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W31- Leaflet | Pick Test (ISO 3783)

Pick Test (ISO 3783)
AMSTERDAM - Multi-purpose printability tester
Version: 2022-09

Introduction

Pick is the name commonly given to damage to the paper surface occurring during the printing operation. When the printing form is lifted from the paper, the ink exerts on the paper a force, which increases with increasing viscosity and tack of the ink and with increasing printing speed. When this force exceeds a critical value, which depends on the paper, the surface of the paper is damaged.
The minimum printing speed at which pick occurs is a measure of the pick resistance of the paper.

W31 Leaflet describes the dry pick test according to ISO 3783.
W99 Leaflet describes the pre-wetted pick test to measure the influence of fountain solution compared to ISO 3783.

Principle

The paper or board is printed with a pick-test oil of known viscosity, at constant printing force and at an increasing velocity. Pick velocity and pick resistance are derived from the distance between the starting point of the print and the point on the print where the first damage is observed.

In the case of board when the adhesion between the outer layer and the next layer is too low, delamination between the layers can occur during printing.

Pick: IGT – ISO 3783, print

Method of operation

Pick: IGT – ISO 3783

Standards

The method W31 has been standardized internationally in e.g. ISO 3783:2006.
In the Netherlands in NEN 3095:1990 nl.

Materials

  • [402.301.441.412] Printing disc, 10 mm, black aluminium, scale (pick and delamination)
  • [404.004.010] Pick test oil low viscosity or
  • [404.004.020] Pick test oil medium viscosity or
  • [404.004.030] Pick test oil high viscosity or
  • [404.004.070] Pick test oil extra high viscosity
  • [404.001.005] Paper packing 55 mm
  • [441.000] Pick Start Viewer and/or
  • [441.000.040.190] Delamination viewer V shape
  • [441.000.040.280] Delamination viewer U shape
  • [466.000.710] IGT High Speed Inking Unit 4 (HSIU)
  • [466.003.003] Top roller – 4 segments – conventional inks
  • [408.000.200] IGT ink pipette 0,01 ml resolution

Testing conditions

Standard test atmosphere according to ISO 187 (23,0 ± 1,0 °C and 50 ± 2% RH).
When using the software analysis license, the actual temperature and RH% need to be entered in the fields [°C] and [RH%] to enable correct calculation of Pick Resistance. These data are also saved with each test performed.

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 – multi-purpose printability tester

  • Printing speed: increasing, end speed at choice
  • Printing force: 350 N
  • Pick test oil film thickness 8 µm
  • Camera lamp low (Not applicable for Amsterdam Basic type)
  • Checkbox Scan activated  (Not applicable for Amsterdam Basic type)

IGT High Speed Inking Unit 4 (HSIU)

  • Water bath: 23,0 °C (73,4 °F)
  • Mode 3:
    • Startup time [5 s]
    • Distribution time 1 [30 s] | Distribution speed 1 [0,5 m/s]
    • Distribution time 2 [10 s] | Distribution speed 2 [0,2 m/s]
    • Inking time discs [20 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 method Pick: IGT – ISO 3783.
  3. If desired, touch the checkbox Scan to scan (not applicable for Basic type Amsterdam).
  4. Mount the paper packing on the sector.
  5. Fill the ink pipette with the desired IGT pick test oil.
  6. Set the HSIU in Mode 3 (for changing settings and oil application, refer to your HSIU manual).
  7. Apply 0,28 ml of pick test oil to the inking unit or add 0,02 ml of pick test oil to maintain this layer and distribute the pick test oil.
    • NOTE: Do not add pick test oil more than 4 times.
    • NOTE: For another type of top roller see the manual of the inking unit.
  8. Place the printing disc on the shaft of the HSIU and ink the printing disc.

