Preserving 20th Century Glass Cinema Slides

In 2005 the NFSA embarked on an ambitious project to digitally preserve some 10,000 glass slides in the national collection.

NFSA conservator Shingo Ishikawa and digitisation specialist Darren Weinert talk about cinema slides and their history, manufacture and preservation.

Image: One of a set of hand-painted cinema slides for the song
Eileen My Own, USA, 1906

A short history of the cinema slide

Magic lantern slides consisting of hand-painted images on glass date back to the 17th century.1 Developments in photography during the 19th and early 20th century made it possible to produce lantern slides in greater numbers, using a range of techniques.

In 1847 or 1848, French inventor Claude Félix Abel Niépce de Saint-Victor successfully used albumen to make a photographic negative glass plate.2

Brothers William and Frederick Langenheim in the US extended Niépce’s work, using a negative plate to print a positive image onto glass. The transparent positive image proved suitable for projection. In 1850, the Langenheim’s patented the ‘hyalotype’, a name coined from the Greek hyalos, meaning glass.

Hand-coloured engraved label from box containing a toy magic lantern

Label from a box housing Ernst Plank’s ‘The Standard’ toy magic lantern, Germany, c1875 NFSA: 530696

When the collodion or wet-plate process was introduced in 1851, lantern slides were printed using the new method. The popularity of glass slides increased after the introduction of the easier to use dry-plate process in the early 1870s.

Well before the novelty of the cinematographé had become established as cinema in the very early 20th century, lantern slides were widely used for public presentations. The 1900 production Soldiers of the Cross,3 by the Limelight Department of the Salvation Army, incorporated approximately 200 glass cinema slides to heighten the impact of the silent moving image footage. The slides were used as freeze frames or to provide lengthy intertitles.

Glass slides were still in routine use by amateur photographers and public speakers until the mid-20th century, when they were eclipsed by the more economical and practical 35mm colour slides popularised by Kodachrome.

The manufacture of glass cinema slides

A cinema slide consists of an image supported on a glass substrate or base (82mm, 3½ inches square), with a cover glass to protect the surface of the image. The two pieces of glass are held together with gummed paper or cloth tape. Often an aperture mask, cut from high quality black cardboard, is positioned between the pieces of glass. The mask may be cut in a variety of shapes, including square, rectangular, circular or oval or, more rarely, complex silhouettes such as hearts.

Cinema slides with photographic images were produced as duplicates from original or composite negatives.4 To print the image onto the slide, two methods were commonly employed – contact and optical.

Cinema slide cross-section, showing layers of glass and paper

Cinema slide: cover glass used by theatre owner to write screening details (left), and slide production company’s identification label (right), peeled back to reveal the tinted slide surface, NFSA 2011

Contact printing uses a frame to hold the emulsions of the negative and slide together in close contact. A light is shone through the negative exposing the emulsion of the slide. The slide is then processed using photographic developer, stop bath and fixer and then washed and dried. Once dry, the slide is mounted with the optional aperture mask and cover glass and then bound together with gummed tape.

The optical printing method exposes the image by projecting the negative, or negatives,5 onto a slide coated with emulsion. The processing procedure is the same as that used in contact printing.

From the 1850s to the 1960s, most photographic slides were produced in monochrome, with colour added later in the form of chemical toning or dyes.6 The dyes were applied in thin coats so as not to obscure the fine photographic detail. Multiple colours could be used to create the impression of a full-colour image. The skill with which the colours were applied ranged greatly from large blobs of colour to fine applications with delicate brushstrokes.

During the 1960s and 1970s cinema slides incorporated cut sheets of processed photographic film mounted between two sheets of plain glass, a technique that took advantage of advances in colour photography and was cheaper than using layers of glass. The slide dimensions were kept the same to ensure compatibility with existing projection equipment.

While many cinema slides were photographic in origin, others were screen printed, handwritten or typed in ink or paint directly onto the glass substrate or onto materials such as cellophane. The finished product ranged from text or simple line illustrations to sophisticated hand-coloured graphic designs.

