Figure 7 shows the results of iodine (= starch) mapping for untreated, starch treated and starch-polymer treated samples of the same paper. It is immediately obvious that starch coverage is lowest on the untreated paper and highest on the starch plus polymer treated paper. The addition of the polymer to the starch mixture increases its wetting capability, allowing it to cover more of the surface. In terms of print quality, (wicking, feathering, print through and show through) these papers rank in the same order, the untreated base sheet having unacceptable print quality and the starch + polymer treated sheet having the highest print quality. This indicates that with all factors equal, simply increasing the starch coverage improves print quality. It is also interesting to note that the distribution of starch parallels the distribution of pcc (Figure 7d). This is contrary to conventional thinking which would suggest that starch would not be associated with pcc due to the low surface energy of pcc.

Figure 7 Iodine maps of the same paper subjected to different treatments. a) starch + polymer treated, b) starch treated, c) untreated, d) Ca map of same area as a)..