The Reconstruction of the Holtermann

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What do you do when one of the world’s largest wet-plate glass negatives, a nineteenth century panorama of Sydney weighing over 30kg, smashes into hundreds of pieces?

Person from the Library's Collection Care reassembling a section of the shattered Holtermann wet-plate glass negative for digitisation.

One of the six sections, digitised in several overlapping frames to capture the incredible detail of the original negative.

That was the puzzle facing the State Library of NSW in 1982.  The plate was one three giant glass plates created by Charles Bayliss for Bernard Holtermann in 1875.

It was part of a hoard of 3500 glass plate negatives discovered in a garden shed in Chatswood in 1951.

The find proved to be the most important photographic documentation of life during the Australian gold rush; a unique record of a generation experiencing an era of opportunity.

Almost 35 years ago, one of the giant glass negatives shattered. Attempts were made to repair the plate but no satisfactory solution was discovered.

It was boxed and put into storage. The question of how to recover it remained unanswered until now.

The thickness of the trays allowed the weight of the glass to be supported without bowing, which in previous tests, had resulted in distortion patterns.

The broken 8mm glass plate is comprised of 291 identifiable glass fragments, plus additional shards, right down to powder. 

At the 18th Triennial Conference of the International Council of Museums - Committee for Conservation, in Copenhagen on 4-8 September 2017, a paper will be presented which explores the collaborative efforts to preserve, reassemble, recapture and rehouse the artefact.

From physical rebuilding to best practice digital imaging, the reconstruction of the Holtermann plate involved four conservators and the expertise of our Digitisation and Imaging Team.

The plate was assembled into six sections on 15mm acrylic trays, thick enough to support the glass without bowing or distorting the image, and digitised using a custom built light box, lighting the glass from below. 

For capture our Digitisation and Imaging team used a 50 mega-pixel Hasselblad camera, and to maximise resolution, each of the six sections was digitised in overlapping frames, then stitched together. 

The high resolution photographic image laid over the broken plate to match up the details

The team at UTS developed Artificial Intelligence methods to map the broken areas of the glass plate and align them with the high resolution image. 

The resulting image is a massive 20,000 pixels long, weighing in at about 3 gigabytes. The Library was also finally able to calculate the size of the original negative, measuring it at 151.7cm x 96.5cm, and confirm it is indeed one of the world's largest collodion glass-plate negatives.

The Library also collaborated with University of Technology Sydney (UTS) Big Global Data Technologies Centre. Using artificial intelligence mapping techniques, images from a large contact print taken before the plate was broken, replaced the areas of the negative that had been shattered. 

The resulting image is a miraculous restoration of what was thought to be lost.

The painstaking process, which took incredible precision, will be described in the upcoming edition of SL magazine.

Read more about the Holtermann Collection.

 

Thanks to Anna Brooks, Lang Ngo, Nichola Parshall, Catherine Thomson, Collection Care, Bruce York, Joy Lai, Matthew Burgess and the Digitisation and Imaging Team.

Restored panorama of Sydney from the Holtermann collection.
Restored panorama of Sydney from the Holtermann collection.