Lead figures can suffer a form of deterioration known as «lead rot« (mal del plomo). This phenomenon shows up as a whitish or greyish powder on the surface of the figure and, if left untreated, can cause the miniature to disintegrate completely.
But… what exactly is lead rot?
Lead rot is a deterioration of the metal’s physical and chemical properties caused by an electrochemical reaction with its surroundings — in other words, the metal reacts in different ways depending on its environment. The speed of this corrosion depends on factors such as temperature, humidity, ventilation and the composition of the metal.
The result is the appearance of a whitish-grey substance, lead carbonate, which can even form over the paint on the figure. Over time, this corrosion builds up crusts, causing the metal to swell and increase in volume. If it continues, it can start to crack and shed pieces — as if the figure were disintegrating! The problem is that there’s no magic solution to stop it completely; we can only try to prevent it or slow it down a little.
At the museum, we are researching restoration methods for this problem.
What causes lead rot?
High humidity and poor ventilation in some environments encourage corrosion. Lead also reacts with gases in the air, and pollution speeds up this process. Contact with materials such as cardboard, newsprint or untreated wood, among others, also contributes to the damage, as they release acids that attack the lead. Finally, lower-quality figures are more vulnerable to deterioration due to porosity and cracks that trap moisture.
And the consequences?
Corrosion in lead figures causes a loss of detail, covering reliefs and textures and making them less visible. Over time, the figures become extremely fragile and easy to break. If the damage keeps progressing, the deterioration becomes irreversible, and the miniature can end up disintegrating completely. What’s more, the lead dust generated during this process is toxic, posing a health risk if accidentally inhaled or ingested.
How to prevent lead rot
To prevent it, figures should be kept in a dry environment (under 50% humidity), using silica gel inside plastic boxes or treated wood cases. Figures should be painted and varnished for protection, avoiding handling them with bare hands, and stored in ventilated display cases. In humid areas, use dehumidifiers and avoid storing them in places prone to condensation, such as basements or garages.
How to treat affected figures
At the first signs of corrosion, it’s essential to act immediately to stop it from progressing. It’s recommended to wash the figure with distilled water and sodium bicarbonate, making sure to dry it completely, and then apply a protective measure and a barrier such as Paraloid to help preserve it.
About the author — Alejandro Noguera Borel, Director of the Museo L’Iber and of Fundación Libertas 7. In the world of the lead soldier since the 1970s.
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