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W59 – Leaflet | Mottle: Water Interference Index / Curve | Amsterdam 5/6

W59 - Mottle: Water Interference Index / Curve
AMSTERDAM 5/6- Multi-purpose printability tester
Version 2022-09

Introduction

Mottling is an unwanted variation in optical properties of the (mostly solid) print, appearing as small dark and light areas at the surface of paper (board) caused by ink, paper or press (circumstances). Mottle is affected by type of ink, colour sequence, construction of the printing press, printing speed, rubber blanket, damping fluid and, most important, the paper composition. Variations in the surface characteristics as absorption, smoothness and formation play an important role in mottle and are caused by the production process and the components in the paper.

In the following W-leaflets several mottle methods are described:
W57: Back Trap Mottle
In back trap mottle paper is printed and the ink of the printed strip is set off 4 times to 4 clean printing discs with interval times.

W58: Print Mottle
A paper strip is printed 4 times with the same printing disc.

W59: Water Interference Mottle
Water interference mottle is the uneven printing result, caused by insufficient and uneven water absorption of the paper, followed by uneven ink absorption.

W92: Ink Trap Mottle
Ink trap mottle is the uneven printing result caused by a trapping in tack and/or viscosity of the ink in wet-on-wet printing and is also influenced by an uneven absorption of the ink in the paper.

These tests can all be done in two method settings:
1. Method Index: the result is scanned and saved after the last print.
2. Method Curve: the result is scanned and saved after each print.

Principle

Paper is dampened and printed with IGT mottle test ink. Subsequently this print is brought into contact 4 times with clean printing forms (rubber blanket).

Mottle: Water Interference, print

Method of operation

Mottle: Water Interference Curve

The paper to be tested is dampened and printed with IGT mottle test ink.

Method index: the printed strip is brought into contact 4 times with clean printing forms (rubber blanket) with interval times of 10 s. After the last pass, the test result is scanned and analysed.

Method curve: the printed strip is brought into contact 4 times with clean printing forms (rubber blanket) with interval times of 15 s. After each pass, the test result is scanned and analysed.

Materials

  • [402.354.002] Dampening disc 0,25 µm or
  • [402.354.005] Dampening disc 0,50 µm or
  • [402.354.010] Dampening disc 1,00 µm
  • [435.031.412] Doctor blade holder
  • [180.431.710.001] Doctor blades + polishing foil
  • [404.001.005] Paper packing 55 mm
  • [402.089.412] Printing disc, rubber blanket, 50 mm, pin (5x)
  • [404.800.010] IGT mottle test ink
  • [408.000.200] IGT ink pipette 0,01 ml
  • [466.000.710] IGT High Speed Inking Unit (HSIU)
  • [466.003.003] Top roller, 4 segments for conventional inks
  • At least 3 strips of each paper to be tested, dimension 55 x 340 mm
  • Lint free rags
  • Cleaning naphtha

Testing conditions

Standard test atmosphere according to ISO 187 (23,0 ± 1,0 °C and 50 ± 2% RH).

Sample conditioning

Be aware of the fact that a different way of conditioning of the samples can have influence on the results.

Standard settings

AMSTERDAM 5/6 – multi-purpose printability tester

  • Printing speed: constant, 0,2 m/s
  • Printing force: 500 N
  • Number of set-offs: 4
  • Interval times: 10 s (method index) or 15 s (method curve)
  • Ink film thickness 8,0 µm
  • Camera lamp high (not applicable for Amsterdam Basic type)
  • Checkbox Scan activated (not applicable for Amsterdam Basic type)

IGT High Speed Inking Unit 4 (HSIU)

  • Water bath: 23 °C (73,4 °F)
  • Mode 2:
    • Start-up time [10 s]
    • Distribution time 1 [20 s] | Distribution speed 1 [0,5 m/s]
    • Inking time discs [15 s]

Preparation

  1. Cut paper strips of 55 x 340 mm and mark with top and/or bottom side, machine and/or cross direction  and a code for the paper.
  2. Select either method Mottle: Water Int Index or Mottle: Water Int Curve.
  3. If desired, touch the checkbox Scan to scan and save (not applicable for Basic type Amsterdam).
  4. Mount the paper packing on the sector.
  5. Fill the ink pipette with the IGT mottle test ink.
  6. Set the HSIU in Mode 2 (for changing settings refer to your HSIU manual).
  7. Apply 0,35 ml of ink on a segment of the top roller.
  8. Place the printing disc on the shaft of the HSIU and ink the printing disc.

