I have posted some new updates to the Grand Trunk Southern thread in the Layout Engineering area, in which I note that I am ready to move on to scenery. I know the basic formula for ground goop, but have found it very difficult to find fine vermiculite in Southern Ontario. My question, is that I assume it is just used as a filler as opposed to having a role in binding the materials together. In that case, could it be replaced with other fillers, such as fine sawdust, or in fact, just double up on the amount of sculptamold. I bought a 50lb box of sculptamold about 10 years ago and it is probably more than double what I need for this layout, so it is not a cost issue. Any input would be appreciated.