Our recipe from the other night produced a much stronger planter, though I think there’s still room to add a coat of wheat paste to the outside. The rare earth magnets do well if there’s two, but I think the best solution will be to adhere them to the outside of the planter, or embed them in the pulp (which would make things a bit more difficult). Ideally, we’d use one magnet per planter.
This planter is about the size of a cigarette carton, but should be perfect for a sprout of wild flowers or cat grass or something more interesting, with lots of depth for the roots to do their thing. Plus, we’re now thinking that there’s a good amount of surface area to work with for some text / stenciling / recipe, etc.