by Tessa de Alarcon
So I have written before about desalination to stabilize ceramics with soluble salts, but this time I’m going out into the world, and setting up a desalination station for the Naxcivan Archaeological Project in Azerbaijan.
I had been given a heads up from colleagues Brittany Dolph Dinneen (the previous conservator on site) and Jennifer Swerida (project registrar), that soluble salts may be an issue with the ceramics from the project’s excavations. Salts can be tricky to identify with freshly excavated material, as the ceramic vessels won’t have visible issues until a while after their excavation; once the salts from the burial environment have had time to go through a few cycles of crystallization and deliquescence.
Here at on the Naxcivan Archaeological project, the salts are mostly manifesting as a white haze over the surface of ceramics.
A few are also showing clear crystallization, but the hazing has been the more frequent symptom of the salt problem, especially as this hazing was not observed when they were first excavated.
To confirm that what we were seeing was in fact soluble salts, I poultice the surface.
Once the cotton poultice was dry, I removed it from the surface, re-wet and checked the conductivity, and tested it for nitrates and chlorides with test strips (there are lots of other types of soluble salts, but these are two common ones that are easy to test for). The results were positive, and as you can see the poultice also removed the white haze clearly showing how soluble these salts are.
The next step is getting the water, and while we used to use a similar system at the museum to make deionized water, the scenery is pretty different.
The pot then soaked for a day, while I checked the conductivity until it reached the end point of the desalination process.
Once it was removed from the water I rinsed it with fresh clean water, blotted it dry, then left it to air dry.
Finally, here is the bowl after desalination. As you can see it is now white haze free. Most importantly, it can now be handed over to the Naxcivan Museum with no risk of damage from ongoing salt cycles.
As a final note, it has not been all work, I did get to hike up to the current excavation and I wanted to end on this photo taken from the site, as Azerbaijan is stunning, and I can’t resist the opportunity to share.