USEFUL INFORMATION THE MANUFACTURING PROCESS Mould Making Each Haddonstone design is made to order. If the order is for a standard design, production can commence as soon as a colour has been agreed. If a custom design is required then a mould needs to be made. For a relatively simple design, such as a window sill or coping stone, wooden moulds will be manufactured in the company’s wood shop. One of the skilled in-house carpenters will interpret drawings to produce a precise mould, the exact reverse of the shape ultimately
Creating a wooden master model for a new column.
required. Timber moulds have a comparatively limited life compared to their fibreglass equivalents. However, the speed with which timber moulds can be produced, combined with their relatively low cost, normally makes this type of mould more economical for the client. The production of a fibreglass, rubber-lined mould in the company’s studio is much more time-consuming and is only undertaken if the design is complex or if there are likely to be numerous castings. The work is one of the most highly skilled within Haddonstone, benefiting greatly from artistic and practical skills. Before such a mould can be made, it is first necessary to have a model. This can come from a variety of sources: it could be created within the wood shop; it could have been carved from scratch by an in-house craftsman, normally in plaster, either replicating an antique piece for a restoration project or afresh for a new design; it could be a pristine antique stone; or it could be a damaged original requiring restoration. Once the master model has been created, the mould-making can begin, commencing with rolling clay to a set thickness and covering the entire model. Over this a fibreglass case is formed. As this case will be completely inflexible, it has to be designed in such a way as to allow its later removal. For this reason, some fibreglass cases can comprise of more than ten sections. Then the fibreglass case is opened, the model extricated and all traces of clay removed. The case is then reassembled around the model, there now being a void where the clay had previously been. Into that void is poured a specially developed rubber which has enough fluidity to fill every cavity whilst avoiding any air bubbles, which would be seen in the finished design. After the rubber has set, the fibreglass case is, once again, opened and the model placed into storage. When the fibreglass and rubber case is reassembled, the
High-tonnage silos store raw materials needed to produce Haddonstone.
void now left in the centre is the precise shape and size of the finished design. Particular care is taken to ensure that any seam is in a position where it is least noticeable. Whether wooden or fibreglass, without a first-class mould it is impossible to create a first-class product.
Manufacturing For semi-dry cast Haddonstone, the principal materials are limestone, white cement, sand and a small quantity of water. This produces the Portland colour with other colours requiring the addition of pigment into the mix. Other key ingredients include plasticisers to improve workability and aid compaction as well as waterproofers for durability. To ensure complete control of the production process, every single batch of raw material delivered to the Haddonstone manufactory is quality checked, before use. The constituents of the mix are stored in high-tonnage silos adjacent to the production area, before being mixed in small quantities via computer controlled batching equipment and taken to a workstation. At this stage, the mix has the feel of damp sand or earth.
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