This is how i made the rock formation on my Matilda vignette.
Things you need:
1 – Oasis Floral Foam (the green brick).
2 – A real rock or a rock like object which is to be replicated.
3 – Tile grout, celluclay or similar casting material.
Oasis is an interesting substance, ie you can shape it but got to be gentle otherwise it crumbles into dust very easily and once it’s shaped, unlike a sponge, it will retain it’s new form – it’s a one shot affair and there is no turning back!
The stone in the above picture is a real stone, however it’s a geological sample and is of value, hence my need for replicating it without damaging it in the first place, otherwise i’d go ahead and use it eventho it’s going to be a lot more heavy. All i did was to press the stone directly into the oasis tipfirst, easy and steady with as equal amount of pressure as i could apply with and that’s all - rest i mixed tile grout poured it into the oasis. End result was very much satisfactory for the 1/72 scale imho.
Beware not to introduce any runny / liquid substances into the oasis tho, it’s purpose is to absorb very large quantities of liquid and retain it (blackmagik voodoo), florist’s material remember?
It’s uses are not simply mold making, i have used oasis as a base before on this Merkava vignette. It can be shaped and textured with a heat source rather easily such as a cooking torch, lighter or even a hot knife. Be cautious tho, it can turn into dust real easily which can be messy as well as hazardous!
Hope it’s of use to someone out there, happy modelling all!