Paper Conservation: Decisions & Compromises

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Fig. 2 incorporate scale bars in images. Without user intervention distances and areas on a digital plane are expressed in pixels and square pixels. Once the distance in pixels is known then the preferred unit (μm, mm, etc.) can be added. Any future measurements made on the image will present quantities in the newly assigned unit. 4. Watermark Extraction Bandpass filter: The subject of interest of an image for a particular user can sometimes be obscured by other features such as a watermark hidden under lines of text. Bandpass filters can be used in ImageJ to filter out unwanted pixel structures. An upper size limit filters out large structures (shading correction) and a lower limit filters out small structures (smoothing). ImageJ uses a Gaussian filter in Fourier space allowing isolation of important features for research. There is an extra option to suppress horizontal or vertical stripes, which is similar to subtracting an image that is only blurred in the horizontal or vertical direction in the original. 5. Colour Management RGB Pixel Values: Colour charts should always be included in the image capture procedure to ensure that the RGB pixel values of the object being imaged can be compared to a standard. This is important in cultural heritage for the accurate preservation of colour in collection items, specifically photographic collections and illuminated manuscripts. Colour is expressed as an RGB triplet (r,g,b), each component of which can vary from zero to a defined maximum value. This value can be determined with ImageJ. If all of the RGB components of an image are at zero, then the image is black. Conversely if all of the RGB values are at a maximum, then the image is white. 6. Provenance Determination Colour Space Converter: Converting images from the RGB to other colour spaces can reveal hidden text and help determine the provenance of archival material. Colour can be specified by three parameters in a colour space and there are mathematical relationships that enable the parameters of one colour space to be transformed into another. The colour of an image is most often described in terms of the percentage of red, green and blue hues combined. Images such as these exist in RGB colour space, but there are other ways to describe the colour of a pixel using different colour spaces. Alternative ways of describing colour numerically are useful for making certain calculations easier and making colour identification more intuitive such as by describing colours by their hue, saturation and luminance. Two ImageJ plugins allow for the conversion of a standard RGB image into another colour space called ‘Colour Transformer’ (Barilla 2012) and ‘Colour Space Converter’ (Schwartzwald 2007). ImageJ can generate as many as fifty-two combinations of the original image in different colour spaces. 7. Degradation Monitoring Stacks: Degradation features in a collection item can be monitored over time by comparing sequential images. An image stack is a collection of images of the same size and bit depth usually taken over the same region of interest where the scene is not changing due to motion. ImageJ can display these spatially or temporally related ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013 128
Fig. 3 Fig. 4 images in a single window allowing the user to scroll between images and monitor changes in the region of interest. Individual images within a stack are called slices. Cameras can be positioned in areas to collect photographs which can be compared to determine the rate of dust collection or mould growth in a cultural heritage site. Placing images into a stack allows for immediate identification of changes. Multispectral images can be opened as a stack in ImageJ to compare the behaviour of parchment and pigments across the electromagnetic spectrum. 8. Artifact Interpretation Merging and Splitting Channels: Pseudocolour images are used to make features such as deterioration artifacts stand-out so that they are easier to interpret. Pseudocolour or false colour images are single channel gray images of 8, 16 or 32-bit pixel depth that have colour assigned to them via a look-up table (LUT). They reflect differences in image intensity rather than differences in the image colour. This type of processing has application for multispectral imaging where three bands revealing different information are chosen and assigned to the colours red, green or blue. These images can be merged to create a pseudocolour image highlighting important features (Fig. 2). Sometimes image information can be observed more readily in single channel view than in RGB combination. An RGB image can be deconstructed in ImageJ using the Split Channels tool. The RGB original image separates into three grayscale images, in three different windows representing red, green and blue colour channels. 9. Scholarly Understanding and Publication Rotation and Transformation: Captured images are often at an unsuitable orientation for publication. It is also useful to compare writing on one side of a page with that on the reverse to determine if faded text is obscured by ink overleaf. Within the Transform menu are options “Flip Horizontally” (replaces the image or selection with a mirror image of the original), “Flip Vertically” (turns the image or selection upside down), “Flip Z”, “Transform”, and three related to rotation which contains commands that rotate the active image or stack. Image straightening or image rotation is inadvisable prior to digital restoration unless the image is rotating through 90° or 180° (due to the regular geometry of pixels). Slight rotations are achieved without apparent visible effect on the image, but a rotation results in the rewriting of colour values and slight blurring of boundaries (Fig. 3). For cultural heritage collections, the boundaries of letters and artefacts are crucial to defining context (McFeely 2006). 10. Boundary Definition Unsharp Mask: Unsharp Mask is applied to compensate for poor focus during image capture ei- ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013 129