Analysing the stability of cinema slides

Well processed photographic silver images are quite stable because the image is buffered from the external environment by the glass and tape binding. Although the actual dyes used for an individual slide may be from almost any source, they have generally proven to be stable, especially compared with early colour photographic processes. As indicated in the graph below, research by the NFSA in 1993 on commonly used hand-colouring dyes found that, under accelerated aging tests, the dyes had little if any effect on the silver image.

graph showing accelerated aging tests of hand-coloured dyes and silver images

Graph showing the results of accelerated aging tests on typical hand-colouring dyes and silver images combined. The control is a silver-only image, NFSA, 1993

Glass, while fragile, is a stable substrate for the slide and for the image it supports. Apart from physical breakage, the point at which most slides fail is the tape binding the two sheets of glass. The tapes used were either cut from bookbinder’s cloth or a tough paper. Black tape was commonly used, but other colours were favoured for a range of purposes, for example, to identify a particular series of slides.

There is very little in the historical literature about the nature of the gum used to adhere the tape to the glass. Using an FT-IR spectrophotometer we analysed samples of the adhesive taken from expendable slides. The results below indicate that the adhesive was probably a vegetable gum such as gum arabic.

Spectrum test results on vegetable gum

Results of a spectrum search confirm sample adhesive is vegetable gum, NFSA 2010

The NFSA’s glass slide preservation project

In 2005, the NFSA embarked on a major preservation project that resulted in the identification of some 10,000 culturally significant glass slides in the collection, some of which had not been accessioned. The majority are cinema slides such as the stills and intertitles from Soldiers of the Cross. There are also choreutoscope slides7 in both strip and disc shapes, song slides from the early 1900s and theatre advertisements from the early to mid-20th century.

The project has involved collaboration between curators, conservators and digitisation and storage specialists across the NFSA. Management of the project involves a number of key tasks, including:

  • creating a complete listing of glass slides that had not been accessioned
  • examining and creating condition reports
  • cleaning and other conservation treatments as required
  • entering descriptions and accessioning details into the NFSA’s collection database
  • digitisation and re-housing of each slide
  • rights clearance
  • upload of digitised copies of each slide to the NFSA’s online collection database.

Conservator cleaning glass cinema slides

Conservator Shingo Ishikawa inspects and cleans glass cinema slides, NFSA Canberra 2011

Examination and condition reporting

The slides were initially grouped by source or donor. If the source was unknown, the slide was grouped by the image content. Each group was entered onto the collection database, with a brief content description, including size and number of glass slides and a brief condition report. This list was then used by curatorial staff to determine a priority list for further preservation work. Although the listings have been completed, cleaning, accessioning and digitisation work are still underway.

Cleaning and other treatment

Once sorted and prioritised, each group of slides is sent to the Documents and Artefacts Conservation laboratory. Each slide is further examined and where necessary the condition report is amended.

At this stage any necessary treatment to stabilise or prepare the slides for digitisation is also carried out. The most common treatment required is cleaning and repair. Cleaning of the glass slides involves removal of any surface dirt, fingerprints, accretions and adhesive marks from the glass that would otherwise obscure the image when it is digitised.

Screen grab of NFSA database

NFSA collection database (detail), showing condition of individual slides, 2009

Cleaning commonly involves passing a soft brush over the surface to remove light dust. Heavier soils are treated using a 1:1 water and ethanol mixture on a cotton swab. Mechanical cleaning is carried out using a scalpel blade to gently scrape away surface accretions and extraneous adhesive residues. Any loose paper or cloth tape is re-adhered to the glass. If any tape is missing or the glass is loose, gummed hinging paper is used to replace the missing tape.

If the base (the component that holds the image) is cracked or broken, then the base glass is sandwiched with a layer of glass cut to the same size and the whole object is bound together with gummed paper tape. Gummed paper tape is made of buffered paper and a water activated adhesive that holds well to the glass components. If a slide has a damaged cover glass but the base and image are intact, then only the cover glass is replaced.

