Size Estimation Chart (Transparency) The TAPPI Size Estimation Chart, is a transparent chart used to measure the size of spots, defects, or inclusions over the range of 0.02 to 5.00 square millimeters in paper and other industrial materials such as textiles or plastics.Instructions for use of this transparency are outlined in TAPPI Test Method T564. The chart can be used in a large number of applications where there is a need to estimate a size (area) by way of a direct comparison to a known circular area. Applications may include, but are not limited to, the measurement of visible ink spatter on printed surfaces, the estimation of the growth rate of bio-colonies, air inclusions in transparent plastic castings and films. These charts also serve as quality assurance resources to determine the size of imperfections in medical tubing, plastics and other materials. Dirt Estimation Chart (Opaque) The Dirt Estimation Chart is the right tool to estimate the equivalent black area (EBA) of dirt or other coloured specks. The round black spots on the white background of the TAPPI Dirt Estimation Chart make the same visual impression as the dirt speck on the material in which it is embedded. The opaque material of the chart is conducive for detecting any foreign matter imbedded in material which, when examined by reflected, not transmitted, light has a contrasting color to the rest of the surface.