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Hard Porcelain Body: Kaolin, Felspar, Flint and Chalk, the Sèvres Paste
Hard porcelain is white kaolin made just fusible enough with ground felspar. Andrew Ure (1839) gives the Sèvres paste: 63–70 parts washed kaolin, 22–15 felspar, about 10 flint powder and 5 chalk, mixed as slips, stiffened on plaster and left to ripen damp for months before it is trodden and used.
The picture: centring porcelain paste on the wheel in the Grand Atelier of the Sèvres manufactory.
Advanced
Days to mix, months to ripen
Instructions
1
1
Calcine and grind the felspar
Calcine and grind the felspar
Pick felspar free of dark mica and rust. Heat it red hot in the kiln and quench it so it crumbles, then crush and grind it very fine with water and sift.
Materials for this step:
Feldspar Chunk2 kg
Water10 litersTools needed:
Kiln
Quench Bucket
Mortar and Pestle
Muller
Fine Mesh Sieve
Heat-Resistant Gloves
Dust Mask2
2
Flint powder
Flint powder
Calcine and quench flint the same way and grind it to a fine powder with water.
Materials for this step:
Flint Nodule1 kgTools needed:
KilnQuench BucketMullerFine Mesh SieveDust Mask3
3
Weigh and mix the slips
Weigh and mix the slips
Weigh the dry kaolin, felspar, flint and chalk in Ure's proportions, stir each into water and mix them into one smooth slip; pass it through a fine sieve.
Materials for this step:
Kaolin Clay Powder6.65 kg
Calcium Carbonate - Whiting0.5 kgWater15 litersTools needed:
Balance Scale
VatFine Mesh Sieve4
4
Stiffen on plaster, ripen
Stiffen on plaster, ripen
Pour the slip onto plaster bats to draw the water out without heat. When it is a soft paste, store it covered and damp for months to ripen.
Tools needed:
Plaster Bat5
5
Tread and ball it
Tread and ball it
Before use, work the paste hard on the wedging table (Sèvres trod it barefoot) until even, and keep it in damp balls.
Tools needed:
Wedging Table6
6
Ure's Sèvres paste, scaled
Ure's Sèvres paste, scaled
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7
7
Limits
Limits
The recipe and handling are Ure's; calcining the flint and the batch size are ours. Grinding flint and felspar makes fine silica dust that harms the lungs over time: grind wet and wear a mask.
Materials
5- 2 kgPlaceholder
- 25 litersPlaceholder
- 1 kgPlaceholder
- 6.65 kgPlaceholder
- Placeholder
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