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In this present study, electrophotographic printing is made on papers which are subjected to different recycling numbers, and this paper aims to examine the colour changes of this printing type.

Four-colour electrophotographic printing is carried out on adhering to the INGEDE 11p standard recycled papers four times under the same conditions. Colour measurements are made by means of electrophotographic printed colour scales printed on these recycled papers. Colour measurements are made with the X-Rite eXact spectrophotometer according to the ISO 13655:2017 standard. As a result of colour measurements, colour differences (ΔL′, ΔH′, ΔC′, ΔE₀₀) of recycled papers are determined using some formulas.

According to the values obtained after four recycling, the highest ΔL′ value is found to be 4.80 yellow and the lowest 1.92 black. Again, according to the measurement results, it is determined that the highest ΔE00 is yellow colour with a value of 5.66, and lowest ΔE₀₀ is black colour with a value of 1.98. In ΔH′, black colour is the highest value of 12.61, the lowest value with −2.05 is obtained in magenta colour. It was observed that the highest ΔC′ value is 2.98 in yellow, and the lowest value is −0.28 in black.

In the printing industry, sometimes customers want to monitor the colour differences in the printing by taking the L′a′b′ obtained values as a result of printing from the printing houses. If the colour differences exceed the tolerance values, then they can interfere with the printing. As a result of the calculations, colour changes in electrophotographic printing are observed with many parameters. This study can be a pioneer for the studies that can be done on this subject.

This study aims to examine the colour changes affecting inkjet prints after the recycling of papers.

For recycling, papers prepared with the INGEDE 11p standard are recycled four times. Pulping, storage, flotation, beating and bleaching processes are applied for each recycling, respectively. Inkjet prints are made on the obtained test papers, and colour measurements are made using an X-Rite eXact spectrophotometer according to the ISO 13655:2017 standard. These processes are applied again to the papers which are recycled four times, and the results are analyzed. In addition, the values of ΔE₀₀ ′, ΔL′, ΔH ′ and ΔC′ are calculated according to ISO 11664-6:2014 standard by making some calculations according to obtained the L′a′b′ values.

It is determined that the ΔE₀₀ value increases after each recycling in cyan magenta and yellow colour, whereas it decreases in black. The highest ΔE₀₀ value is calculated after the fourth recycling stage is yellow with a value of 8.33. The lowest ΔE₀₀ value detected is black with a value of 0.76 after the fourth recycling stage. This paper observes that the colour with the most variation in hue angle among recycling repetitions is black and the colour with the highest hue angle value is yellow. It is seen that repeating recycling causes increase in the chromatic values of the prints.

After the fourth recycling stage, colour changes have reached an important point and can cause important printing problems. In this case, the customer’s approval must be obtained to continue printing. This case is valid for ΔE₀₀ values. Colour differences for print contrast, trapping and print chroma values are either not very important or are positive for quality.

This paper aims to determine the most practically applicable color-difference formula for yarn-dyed fabrics woven from warp and weft yarns in different color depths and to establish color-difference tolerance for perceptibility by evaluating yarn-dyed fabrics visually and instrumentally.

A total of 108 sample pairs were evaluated by a panel of 13 observers with perceptibility method under three typical light sources (A, D65 and cool white fluorescent). The data sets were statistically analyzed by the homogeneity of variance test (F-test), analysis of variance, standardized residual sum of squares and performance factor/3.

Light sources had a slight influence on the visual assessments of yarn-dyed fabrics. Among the eight color-difference formulae for measurements of yarn-dyed fabrics, CIEDE2000(2:1:1) outperformed all other tested formulae, and the color tolerance for the perceptibility of CIEDE2000(2:1:1) was 0.62. When the homochromy index (K) of warp and weft yarns of yarn-dyed fabric was lower than 1.25, the color difference based on ΔE*00(2:1:1) between the two samples was acceptable in terms of the color tolerance for perceptibility (i.e. 0.62).

The warp and weft yarns in different color depths could be woven in fabric with a relatively uniform color appearance.

This study could contribute to cost savings by reusing disqualified dyed yarns during the weaving manufacturing process.