The focus at this stage of the project is accessioning, digitisation and rehousing. Only the minimal amount of treatment necessary for the object to be safely handled and digitised is carried out. Any glass slide that requires a more advanced conservation treatment is noted in our database for future treatment. Regular condition checks are included as part of a cyclic maintenance program.

Digital preservation of glass slides

Batch scanning glass slides

Glass slides ready to be batch scanned on a flatbed scanner, NFSA 2011

The NFSA is committed to making the collection more accessible to the public. Glass cinema slides are an important and popular part of the collection. However, repeated handling increases the risk of damage to these intrinsically fragile objects. Digitisation enables the NFSA to make glass slides available for viewing online to everyone, while at the same time reducing the need for retrieval and handling of the original item.

The digitisation of cinema slides is carried out at the NFSA on a Kodak iQsmart 2 flatbed scanner, using oXYgen Scan software. The table below outlines the technical standards the NFSA uses for the digitisation of cinema slides:

Digitisation standards table

Preservation file Distribution file Browse/Access file
Image bit depth: 16 bit Image bit depth: 8 bit Image bit depth: 8 bit
Colour space: Adobe-RGB (1998) Colour space: Adobe-RGB (1998) Colour space: Adobe-RGB (1998)
Resolution: 1500ppi Resolution: 1500ppi Resolution: 72ppi
File type: tiff File type: tiff File type: jpeg
File size: 142.97MB File size: 71.5MB File size: 41.4KB
File dimensions: 5004 × 4992 pixels File dimensions: 5004 × 4992 pixels File dimensions: 640 × 640 pixels

There are several issues that require consideration when selecting a scanner and software. The condition of each slide will also have an impact on the way scanning is performed.

Cinema slides have depth – the emulsion sits at least the thickness of a base or cover glass away from the point of focus of a flatbed scanner. Some flatbed scanners do not have a sufficient depth of field to effectively capture the glass slide image. This is particularly obvious when the slide has the emulsion on one side of the glass and hand-colouring on the other or when the slide is actually two glass plates combined. Depth of field issues, as in the example below, can also be encountered when curved or warped glass plates will not lie flat on the scanner.

Scanned image showing loss of depth of field

Blurring in the right half of the scanned image indicates that depth of field has been exceeded, NFSA 2011

When the glass of the slide is in direct contact with the scanner glass, Newton’s rings are likely to form on the surface, as in the example below. Newton’s rings occur when light is reflected between the glass plate and scanner surface. The only way to eliminate this is by moving the two surfaces apart or by using anti-Newton’s ring glass on the scanner. To separate the two surfaces a simple thin card matte can be used. However, this may introduce further depth of field issues and a close inspection of the resulting scan is required to determine whether the slide image is in critical focus.

Glass slides are often hand coloured and the dyes will almost certainly have different peak absorbance and transmission characteristics to the photographic dyes found in chromogenic colour processes. Scanners may be optimised for capturing the critical colour fidelity of colour photographic emulsions. Correcting the scanned image to accurately reproduce the correct colour and vibrancy can be complex.

Newton's rings on glass slide

An example of Newton’s rings between the layers of a glass slide, NFSA 2011

Because the slides are designed to be viewed via projection, we first scan them as transparencies. However, this process will not record text that is written on the covered edges, such as the manufacturer’s details. To record this digitally another scan is made with the scanner in reflective mode.

Some cinema slides were created using printed dot screens. When scanned, these screens can interfere with the scanner sampling frequency, creating unwanted textures, or moiré patterns in the duplicate (see example below). To eliminate moiré patterns the slide is scanned at a slight angle to disrupt the relationship between the inherent image pattern and the scanner sampling frequency.

Moiré patterning in this earlier version of the NFSA logo was one of the reasons for its replacement in the 1990s

Condition may also affect the way the glass slide is digitised. For example, a crack in the glass may scan better length ways than across the scanning head. Determining the best scanning angle can be a matter of trial and error. Angled scans can be corrected to a normal viewing alignment in the final file by rotating the image during post-processing.

