Listed on this page are technical questions that are frequently asked about TAPPI Standards and TIPs. If your specific question is not listed, it may be that you need to be put in touch with a particular expert in that technical area. Send your technical questions to if you do not see you question covered here. What is the difference between the opaque TAPPI Dirt Chart and the transparent TAPPI Dirt Chart? The opaque TAPPI Dirt Estimation Chart is a photographic print of the original chart developed for use with TAPPI T 213 “Dirt in Pulp” and T 437 “Dirt in Paper and Paperboard.” The basis for these two tests is to determine the numerical or visual estimation of dirt in paper, paperboard, or pulp in terms of equivalent black area (EBA). EBA of a dirt speck is defined as the area of a round black spot on a white background on the Dirt Chart which makes the same visual impression on its background as does the dirt speck on the particular background in which it is embedded.

Reflected light is the proper basis of comparison. Only the TAPPI Dirt Estimation Chart, printed on the opaque, white background can properly be used in the tests. Photocopies, transparencies, plastic-covered cards, or printed reproductions of the chart (including the reproductions of the charts printed in the Test Methods for informational purposes) will not give equivalent results and must not be used in order to run the tests as specified in the Test Methods. The official Dirt Estimation Chart for use with T 213 and T 437 must be ordered and purchased separately from the Test Method. Another method, T 537 “Dirt Count in Paper and Paperboard (Optical Character Recognition – OCR),” was developed in 1981 and is intended for the numerical estimation of cleanliness for OCR purposes of paper and paperboard in terms of the frequency of dirt, specks, or marks. Fotografia Per Principianti Pdf To Word more.