Investigation and comparison of hardness meters
Cigarette filter hardness is an important factor in consumer perception of cigarette quality. Many different hardness testers are produced and used within the industry, each using a unique design and testing protocol. The variations among the testers inevitably lead to differing hardness values among the instruments. Understanding both the operation of the individual testers and also the variances between hardness testers is essential in comparing the values obtained on different instruments. The Filtrona Digital Hardness Tester (DHT, no longer produced) has been used in our lab for hardness testing and is the basis for current models in our database. For this study, a Quality Test Module 7 (QTM 7), a hardness meter produced by Cerulean (formerly Filtrona Instruments), was compared to the DHT. Rods representing a span of hardness values were tested with both instruments and a correlation between the DHT and the QTM 7 was developed. The penetration data from the two instruments exhibit a strong linear correlation (R2=0.9925). Additionally, various adjustable parameters on the QTM 7 were investigated to observe the effects on hardness readings. For filter rod penetration, an increase in both load amount and load duration led to an increase in rod penetration. The speed of compression of the filter rods was also studied. Results showed that compression speed had a negligible effect on rod penetration and the resulting hardness of the filter rod. Understanding the relationship between hardness testers and the parameters that influence hardness data is important in comparing hardness values among various instruments and our database model.