I've tried making sand dunes for our FFL/Arab campaign. The results so far have been OK, but there's definitely room for improvement. First, I cut out the shapes of the dunes in thick card. I decided to go for a teardrop shape, rather than the more classic crescent. Then, I used a can of polyurethane insulation foam to make the basic form of the dunes. Be VERY careful using this stuff, use a well-ventilated room or do the work outdoors, wear old clothes, and wear the polythene gloves you get with the can. My first attempts resulted in shapes which were a bit too big and splodgy, but I soon got the hang of controlling the foam, and a teardrop shape is easy to do. With some dunes, I added a little extra shape by hand, by patting them with gloved hands before the foam set. I then left the foam "skeletons" to cure for a full day. After curing, I found that some of the dunes had to be trimmed to shape and I used a bread-knife to do this.

All of the dune "skeletons" had very irregular surfaces where the foam had pitted, so next, I covered them all in a layer of ready-mixed wall filler (and I had to use quite a lot). Try to put the filler on as smoothly and evenly as you can. When the plaster was dry, I sanded it as smoothly as I could, then pained the dunes with a dark terracotta emulsion paint followed by dry brushing with a sand coloured emulsion. I was able to make about seven or eight big dunes from one large can of foam. The process was expensive, and a bit messy, but the results look OK. I think the technique could be refined a lot. One idea might be to make moulds for the dunes or some sort of formers and spray the foam into these to give a better shape. I'd also try to apply the plaster more smoothly and maybe use an electric sander to further smooth them later. Then, I'd cover the dune in watered-down PVC glue followed by fine sand, to give a better texture for painting.

In our games, hills are always represented by contours, so the dunes look different. We don't have enough dunes to lay together into a proper dune field, so we try to evenly space the dunes so that they make up a terrain template. The effect seems to work well as we can use the flat spaces to conceal units in the dune field, and move them through it, with the dunes effectively blocking line of sight.

Hope you find these suggestions useful.