Ken Horstman Studios

Update to Reconstituting Clay

In my most recent batch of pots I’ve had some problems with “Scumming”,  water soluble salts coming to the surface  sometimes in drying and other times when gazed firing.  It will leave a bumpy rough surface which is not very attractive.  One of the mysteries is that it seems to happen , not to all pieces but to a series of pieces.  

In doing some research I came across this article by Jeff Zamek     one suggestion was a clay body with a lot of bentonite may have this issue ( I use a porcelain body) Another possible cause the article suggested was too much deflocculant such as Darvan 7 could add a soluble salt to the clay.  I’ve always added a teaspoon of Darvan 7 to my water and then added my dried clay scraps and mixed it up.  Never really noticed a problem.  But recently what I have done is when my throwing water is getting thick I add a teaspoon of Darvan 7 and then addition scraps of clay.  Use an immersion blender and making almost a casting slip pour it in my drying slab and recycle it. I feel that may cause of too much soluble salts in a small batch of recycle clay.  The article also recommended adding up to 2% Barium Carbonate to possibly reduce the effects of the soluble salts.

I will just add my throwing water slop to another bucket and add water and barium carbonate  to this mixture when I recycle a bigger batch of clay.  I will follow up in a future   See you in the next post

link below to drying slab  

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