Materials 2025 , 18 , 228
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suggests that they seem to be not as rough as the product T15, but also not as smooth/soft as the product T17. To help us better analyze this last point, let us consider Figure 10, which shows the top surface of the product T20 in detail.
( a )
( b )
Figure 10. Images of the surface of the front side of the tissue product T20: ( a ) global view; and ( b ) magnified view (4 × ) of the area contained in the red square. It can be seen in Figure 10 that, in fact, the surface of the product T20 is not as rough as the product T15, but, on the other hand, it is also not as smooth/soft as the product T17. The creping lines of the base paper are easily distinguishable but more dissimulated, which is revealed to be an intermediate situation between the products T15 and T17. Finally, to complete our analysis concerning this last product, let us verify, in Table 8, the positions (ranks) that were obtained on the four used assessment methods.
Table 8. Basic characteristics and corresponding positions (ranks) of the product T20 obtained for the 4 considered assessment methods.
Number ofPlies
TSA Rank
SUB Rank
KES Rank
OPT Rank
Product ID Line
Thickness
Commercial
High
2
11
9
13
28
T20
From Table 8, this particular product has very similar ranks for the TSA (11), SUB (9), and KES (13), and has a completely different rank for the OPT method (28). This product is a 2-ply commercial product with a high thickness, being a very peculiar case, precisely because of this fact, namely, being very thick but only having two plies on its composition. This is also related to the different rank obtained with the OPT method compared to the other three. By observation of the back side of the product T20, shown in the Figure 9d–f, it can be seen that this surface of the product is filled with an embossing pattern of deep holes. This structure was created on the back side of this product precisely with the purpose of increasing the thickness of the product, which is normally a good thing in terms of the overall softness sensation, due to its increased bulk. However, this created structure also resulted in two other things. The first was an increase in the overall roughness of the paper because the deep holes are easily felt when touched. The second was an increase in the paper’s rigidity. Both things together lead to a product perceived as being less smooth/soft and less flexible, being the most likely reasons why the TSA, SUB and KES methods place this product on the 9–13 ranks of the Table 8. The OPT method, on the other hand, ranked the product T20 as being the second best, with a rank of 28, meaning that it clearly overestimated this product by taking too much into account the thickness of the product, and less into account its other aspects. Considering the obtained results using the four methods, and, by an analysis of the images shown for this last case study, there are no
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