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W50 | W72 | W80 – Leaflet | Ink Transfer

Colour / Density / Transfer
AMSTERDAM - Multi-purpose printability tester
Version: 2022-09

Introduction

In order to determine the properties of printed stock it is essential to know the exact layer thickness of the printed ink. In relation to this ink flim thickness, colour, density, light fastness and resistances can be measured.
The following listing shows the different methods, dependent to the roughness of the paper used:

W50-AMS - rubber 85 Shore A for very smooth papers.
W72-AMS - rubber 65 Shore A for very smooth or rough papers.
W80-AMS - rubber blanket for very rough papers.

All these tests are described for conventional offset inks. For UV-inks special printing forms, top roller for the inking unit and a UV dryer are needed. Consult IGT Testing Systems for the right articles.

Principle

The paper strip is printed with an ink on the printability tester. Before and after printing the printing disc is weighed on a digital analytical balance with an accuracy of at least 0,1 mg. From the printed amount of ink and the size of the print the ink transfer expressed in g/m² can be calculated.

After drying the ink the printed samples can be used for further determination of properties.

Colour / Density / Transfer: print

Method of operation

W50 W72 W80: Colour / Density / Transfer

Materials

  • [ 402.634.412] Printing disc with black rubber, 85 Shore A, pin, 50 mm (W50)
  • [402.687.412] Printing disc with black rubber, 65 Shore A, pin, 50 mm (W72)
  • [402.089.412] Printing disc with rubber blanket, pin, 50 mm (W80)
  • [404.009.029] Strips of reference paper, 55 mm, IGT code C2846
  • [466.000.710] IGT High Speed Inking Unit (HSIU)
  • [466.003.003] Top roller, 4 segments for conventional inks
  • [511.100] Digital Analytical Balance
  • [408.000.200] IGT ink pipette 0,01 ml resolution

  • Ink to be tested
  • If desired, strips of paper to be tested, preferable 55 x 340 mm², 3 strips per sample
  • Lint free rags
  • Cleaning solvents naphta and ethanol

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 – MULTI-PURPOSE PRINTABILITY TESTER

  • Printing speed: constant 0,2 m/s
  • Printing force: 625 N
  • Ink film thickness 2,4 µm

IGT HIGH SPEED INKING UNIT (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 and mark with top and/or bottom side, machine and/or cross direction and a code for the paper.
  2. Select method Colour/Density/Transfer.
  3. Fill the ink pipette with the ink to be used.
  4. Set the HSIU in Mode 2.
  5. Apply 0,10 ml of ink to a segment of the top roller and distribute the ink.
  6. Place the printing disc on the shaft of the HSIU and ink the printing disc.

NOTE: The amount of ink mentioned above is a guide line to reach an ink transfer of about 1 g/m². Dependent to the type of paper, the type of ink and/or the desired ink film thickness this amount of ink must be changed.

Execution

  1. Mount a strip of paper or board to be tested on the sector.
  2. Touch the button [PRINT] to rotate the sector and the 1st printing shaft into the start position.
  3. Weigh the inked disc on the precision scale (G1).
  4. Place the printing disc on the 1st printing shaft.
  5. Press both side buttons to make a print.
  6. Release the side buttons when done.
  7. Take the printing disc from the shaft.
  8. Weigh the disc on the precision scale (G2).
  9. Clean the printing disc.
  10. Remove the printed strip from the sector.
  11. Clean the rollers of the inking unit or use a clean segment for the next test.
  12. Touch [BACK] and start up a new test. It is recommended to perform the test at least three times.

Store the printed strips in the standard atmosphere at a safe place so that it cannot be damaged for at least 24 hours.

Cleaning

  1. Clean the rubber printing 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.

Assessment

  • For ink transfer:
    1. Measure the length (L) and the width (W) of the print in cm.
    2. Calculate the ink transfer in g/m² with the formula:

Ink transfer =  {10,000 / (L * W)} *  (G1 – G2)

L  =  length of the print in cm

W =  width of the print in cm

G1 =  weight in g of printing disc with ink before printing

G2 =  weight in g of printing disc with ink after printing

  •  For ink film thickness:

Calculate the ink film thickness (mileage) in µm with the formula:

Ink film thickness (µm)Ink transfer (g/m²)  /  Specific weight  ink  (g/cm³)

  • Calculate the average and if desired, the standard deviation.
  • Measure the desired properties.

NOTES

Due to drying of the ink, it is not advised to add some ink to the same segment of the inking unit after a test. Clean the used segment first or choose the next segment of the top roller.

Randstad 22 - 02

1316 BX Almere

The Netherlands

P.O.box 22022

1302 CA Almere

The Netherlands

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