Glass slides are digitised with any defects that cannot be easily removed in the conservation process, such as crystal patterns that form as deterioration by-products of the slide. This digital copy can be used at a later date to ascertain whether the slide is in a stable condition or any further damage has occurred. Scans are also made when further conservation is undertaken, to document the ‘before and after’ condition.

Scanner settings will depend on the end product. If a large poster is to be produced from the digital file, the scanning operator needs to know the final poster size in order to calculate the correct output file size. Calculating these requirements involves a simple mathematical formula. To set the largest size that may be printed from the distribution file, divide the pixel size of the image by the printing resolution required, for example: 5004 pixels / 300 ppi = 16.68 inches. The digitisation standards table can be used to determine output sizes.

Because cinema slides are fragile, handling and scanning is undertaken by staff trained in working with fragile objects. Gloves are worn and steps are taken to ensure safe storage of the slides.

Packaging for long-term storage and access

Digitisation of slide images provides a preservation copy, as well as access copies for research and online viewing. However, the primary preservation strategy is controlled environment storage, which ensures that the original object is available for the maximum length of time into the future.

The NFSA’s storage strategy includes appropriate enclosures. Before entering long-term storage each slide is individually placed in a four-flap folder made from photo-safe archival quality paper. The folders are then placed inside a polypropylene archival sleeve with the label attached. The standard-sized slides are stored vertically in metal drawers with dividers. Unique-sized glass slides or special collection materials, such as Soldiers of the Cross, are stored in custom-made boxes that provide extra buffering from the external environment.

A four-flap folder used for storing glass slides, NFSA 2011

Glass slides that require special attention, such as those with lifting emulsion layers, are stored in custom-made boxes to prevent further damage from occurring during handling.

The accessioned glass slides are stored in the same controlled environment as the rest of the document collection. The temperature and relative humidity are set at 18 degrees Celsius (± 2 degrees Celsius) and 40 per cent RH (± 5 per cent). These conditions are at the top end of, but still within, the range recommended for glass plate negatives by ISO 18918: Imaging materials – Processed photographic plates – Storage practices . Stability in environmental conditions is important for photographic emulsions on glass. Consequently, temperatures in the NFSA storage vaults rarely fluctuate, even within the full deflection of the set point range.


The NFSA’s glass slide project is ensuring that over 10,000 historically significant slides in our collection are preserved under controlled conditions for future generations.

As work progresses on digital preservation, copies of these slides are uploaded to our online collection database, providing virtual visitors across the globe with access to Australia’s audiovisual heritage.

A version of this essay was presented at the Australian Institute for the Conservation of Cultural Material (AICCM) conference in Melbourne, in 2010.

More about glass slides:

AJ Abbott – spiritual communicator
Cinema slides in the NFSA collection
The History of the Discovery of Cinematography
Illustrated song slides in the NFSA collection
Lantern Slides: History and Manufacture
What’s that bug? Magic lantern surprises


1 The most widely accepted theory is that Christiaan Huygens developed a lantern slide system in the late 1650s.
2 Niépce de Saint-Victor was related to Nicéphore Niépce, who is credited with taking the first photograph in 1827.
3 Although Soldiers of the Cross has been referred to as the world’s first feature film, it may be better described as an ambitious, pioneering multi-media event comprising cinema slides, short reels of moving images, live actors and an orchestra.
4 Composite negatives are created by combining two or more photographic images, often by optical printing.
5 Titles or additional images may have been composite printed onto the slide.
6 Chemical toning changes the colour of a silver photographic image by reacting to the silver in situ with other chemicals such as sulphites or iron compounds. This gives an image that has clear highlights and coloured shadows, as opposed to adding tints where the resultant image has coloured highlights and black shadows.
7 The choreutoscope, a precursor to motion pictures, used magic lantern slides. Each slide contained six separate pictures depicting a slightly different stage in a simple movement. The pictures were projected in rapid succession to give the impression of movement.



If you want to know more about the history and development of glass slide technology, The National Film and Sound Archive Library has a large number of books and journals about glass slides and optical lanterns, and other pre-cinema technologies.

