(?). It might actually be easier to coat a small child's ball (like a rubber superball) than to cast a mold and join the pieces together. I've had success with tennis balls but I think that's larger than you have planned.

If you're decide to coat a rubber ball with 'tufa first cover it with drywall tape or something to give the 'tufa a purchase. Also, it works better for me to apply several thin layers.

peak

Here is a link that might be useful: help with round tufa balls

Hi peak
The ball is actually 4" inches in diameter and the tufa will go inside the ball. Same size as my posts.
I will cut the ball in half and stuff both sides full of tufa. Put my rebar between the two halves and tape the ball back together.
I will line the inside of the ball with handiwrap so I can easily remove the ball once the tufa sets up.

David, don't worry about the rebar turning free, it will stick to the tufa so strong, you won't be able even to move it. To have pockmarked surface, I use big pieces of salt ( the kind we use now, on ice) to put inside the mold, the tufa won't stick to it, irregular holes, if some got too deep into the tufa, you can wash it out with water later. Or the rain will do.

Andrea

Tufa balls galore! Hmmm... which ones are solid and which ones will float???

{{gwi:65465}}

Nice balls :)

Ooh GC those ar etoo cool!!

David, I agree that there is no need for nails in the rebar. Concrete will hold very strongly to the metal. No worries there. But if you really want to be sure I'd think bending the tip a bit off center would work just as well and be alot less trouble than trying to drill through rebar.

Also I think if you don't have some way to support the ball mold you'll get slumping. Maybe have a box of damp sand handy to hold the lower half in shape and keep it from flattening out under the weight of the tufa. I think glas light globes would be alot less hassle all around, but will be a little more expensive.

Mike

Thanks Mike.

I'm going to try to find glass globes in a 4" size.
I think they are pretty cheap although a reusable mold would be nice.
I'm going to pick up some plaster of paris next trip and see if I can make a 2 part mold of a glass ball.

I saw some floating balls at Sorticulture a couple of years ago. They were made around the wiffle type ball (of course without the holes) and had gems embedded on the outer portion of the tufa. Very fun and simple to do.
Dena

Well I'm on the job!
First ball is in the 4" candle mold and I'm nervous.
I oiled it up (Olive Oil, extra virgin, it's all I have :) )but I suspect Crisco or lard might work better.
The mold was over $20 CDN with tax.
I'm going to have to use it sparingly as it's a bit fragile and I'm sure the caustic concrete is not going to be kind.

I needed a small mold of a frog (any CDN online suppliers?)but forget to get while at the candle shop.
Considering it's -30C today I'm not going out.

Woohoo! Hope it comes out great!

BTW, I thought the same thing about Crisco but it didn't work well. I don't know why.

Deb

David, What about carving out the ridgid foam insulation for two half ball molds? I'm also wondering if you could press something into the foam to get a smoother half sphere. I'm taking silversmithing and we use dapping punches to form spheres. Wondering still (we learned how to do cuttlebone castings last semester) if you could make the two half spheres in the ridgid foam, carve out where the ball would be then cut out a funnel shape to the top of the mold. Tape the two sides together then pour a "wet" mix in through the funnel. You'd have to shake or tamp the mold to get out air pockets.
Didn't the plastic wrap leave lines and wrinkles on the ball? I spray just about everything with PAM cooking spray. Billie

Hi Billie
Using foam for the ball molds sounds like an excellent idea.
I might be able to coat one of my balls with coarse grit and use a drill to spin the ball into the foam cutting the mold. I think filling each half and then pressing the molds together is the only way to avoid gaps.
I was using too dry a mix which was silly considering the balls don't need strength.

Plastic wrap left very tiny lines which polished off very easily. The balls have a 10mm rebar in them.
I chucked this in my drill press. I waxed up the palms of heavy leather gloves and using glass sand blasting grit (it sticks nicely in the wax) I just hand polished the balls at high speed. The gloves stood up very well with no wear at all.
I have two balls now, neither are great (gaps in the surface so I'm going to a wetter mix.

I'm involved in a renovation this week so it will be next week before I can get back at it.
I have pictures and will document my steps (working and not working) on one of the freebie webshot sites when I have a bit more time.