Positive prints, making

The fixed plate is now a negative , for those patches on which most light fell are black. The process is reversed in printing to make the positive —the printing paper having a covering of silver chloride or bromide or a mixture of the two. This, in turn, is developed and fixed as was the plate or film. 

Materials are now available which allow rapid access to positive colour reflection prints. This is achieved by incorporating, at the time of manufacture, into special picture-making units, all the chemicals required for the subsequent processing of the units. Thus, a viscous alkaline activator solution is contained in a pod and layers which cause the lowering of pH, after development of the unit has taken place, are included (B-77MI11403, B-79MI11400). 

Similarly, a fast and simple method to produce print-quality like Ponceau replicas from blots was recently described (68). The positive replicas are the same size as blots and can be stored without loss of intensity. This makes them useful for localizing immunoreactive spots in complex 2D electrophoretograms. 

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