Saturday, March 25, 2017

Scanning Lantern slides

19th Century Magic lantern
 projector Wikipedia

Some time ago a client approached me about digitising a collection of early lantern slides.  Lantern slides are squarish glass slides that contain a mounted photographic transparency and are designed to be displayed in a magic lantern projector. Magic lantern projectors date back to the 17th Century and use a concave mirror at the back of a light source to direct the light through a lantern slide onto a lens which is adjusted to display the image on the slide onto a wall or screen.  Early lantern slides were hand painted images, then later the slides were printed using either photographic or photomechanical processes.

Lantern slides are positive images made from a negative. The image is mounted on a glass plate and covered with a glass cover which is taped at the edges. Lantern slide shows were either for entertainment or educational purposes. My client's slides dated from the 1920s and were black and white photographic images her Grandfather used to illustrate a presentation he made to the Nelson Literary Scientific and Philosophical Institute.  The slides and talk were about the hill tribes of Assam in north east India where he lived for some years.

Oridinary scan of image captions
Scanning the slides involved a two stage process - a reflective scan to record the image surround which contained important image captions and a second transparent positive scan.  In the second scan the scanner light is transmitted through the slide in the same manner as a magic lantern. The combination of shining light through the slide; the fact the slide sits directly below the scan head with no additional scanner glass and the auto focus function, enables a very clear high resolution scan.  Lantern slides are encased in glass so it is important to identify the emulsion side to get a clear scan.  Like glass plate negatives Lantern slides need to be handled carefully with gloves to avoid fingermarks and breakage.

Slide Scan
Final image

Final image
Final image

Copyright Carterworks NZ

Friday, March 17, 2017

Chemical damage of photographic prints

Sometimes I receive photos to restore that have suffered from chemical damage and it is one of the reasons why it is so important to capture a digital copy of a photo before it deterioates further. Chemical damage includes a whole range of reactions - two common ones being silvering out and sulphiding.

Silvering out is caused by chemical breakdown of the silver used to form the image in 19th and 20th century photographs.  The silver reacts with atmospheric contaminants such as hydrogen sulphide and peroxides leaving a bluish or green tarnish in the darker areas of the photo....

Scan by Carterworks showing silvering

Sulphiding is where this reaction causes the photo to change from black to brown and create overall fading.

Scan by Carterworks showing sulphiding

Over time these chemical reactions lead to a loss of photographic information or unsightly distortions and marks on the image.   Luckily both these images were captured in time and have been restored by Carterworks.

Restoration by Carterworks

Restoration by Carterworks

The National Gallery of Australia recommends that photos should  be displayed away from direct light, ideally behind UV glass and in temperatures of around 21 C and with a relative humidity of 50%.  They also recommend that photos

be mounted and framed or interleaved and stored with archival quality chemically stable acid-free plastics such as polyethylene, polypropylene or polyester. Archival paper products should be neutral pH, unbuffered and lignin, sulphur and peroxide free. One sure way to determine if something is archival quality is to check if the material passes the American National Standards Institute Photographic Activity Test (ANSIPAT) .


In NZ you can get these archival storage materials for your photos and documents from:-

Conservation Supplies (online and in Havelock North)
Port Nicholson Packaging in Wellington

Copyright Carterworks NZ