Why did some medieval frescoes survive and others did not?
Reading Time: 1:50 min
The survival of medieval frescoes depends on a combination of materials, technique, environment, and later human actions. When several favourable factors came together, frescoes could last for centuries. When they did not, damage or loss followed – sometimes very quickly.
Factors Favouring the Long Life of Frescoes
Good Technique and Materials
– True fresco (buon fresco) was painted onto fresh, wet lime plaster.
As the plaster dried, the pigments became chemically bound to the wall, making the painting very durable.
– High-quality lime plaster, well mixed and properly cured, created a stable surface.
– Mineral pigments (earth colours, ochres, iron oxides) are naturally resistant to light and ageing.
Stable Building Conditions
– Dry, well-built walls, often thick stone masonry, protected frescoes from moisture.
– Limited exposure to direct sunlight, which reduces fading.
– Stable indoor climate, with slow changes in temperature and humidity.
Continuous Use and Care
– Chapels that remained in regular use were more likely to be maintained.
– Roofs, gutters, and walls were repaired, preventing water from reaching the paintings.
– Some frescoes were later whitewashed rather than destroyed, which accidentally preserved them beneath lime layers.
Factors that Shorten the Life of Frescoes
Moisture and Salts
– Rising damp from the ground draws water and salts into walls.
– As salts crystallise, they cause flaking and powdering of paint and plaster.
– Repeated wetting and drying slowly weakens the surface.
Poor Materials or Technique
– Secco painting (painting on dry plaster) is less durable than true fresco.
– Organic pigments and binders fade or decay more easily.
– Thin or badly prepared plaster layers crack and detach.
Structural Movement
– Cracks in walls caused by settlement, earthquakes, or roof failure break the painted surface.
– Even small movements can cause plaster to detach from the masonry.
Factors that Cause Rapid Damage
Water Ingress
– Leaking roofs, broken gutters, or damaged masonry can destroy frescoes within years – or even months.
– Flooding or long-term water exposure leads to staining, salt damage, and loss of paint layers.
Later Alterations and Neglect
– Frescoes were often plastered over, scraped, or deliberately destroyed during religious or stylistic changes.
– Abandoned buildings suffer from rapid decay due to lack of maintenance.
Inappropriate Restoration
– Use of cement, synthetic paints, or modern sealants traps moisture inside walls.
– Hard modern materials are incompatible with soft medieval lime plaster.
– Overcleaning can remove original paint layers irreversibly.
Human Activity
– Touching, vibration, smoke from candles, and earlier heating systems all contribute to wear.
– Modern pollution accelerates chemical decay in exposed sites.