Lime mortar mix

[Dubbly]

It's been suggested I use the following mix to re-point the side of a 1882 stone built house.
1 x 3.5 Hydraulic lime
5 crushed dust ( Travis Perkins)
2.5 black sand (aka Bowland Stone mortar)
I've seen local walls done in mortar and it's very dark when it goes on and lightens over time.
Does the mix sound about right ?
Is it getting too warm to repoint the 3 storey south-southwest facing wall which gets full sun from around 1300 ? It's scaffolded so could take wet sacking/dustsheets covering soon as it's done. How long should the covers stay on ?

 

[livias]

Do a test piece to see it the colour is satisfactory. You can point now thats fine, but don't stint on the hessian hung away from the surface so there is good airflow and water it too. Leave covers on as long as possible which is generally one of - you can not slide a fingernail into the mortar or the scaffold needs to come down