Require a minimum quantity of thermite (1u? 5u?) to break down a wall

[rulib]

As things stand, thermite in ANY quantity can break down a wall.  I have on numerous occasions taken a beaker of water out of a water tank, dumped it on the floor, added a beaker of thermite+phlogiston, and had an Endless Supply Of Thermite on tap.  It also means you can top your thermite beaker up with anything (water from a water cooler, weld fuel, whatever) and so long as you never use it entirely up,  you can rejuvenate your master key.

I propose raising the threshold here from "any thermite" to "1-5 units of thermite" so that endless dilution becomes impossible.  I would even be happy with 1 unit and would be unhappy if the amount were much greater than 5.