Wednesday, July 7, 2010

First clay recipe: CDF P-MF #1

I just got some SEM (Scanning Electron Microscope) images done of the commercial plaster-based powder we have been using with the machine...

SEM’s of commercial powder. Note the angular morphology.

It looks like the largest particles are about 100 microns (equivalent of a 140 mesh). However, when sifting, I found residue on screens as large as 40 mesh (417 microns). Perhaps there just happened to not be any of these larger particles in view of the SEM samples. In any case, I’m going to trust the mesh over the SEM.

With the porcelain clay dried, I milled it through the jaw crusher and plate mill. I then screened it through the 40 mesh screen. The powdered sugar and Maltodextrin were also screened through the 40 mesh screen. The Maltodextrin left a small residue on the screen which I didn’t include in the batch.

The final recipe is:


66.6% CDF P-MF Cone 6 Porcelain (-40 mesh)
16.6% Powdered Sugar (-40 mesh)
16.6% Maltodextrin (-40 mesh)

(Note: -40 mesh means smaller than 40 mesh)

Everything was weighed out, then placed in the dry mixing bucket and left to mix overnight. I have made an improvement to the bucket. The fins now extend all the way up the bucket. Also, I have installed a coarse screen which bisects the bucket (thanks for the idea, Mark) to further promote mixing.

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