Unique beauty - hand made clay roofing tiles

Materials World magazine
,
2 Sep 2011
hand-making tiles

Neil Tobin, Managing Director at Keymer Tiles and Chairman of ICTa,
describes the manufacturing skills that lie behind
the natural beauty of hand made clay roofing tiles.

The manufacture of true hand
made tiles begins with the careful
selection of the clays, which tends
to be local to that particular area. The
Weald of Kent and Sussex and the Gault
of Cambridge are just two examples.
The colours of the raw clay vary, and it
is a mixture of these that is layered
together to form a kerf and allowed to
weather for at least a year. The kerf is
then mixed together in a souring shed
where water is added. Unlike most other
clay manufacturing processes, for hand
made tiles it is essential the clay is kept
wet and malleable for moulding.

Through the mill

The original method of hand throwing
tiles is now discouraged, due to
repetitive strain injuries, so the clay is
put through a milling process to produce
a ‘batt’ from which the tile is made.
This process consists of a wet pan,
high-speed rolls, a pug machine and
batt machine. Before the introduction
of these machines, the maker would
collect his clay in a wheelbarrow from
the stockpile. Today, most extruders are
de-airing and force the clay out at high
pressure, thereby aligning the particles
in the clay, which creates a machinemade
tile. A pug is very low pressure
and is used merely to bring the milled
clay back together, in a form that can
produce batts, without aligning the
clay particles.

The hand-makers use a process that has
been passed down through generations.
The clay batt is dusted with sand, placed
into a mould and pummelled, then the
excess clay is bowed off. The sand, which
has been mixed with manganese dioxide
to produce the correct colour, acts as a
lubricant enabling the tile to be released
from the mould.

A punch forms the nibs and a strike
plate impresses the maker’s name and
identification mark. Two nail holes and
an identification code are also struck
into every tile. A master tile maker will
produce 2,000 standard size tiles each
day, but less then half that number if
making special tiles. The bench and
mould are individual to each maker,
and the moulds require constant
checking to avoid any uneven wear.
This process, carried out every week,
is known as ‘lumping up’.

Hardening up

The tiles are stored on individual curved
trays that gives them their camber or
curve. They remain on the trays for 10
days, during which time they dry and
harden enough to be handled. The
drying process also causes them to
shrink in size by seven per cent.

They are then checked for quality and
placed in a crate to be transported to the
setting/drawing dock. The dried tiles are
checked again before being set onto a
kiln car, which involves building an
8.2m3 block of 5,400 tiles. Three of the
outer walls are built first, then the space
in between is filled before the final outer
wall is constructed.

The completed kiln cars are then moved
into pre-kiln heaters, where six cars at
a time remain for up to 40 hours, at a
temperature of 110°C. This reduces
the moisture content to below one per cent. If
excess moisture remains in the tiles, it
will turn to steam in the making process
and blow the tile’s face. When the tiles
are fully dried, they are taken to the
shuttle kilns. These large steel structures
are lined with ceramic fibre tiles to
retain heat. Each one has three banks
of burners fired by natural gas. Six kiln
cars are placed in each kiln where the
final process takes place – the
temperature in the kiln is slowly raised
to 960°C then held on ‘soak’. This
ensures the tiles are fully vitrified and
will remain durable and frost-resistant.
The kiln is then allowed to cool. This
process takes seven days, and during this
time the tiles reduce in size by a further
five per cent.

The cars are then taken to the
setting/drawing dock where they are
checked for quality before being placed
into a crate ready to be transported to
the customer.

Unique touch

The making process
ensures a variation
in the individual tile
– clay has a memory
and, as each tile is
moulded, the
maker’s efforts are
highlighted in the
subsequent drying
and firing processes.
The traditional
single camber – as
opposed to the
more modern
double cambered product used by many machine-made
and concrete tile manufacturers –
ensures a unique variation in each tile
that gives a roof movement. Hand
made tiles do not all sit flat next to
each other in total conformity, but in
gentle undulations reminiscent of a
centuries-old cottage.

The biggest advances over the years
have been in drying and firing, with
more efficient kilns that use less of our
natural resources. With so much effort
going into the making of each tile, the
cost of production and, therefore, the
selling price is much higher than
machine-made tiles.

In demand

Despite the introduction of the
handcrafted tile and
the cry from every UK manufacturer
that there are ever more imports that
do not have to conform to our rigorous
standards, sales have remained resilient.

Why? Because people recognise the
beauty of a hand made roof – how it
enhances the aesthetics of the property.
Old clay roofs that need replacing can
only retain their elegance through the
use of hand made tiles.

Heritage and conservation organisations
are holding their ground and insisting
that traditional materials be used and,
where available, local materials that
reflect the area in which the property is
situated. Export sales are also growing,
thanks to the increase in the replication
of traditional UK buildings using UK-manufactured
products. The use of
hand made clay tiles is seen as the
ultimate accolade, and the guarantee of
a unique roof can be a final selling point.
Hand made clay tiles will always be in
demand by those that require the very
best in building materials and respect
both the aesthetics and tradition of
our built environment.

Battle of the tiles

Figures maintained by the Clay Roof Tile Council show a marked increase in the sale of hand
made and handcrafted tiles. The introduction of handcrafted tiles is fairly recent and a cause
of consternation to traditional hand makers. After much consultation, the Council agreed on
the following official definitions:

  • A hand made tile is a tile formed by hand in a moulding frame.
  • A handcrafted tile is a tile manufactured by machine to replicate features of a hand made tile.


Further information

Neil Tobin, Managing Director of
Keymer Tiles and Chairman of ICTa.
Tel: 01444 232 931
Email: info@keymer.co.uk