So... I added some shades to rocks at random - in total I have 4 different greys and black. Black wash around lava river is still to be done - I will use the technique you guys suggested: wet the rocks, add a bit of black paint and then spread it around.
Also I tested adding more texture to one of the rocks and it made a massive difference. The type of texture is wrong (as it was a quick test with aluminum foil) but it behaves exactly as on the tutorials when being painted - the conclusion is that the large flat surfaces are making it looking weird. I think I got wrong the ratio between the model and rock sizes. I would make them roughly half the size If I were to start from scratch. I am going to have to take a hit on this aspect. I will add some other elements and then reevaluate if the rocks need to to be redone.
Next step is test casting of stone blocks and lava river. I think I have the blocks covered (everything is easy until you actually try to do it...) - I am looking for this style to get a nice contrast with the rocks:
Blocks will be casted with hard casting plaster with addition of buff powder pigment then weathered with sand and powder pigment (probably black and burnt ochre). Can I use acrylic paint instead of buff powder pigment (added to the plaster before casting)? I am also afraid buff will have to much red tint but we will see.
Now with the lava river I would really appreaciete some more help. The plan is to have programmable LED's iluminating it from below (electronics I can cover easily). I have matt perspex installed already:
Next I would like to use some base layer about 5mm thick. It should diffuse the light outside of the perspex but not cause too much of a loss to the intensity. On top of it I will put red glass chippings for textrue and color. Then I would like to cover it with epoxy resin.
I was thinking about using acrylic structural gel from The Range for the base but I have no idea if it will be suitable. I do not even know if it cures transparent or translucent. Other ideas were silicone and hot glue. Hot glue is roughly the transparency I think I should use but applying it to such a big area in relatively uniform manner is not an easy task. I could also mix the resin with someting that would make it translucent. The resin itself should probably be not self leveling as I think the bumps from glass chippings will look much better than flat surface. Would it be possible to just use the structural gel? I would appreciate any suggestions.
Thanks
Michal