A quantitative evaluation of paper printability has continually been a main concern to both papermakers and printers,and this thesis,utilizing a new stochastic approach called "Dynamic Data System(DDS)" analysis, develops certain quantitative indices for determining the printability of various grades of papers. Furthermore, a mathematical model is determined for the paper surface from profile data and the model is used for the physical characterization and analysis of the printing process.

Among the several paper properties which influence its printability, the surface smoothness is considered to be the most important characteristics. A highly sensitive tracing instrument is used to collect surface smoothness data in terms of profile heights. The profile heights are assumed to be a random variable and are represented in terms of the spectral moments,because of the inherent stochastic nature of the paper surface. These moments are used to develop such statistical geometric properties of a surface as the density of summits, contour length, excursion area, percentage void and the sharpness index, etc. in order to characterize the paper surface for the printability evaluation.

The printability criteria are developed for the various grades of papers used in three different printing processes- Letterpress, Gravure and Offset, but the heavy and light weight letterpress papers are analysed separately. The number of peaks, the percentage void at a specified level of depression, and the variances of profile slopes and curvatures are a few of the indices proposed for the printing quality prediction of the heavyweight papers. For the lightweight papers, the moment ratio, the sharpness index and the percentage void are derived as useful printability indices. An application of these indices to a number of paper samples shows that the new indices are capable of evaluating coated paper printability in a quantitative manner.

In addition, the cavity width and depth distributions are used to derive such printability indices as the acuteness of pits, pattern depth and surface irregularity for the gravure, embossed/dull and general purpose offset papers. A large number of paper samples were tested using the new indices, and the results in all the cases indicate that the wire side of a paper is rougher than the felt side. Furthermore, the pattern size of the embossed paper can be easily identified from the dominant peak in the cavity width distributions. Printability evaluations by the new indices are compared with the results of other smoothness testers such as the Sheffield, Bekk, Parker Printsurf, Fogra-KAM and Smith Gravure, and the results are found in close agreement with each other.

The optical properties such as gloss and optical unevenness are also evaluated by the DDS approach. The surface reflectance measurements are obtained from an optical scanner. The average specular reflection coefficient is derived and is used as an index to characterize paper gloss. The relationship between the reflectance profiles and the smoothness profiles is studied through an interrelationship model. The spectral density curves for the diffuse reflectance data are used to characterize the lightness variation of the paper samples.

The results of the current research show that the method can be computerized and directly applied in a paper mill for quality control purposes.