Holger uses Bronze Age technology to cast bronze sculptures with clay moulds in combination with the lost-wax process and charcoal-fired furnaces. Using local materials, sustainably produced charcoal and recycled bronze makes the process carbon neutral, offering sculptors and crafts people an environmentally sustainable, inexpensive and low-tech approach to produce sculpture. Holger has been working with Umha Aois experimental archaeology group since 1997 and has given papers and demonstrations (TAG 2010, EXARC 2015 and WAC 2008) and research workshops for the University of Cambridge.
In the Bronze Age carved stone moulds were used alongside wooden patterns pressed into a mix of clay, sand and horse dung. Recent finds indicate the use of lost-wax technology in the Iron Age, a technique which remains in use for casting artwork to the present day. After the base metals are extracted from the ore by smelting, they are blended into base metal ingots of 90% copper and 10% tin. These are heated in a crucible within a small clay-built pit-furnace. Charcoal is used in combination with hide bag bellows to reach the required temperature of 1,200ºC. Once molten, the metal is poured into the prepared moulds, which are then broken open.
Download PDF of casting tips
Furnace set-up with replica goatskin hand bellows (LBA found in Denmark)
Night casting at Umha Aois symposium
Freshly poured moulds and empty crucible
Pouring a mould from a pit furnace at Allihies
A LBA socketed axehead in its mould fragment (Booleybrian Hoard, Co. Clare)
A pit furnace, moulds and crucibles
A replica of the LBA Dunmanway horn is broken out of the mould. Pouring cup and mould thickness are clearly visible.
Fragment of a broken LBA horn mould and miscast of a horn. The vented core is evident
After casting a handbell at Umha Aois 2011 in Doolin.
Casting at Umha Aois 2012
A 5 minute video of casting a small MBA socketed axe head, using a charcoal horseshoe furnace and leather bellows at the Umha Aois symposium in 2012.
Ireland had no tradition of towerbells, instead handbells were used throughout the middle ages, of which more than seventy were found. Over the centuries many of these bells were safeguarded by families of hereditary keepers, erenaghs, passed down through generations and often used for keening. Holger has been commissioned produced facsimile replicas of the 12th century Drumholm Bell from Donegal, St. Senan's Bell and the 9th C. Bangor Bell (North Down Museum, Bangor, see video below). Handbells are masterpieces of early metalwork although their casting methods remain speculation. Holger has been working with the experimental archæology group Umha Aois and historian Cormac Bourke to resolve many of their mysteries.
Casting the Bangor Bell
A six-minutes video of the complete process of making a replica of the 9th century Bangor Bell, using authentic moulding methods and the lost wax process. The finished bell weighed 10kg and is 40cm high.
Bangor Bell Replica
Reproduction of two of two replica bells commissioned for display by North Down District Council at North Down Museum, fabricated with authentic medieval methods. The bells are full size and a half size replicas of the 9th century Bangor Bell.
Thanks to Karen Hendy (detail work and mould making), Cormac Bourke (historic advice) and Donagh Carey.
Making the Bangor Bell Replica
5min video of making the replica of the Bangor Bell in 2015
Bronze Age Horns
Irish Bronze Age horns are masterpieces of early metalwork although much of their casting methods remain speculation. Holger has been working with the experimental archæology project Umha Aois since 2008 to resolve many of their mysteries. As no archaeological artifacts of the process itself have been found to date, a definite conclusion about the method of casting has yet to be established. While some researchers (Holmes, 1978 and O'Dwyer, 2004) maintain an approach with a two-part moulds, a successful experiment to proove this method has yet to be concluded. The lost wax process appears to be possible, but any successful outcomes need to establish if they display the unique characteristic details of the originals. Simon O'Dwyer (Prehistoric Music Ireland) produces satisfactory results using lost wax with contemporary ceramic shell moulds. He has demonstrated clearly the surprising range of styles with which these instruments can be played to produce astonishing sound. The horn in the photographs - based on the Dunmanway horn - was cast in 2013 and more information about its history and the process can be found here.
Curachs and Voyages
Ireland retains an understanding and knowledge of seafaring skills which can help to create to a more sustainable way of life. By preserving and developing the skills, future generations can make the most of Ireland's unique position and heritage, upholding and nurturing long established links with the sea and other communities across Europe's Atlantic seaboard. Holger has been making curachs since 2001 and has built a 25' Kerry Naomhóg, several Dunfanaghy, Tory Island and Bunbeg curachs. He also offers curach making courses for communities and organisations, resulting in more than fourty currachs to date. In 2005, Holger initiated Lough Neagh Boating Heritage Association, a group dedicated to researching and building traditional Irish boats on Lough Neagh.
Excerpt from Traditional Boats of Ireland (2008) chapter about boat materials (PDF)
Four-hander Kerry Naomhóg, 27ft, 2006-2007
Four-hander Kerry Naomhóg, 27ft, 2006-2007 (Dunfanaghy Curach in the background)