Sounds great to me. Who knows...in another 40 years or so it could be a major roadside attraction..."Exit Now to See the World's Largest Ball of 'Tufa".

With that in mind, I don't know of any reason why you couldn't continue to add to it ad infinitum. Just use some bonding agent to make sure the new layers stick to the old. Have a Ball...a HUGE one.

Tango--would just wetting the original ball be enough to bond or is a agent nescesary?
Paws

Wetting thoroughly is the minimum requirement, but some kind of bonding agent will adhere the new layers much more securely. If you have some "Elmer's" type water-based glue, that can be diluted and works quite well as a bonding agent. The basic chemistry is almost identical to the commercial "Bonds". Do NOT use urethane glues such as "Gorilla Glue"...they expand as they cure.

Thanks Tango--Have several projects I want to add to as the fall/winter progresses.
Paws