How are the large hydrogel beads you get from Amazon etc made? In particular how do they make such big spheres? I know calcium alginate hydrogels can be made up to about 3mm by dropping droplets of alginate solution into calcium ion solution. You can mold big spheres 20-30mm+ but to mass produce for so little money there must be a trick! I'd like to know so I can make my own with controlled sizes and dyes.