Here is an old British toy that had a lot of good intentions, but also some unanticipated drawbacks.
Buildings were constructed on allegedly waterproof waxed card bases. The bricks etc. were stuck together with a mortar made from a mixture of flour and chalk powder. It required a great amount of skill to erect buildings accurately, very time-consuming and beyond the patience of most of the children it was aimed at (8 to 14 years). Especially so in cold houses (as most British homes then were) it would take several days for the building to 'set'. Reusing the components involved a process of dunking the entire model in a large bowl of warm water. After the model fell apart the bricks and plaster pieces required lengthy rinsing to remove all organic traces to prevent mould growing on them.
I wonder how well they sold in the USA, as touted in the ad below, from Boys Life for September 1948.