I paint pastels on mountboard. I prime it front, edges and back with acrylic primer and then use a mixture of pigment, marble dust and primer to put a darkish surface on it that will take pastel. As I tend to overdo the pastel marks (I guess that I still think I am painting in oils) and I don't want to keep fixing the painting too much, the support surface clogs up quite quickly. Recently I have been using a thin acrylic underpainting to provide a starting layer that does not affect the 'bite' of the surface. I have even mixed marble dust with the colours in an attempt to keep everything 'rough'. I am not sure about the technique but it has been fun to try when the chances of being allowed out to paint are nil and all is dark and wet out there anyway.
This one of the Salute is pretty extreme for me but helped to prove the concept:
Salute - Evening
I was starting another one of the Salute from the Accademia Bridge - actually I had 10 pastels on the go at that stage - when Maddy came in and shouted: 'Stop - leave it as it is - you have already overworked the first three'. 'But I am just getting started and there is hardly any pastel on it'. 'Leave it alone'. Like any good Dalek I obeyed. I can see what she means but the temptation to keep developing it is irresistible.
Salute from Accademia Bridge - First State
Probably the most successful so far has been this one of the San Marco facade. Maybe the 'architectural' views are more suitable for pastel but I shall persist with the watery ones as well and see what comes out.
San Marco Facade
The days are getting longer, my autumn-flowering snowdrop (galanthus reginae-olgae subsp. reginae-olgae) will soon be joined by Galanthus 'John Gray' and the other early snowdrops and I can't wait to get out there and paint once the rain stops!