Ballast cement

PVA glue mixed 50/50 with water, and just a drop of washing up liquid.

Get a plant spray and a BIG eye dropper (chemists sell them) - lay the ballast and pump a mist of water over it with the plant spray (do not point at the ballast).

Mix up PVA with water and apply with the eyedropper (carefully). If the ballast is dampened this works okay.

Worth getting is 'book binding PVA' which stays 'rubbery' and helps with the noise.

HTH

Mike

Try water based matt varnish watered down 50/50

I prefer to use copydex mixed 50/50 with water and a drop of washing up liquid. Advantages are it does not go rock hard like PVA but stays rubbery and you can take up your track and reuse.

Martin

Small point to add to other people's recommendations:

The pre-wetting spray should have a dollop of isopropyl alcohol in it, or else a drop or two of dishwashing detergent. This will reduce surface tension, and the stuff will actually soak into the ballast

NB that the glued ballast will be a shade or two darker than the original colour, so allow for that when concocting your mix from the supplied colours.

I've always wetted the ballast with 70% isopropyl ("rubbing alcohol" as it's called here in the states). Then a mix of artists matte medium and water - about 3 parts water to one part matte medium, but that may vary as the density of the matte medium seems to vary from one bottle to another. There's a cheaper matte medium sold as "Mod Podge" at craft stores, but I don't know if it's available in the UK.

Oops - well spotted, forgot the detergent

Mike