Saggars Used


All of the saggars used in the Last Bottle Oven Firing were specially made for the event THE DIAMOND CLAY CO. LTD of Hartshill, Stoke-on-Trent.

Careful planning went into ensuring the correct quantity and shapes were ordered for this specific firing. The inside walls of each saggar were washed with glaze before the firing (to prevent the porous saggar effectively 'sucking glaze' from the products it contained) and the top rim and bottom edge of each was smeared with 'slop bone' wash (to prevent wad clay sticking to saggars in the bung.)

750 Oval saggars
  • 9” (23cm) inside width x 18” (46cm) long x 12” (30cm) high
  • All washed
  • Each saggar identified with cobalt stencil signifying last firing
  • 694 actually required

500 Round saggars
  • 11” (28cm) inside diameter x 12” (30cm) inside height
  • All washed
  • Each saggar identified with cobalt stencil signifying last firing
  • 480 actually required

51 Oval hiller saggar and oval bats
  • To suit oval saggars as lids. Traditionally very low height saggars called hillers were used to cap the top-most saggar in a bung in the oven. It was not possible to obtain this sort of saggar for the Last Bottle Oven Firing so flat refractory bats were used instead. They were washed with slop bone to prevent them sticking to the saggar below.

32 Round hiller saggars and round bats
  • To suit round saggars as lids. Washed.

In addition, Gladstone provided 0.5 cwt (25kgs) broken saggars

  • for use as packing and scotches (wedges) between bungs of saggars in the oven to stabilise them. 

0.5 cwt (Half Hundred Weight ) broken saggars 
  • For use as packing and scotches (wedges) between bungs of saggars in the oven
  • From Gladstone yard

The trial layout of saggars in the oven

On Saturday 22 July 1978, at 09:00, Mr. Alfred Clough (Fireman responsible) together with a team of volunteers, planned the layout of saggars in the bottle oven which was to be used for The Last Bottle Oven Firing in The Potteries.

The oven at Hudson and Middleton Ltd. had not been fired since the early 1960s. Little was known about how it was used or how saggars were placed in the oven. The trial layout concluded that the following saggars were needed and how they were to be laid out:

ARCHES     14 bungs of oval saggars, 14 high
1st RING      27 bungs of oval saggars, 14 high
2nd RING    17 bungs of round saggars, 15 high
3rd RING     11 bungs of round saggars, 15 high
4th RING      4 bungs of round saggars, 15 high
FILLING IN 10 bungs of oval saggars, 12 high on average

TOTAL BUNGS = 83 comprising:  51 ovals and 32 rounds

Hillers (or bats) to cover the topmost saggars in the bungs = 83

TOTAL OVAL SAGGARS = 694 (go for 750)
TOTAL ROUND SAGGARS = 480 (go for 480)


During the firing of a bottle oven some areas became hotter than others. It was found impossible to ensure all quarters of the oven were consistent. Mr. Clough, the fireman, together with Ted Lockett, the Cod Placer, discussed the position of particular wares in particular places. White ware would be placed in hotter spots. Wares with coloured decoration needed relatively cooler spots if the colour was to survive.

Here are Mr. Clough's hand written instructions.

Arches 14 Bung - 14 High
First Ring 27 Bung - 14 High
First Ring and Arches = 41 Bung

Bottom 3 saggars - Coloured Glazes (Strong colours, not yellow finish)
Top 4 saggars same
Middle 7 saggars White

41 x 7 = 257 Coloured
41 x 7 = 287 White (not Red Clay)

After the First Ring and Arches
Any colour and deco which will stand up to a 12 Bullers Ring



This firm was established in Stoke in 1933 to supply prepared saggar marls to the pottery industry. These marls, made from Scottish fireclays, produced saggars which gave better service than the traditional saggars prepared from local clays.

The Diamond Clay factory at Hartshill (between Stoke and Newcastle-under-Lyme) specialised in the production of high-fired saggars.

Batts, props, setters, and other types of furniture were produced to meet the specific requirements of customers in the China, Earthenware, Porcelain, Tiles, Sanitaryware and allied industries at home and abroad.