Experimental manufacture of a hypocaust boxflue tile

(To download [2.6MB] and view a movie of the process, click here)

Little work has been done in archaeology on Roman boxflue tile. The team at Whitehall Farm Roman Villa, under Archaeological Director Stephen Young is currently examining the numerous boxflue tile fragments that have been found during excavations, looking at ceramic fabrics, mortar key designs and tile dimensions.

Dr. Martin Weaver decided to look at how these box-flue tiles were produced. Many of the tiles had a thickened end indicating that the tile was removed from a former and stood on end for firing, some fragments also showed a join at one edge that, in his opinion, indicates the wrapping of a sheet of clay around this former.

Martin used stoneware clay for the reconstruction with sharp sand inclusions. He produced the mortar key design by using a five tooth comb and this accurately replicated the patterning seen on tiles recovered from the Whitehall site. The critical factor for success is to ensure that the clay is the right consistency: too wet and it will not slide off the former; too dry and it will not bend without cracking, causing weak points when fired.

Flatten clay and dust with sand to help it detach from the former

Cutting rolled clay to rough size

Roll clay around former:
former constructed to average size of Whitehall boxfue

Wrapping complete

Smooth clay on to the former for a good fit

Seal join with water

Five tooth comb for applying design
(made from and adhesive applicator)

Cut the side vent

Former removed

Completed boxflue tile showing vent

... and here's one I fired earlier

For more about Martin's conservation work,
CLICK HERE (you'll be taken to another web site)

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