what kind of fiber is added to the mix and where can i get it?
Go to a concrete supply store. Look up where in you area they sell and or deliver concrete. There maybe a retail store that sells supplies. Ask for a bag of fiber.
FYI - Typically I only use fiber if I am making a very large hypertufa container - like 2-3ft. Smaller pots maybe up to aprox 22" really do not need fiber in the mix.
Have fun Joe
Here is a link that might be useful:
that's a nice effect with the glass shards imbedded in the pot wall.
what do you do to dull the edges of the glass to keep from getting cut while handling the pot?
I bought a bag of glass glass mulch at a garden center. It is not all that sharp.
Here is a link that might be useful: The Blog