Toner density

The most common bleaching agents are copper sulfate, potassium permanganate, potassium ferricyanide, and potassium or ammonium dichromate. Most B R toners require a darker print than usual as there is often a loss of density. However, this is not always the case as copper bleaches will intensify the print. 

Another combination is to use any sepia or polysulfide toner, then Kodak T-26 Blue Toner. To use this combination, wash the print thoroughly after using sepia or polysulfide toner then use T-26 as per directions. The red tone should appear after approximately 15 to 30 minutes in this solution at 90F/32C. This technique usually produces a density loss in the shadows. Start with a print that has higher-than-normal contrast. Cold-tone papers will produce a truer red warm-tone papers will produce an orange hue. 

Selenium begins by converting the densest areas of the print, then the mid-tones, and finally the areas of least density, the highlights. When used at dilutions of 1 19 or greater and a time not to exceed five minutes, selenium toner will not affect image tone with many papers.3 Unfortunately, recent tests indicate that selenium is a less than perfect archival toner,... 

Schmidlin (56) has pointed out that the commonly observed broad range of van der Waals forces between toner and carrier particles causes xerographic development to require much higher electric fields for toner release than those required to establish a sharp threshold. In fact, he argues that if the adhesive forces between these surfaces could be made sufficiently small and uniform ("noise-free"), it should be possible to reduce electrostatic charge density required for a given... 

Figure 4 shows the current density as a function of the applied electric field for the two Hitachi toners. These toners may be considered as solid state colloidal suspensions of iron oxide and carbon black particles in a polymer resin. Note the scale of the axes in these toners, and most toners measured, the experimental data was of the form... 

The statistical fluctuation or noise level of a toner image is also by these postulates dependent on the particle size distribution. The function which relates the statistical fluctuations to spatial frequency is the Wiener spectrum, which is the Fourier transform of the optical density autocorrelation function. In terms of toner images, it is a measure of the dimensional extent over which the presence or absence of a particular toner particle will contribute to density. The density fluctuations can be measured as a function of position, normally with a slit aperture. This is schematically represented in Figure 6 where the left-hand sketch is related to large particles and the right-hand one to small particles. The density data can be used to calculate noise power or Wiener spectrum (8). Formally, the Wiener spectrum is ... 

Figure 6. Schematic of toner deposits and optical density traces, obtained using a slit aperture, of large particles (left), and small particles (right).

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