Restoration of school map poster from the spanish civil war period

Restoration of school map poster from the spanish civil war period

Fragment (view complete text on the original post):
The main degradation was the varnish layer (shellac) which causes cracks and dries paper fibres. At the end this oxidizes and turns yellow the object. Its relatively large scale (121 x 117 cm) does not help on its conservation either.
Damp stains were also a minor damage (in terms of physical and chemical stability of the object), though at first glance they were very annoying.Micro cracking of the varnish affected the clarity of the work, dampening colours and blurring lines.