The principles of iron casting are pretty much the same as they have been for centuries; the technology, skills, materials and understanding have all progressed. Michael Hinchliffe, managing director, Hargreaves Foundry, gives us his view.
Something foundries hear all too often nowadays is “Oh we didn’t know anybody could make those any longer”. Well that just isn’t true. Modern foundries are probably better iron casters than our Victorian forebears and anything they could make we can make.
What is a bespoke casting?
Bespoke castings may be one-offs or multiples, but they are generally unique to a specific project or building. Many bespoke castings are manufactured for Heritage or Restoration projects; however bespoke castings can be made based on new designs as well. It doesn’t really matter what the shape or size, whether an ornate rainwater head, a radius gutter, or a large column, it can still be made in cast iron.
What products are made in cast iron?
Cast iron features strongly in our built environment, both traditional and modern. Well known products are: above and below ground drainage, street furniture, lighting standards, railings, columns, manhole and storm drain covers, window frames, pavement lights, decorative features such as urns, pergolas and water features – the list goes on. There are literally thousands of products made of or featuring component parts in cast iron.
How are castings made?
Briefly, a pattern of the item required is made. Patterns are traditionally made of wood and are an exact model of the finished product. Patterns are encased in sand moulds, which, when set, allow the pattern to be removed leaving a cavity into which molten iron can be poured at 1,350°C. Once cooled, the casting can be shot blasted and finished in a process known as fettling, ready to be painted.
The skills required for these processes, pattern making and moulding, are traditional craft skills and require a high degree of training, expertise and hand skill. That’s not to say that things aren’t changing, especially in pattern making. In some cases, CAD files handed on directly from architects can be used to mill patterns out of model board. Some smaller patterns are now being made using digital printers. However, to be able to make this work, designers or programmers need to work closely with people who have a thorough understanding of pattern making, foundry process and casting iron in sand moulds. Without allowing for metal shrinkage, knowing how to add taper so that patterns can be removed from moulds and how to
design a method system that allows metal to flow into the mould and gases to escape, you won’t be able to produce a casting either precisely, or more importantly, safely.
Is cast iron still relevant to the architecture of the 21st Century?
Well, I’d say a resounding yes to that, and not just for heritage products. And we can prove it. Just look at One Pancras Square featuring 396 bespoke cast iron columns with a basket weave design, all of which were made entirely from recycled scrap iron. This is a modern, award winning building designed by David Chipperfield Associates, which also achieved a BREEAM rating of outstanding with a score of 89.3 per cent. And therein lies another critical benefit of cast iron – its sustainability. Cast iron can be recycled indefinitely without any decline in its properties. Foundries have always recycled scrap iron, it is after all cheaper with no reduction in performance. It is important to stress that this is genuine recycling, not down cycling where products can be re-used but have inferior properties compared to their original usage.
Another benefit of cast iron is its longevity and value. Cast iron products are legendary for their durability and long life. Never mind a ten year builders’ guarantee, properly maintained cast iron products will last the life of a building. Not only that, but when the building has served its purpose and is eventually demolished, the cast iron can be recycled and used again for exactly the same purpose. Given how important sustainability is to architects when designing new buildings, cast iron makes a strong case for inclusion, whether for structural products, decorative features or purely functional products such as drainage.
So, if you want to include cast iron in your projects, you can be confident that there are still foundries that can make them for you and will be happy to demonstrate that they are every bit as skilled as their Victorian counterparts.