Execution

Doctor blade in holder
  1. Mount a strip of paper or board to be tested on the sector of the Amsterdam.
  2. Place a dampening disc on printing shaft 1.
  3. Mount the doctor blade holder onto the two pins of the accessory holder with the blade pointing to the right and downward.
  4. Place a small strip of cotton pad (5 x 50 mm) just left of the doctor blade on the dampening disc.
  5. Place the printing disc with ink on printing shaft 2. Place the clean discs on the other shafts.
  6. Touch the button [Print] and press both side buttons: the sector and both shafts rotate into the start position and the doctor blade lowers.
  7. Release side buttons and apply dampening fluid onto the cotton pad. When done press both side buttons again.
  8. Keep both side buttons pressed to doctor the dampening disc, moisten the paper on the sector and make the first print.

For method index:

  1. After making the initial print, the first interval time of 10 s is entered.
  2. Release the side buttons and immediately replace the inked disc on shaft 2 with a clean one (only for Amsterdam 5).
  3. At the near end of the interval time a warning signal is given. Press both side buttons to bring the clean disc into contact with the print on the sector. The first set-off from the print is made.
  4. The second interval time of 10 s starts. Release both side buttons.
  5. When a warning signal is given press both side buttons and repeat points 11 and 12 until all cycles (standard preset: 4) are done.
  6. Keep side buttons pressed. The camera lowers to scan the print.
  7. Release side buttons when the display shows DONE.
  8. The print is scanned and analysed and the camera moves upwards. Save or discard the results.
  9. When press [SAVE] a pop-up keyboard appears to name and save both data and image.
  10. Remove the test strip from the sector.
  11. Before starting a new test, clean the disc and use a new segment of the inking unit, apply ink and start inking the disc again.
  12. After finishing all tests, press [BACK].

For method curve:

  1. After making the initial print, the camera lowers and scans the print and the first interval time of 15 s is entered.
  2. Release the side buttons and immediately replace the inked disc on shaft 2 with a clean one (only for Amsterdam 5).
  3. At the near end of the interval time a warning signal is given. Press both side buttons to bring the clean disc into contact with the print on the sector. The first set-off from the print is made and the camera lowers to make a scan.
  4. The second interval time of 15 s starts. Release both side buttons.
  5. When a warning signal is given press both side buttons and repeat points 11 and 12 until all cycles (standard preset: 4) are done.
  6. Keep side buttons pressed. The camera lowers to scan the print.
  7. Release side buttons when the display shows DONE.
  8. The print is scanned and analysed and the camera moves upwards. Save or discard the results.
  9. When press [SAVE] a pop-up keyboard appears to name and save both data and image.
  10. Remove the test strip from the sector.
  11. Before starting a new test, clean the discs and use a new segment of the inking unit, apply ink and start inking the printing disc again.
  12. After finishing all tests, press [BACK].

Cleaning

  1. Clean all discs with lint free rags and cleaning naphtha.
  2. Clean all rollers of the inking unit, including the metal ones with lint free rags and cleaning naphtha.
  3. Make sure the Amsterdam is clean and if necessary clean with some ethanol or cleaning naphtha on a lint free rag.

Assessment

The results are automatically analysed and shown in the display; the mottle is recorded in 3 values: contrast, cloudiness and orientation.

Test result

For the method curve, data are given for each scan. The first scan is the initial print, the subsequent scans are mottled.
For the method index, only one scan is made at the end. Magnification of the scan via touch screen is possible.

Touch the textbox [Batch] on the left of the display, fill in the information and push [OK] save both data and image push [OK] again.
Afterwards the data and images can be transferred to a USB stick. For the correct procedure please refer to the manual of the Amsterdam.
Data are saved in a CSV format that can be loaded into Excel. Images are saved as PNG files. The data will relate the results to a specific image to enable you to combine both.

NOTES

  1. Shelf life Mottle ink: 3 years, period after opening: 1 year.
  2. Be aware that due to aging or intensive use the life time of the discs is limited.

Randstad 22 - 02

1316 BX Almere

The Netherlands

P.O.box 22022

1302 CA Almere

The Netherlands

+31 20 40 99 300 +31 20 40 99 339 info@igt.nl
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