Ether and acetone indeed were for speeding up the drying. However with
isopropyl alcohol I got some difficulties with the highlights: They tend
to loose contact. So I switched back to aquaeous solutions...
It is rising the pH and thus lowering the papers speed and increasing
the contrast. This helps to prevent somewhat the "dark effect", the
increase of speed after the tissue had been dried and should help to get
more consistent results. As far as I understand from reading the
intaglio printing literature, adding ammonia was common practice when
large amounts of carbon tissue had to be prepared in the morning or in
the evening to be ready for next day's use and were used throughout the
day.
Klaus Pollmeier