By Carolyn Sirett, Conservator
These past few months the Conservation lab has been filled with archaeological treasures from fur trading posts throughout the province. Artefacts range from small silver buttons, to beads, to awls and even the tiniest of padlocks. My concentration however has been on the treatment of artefacts composed of iron. These objects are usually covered in bright orange, red or brown corrosion products with mud and other debris attached – essentially a conservator’s dream! We love to clean the dirtiest of things because not only does the artefact show beautifully afterwards, but we have the chance to uncover mysteries such as maker’s marks or small design details. Although the main goal of the process is to stabilize the artefact and slow the corrosion process, when these mysteries expose themselves we can’t help but get a little excited.
Cleaning iron has its challenges and I am glad to have been trained in the conservation profession with the latest technology of today. The process of cleaning iron artefacts traditionally involved using a lot of muscle and painstakingly scrubbing off layers of dirt and corrosion with steel wool, glass bristle brushes, dental picks and wooden probes. This takes many hours and almost always leaves a few areas un-cleaned due to a lack of accessibility.
Today the process of cleaning iron artefacts has been simplified; reducing hours of work into a task that now only takes a few minutes. Our lab is fortunate enough to have in its possession a piece of equipment known as an air abrasive unit, which I also like to refer to as my magic conservation wand. Harry Potter would be so jealous. Air abrasive cleaning uses different types of fine powders that are added to a controlled air stream and then dispersed through a fine tipped pen. The pen is controlled by the user who directs the air stream at the artefact and moves it over the surface to the areas needed to be cleaned. And the results are awesome! Because you can direct the air flow to where you want it go – those teeny unreachable places that caused so many headaches, can now be blasted clean.
The different types of powders we use to clean artefacts with include sodium bicarbonate, aluminum oxide, crushed glass, plastic bead and even crushed walnut shell. Here are a few before and after photographs of some things that have been recently treated via air abrasion from the archaeology collection. Air abrasive cabinet and machine – not that exciting
Before and after photographs of axe head cleaned with air abrasion – way more exciting!
Before and after photographs of partial copper kettle cleaned with air abrasion.