Backlit Particles

Hi Folks,

Any thoughts on getting particles to be backlit only ?
I did notice a backlit component to the hair material, (not used) I can’t find any documentation.

I use a translucent surface material with the unlit shader and the smoke effect seems so much better from the unlit side (ie backlit)
The lighting on the lit side seems to bleach out much of the subtle detail /shape.

Thoughts most welcome