Agriculture Reference
In-Depth Information
The niche had a jumbled and disrupted appearance, having lost the glori-
ous precision of gauged work maintained in other areas of the Orangery. The
semi-circular bonded arch face, with its intricate mouldings, had lost so much
of its detail that the profile was only fully detectable on one original brick. The
hood of the niche was blackened with sulphation and much of the surface had
de-laminated. Where open blisters had formed, surfaces were friable. The boss
feature appeared to be a scallop shell, although most of the outer edges had
disappeared. Originally an exceptionally fine piece of brickwork with joints less
than 1 mm, it was so badly decayed that its true form was barely discernible.
Due to the advanced level of decay, it was decided that a bold attitude
towards brick replacement should be adopted. Each element of the niche was
considered on its merits and an appropriate approach was established.
The niche body was distorted, possibly through structural movement. Using
measurements from the survey, a full size plan drawing was produced and
a templet was made of the shape of the curved bricks that make up the main
body. This templet was handed to the joiner who made a cutting box out of
robust hardwood. Two pieces of 18 mm thick timber cut to the exact shape of
the barrel curve were fixed to a sturdy baseboard at the correct width apart to
accommodate two 62 mm rubber blanks, with a space between them for wedges.
The sides of the box had to be at perfect right angles to the base and all dimen-
sions thoroughly checked. The bricklayer is reliant on the robust and precise
nature of the cutting box to produce work to the required accuracy for joints of
2 mm or less, and it is therefore helpful if the joiner has some understanding of
the gauged work process.
Red rubbers were cut to the correct gauge to be placed in the box for cutting
to the curve. One way in which modern technology can help to speed up the
process of gauged work is with the use of electric bench saws. These machines
typically have a 14 inch (350 mm) diamond blade and can be used wet to min-
imise the considerable dust generated. A rubber block can be reduced to gauge
in a matter of minutes. Before using the bench saw, the block must be bedded
and squared by hand so that it can go through the saw on a flat and true bed.
Although these machines are immensely useful and economical, it is important
to remember that they cannot always be as accurate as hand cutting and rub-
bing, due to slight movements in the blade as it turns. For this reason, it is a
good idea to cut the blanks 1-2 mm oversize all the way round, and to hand fin-
ish on the rubbing stone.
Once these correctly gauged blanks had been produced, the next stage was
to hand cut them in the box with the traditional bow saw. A temporary work-
shop was set up on site. First of all, the box was thoroughly swept out to avoid
any build up of brick dust that would throw the brick out of line during cutting.
Two brick blanks were placed in the box and tightly wedged with small wooden
packers. On a firm bench, the box was then fixed down with a piece of timber