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Paper Conservation: Decisions & Com
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Content Lieve Watteeuw Introduction
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Michael Wheeler | Nicholas Barnard
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New Trends in Preservation in the D
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and monitoring against adverse envi
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Steve Hobaica, Patrick Loughney, Ma
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The Albums of Duke Charles de Croÿ
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Fig. 4: turning the supporting pape
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Fig. 2: Close-up of some of the los
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manuscript paper, the binding would
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Figure 2 partial sewing: the blue d
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Books in Exhibitions: History and A
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Fig. 4 Museum in London and the pre
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Risk and Safety of Illuminated Manu
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Fig. 2 Atlas, the Crown papers are
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Acknowledgments The authors would l
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Verdigris I: Compromises in Conserv
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Verdigris 2: Wet Chemical Treatment
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Integrated Modelling: The Demograph
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Fig. 3: The consequence of 50 insta
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Characterisation of Historical Pape
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pling is required, tide-lines are c
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Study of Phytate Chelating Treatmen
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Evaluation of stochiometric effects
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Practice and Progress in the Conser
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Fig. 1 Fig. 2 plex picture and prov
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Fig. 2: Coloured paper strips place
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the fire (on the other hand paper,
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inform decisions on conservation tr
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This paper summarizes what is known
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2. Methods An interdisciplinary met
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Fig. 4: Dyed endpaper pasted at the
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Preservation of Architectural Drawi
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Notes 1 According Salvador Muñoz V
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course of time under the influence
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the curators in review of the treat
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cellulose powders with cellulose et
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Authors Xing Kung Liao Conservator
Page 78 and 79: Fig. 2: Our Railroad Workers and th
Page 80 and 81: The Restoration of Cartoons at the
Page 82 and 83: tation presumes that the works are
Page 84 and 85: To Remove or Retain? - Extensive In
Page 86 and 87: Fig. 4 repeated applications until
Page 88 and 89: The Migration of Hydroxy Propyl Cel
Page 90: tion issue allowed a visualisation
Page 93 and 94: Ethical Considerations Concerning t
Page 95 and 96: emoved with damp cotton swab. Then
Page 97 and 98: Conservation of a Book of Hours fro
Page 99 and 100: Fig. 4: Pigments movement and conse
Page 101 and 102: Notes 1 Brazilwood lake, lapis lazu
Page 103 and 104: pages, which would easily have torn
Page 105 and 106: The Microflora Inhabiting Leonardo
Page 107 and 108: Acknowledgments The authors would l
Page 109 and 110: Microorganisms in Books - First Res
Page 111 and 112: hyaline white mycelia on and in the
Page 113 and 114: Deconstructing the Reconstruction E
Page 115 and 116: Fig. 3: Poster after 2012 conservat
Page 117 and 118: Conservators’ Investigation of Ch
Page 119 and 120: had been used, may be false-positiv
Page 121 and 122: function will provide a holistic pi
Page 123 and 124: Fig. 2: Patriarchs of Chan Buddhism
Page 125 and 126: ing techniques, which build upon fu
Page 127: Applications of Image Processing So
Page 131 and 132: Analysing Deterioration Artifacts i
Page 133 and 134: Fig. 3 similarity maps. Similarity
Page 135 and 136: Strategy in the Case of a Wrecked P
Page 137 and 138: without preliminary consolidation.
Page 139 and 140: Fiber Optic Reflectance Spectroscop
Page 141 and 142: Fig. 3: 18 th century paper seal, i
Page 143 and 144: Fig. 3 Fig. 4 of responsibilities r
Page 145 and 146: Characterising the Origin of Carbon
Page 147: Fig. 3: Sampling depth for ATR spec
Page 150 and 151: Fig. 2: Filmoplast® tape attached
Page 152 and 153: Pluchart, F. 1971. Pop Art Et Cie.
Page 154 and 155: Fig. 3: The reverse of left screen
Page 156: porting the reverse of severe creas
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Paper Conservation: Decisions & Compromises

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