I put the following experience forward as a parallel that may be relevant
to your problem of the gum arabic acquiring the consistency of phlegm or
snot or something that would be more appropriate to a sheet of Kleenex than
a gum print.
When using either Gloy or gum to make gum prints I have found that if I
used Liquitex cobalt blue and mixed it with the gum or Gloy it immediately
assumed the glutinous consistency to which you refer. It was clear that
there was something in the Liquitex cobalt blue that had that effect for
it did not happen either with other Liqutex colours or with water-colour
cobalt blues but there is a tendency for it to happen with other acrylic
cobalt blues. Liqutex just happened to be the first acrylic colour I used
when, one day,I could not get a tube of W & N water-colour.
It was clear that there was something in the Liquitex cobalt blue that was
causing cross bonding resulting in the strange consistency. While I found
this an interesting problem, it had no practical significance as the
addition of a saturated solution of dichromate caused the 'phlegm' to
return to its normal consistency.
So I just went on to produce the gum print with the beautiful blue !
What caused the 'phlegm' remains an intriguing puzzle.
Terry King