Conserving iron

20 Dec 2019

Cym Storey, Conservator, Colchester Museums

While in one of the museum store rooms recently I came across a set of four painted cast iron stove panels (COLEM:1926.5196) in need of conservation. The panels were very dirty and corroded, and losses to the surface paint layer were evident. I took them to the conservation lab for further assessment and treatment.

I asked one of our Curators, Sophie, about the panels, and this is what she had to say:

“These stove panels, also known as firebacks, are traditionally used at the back of a fireplace to protect the wall and radiate heat into the room. Firebacks began to be made in Britain in the early 1500s. They were often decorated either with heraldic coats-of-arms, motifs inspired by nature, or with classical or religious scenes.

These panels show scenes from the Bible including Jesus meeting the Samaritan woman at the well from the Gospel of John, in John 4:4–26. Also depicted is a man holding a chalice – this could be Jesus or St John the Evangelist who in portraits is often shown holding a chalice or cup, referring to a story in which a pagan priest challenges John to drink a cup of poison without being harmed.

These firebacks date from 1820-1830, and although there are a few other firebacks in the museum collection, these are the only ones from this period. They were donated to the museum in 1926, but unfortunately we don’t know where they were used.”

For this blog I will focus on the treatment of the smaller of the two panels depicting the well scene. Here is what it looked like when it arrived in the lab.

The first step was to remove loose surface dust, dirt, corrosion and flaking paint with a brush to get a better view of the surface. At this stage it became clear that multiple thick paint layers had been applied in the past, obscuring details. The metal was also corroding underneath the paint, pushing it off the surface in some areas. This created a mottled appearance that was quite disfiguring.

At this point I had to decide what level of treatment was most appropriate for the panel. I could simply put it in dry storage to prevent further deterioration and leave it as-is, or I could remove the paint and corrosion. I decided to go ahead and remove the paint and corrosion for the following reasons:

  1. It was not possible to fully assess and treat the corroding metal because of the paint.
  2. The thick, partially missing paint layer severely obscured the design; removing the paint would allow me to both treat the metal and bring out the surface detail of the panel.
  3. The panel was hardy enough to withstand the proposed treatment.

I started out trying to remove the corrosion and paint layers mechanically with wire brushes, scalpels, vibrating tools and cocktail sticks. This worked well in some areas but not others. In the end the paint had to be softened chemically and scraped off to achieve a uniform result.

Wire brushes were used to remove most of the softened paint and surface corrosion. Luckily the corrosion was superficial and not too disfiguring.

At this stage I applied alcohol to the remaining paint, which re-activated it into a paste. This allowed me to spread it across the surface in a thin, even layer. The last stage of treatment was to apply a thin coat of microcrystalline wax to the surface by tamping it in with a brush.

The wax was left to dry, then buffed with a soft cloth to bring up the shine on raised areas. The wax will help protect the surface from handling and any fluctuations in environment, helping to prevent corrosion from occurring again.

The transformation of the panel was truly amazing. Take a moment to look back at the ‘before’ image of the panel. Now see how it looked after treatment.

So many details emerged that were completely obscured before. You can now see clearly the facial expressions of both figures, as well as details such as the stones forming the sides of the well, the texture of the rope, leaves in the trees and waves in hair and clothing. The whole scene just springs to life and has an impact that it didn’t have before.

All four panels were treated in the same way.

This was a really satisfying project, and I was pleased to see such a good result when the panels were in such a poor state at the outset. They are now stable and able to be fully seen and appreciated. The panels are currently in our metals store room, a low-humidity space ideal for the long-term preservation of metal objects in our collection.


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