I think I have at last discovered the perfect mortar mix for Hornton
stone, which I think would work well with any soft stone or old
bricks. It's quite sticky and easy to use, and dries to a sandy
colour. The quantities have to be measured in a bucket:
8 sand. I ask for "plasterer's" sand, though it may be called mixed
building sand elsewhere. It's a mix of sharp and soft.
2 lime. Any hydrated lime.
1 cement. I use Mastercrete. I'm convinced it dries to a slightly
darker colour than Blue Circle Ordinary Portland Cement. I also
suspect that the additives it contains make it easier to use. I also
like the fact it can be stored outside.
I find putting a 1.5 buckets of water in the mixer first gives a good
consistency, which can be adjusted if necessary.
The advantage of this recipe is that it's about as cheap as you can
get, and looks just as good as more expensive mortars.