The Eviction of Zuul: Paper poulticing food stain from a high fired ceramic

Sarah Giffin

We begin the story with an unassuming blue transfer print bowl, probably from the 1970s:


So clean. So white. Nothing that would ever make you think “Gee, I think there might be a food stain permeating the entirety of this ceramic” or “Perhaps this bowl is actually a portal into the underworld”. Nothing except a little bit of stain along the fracture surface of the big fragment.

Because I am a student, and because we are encouraged to try out different methods of treatment, I decided that it would be interesting to try to poultice the stain out of the break surface. For those uninitiated in the ways of the paper poultice, poultices are usually used to try to draw a stain out of a semi-porous material through capillary action; as the surface of the poultice dries out with evaporation, the stain is moved out of the wet porous material and into the paper on top. That being said, the first step was to soak the bowl to maximize the efficacy of the poultice.

That’s when I got my first glimpse of the demon stain, which the lab named Zuul (from Ghostbusters!).


So I decided to soak the bowl to move the stain around as much as possible…


All of that orange is food stain. Food stain seeping from the depths of the bowl.  Who knew an otherwise white bowl could contain so much orange? It’s probably tomato soup or gravy that over the years soaked through the cracks in the glaze as the bowl was eaten out of repeatedly.

I originally decided to poultice just the edges, but found that it wasn’t sufficient. That was, until I made a discovery…


That orange spot is a piece of paper poultice that accidentally fell on the glaze surface.  Zuul has turned the paper bright orange as it comes out of the glaze. After this miraculous discovery I decided to change my strategy to full surface poulticing.

I poulticed…


And poulticed…


And poulticed…


And I poultice some more for two and a half months until I could poultice no longer, and still Zuul continued to ooze from the depths.


Sometimes we wondered whether or not this was still stain or portal to the spirit world. Unfortunately, although much of the food staining (Zuul) was removed from the bowl, stain still remains particularly in the glaze cracks. This means that the future treatment of this bowl will involve controlled bleaching to try to eliminate the orange colour.  However, bleaching will not physically remove the stain like poulticing did.  It will only eliminate the orange colour from the surface of the stain.


Although the soaking and poulticing treatment ended up causing residual staining in the glaze, it proved to be an excellent learning experience for me. Not only was I able to see how readily stains can mobilize when soaked in water, but I also became a poultice-making pro, and can now expertly apply an effective poultice in a variety of methods.  But let this serve as a warning:  don’t eat out of dishes with glaze cracks.  If you do, Zuul might make an appearance again.

3 thoughts on “The Eviction of Zuul: Paper poulticing food stain from a high fired ceramic

  1. Pingback: Inpainting Decision-Making: An Introduction | Conservation Lab Chat

  2. Have you tried cleaning with ammonia and baby shampoo combination. If its gravy or oily substance the ammonia should disolve it and baby shampoo is a good surfece cleaner.


  3. Pingback: Summertime, and we’re taking it easy! | Conservation Lab Chat

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