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I recently purchased a light green Fondoso pitcher. (I’m not sure of the official color’s name, but it’s a jadeite hue.) Its interior is glazed in white. I brought it home and gave it a couple thorough washings with dish soap. It doesn’t have any obvious discoloration, and when filled with water, the water remains clear and tasteless. However, any time water contacts the exterior of the pitcher for more than a brief hand-wash and dry, it leaches a rusty brown color. The residue is not sticky and has no smell. It’s easily removed. I submerged the pitcher for about the last 24 hrs. and have had to change the water twice because the water has gotten so discolored. It looks almost like tea after a few minutes!
I’ve never seen anything like this. Is this common with Red Wing pottery or with this line or glaze? The only thing I could think of is that red clay was used and the glaze is thin, but even that seems a stretch. Is there anything I can do to clean it so that the film no longer forms? Any expertise you can offer would be most helpful.
Red Wing did not use red clay to make dinnerware, so that’s not the source of the rust colored residue that is leaching from your pitcher. The problem is almost certainly due to crazing. Crazing occurs when the clay and the glaze shrink at different rates, leading to fine cracks in the glaze. This was a common problem with the glazes used to make early Red Wing dinnerware such as Fondoso. Once an item is crazed, liquid held by the item can seep through the glaze and into the clay. Most likely the rust colored material you see came from coffee, tea, cola or some other dark liquid that seeped into the body of pitcher over repeated uses long ago.
As you have seen, soaking the pitcher in water will draw the contaminants out of the clay. The easiest and safest way to clean your pitcher would be to simply submerge the pitcher in water for as long as it takes to remove the contaminants. Change the water when it is dirty. When the water remains clear your pitcher should be clean. This process may take weeks or longer. Some people use bleach (I do not recommend this) or hydrogen peroxide (the 30% or 40% strength found at beauty supply stores, not the 3% strength used to clean wounds). Baking the item on low heat has been used to remove greasy contaminants.