Jan Thurling on 15 May 2012, 11:14 a.m.

Really useful article. I picked up a few at a collectables fair, attracted by their wonderful bright and shiny allure.

Then had the dilemma of working out how to store them sensibly, and also understadning their historical development. Your article has provided great pointers, and I hope informs other people who have examples to continue to care for them properly.

Wonderful to see NFSA taking an interest in this honorable medium! Time for the magic lantern and the cinema slide and the NFSA people to get together?

David Donaldson on 23 Oct 2012, 2:57 p.m.

My father has approximately 100, glass slides from 19 century with French landscapes.we r curious about their prisrine conditions ttyl soon Dave Bedard

David John Bedard on 12 Oct 2013, 7:29 a.m.

Thanks for an insightful article - I bought some slides dating to 1913 and this article will help me clean and store them correctly.

Very interesting article.
I have slides that require restoration.
I have been searching for the buffered paper you mention or the way to bind the edges.

Is there a supply source you could recommend both Canada and USA.

Thank you

Hi C.C.

Thank you for your comment. Glad that you found the article interesting and somewhat useful.

As for the supply sources in Canada and USA. I found that Gaylord has a good range of photo print and glass slides storage materials.

I am sure there are plenty of others but you should be able to find anything you need from that website.

Good luck! Shingo

Thank you for an interesting site. My dad worked for Whitfords Theatre Ads in Sussex St Sydney. He was an advertising salesman. I was taken to the art room a few times to see the artists working with fine brushes creating slides for client's products. I would love to hear of more about this company specifically.
James Baker NSW

James Baker on 05 Feb 2015, 6:36 p.m.

my late mother used to be a artist who painted these glass slides she worked for monks and blanks in Adelaide south Australia and then she moved on to val morgan advertising and david koffle also I have a few of her handpainted pieces and they are my treasures

michelle frick on 19 Mar 2015, 5:39 p.m.

Hi James and Michelle,

Thank you very much for sharing lovely story of your family members working in this field. Sadly there are not enough information and stories available on making of the actual theatre glass slides or Whitfords Theatre Ads Company. Michelle it would be wonderful if your late mother has left any paints that she used to use on the slides or any stories about working there?

Thanks for your very useful information.
At Blue Mountains Library we have started uploading our collection of local cinema slides to Flickr -

John Merriman on 02 Mar 2016, 12:08 p.m.

Where can I buy repair supplies, particularly gummed black tape for binding the glass together?

I was wondering if anyone knew of any slide and film conservation courses within the uk.I have about 700 glass slides that I would like to conserve and scan properly.

Alan Whyte on 06 Jul 2016, 1:45 a.m.

Hi Alan

Thank you for checking and commenting on this. I am not aware of specific slide and film conservation courses in the UK, I know that there are several university that offers Conservation degree which are mostly post graduate and takes several years to complete.. but I don't think that's somethign you are after? You would probably do better to look for short trainings or workshops on the conservation on glass slides and digitization. ICON the insitute of conservation is a very useful site to connect with local photographic conservators in UK and also find out if there are any training or workshops that you maybe interested in. Sorry I cannot be more helpful. Best of luck with your glass slides collection!

dear shingo unfortunately my mother passed away in February 2014 she had boxes of powders that were mixed by her and big bottles of paints dad made her a special desk to fit the slide with a drawer in it for her paint brushes I remember being enthralled watching her paint these glass slides unfortunately when they went into a nursing home the public trustee threw out or sold all the stuff in the shed where they were stored i was disgusted with the way they dealt with things but they are gone a few years ago a man from some historic society in prospect south Australia rang and said he had my mothers work book and some other things associated with slides but i never followed it up i still have his number somewhere and ill contact him

michelle frick on 08 Sep 2016, 1:13 p.m.

i just read the names of your other contributors and noticed the above mentioned mans name in your list his name is david Donaldson if he reads this he rang a betty june colegate of blair athol quite a few years ago who worked for monks and blanks i am her daughter michelle who answered their phone

michelle frick on 08 Sep 2016, 1:17 p.m.

Post your comment