Here at Listed Window Refurbishment we use burnt sand and linseed oil mastic as this is the original method for sealing the outside facing of the sash window to the stonework ingo.
Pointing of windows, like painting, is not really a repair we would class this as general maintenance and if properly applied it will last for years.
Patch up repairs to pointing is a waste of money and when re-pointing it is better to rake out old pointing completely, pack the cavity with a recognised material then coat with PVA. Finally, apply the traditional sand mastic.
It is hand applied using a pointing trowel.
The mastic is available in blonde and red colours to match the sandstone building.
This method of sealing is the preferred option for listed buildings and conservation areas in Scotland for its original look.
It can be painted after the surface oil in the mastic has dried out after a few days.
If the mastic is left unpainted it can dry out completely and start to fall out all together after a few years.
This is usually the case with most neglected sash windows.