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Graphite-Clay Crucible: Plumbago and Fireclay, the Battersea Works Way (Thorpe 1912)

T. E. Thorpe (ed.) · Public domain

أنشأه

Forge

4. نوفمبر 2026

Graphite-Clay Crucible: Plumbago and Fireclay, the Battersea Works Way (Thorpe 1912)

A graphite (plumbago) crucible is a melting pot of graphite bound with clay: fine grained, it stands the highest heats and sudden changes of temperature, and Thorpe counts it of great value for melting metals. Thorpe's Dictionary of Applied Chemistry (1912) gives the Battersea works process: Ceylon plumbago ground, sifted and digested with dilute sulphuric acid to take out most of its iron, kneaded with about its own weight of fine fireclay, pugged, cut into blocks, pugged again, thrown on a wheel or moulded, dried and baked in saggars. Acid strength, sizes and baking heat are not given. Source: Thorpe, Dictionary of Applied Chemistry vol. II (1912), CRUCIBLES, p. 170. Picture: that paragraph.

متوسط

Several days with drying and baking

التعليمات

Read Thorpe

"Hand-picked Ceylon plumbago is ground, sifted, digested with dilute sulphuric acid to remove the greater part of the iron, and mixed and kneaded to a stiff paste, with about an equal weight of fine fireclay."

Grind and clean the plumbago

Pick over the plumbago by hand, grind it and sift it. Digest it with dilute sulphuric acid to remove the greater part of its iron, which would otherwise pass into the melt; the strength and time are not given.

المواد لهذه الخطوة:

غرافيت طبيعي1 half by weight

الأدوات المطلوبة:

مطحنة

غربال

حمض الكبريتيك المخفّف

ماء

قفازات نتريل

نظارات أمان

Knead with fireclay and pug

Mix the plumbago with about an equal weight of fine fireclay and knead it with water to a stiff paste. Pass it through a pug mill and cut the column into blocks. Pass the blocks through the mill again when you are ready to make crucibles.

المواد لهذه الخطوة:

طين حراري1 half by weight

ماء1 to a stiff paste

الأدوات المطلوبة:

ميزان رقمي دقيق

مِعجَنة الطين

Form the crucibles

Make the crucibles by hand on a wheel, or mould them. Sizes are not given (unknown).

الأدوات المطلوبة:

دولاب الخزّاف

أبعاد غير معروفة

Dry and bake in saggars

Dry the crucibles, then bake them inside saggars. To slow the burning out of the graphite in use, a crucible may be dipped in a paste of clay and a solution of borax.

الأدوات المطلوبة:

صندوق حرق حراري

فرن حراري

مسحوق البوراكس

History and honest limits

Thorpe notes that graphite crucibles are of great value for melting metals but little used for assaying, that the graphite is slowly burnt by metal oxides and furnace gases, and that iron left in the graphite can pass into the metal. He also gives Digby's 1893 mixture of coarse and fine plumbago, Russian clay, china-stone and gas carbon, a different route. The acid strength and time, the sizes and the baking heat are not given; refractory clay stands for his fine fireclay.