Digital BW, The Print

Coating is applied for several reasons:
1) Deeper blacks (L* goes from 21-uncoated to about 11 after coating)
2) Protection of the print (gelatine based emulsions are not permeable
to water)
3) general look of the print

Hopefully, you never need to reapply coating. However, being gelatine
a natural product, could get damaged if stored improperly (much like
silver-gelatine prints). The main difference is that, once the
emulsion in silver gelatin is ruined for any reason, that is forever,
as the image is in the emulsion. With Carbon-gelatine, the image is in
the paper, namely underneath the emulsion, and a good conservator can
easily repair a ruined emulsion without affecting the underlying image

Daniela