Agriculture Reference
In-Depth Information
1,100ºC over 20-22 hours with a 48-hour cooling period. The loss in firing is
about 2%.
Of the trials, Mr Matthews says:
Initially we took our standard Chalfont Red hand made facing brick to Gerard
Lynch to see if it was suitable for a rubbing brick. Following discussion it was felt
that the brick showed promise and further development were justified.
Trials proceeded on two fronts under the guidance of Andrew Hales, our most
experienced brickmaker. First the normal Chalfont red brick was fired at 900ºC
for 36 hours in our intermittent test kiln. A batch of Chalfont clay was mixed with
extra sand. This was done in two ratios, one at 2 parts clay to one part sand, and
another at one part clay to one part sand. These mixes were not sieved or put
through the normal clay preparation system and so resulted in a course clay mix.
After drying these bricks were placed into the top of our normal Scotch kiln, they
were loose-set in chambers that had been set within the normal bricks either side
of the kiln, about four feet from the kiln walls in order to achieve a lower firing
temperature.
The resultant bricks were again taken to Gerard Lynch's workshop for rubbing
and cutting trials. The normal Chalfont brick fired at 900ºC was found to be still
too hard, though the colour achieved was most pleasing being light orange and
we will now add this to our standard brick range. The bricks that were made using
added sand were felt to be much nearer the mark, particularly the brick with the
one part sand to one part clay. This rubbed well and cut very easily and precisely
with the bow-saw. It was also a remarkably close colour and textural match to a
Warfield [Berkshire] rubbing brick (
c
.1740) that was present in his collection of
historic rubbers.
Over the last few years we have continued to trial the manufacture rubbing bricks
and have discovered that we now have several options developing. We have found
through test cutting and moulding using the traditional bow saw technique, that
the clay used to produce our existing range of Chalfont facing bricks needed very
little to be done in terms of altering the materials, only the technique of mould-
ing, kiln setting and firing. Also the natural quality of the Chalfont clay is giving a
colour range of rubbers of orange through to bright red. Although our emphasis
has been to produce a fully-washed rubber we also wish to market an un-washed
rubbing brick as well; that will match bricks from the historic periods that pre-
date refined brickmaking techniques.
It is our intention to supply a range of rubbing bricks to suit the current new-
build and conservation/restoration market that are priced to give us a sensible
return on our manufacturing and within the budget of our clients. As part of this
we also wish to be helpful to colleges and other establishments, who are provid-
ing education and training in gauged brickwork with limited funds, to enable
them to obtain a selected grade of rubber set-aside for educational purposes.
