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Imprint Variability

This is about observing the variability in time of the imprints produced by a single paper making mould. Because paper expertise is largely based on the assumption that two imprints of the same mould are near identical, it is crucial to know the degree of variability to expect.

Therefore a series of experiments is intended consiting in taking at regular intervals image reproductions of a stack of wet papers, samples of dried papers, and images of the sieve, for the life span of the mould. Thereafter a mathematical model of the dynamical proprieties of the sieve can be constructed and an estimation of the variability gained from it.

Decisions of meeting 2007.07.11, Fabriano

Protocollo per la sperimentazione sull'usura della forma

Saranno effettuate prove per stabilire:

  • la grammatura della carta,
  • il tipo di impasto (lunghezza egrassezza delle fibre).

Produzione: 100 fogli al giorno
Collatura: sintetica in pasta
Feltri: sempre gli stessi (sintetici o in pura lana)
Asciugatura: all'aria

All'inizio della sperimentazione e poi ogni 1000 fogli realizzare:

  • 3 fogli non pressati
  • 3 fogli pressati
  • 3 frottis dell'intero foglio (fare prove con scanner 600 dpi tif)

  • 3 fogli con ponitura verticale
  • 3 fogli con ponitura orizzontale (con gli stessi tempi di scolatura)

Road map

  • 2009 February - Incorporation of last data batch in the analysis
  • 2009 February - Third collection of recorded material at the papermills
  • 2008 September-December - Analysis of recoreded material, preparation of results repport
  • 2008 August - Second collection of recorded material at the papermills
  • 2007 November-December - Analysis of the 1st batch of collected material & evaluation of experiment
  • 2007 September-November - First collection of recorded material at the papermills
  • 2007 July - Moulds are ready, experiment starts at the participant papermills
  • 2007 February-Mars - Mission to Fabriano for paper mould production
  • 2007 January-February - Determine needed hardware and acquire hardware
  • 2006 December - 2007 January - Establishment of an experiment protocol
  • 2006 November 29, Paris - first meeting for this experiment

Task groups

  1. Coordination, budget: VladAtanasiu
  2. Protocol: JeanLouisEsteve, EzioOrnato, MoniqueZerdoun
  3. Hardware: JeanLouisEsteve, GiorgioPellegrini
  4. Production: JacquesBrejoux ( Le Moulin du Verger, Puymoyen, France), GiorgioPellegrini & FrancoMariani? ( Museo della Carta Fabriano, Fabriano, Italy), Moulin Richard le Bas ? (Ambert, France)
  5. Liaison: JeanLouisEsteve, FrancoMariani?
  6. Analysis
    1. historical: JeanLouisEsteve, EzioOrnato, MoniqueZerdoun
    2. mathematical model: VladAtanasiu, ?



  • Issue:
    1. we don't know how well a mould made today models a medieval mould
    2. no mould older than 200 years survives that could be taken as a historical model

  • Proposed solution:
    • the experiment dosen't pretend to reconstruct a historical mould
    • we hope to find that the variation in mould mouvment yields a generalizable pattern across a range of different moulds and working conditions; this would reasonably enable to extrapolate the findings to the past moulds and imprints

Similar experiments

  1. PeterTschudin, Swizerland, has done some experiments about imprint variability

Transformation chain

List of variability factors in sieve imprint are given in HandbookAppendixLoeberCriteria and HandbookAppendixLoeberExperiences. Hereby some additional factors.

  1. sieve wire variation
    1. depends on... total mould usage time
    2. solidness of mould making (wood, joints, knots, wire)
    3. "violence" of handling
    4. papermaker's sieve handling movements during work
  2. wet paper
    1. number of papers on stack
    2. proprieties of the felt between papers (imprint, absorbtion proprieties...)
    3. papermaker's sieve handling movements during setting the wet paper on the felt
    4. drying method
  3. dried paper
    1. inking (handwriting, print...)
  4. imprint reproduction
    1. by human (freehand)
    2. by analog machine (backlight, radiographic...)
    3. digital (optical cameras, radiographic, surface laser scan...)
  5. digital processing
    1. image processing transformations (resampling, Fourier transform...)
    2. features measurements (landmarking...)
    3. mathematical model of the imprint variation

HELP To help you visualize some of these factors watch JacquesBrejoux making paper (movie in French), as well as photographs of the papermaking process (stills and legends, in French).

Experiments to conduct

Each of the factors of the imprint transformation chain can be subject of an experiment. Here are those that are proposed to be conducted within Bernstein.

