I’d say it doesn’t swell enough for you to tell, unless something is really wrong with the board construction.
However grinding debris can smear across the surface being examined and individual fibers can pop out (including non-conductive fill material from a capped thru hole for example), those would be attributable to micro sectioning and do not reflect construction.

> On Mar 8, 2017, at 11:21 AM, [log in to unmask] wrote:
> 
> Fellow TechNetters:
> 
>   Does PWB laminae swell during the cross sectioning process on an encapsulated mount?   During a 100x Optical inspection of the glass weave cloth I get a blur image.   I get a sharp image of the glass cloth in the SEM.   I can even count the individual rods and measure their diameters.
> 
> Victor,