Where curlicues rule

  • A completed baluster casting is removed from its mould.
  • A few more touches, and this balustrade is complete.
  • Green sand comprises silica sand and fine bentonite clay To create the green sand for the moulds, its ingredients are first mixed, then water is added until the correct consistency is achieved.
  • The molten aluminium is cast at temperatures between 650°C and 720°C. Longer, thinner moulds require higher temperatures because the aluminium has a greater distance to travel. For thicker, shorter moulds, the opposite is true.
  • Here Teichmann calculates the core"â„¢s diameter for a lamp post that"â„¢s about to be cast.
Date:31 July 2007 Tags:,

A modern foundry faithfully reproduces the ornate beauty of the Victorian era

Grand verandas festooned with broekie lace, ornate balustrades, elaborate roof crestings and extravagant spiral staircases… Victorian houses are relics of an era when curlicues ruled, “fancy” was rarely used in its ironic sense, and no one could imagine a decorating concept based on “less is more”.

That said, the rich architectural heritage of South Africa’s Victorian houses has made them increasingly popular, and growing numbers of owners are spending big bucks on restoring these houses to their original, authentic splendour. The word “authentic” is key here: it doesn’t mean ripping out the rusty remains of a cast iron balustrade and replacing it with something similar from a local foundry, but actually going to the trouble of replicating the original design.

That’s where the guys at Heritage Castings come into the picture. This Cape Town-based firm will faithfully reproduce Victorian “filigree” items in cast aluminium, using the same time-honoured foundry processes used to craft the 19th century cast iron originals.

Owner Max Teichmann has two great passions in life – the Victorian era, and fixing up old things. He first walked into the foundry as a potential customer and was so impressed that he ended up buying the company. But if you really want to see him become animated, all you have to do is turn up with an unfamiliar design.

Says Teichmann: “We become very excited when we get a new pattern into our range, because we’re in the business of keeping this era alive. If we don’t get a chance to make a copy, it’s gone forever.”

Once reproduced, the original piece is stored safely and the “live pattern” (or copy) goes on to the foundry’s rack in preparation for production. To date, the firm’s archive of originals extends to about 1 000 pieces, including friezes (decorative panels), corner brackets, bollards, lamp posts, fences and gates.

Although decorative cast iron is available locally (see link at the end of this article), the range of Victorian designs is limited. Then there’s the durability thing: cast iron is highly susceptible to rust, and requires a lot of maintenance to remain in pristine condition. It’s also difficult to work with (try to drill a hole in a cast iron piece, and you’ll see what we mean).

Says Teichmann: “A hundred years ago, it was a skill passed down from father to son, and they produced castings of such good quality that no fettling was required.” Put simply, the poorer the quality of the mould, the more the molten metal will seep out of its core: this excess then has to be fettled (filed away) from the casting.

“Our castings are good, but we are continuously striving to reach the level of workmanship produced by those guys.”

Whereas modern processes such as die casting and CNC cutting provide more accurate and efficient manufacturing options, they are incapable of recreating the intricate patterns that the Victorian journeymen created manually. As Teichmann puts it, “It’s a bit like trying to replicate the Mona Lisa!”

Nowadays, aluminium is the metal of choice for good reason. For a start, it doesn’t rust, so it’s virtually maintenance-free. Second, it weights about 3,5 times less than cast iron – a point worth considering if you intend sprucing up your home with some decorative trim. Aluminium also makes sense from an assembly point of view, says Teichmann, explaining: “A single person can barely move a cast iron gate, let alone mount it.”

Although many of the foundry processes can be modernised, that’s not an option when you’re in the business of recreating originals. Instead, Teichmann called on his considerable experience in the automotive OEM (Original Equipment Manufacturer) industry, focusing on research and development and introducing his team to modern manufacturing philosophies.

He recalls: “There was no one who could tell us the correct pouring temperatures for the various castings… we had to establish that for ourselves.” They also needed to experiment with varying pouring speeds and pressures to achieve optimum results. Teichmann’s findings confirmed what the craftsmen of old knew all along: you should “always pour as cold as possible and as hot as necessary”.

As Teichmann tells it, the colder you pour the molten metal, the better the surface finish of the casting. Molten aluminium is cast at temperatures between 650C and 720C. Longer, thinner moulds (such as those for lamp posts) require higher temperatures because the aluminium has a greater distance to travel. For thicker, shorter moulds, the opposite is true.

To create the green sand required for the moulds, silica sand and fine bentonite clay are mixed in a large vat with a heavy cast iron floating wheel that resembles a gigantic cake mixer. Water is then added to the mix until it achieves the correct consistency. There are two ways to monitor the quality of green sand before committing to a casting – and both require a tactile approach. To check the moisture content, you take some of the mixture in your hand and squeeze it into a tight sausage. The amount of residue that remains on your palm after opening your hand indicates the moisture level.

Teichmann elaborates: “If the sand is too wet, it will give the casting a rough surface or chill the molten metal too rapidly, but if the sand is too dry, the mould will fall apart.”

To check whether the mix has the correct clay content (and thus enough bonding strength) to maintain an impression, you break the sand-sausage with your fingers, paying careful attention to the amount of pressure required to do so. A smooth cast requires less bonding strength than a cast with complicated detail.

Loose patterns are the simplest to cast. The “live pattern” to be replicated is placed on the ground in the centre of the bottom moulding box (known as a casting flask; the top and bottom halves are called “cope” and “drag” respectively). The drag is filled with green sand and compacted (a process known as ramming).

But even a supposedly simple procedure such as this requires a degree of finesse. For example, if you over-ram the sand, it becomes too hard, and the mould will break. If you don’t ram enough, the mould will be too soft, and you won’t get any detail on the casting. It gets even more complicated: you also don’t ram equally over the entire mould, because areas with more detail require more attention.

Says Teichmann: “We have a pneumatic hammer that’s used for the rough work such as filling boxes, but we get better results when ramming is done by hand.”

The drag is then turned over and some of the compacted sand is delicately cut away to reveal half of the piece to be cast. Here’s where you appreciate the skill of the Victorian artisans: intricate details aside, each piece features “draw angles” that enable them to be easily removed from the mould. The surface is stabilised with a sizing compound – allowing the two halves to be separated later – and the cope is fitted into position. After the cope has been filled and compacted, the two halves are separated, and sprues (paths for the metal to enter the mould) are carved into the green sand. The “live” pattern is then removed, at which point the mould is ready for casting.

Other casting methods used by Heritage Castings include boarded patterns and gravity die casting. The former method is suitable for large items such as lamp posts, whereas gravity die casting is most effective for small, higher-volume items such as table

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