  1. Sieve wire variation
    1. object: record at regular intervals the variation of the sieve wire over the entire lifespan of the mould from (1) reproductions of the sieve itself and (2) from imprints of the sieve in papers
    2. goal: better understanding of the impact of the sieve wire variability on the imprint variation
  2. Wet paper stack variation
    1. object: document at long intervals the variation between individual papers of the same paper stack (i.e. produced one after the other in time)
    2. goal: better understand the impact of paper stacking and drying
  3. Freehand watermark contour reproduction variation
    1. object: subjects are making freehand copies of watermarks seen through transparency in (1) books, in (2) single sheets
    2. goal: better understand the subjectivity implied in freehand copies of watermarks
  4. Freehand watermark landmarking variation
    1. object: subjects are selecting an unspecified number of landmarks on watermarks
    2. goal: better understand the impact of interactive watermark expertise (subjects are selecting landmarks, the machine compares sets of landmarks)

Experiments protocols

  1. Sieve wire variability
    1. Global sieve movement
      • Objective: This will record the main directions in which the sieve is distorted, as well as the correlation between the movements of individual wires.
      • Protocol: A paper the size of the sieve is put on a level support under the sieve and painted with waterdiluable ink from over the sieve with a brush. This is repeated at regular intervals - say every month -, for each sieve under observation, for the lifespan of the sieve (or at least 2 years). Option : Record the sieve structure with a photographic camera.
      • Rationale: This method has the benefit that it is very simple in instrumentation and results in a 1-to-1 copy of the sieve. It avoids using expensive and difficult to manipulate photographic cameras, and the problems linked to image registration (making sure that all images taken at different times are from the same hight, angle, and without distortion).
    2. Individual wire loosening
      • Note: It has to be decided if this experiment is done or not. See rationale why it could be useful.
      • Objective: Record how the sieve gets looser in time in the vertical and horizontal directions.
      • Protocol:
        1. Vertical direction: Hang a (500 gr?) weight from the center of the sieve and record the distance from the sieve's wooden frame to the bottom of the weight. Repeat the procedure once a month for the duration of the experiment.
        2. Horizontal direction: Hold the sieve vertically, hang a (500 gr?) weight from one of the horizontal wires. Measure the distance between the imaginary horizontal line passing through the points of attachement of the wire to the wooden frame to the bootom of the weight. Repeat the measure for (3 ?) other wires, spread out over the surface, allways the same for all experiments sessions. Turn the sieve 90 degrees and repeat the procedure, then again 90 degrees and again 90 degrees.
      • Rationale: Taking a snapshot of the sieve will not tell us about its dynamic proprieties that changed in time, in particular what the degree of 'bellying' (vertical displacement) and lateral play of the wire mesh are.
  2. Wet stack paper variability
    • Objective:
      1. Observe the differencies between individual papers from the same sieve produced in the same batch.
      2. Observe the variation of these differencies in time.
    • Protocol:
      1. Take backlight images (on a lightbox?) of wet papers, just before or just after being pressed (decide when).
      2. Archive one stack (or 10 papers thereof) of dryied papers (before or after being coated (fr: couche)? or both?). (By stack I mean the batch of papers produced one right after the other and superposed on felt while still wet.) In the analysis stage of the experiment the papers are to be imaged (radiography or backlight) and the differencies of the sieve imprints analysed.
    • Varia: Individual papers have to be given a current number by some mean in order to know they order in the stack and in time. Inserting in the wet paper paste a piece of paper with a printed number on it sounds like a good solution.
  3. Freehand watermark contour reproduction variation
    • Proposal 1 (VladAtanasiu)
      • Objective: Evaluate intra- and inter-subject variation in the interpretation of watermark coutours and their copying by handdrawing.
      • Protocol: GIve the subjects a couple (5?) of papers with watermarks. Let them hold the first paper with a hand, while copying the watermark with the other. Let the subjects do tracings from the same watermark (using a lightbox, a dylux or a glass table). Contiune with the restant papers, then repeat the procedure with the same stack of papers twice.
  4. Freehand watermark landmarking variation
    • Proposal 1 (VladAtanasiu)
      • Objective: Observe where the landmarks are intuitively selected on a shape and what the average number of landmarks are in order to describe a shape.
      • Protocol: The subjects are using a mouse to select landmarks on watermarks displayed on a computer screen. First let them choose as many landmarks as they wish. Then give a specified number of landmarks to select for each watermark.


  • Loeber, Edo G.: Paper mould and mouldmaker / E. G. Loeber. - Amsterdam : Paper Publ. Soc., 1982. - XVII, 83 pp., 125 pp. ill.

-- VladAtanasiu - 31 Oct 2006

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