Desalination of the Parthian Jug

 Today, I worked a bit more on the Parthian jug. Last time, I had noticed salt crystals on the fabric, so I wanted to see if they would come out. To do this, I set up a desalination bath. I placed the potsherds in plastic baskets and soaked them with deionized water. Just rinsing them got off a lot of the dirt. I then submerged them in tubs of deionized water. The initial reading of the conductivity of the water was about 15 μS/cm. A couple hours later, I took out the potsherds, stirred the water, and again took a reading of the water's conductivity. This time, it measured about 300 μS/cm indicating a fairly high concentration of salts in the solution. This means that salts were, in fact, coming out of the potsherds. Although it is still probable that some of the salts that I saw are insoluble, the soluble salts cause more damage than insoluble salts because they change state when the humidity fluctuates. When the relative humidity is high, the clay seems to 'weep' from the moisture in the salts, and when the humidity is low, the salts crystallize within the fabric. This change in state can cause cracks and swelling. The lower the conductivity reading, the better, but to stabilize ceramics you want it below 30 μS/cm (deionized water is around 5, whereas tap water is around 50). The potsherds will remain in the desalination bath for at least a few days until the water tests low enough or the concentration of salts plateaus. Because I will not be there, Claudia will test the conductivity and change the water each day for me.

Bath time: The potsherds are placed in deionized water to draw out any soluble salts.