As I wanted to be able to remove them easily, without handling the wagons, I decided to try incorporating a magnet in each one (an idea I saw for coal wagons in a model railway magazine).
The first stage was to cut cardboard bases to fit the bottom of the wagons and the glue magnets to them.
Then I put some clingfilm underneath the cardboard bases, and then made up the loads with papier-mache.
As none of the manufacturers seem to make limestone I glued ballast to the top of the papier-mache and then painted it white.
Once the paint was dry, I trimmed off the clingfilm so it can't be seen when the load is in the wagon.
If I were doing the job again, I would place the magnets closer to the top of the loads as I had to put several magnets together on the unloading tool (a simple block of wood with a magnet glued to it).
The final photo shows the finished loads in place in a couple of the wagons.
