This mastic is still used today. As its name indicates it serves to perfect the fixing and sealing of the panes mainly on the frames of the doors and windows.
Its main characteristics are relatively low cost, simple manufacture, the use of natural products, and good longevity.
The manufacture of the putty is very easy: Mix 4 parts of finely divided white chalk with a portion of siccatized linseed oil (*). The obtained beige color paste can be used directly. This putty hardens within a few days when applied.
It can be tinted in the mass with coloured pigments during its manufacture, or painted when it has hardened.
This mastic becomes rigid and brittle over time, requiring a repair of the joint after some years.
(*) The linseed oil exposed to air polymerizes (harden) naturally with time. The addition of siccative accelerates this polymerization which makes the putty quicker to "dry" (to harden). In general it hardens in a few days. On the other hand, if the linseed oil is not siccated, the putty will require several weeks (sometimes months) to become hard enough.