We forwarded this question to Gamblin and Robert Gamblin graciously
responded with the following:
Interesting question about Regalrez. Sorry you have issues with 1094,
thousands of us adore it. Just guessing from your brief description is
that most likely your issues with unevenness are because of differences in the
openness in the surface of your work. This most likely would be solved by selective
re-varnishing in those areas, this the way that most painting conservators
Addressing why we use Regalrez 1094 for Gamvar rather than Regalrez 1126:
We are paint, ink, and medium makers, not scientists. We depend upon
the research done by conservation science to identify suitable new materials
for oil painting. The quality of their research and their objectivity is
unparalleled. The studies that our work on varnishes is based on come
from the early 1990’s. (New synthetic resins for picture varnishes, E. Rene’ de
la Rie and Christopher McGlinchey, IIC Brussels Congress 1990)
At that time, Rene de la Rie, Christopher McGlinchey, and their team, mostly
at the National Gallery in Washington, studied several modern synthetic resins,
including mastic and dammar. Two Regalrez resins were included in the
study: 1094, and 1078, but 1126 was not studied, perhaps it had not been
developed by that time.
Important parameters of resins when used as picture varnishes, in addition
to stability, are refractive index and molecular weight. Resins that are
determined to perform the best in terms of light interacting on the surface of
the art and color saturation have values closest to the natural resins such as
dammar and mastic, and also linseed oil which all have similar refractive
indexes and molecular weights.
And as you have identified, the molecular weight of 1126 is higher than
1094,so we then can assume that this resin would cause more light scattering at
the surface of the paint which would decrease color saturation.
I hope you can find your way back to a more stable resin than dammar, but if
not, Rene’s work also showed that including a HALS at 2% into dammar greatly
improves its stability.
Hope this is helpful,