There were a lot of good questions and conversation at PaperCon '18 and the ISO TC 6 Meeting in Korea the last few weeks about Tissue Softness. Here is some explanation of some of the results from the Emtec TSA.
The output of the Emtec TSA goes far beyond just giving a single softness number with excellent correlation to hand feel panel tests. It provides all the data needed to explain the softness number so a determination can be made as to why one product is softer than another. The feeling of softness one gets from a sample is a combination of three main parameters: structure, softness and stiffness. Here is an explanation of some of the outputs generated by the TSA:
TS750 - Structure (smoothness/roughness) Parameter
The TS750 structure peak is the peak at a frequency that falls around 200 - 1,000 Hz. However, this frequency is not fixed like the TS7; it can vary in this range. This peak represents the structure of the sample which includes such things as creping and embossing. Generally, samples with lower structure strength will produce a lower TS750 peak. The creping and embossing process is done to realize a specific structure as it relates to hand feel. Creping and embossing will tend to make this peak higher.
TS7 - Softness Parameter
The TS7 softness peak is the frequency peak that occurs around 6.5 kHz on the noise spectrum graph. This peak represents the pure softness and is influenced by the fiber furnish, the degree of refining, the chemicals and other factors concerning the real softness of the sample. Generally, softer samples produce a lower TS7 peak.
D (mm/N) - Stiffness (deformation) Parameter
This is the deformation of the sample under a defined load and refers to its stiffness.
HF - Hand Feel
This HF number is the calculated figure which corresponds and correlates with the Hand Panel Test. The higher this number is the softer the test sample is and the better it is with respect to hand feel. Hand Feel is when someone touches the sample by hand and ranks it. This is a combination of the other parameters described above: TS750, TS7 and D.