Technical Lead information

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Lead Oxidisation
Like many natural materials, lead is subject to an atmospheric transformation when exposed to the environment. This process, called Oxidisation, is entirely natural and eventually causes the lead to adopt a 'weathered' appearance like that found in traditional stained glass windows.

Why does oxidisation occur?
When lead is exposed to environmental factors, particularly rain or snow, compounds within the metal react to form a natural, nonporous surface coating. This protects the lead by preventing any further reactions with the atmospheric conditions. It is this natural protective barrier, called a patina, that gives the traditional look.

Factors affecting oxidisation
There is no way to tell how quickly oxidisation will occur. The main influencing factors include time of year, weather conditions, location, environment and airborne contaminants.

The process of oxidisation
Several temporary effects are visible during oxidisation and are most noticeable in the initial stages. The lead can take on the appearance of several different colours, often looking bronze, blue, gold and green, creating a similar effect to that of oil on a wet road. This is a natural part of the process and the colours will gradually fade.
Another common part of the oxidisation process is the appearance of discolouration, spotting and white powdery deposits. This occurs when the lead first comes into contact with water. Like the colour changes, this part of the process is natural and temporary. However, as the white powder can often run during wet weather, it is necessary to wipe it off occasionally to stop it staining the glass or the window frames.

Treating the Lead
There is no need to treat the lead as the process will occur naturally. However, Patination Oil can be applied to prevent any discolouration or blemishes in the early stages. Additionally, this controls the process by encouraging the patina to form more quickly. When using Patination Oil, it is important to apply it as soon as the lead profile is installed, as once the natural process starts, and any blemishes appear, it will be too late to use it. Patination Oil can stain glass so apply to lead only.