AS ISO 18935:2019 pdf download.Imaging materials— Colour images—Determination of water resistance of printed colour images.
5 Water resistance estimating procedures
5.1 General considerations
Water resistance is the ability of a print to resist water damage which may manifest itself in a number of ways, such as migration of colorants; changes in the size and/or optical density of image elements; degradation of the image layer, as well as cockle, curl or loss of gloss. The water resistance of prints made by current methods varies considerably. For example, some ink-jet prints sustain no observable damage when the surface is rubbed immediately after water has been poured over the image. While others that do not show any water damage after soaking for hours, lose a portion of their image layer if it is wiped off before drying.
For dye-based inkjet, water resistance of many systems is dependent on three interdependent variables:
ink absorption, coating solubility, and effectiveness of mordant[11. For other systems where the ink is not absorbed into the substrate, water resistance is dependent on adhesion of the colorant to the substrate. In both cases, water-resistant laminates will improve water resistance.
Extensive tests have shown that full characterization of water resistance requires several different methods. Many attempts were made to quantify the test data generated by these methods in interlaboratory comparison, but none were successful. It is likely that within a given laboratory, the tests described in this document are sufficiently reproducible to yield statistically reliable data. However, this is not enough to adopt fixed evaluation criteria. For these reasons, qualitative analysis of the test results is prescribed. This entails grouping of the results obtained from different print materials into water-resistant (no change) or not water-resistant categories. An intermediate level of moderate water resistance is also recognized, although its boundaries cannot be determined exactly.
This document requires the use of deionized or distilled water for all of the tests. The pH of this water is not controlled (unless it is certified, which will be at pH 7) but pH will have little effect on the tests. This is because any water-soluble components in the media coating will dissolve into the water and rapidly change the pH. The final value of this will depend on the media used.
5.2 Control sample
The evaluation of test results based on qualitative criteria for water resistance (as defined in Clause 4) requires that untreated control specimens be used for comparison with water-treated specimens.
6 Test methods
6.1 General
Four test methods are given for water resistance. Method 1 models the effect of water spilt on an image and left to dry. Method 2 tests the physical integrity of the colorant receptive layer. This may be an important feature, as it is possible to have images that may resist smearing and other defects when in sustained contact with water, but will be destroyed if touched before fully drying. Method 3 indicates how images will behave under catastrophic conditions (e.g. flood damage). Method 4 explores the effect of water penetration from an exposed edge, such as an upright book on a flooded shelf.
The test methods discussed in 6.2 to 6.5 all involve the cyan, magenta, yellow, red, green, blue and black colours. For black, the processed black generated by the printer with the user specified driver settings (see 7.1 for more information and warnings) shall be used. As an option, the user may also use black generated in a different manner (e.g. 3- or 4-colour composite, pure black, etc.) if the option is available to the user. Some printer systems utilize more than cyan, magenta and yellow primary colours (e.g. systems that also use additional spot or process colours, such as red, green, blue, orange, and violet). In such a case, the user of this document may include these extra colours in the tests. All print specimens shall be allowed to dry at ambient conditions for at least 24 h prior to proceeding with the test.
NOTE Figure 1 shows some example test patterns that were generated using a simple drawing program on a computer.
6.2 Method 1 — Standing water evaporation
The test target consists of cyan, magenta, yellow, black, red, green and blue colour blocks of convenient size (-2 cm2) with a chequered board fill pattern (1,5 mm2) printed at the maximum density for that colour allowable by the printing system. Another set of chequered board squares is also printed at 0,5 ± 0,1 density above A 0,1 ml drop of water is then placed onto the centre of each colour patch and allowed to dry for at least 24 h at ambient conditions.AS ISO 18935 pdf download.