If you do a search on the hypertufa forum just using the word "sphere" it will bring up a lot of threads. They tell what type of ball, whether they worked inside or outside their mold and how they made them. You can even purchase a two part mold online.
Wouldn't advise putting something in the center to retain moisture. Instead just keep it in a shady part of your yard. Billie

Thanks! I thought I'd searched, but I obviously had used some other term, because I missed all the threads on this subject. Now to reread all those great posts and come up with a plan ...

Thanks gain - DtD

That's a great picture. I'm intrigued, too.

Hi digginthedirt:
Wow, those spheres are very interesting. Don't know if it's too late to help you but this site has some really good 'tufa info and there's also info on how to grow moss. Might be of help for your project.

Click here for hollow hypertufa garden sphere instructions
Click here for moss growing instructions

I just saw what I think would make a great mold.
Check out the area with sleds, etc. at Target. Thet have a red plastic "Snowman Maker".
Looks like the perfect two-part 12" sphere mold. On clearence for around $7 I don't know why I walked out without one. I'm going back Saturday.
I was thinking the easy way to make it even lighter weight would be to buy a styro ball to encase.

Great Pic! I spoke with a man at a craft show who was selling styrofoam balls covered with lovely green moss that looked much like those (only much smaller). I asked how he made them and at first he didn't want to tell his "trade secrets". I explained that I was wanting to cover tufa containers not styrofoam balls to sell in craft shows. He said he mixed moss and buttermilk in a blender (sound familiar?) and plastered the mixture on the styro. I thanked him and as I was leaving, he said, "Oh, and keep them moist". I think that my attempts to get moss to grow on tufa containers have mostly failed on that last part; it really is tough to keep them moist enough for long enough to get the moss established without a mist system of some sort. Best of luck and I hope this helps!

Good Morning!
From what I've read here the best way to keep moss growing on our creations IS after applying the concoction place the item in a shady damp area preferably in an area where moss grows naturally. Haven't tried this yet but plan to if ever spring weather arrives in Iowa, all we can see is snow and ice, with more on the way today-no green of any kind in sight.
Happy First Day of March everyone- and think GREEN!
Wendy

Remember that new hypertufa is alkaline, and moss needs acidic conditions to grow. Make sure you wash your hypertufa repeatedly to bring the pH down