iron lace

When we think of heritage buildings from the 19th century, chances are we think of decorative iron. From iron lace terraces to country pub verandahs, cast-iron was a popular decorative choice in the 19th century and early 20th century. Simple verandahs were fringed in ironwork, while large houses were graced with cast-iron columns, intricate panels, balconies and staircases. The Heritage Council's Technical Advisory Group provides advice on how to care for this distinctive heritage material.

Decorative ironwork such as iron lace of the 19th century was almost all cast-iron, which developed from earlier elaborately shaped wrought ironwork. Unlike wrought iron which was worked by craftsmen into the desired shape, cast-iron was made by pouring molten metal into moulds. It was attractive as a decorative material as it was capable of bearing great loads, fireproof and cheap. At first it was imported, but soon it was being produced in Australian foundries. From about 1865 Australian motifs such as emus, cockatoos, kookaburras and flannel flowers began to appear in locally designed patterns.

Conserving cast-iron lace often requires replacement of missing sections, or sometimes complete reconstruction of a verandah long since removed. The original pattern of the cast-iron may be found by careful searching the site for remnants of the original material, examining early photographs, or inspecting adjacent identical buildings, such as in a terrace. Spacings of columns, uprights and rails can often be determined by looking for evidence of fixings in floors, pavements or walls.

Foundries can reproduce ironwork using existing pieces as patterns, although care is required because slight shrinkage occurs when the iron cools. A better result may be obtained by producing a new pattern for the casting.

Cast aluminium sections are widely available today. Depending on the significance of the ironwork, an accurate sand-cast aluminium reproduction of the original pattern may be acceptable as a replacement.

Mail order catalogues, sometimes up to 100 pages long, advertised patterns for decorative ironwork.

Care of cast-iron work

Most metals slowly oxidise when exposed to atmospheric conditions, changing to another form such as the mineral ore from which they were produced. Rusting iron and steel produce reddish iron oxide. Some metals such as gold and certain stainless steels are more resistant than others to this process and remain largely unaffected.

The process of chemical reversion, or corrosion, is accelerated by air pollutants, acid rain, salts and the presence of dissimilar metals. In coastal environments metals corrode rapidly under the influence of air-borne salts and high humidity.

So long as it is clean and dry, good quality cast-iron corrodes very slowly, leaving a thin surface film of rust. There are many cases where doing very little, except the occasional brush clean, is an appropriate conservation approach. This applies particularly to situations such as cast-iron grave surrounds in cemeteries located in dry inland areas. The thin application of fish oil-based coatings is an appropriate treatment, but requires regular re-application to maintain a cared-for look. The next level of care is painting, which is dealt with in detail in the Heritage Office's information sheet on Metalwork.

Cast-iron is a very brittle material, and any high impact or stress may cause it to fracture. It therefore needs careful handling and protection from damage if heavy building work is being done nearby.