It's exactly what I was discussing in that thread.
Originally Posted by Michael R 1974
The big mistake is that when people describe prints with excessive grain some talk of grain clumping. Kodak talk about the grain size in films and the graininess in prints.
What a films grain looks like under a microscope can be measured and is quite different from the graininess of a print which is also affected by any surface artefacts of the emulsion.
The thread was taken off path by misunderstanding. Micro reticulation is the surface reticulation of a film or paper. With an RC paper it causes a dull sheen and you can easily induce it with temperature changes, steaming reverses the effect, it can happen with colour & B&W papers, RC or FB. Temperature of drying can play a part as well.