Execution

Pick: IGT – ISO 3783, low lamp
  1. Mount a strip of paper or board to be tested on the sector of the Amsterdam.
  2. Place the printing disc with oil on the 1st printing shaft of the tester.
  3. Touch the button [Print] and press both side buttons to rotate the sector and first shaft into the start position.
  4. Keep both side buttons pressed to make the print and release side buttons when the display shows DONE.
  5. Take the sample from the sector and immediately check with the pick start or delamination viewer and mark the first visible damage of the surface. More detailed information is described in the section Assessment.
  6. Assess the disc on the first point of picking and make a record. (See section Assessment).
  7. Before starting a new test, clean the disc and the used segment of the inking unit (or use the next segment or add 0,02 ml of oil to the segment used) and start inking the disc again.
  8. Perform the test at least ten times per sample.

If the camera was activated

The print is scanned and analysed and the camera moves upward.
The button [Delamination] allows you to enter the delamination distance in mm. Save or discard the results.
Start from point 1 for a next test. After finishing all tests, press [Back] and clean and store all parts.

Cleaning

  1. Clean the disc 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 dry with some ethanol on a lint free rag.

Assessment

If a scan was made

the results are automatically analysed and shown in the display: pick distance in mm, pick velocity and resistance in m/s.

Test result

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.

If no scan was made

Pick Start Viewer

To view the result of picking, place the test strip under the opening of the pick start viewer. Looking from above into the viewer assess the test strip and mark the point where picking begins.

To view the result of delamination, place the test strip in the delamination viewer and by carefully moving the test strip along the U-profile or V-profile check where delamination starts and mark this point.

Measure the pick distance between the starting point of the print (= the centre of the initial print nip) and the point where picking or delamination begins at the test strip. Make a record in mm.

If desired derive the pick velocity in m/s from the velocity table or with the formula:

Delamination viewer U and V

For picking: Vp = 0,005 * Ve * dp

For delamination: Vd = 0,005 * Ve * dd

Herein is:

  • Vp = velocity at point d (in m/s)
  • Vd = delamination at point d (in m/s)
  • Ve = set end speed (in m/s)
  • dp = distance from beginning of the print to beginning of picking (in mm, >50 mm)
  • dd = distance from beginning of the print to beginning of delamination (in mm, >50 mm)
Velocity table

If desired, calculate the pick or delamination resistance from the Velocity Viscosity Product (VVP) in N/m with the formula:
For picking: P23 = Vp * ɳ t / ɳ 23
For delamination: D23 = Vd * ɳ t / ɳ 23

Herein is:

  • P23 = Pick resistance at 23 °C in m/s
  • D23 = Delamination resistance at 23 °C in m/s
  • Vp = Pick velocity in m/s (velocity at the point where picking begins) at the measured temperature
  • Vd = Delamination velocity in m/s (velocity at the point where picking begins) at the measured temperature
  • ɳ t = Viscosity in Pa.s at the measured temperature (see Viscosity table in section “Notes”)
  • ɳ 23 = Viscosity in Pa.s at 23 °C (see Viscosity table in section “Notes”)

NOTES

Viscosity table: viscosity of pick test oils in Pa.s
  1. If picking or delamination occurs at <50 mm from the starting point of the print, the test must be repeated at a lower speed. In case the lowest speed has been applied already a change to a lower grade of the pick test oil is necessary.
  2. If no picking occurs or the picking occurs at >180 mm from the starting point of the print, the test must be repeated at a higher speed. In case the highest speed has been applied already a change to a higher grade of the pick test oil is necessary.
  3. The black aluminium printing disc with ruler, is specially used for paper of which the beginning of picking can be difficult to detect. For other papers it can give additional information. For example: loosened fibres or coating particles may be picked up by the oil before the actual overall damaging of the paper surface takes place. These particles are visible on the disc also.
  4. The viscosity of the pick test oils is temperature dependent. The Velocity Viscosity Product (VVP) may be used to compensate these differences. See Viscosity table.
  5. Pick test oils have a shelf stock time: <3 years; open time: <1 year.

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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