Ink colour stability in proof and prints
Ink colour stability in proof and prints
- Subject: Ink colour stability in proof and prints
- From: "Ernst Dinkla" <email@hidden>
- Date: Wed, 31 Jul 2002 23:51:42 +0200
The issue of drying time and stability of colour in proofs and profile
targets is often discussed on several mailing lists. My experience has been
limited to profile target printing of pigment inkjet inks and I'm lucky to
have a silkscreen drier of 20 feet length with temperature control and lots
of air. To be on the save side and when the time is there I still let the
target dry for 24 hours or longer.
There are some issues in proof printing that I'm curious about. One thing is
how stable offset printed colours are in the first 72 hours. It probably
depends on the hardening methods, heat set, oxidative, UV etc. but is there
any knowledge on that subject ? Conventional press proofs fall in that
category as well. I wonder about this aspect as we know that inkjet prints
change in the first 24>72 hours. Nice to get an offset print right to the 72
hours old proof but what colour does it have when the customer gets it
delivered ? My silkscreen experience tells me that the UV dried colours are
stable, the physical drying colours not that stable and the water based
physical drying not stable at all.
Another issue is whether humidity has an influence on inkjet colour
consistency after say 72 hours. Obvious standards like viewing light
conditions are normal in a printshop. Humidity control in the pressroom as
well and probably also in the prepress department. I'm still curious whether
40 % humidity versus 70% humidity gives different readings by a
spectrometer. Dye inks most likely will be more influenced than pigment
inks. Drying conditions, storing, packaging must have an influence if
humidity plays a role.
The choice for pigment or dye in inkjet proof printing now exists as the
gamut of inkjet pigment inks is bigger than offset inks. Gloss printing with
pigment inks is possible too. The time it takes for dyes and pigments to get
stable colourwise will not be very different. Pigment ink proofs will hold
that stability for a much longer time if fading by light and gasses plays a
role in proof examination. Pigment inks are usually more 'metamerism' prone
than dye inks however. Epson 9600/7600/2200 have an extra light black to
reduce that 'metamerism', will that affect their use as proof printers ?
The last question I have is how much 'metamerism' exists in the usual offset
inks ?
Sometimes it seems that we try to get a stable target for shooting at a
moving target.
Ernst
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