Foam

I want to make a proposal for "foam" as a new block type.

Foam is a unstable material which dissolves automatically after a specific time. One can place it e.g. as a temporal way across a river or a canyon or let it spawn through a dispenser to create a temporal pitfall. It would be very useful when one just needs a block to step on when constructing or when a block is just needed to place some other block on top. Currently most players use dirt for such purposes, but why removing it with a shovel all the time, when a foam block could simply dissolve.

My suggestion is, that gravel needs to be smelted in a furnace an then gives a foam, which dissolves 1 minute after spawning. If this foam is smeled again, a foam which dissolves after 20 secons is given.