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Discussion starter · #96 ·
This guy had an interesting way to make big concrete pots - but only works if you are making them round. Still interesting, though...

DIY How to make large Concrete Planters from A to Z. Concrete Pottery - YouTube
That's where I got the idea from about using sand. I couldn't find the original video and posted a similar one. Seems that's the way they do it in third world countries. I was wondering if I could build a fiberglass mold on the sand, then flip it over.
 
That's where I got the idea from about using sand. I couldn't find the original video and posted a similar one. Seems that's the way they do it in third world countries. I was wondering if I could build a fiberglass mold on the sand, then flip it over.
Instead of sand or fiber glass why not use a shape that has been hard coated as your model?
 
Discussion starter · #99 ·
Instead of sand or fiber glass why not use a shape that has been hard coated as your model?
Well, in the case of the sand, the sand would be the hard model, and then the fiberglass would go over top of that to make a fiberglass mold. So it would be like the object would be made of sand upside down, and that would be a mold for the fiberglass, then the fiberglass would be turned upside down and that would be a mold for the concrete.

In the case of finding something hard to put the foam around to make a mold, are you suggesting that I just go out and find a very large cheap spherical object somewhere?. Maybe like if I found a tank way out somewhere, and made a mold on that on site and then took my mold off and it was cured?
 
Well, in the case of the sand, the sand would be the hard model, and then the fiberglass would go over top of that to make a fiberglass mold. So it would be like the object would be made of sand upside down, and that would be a mold for the fiberglass, then the fiberglass would be turned upside down and that would be a mold for the concrete.

In the case of finding something hard to put the foam around to make a mold, are you suggesting that I just go out and find a very large cheap spherical object somewhere?. Maybe like if I found a tank way out somewhere, and made a mold on that on site and then took my mold off and it was cured?
There are dealers that cut EPS shapes as requested so you have a round shape & have that shape hard coated this shape will be the negative to make a positive the hard coated foam can be used many times. Are you thinking of pouring these molds or hand applying the concrete?
 
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