The anti-slip coating of some modern tanks, like the Israeli Merkava, has always been a headache for the modelers. While some kits have already a quite satisfying texture, others have a poor one, or none at all. In this case, several techniques exist to render this effect.
In this post I want to describe the technique I used for my Merkava Mk. IV. Looking at the pictures shown in this page, you can notice that the size of a single grain is about 5-6 mm (0.20-0.24 in), that in 1/35 scale becomes about 0.15 mm (about 1/200 in).
You can use whichever material has this granulometry: suitably sieved sand (warning: in some countries collecting sand from beaches or riverbeds without authorization is a crime!), marble powder, sanding dust, glitter or, as someone suggested to me, even chinchilla sand!
In this case I'm using some volcanic ash I collected during the 2002-2003 eruption of the Etna volcano, in Sicily. Its grains are actually too big, about 0.2÷0.5 mm:
but after a proper "milling" (I used two iron blocks) the dimensions seem to be close to the desired ones:
The coat can be applied in several ways, the one I use is the following: I apply a mix of water and acrilyc glue onto the surface with a paintbrush, then I spread evenly the powder with a small sieve. In this way the glue, drying, improves the grip of the grains. After that, a coat of primer fixes everything: