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Porcelain Labware: Evaporating Dishes, Crucibles, Funnels and Streak Plates
Mary

Yenziwe ngu-

Mary

14. uMfumfu 2026FI
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Porcelain Labware: Evaporating Dishes, Crucibles, Funnels and Streak Plates

Hard porcelain stands strong heat and most chemicals, so the laboratory's dishes, crucibles and filter funnels are made of it; left unglazed, its white biscuit is the streak plate for testing minerals. Form the pieces, give them a light first firing, dip them in ground-felspar glaze, and fire them hard in saggers, as Andrew Ure (1839) describes for Sèvres. The picture: porcelain evaporating dishes in three sizes, glazed, with pouring lips.
Osezingeni eliphezulu
Weeks with drying and two firings

Imiyalelo

1

Form the pieces

Throw shallow round dishes with a lip and small lidded crucibles on the wheel. For a Büchner funnel throw a cylinder with a flat floor, pierce the floor with many small holes and add a stem. Roll a slab and cut it into small tiles for streak plates.

Izinto zokwakha zalesi sinyathelo:

Ubumba be-porcelainUbumba be-porcelain5 kg

Amathuluzi adingekayo:

Isondo lombumbiIsondo lombumbi
Isigingqi senhlamaIsigingqi senhlama
Isethi yamathuluzi obumbaIsethi yamathuluzi obumba
IrulaIrula
2

Dry very slowly

Ure: dry them very slowly; a little hurry spoils them.
3

Light first firing

Fire them gently so they keep their shape but become strong enough to handle and be dipped in water.

Izinto zokwakha zalesi sinyathelo:

IzinkuniIzinkuni1 as required

Amathuluzi adingekayo:

IsithandoIsithando
Amagilavu Amelana NokushisaAmagilavu Amelana Nokushisa
4

Felspar glaze

Grind felspar very fine, stir it with water and a little vinegar to a thin pap. Dip each dish, crucible and funnel for an instant; the porous body draws the glaze on. Wipe the glaze off the feet. Leave the streak-plate tiles unglazed.

Izinto zokwakha zalesi sinyathelo:

Ucezu lwe-feldsparUcezu lwe-feldspar0.5 kg
AmanziAmanzi2 amalitha
UvinigaUviniga0.05 ilitha

Amathuluzi adingekayo:

UmgquloUmgqulo
Isisefo Senetha EcolekileIsisefo Senetha Ecolekile
Umphongolo omkhulu wokhuniUmphongolo omkhulu wokhuni
Imaski YothuliImaski Yothuli
5

Set in saggers

Set every piece in its own sagger on a flat, sand-dusted base so it cannot stick or sag out of shape; small pieces may share a base if they do not touch.

Izinto zokwakha zalesi sinyathelo:

Isihlabathi EsicolekileIsihlabathi Esicolekile1 kg

Amathuluzi adingekayo:

Ibhokisi lobumba lomliloIbhokisi lobumba lomlilo
6

The hard firing

Raise the fire slowly for about 15 hours to a cherry red, then fire hard until the kiln glows white inside, drawing trial pieces to judge when the glaze is smooth. Cool slowly over days.

Izinto zokwakha zalesi sinyathelo:

IzinkuniIzinkuni1 as required

Amathuluzi adingekayo:

IsithandoIsithando
Amagilavu Amelana NokushisaAmagilavu Amelana Nokushisa
7

Ure's firing, hour by hour

Ilayisha incwadi ye-Jupyter…
8

Limits

The firings, glaze and saggers are Ure's account of Sèvres; the forms of the four wares are ours. A full porcelain firing needs a kiln that reaches white heat.

Izinto

6

Amathuluzi Adingekayo

11

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