Lance Foster
04-30-2007, 07:36 PM
I bought a $2.50 inflatable ball at W-Mart, plus about $40 of expandable sealant foam. Taped a plastic container to the top. Then encased the ball with the foam over a couple of days. Once it dried, I cut off the container, leaving a small rim, released some air, then cut the ball around the circumference of the container. Partially buried it my garden, sprayed a silicone lubricant into it, filled it with Quikrete 5000 (about 2.75 bags). I made a concrete vibrator with the pipe out of a keg and an electric tire pump.
I left it in the mold for 2 days. I was being extremely careful removing it from the hole (as I had placed a trash can lid under the mold with a rope looped below the lid in order to pull it out of the hole). This did not work for crap, so I just rolled it up and out with no damage to the foam mold.
I am not sure if I will be able to reuse the mold (it will take a lot of taping as it is now in 3 pieces: the bottom half, with the top coming off in 2 pieces).
The stone is surprisingly smooth. There are some rough areas around the bottom where the vibrator did not work well. I think I can use some concrete resurfacer to fill in the rough areas.
I estimate its weight at around 220.
I left it in the mold for 2 days. I was being extremely careful removing it from the hole (as I had placed a trash can lid under the mold with a rope looped below the lid in order to pull it out of the hole). This did not work for crap, so I just rolled it up and out with no damage to the foam mold.
I am not sure if I will be able to reuse the mold (it will take a lot of taping as it is now in 3 pieces: the bottom half, with the top coming off in 2 pieces).
The stone is surprisingly smooth. There are some rough areas around the bottom where the vibrator did not work well. I think I can use some concrete resurfacer to fill in the rough areas.
I estimate its weight at around 220.