Digital BW, The Print

Paul,

Thank you very much for that link. I have put added the website to the links
section of the group. I am working my way through the paper. Very
interesting stuff and a lot to digest.

One thing strikes me though. While we need to be informed about conservation
and longevity, I really have to question to what degree we should let this
rule our art. If we feel one set of materials is better artistically, even
though it may not be the best for longevity, maybe we should follow the art.

Martin Wesley

http://www.borderless-photos.de/guests.html



----- Original Message -----
From: "Paul Roark" <paul.roark@...>
To: "DigitalB&WPrint" <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Wednesday, October 16, 2002 3:15 PM
Subject: [Digital BW] Preservation of Inkjet Hardcopies


> I just read a paper entitled, "Preservation of Ink Jet Hardcopies," (M.
> Jurgens, 1999 http://www.knaw.nl/ecpa/PUBL/InkJ-300.pdf ) that has a
number
> of interesting facts that I had not seen elsewhere.  While the article is
> aimed at conservators, it has good explanations of many facets of the
> technologies we are using.  I've put some of my notes below.  My comments
> are in brackets; page numbers are in parentheses.
>
> I Ink Jet Printing [a general overview]
>
> The brighteners used in many coatings are titanium dioxide pigments. (20)
>
> II. Materials Analysis (29)
>
> Pigments and Dyes (31)
>
> The majority of pigments used in ink jet ink today are organic.  Organic
> pigments are produced by chemically "stacking" organic dyes to form larger
> particles.  Formerly water soluble dyes are stacked like wet glass plates
on
> top of each other, forming a crystal-like structure that precipitates out
of
> the aqueous solution. (31)
>
> [This could explain the seeming confusion about whether the pigments we
use
> contain dyes.  They may be dyes that are simply "stacked."  Nowhere did I
> see a description of a coated carbon particle.  I'm begining to wonder if
> the color pigments have any carbon in them at all.]
>
> Smaller pigment particles have better color, gloss and transparency but
> worse lightfastness. (32)  [UC inks come to mind.]
>
> The harder a pigment particle is, the more abrasive it will be in the
print
> head and the more it might endanger the integrity of the fragile nozzle
> opening.  Organic pigments are generally softer than inorganic ones. (32)
> [Metal added to black to make it darker might not be the best solution.]
>
> Organic Colorant Classes (35)
>
> Water soluble azo dyes will have a sulfonic acid group (-S03H).  Azo dyes
> are the most common dye molecule types.  [Imagine what that acid does when
> it hits an alkaline buffer.]
>
> Copper phtalocyanine cyan dyes are counted among the most brilliant and
> stable of dyes.  [The cyan pigment might be a "stack" of these.  It
appears
> to be the most stable in my fade testing.  The key to a good midtone, in
my
> view, is a pure carbon particle toned with cyan pigment.]
>
> Chemically inert pigments employed in ink jet printing include carbon
black,
> diarylide yellows, metal salt reds, pthalocyamine blues, and mono azos.
> [I'm not sure "chemically inert" implies resistance to being broken by UV
> and visible light.]
>
> Ingredients of Liquid Inks
>
> Colorant
>
> Pigment particles are large enough to scatter white light on their
surface,
> whereas dye molecules are much smaller than the wavelengths of visible
light
> and thus do not scatter any.
>
> Substrates
>
> Paper Media (38)
>
> Bond Paper
>
> The most common internal sizing is that of the tree resin called rosin,
> which is mostly an organic acid. (39)
>
> Archival Paper (40)
>
> While the most stable paper is made from cotton, chemically purified wood
> pulp, such as that used in fiber-based B&W photo paper, is also suitable
for
> long term archivability.
>
> The use of rosin sizing would be counterproductive.  These papers tend to
be
> internally sized with synthetic alkaline substances ... buffers ... most
> common calcium carbonate.
>
> Coated Paper
>
> These have better image quality, but ageing characteristics have not been
> explored thoroughly. (41)
>
> Paper-Plastic Combinations
>
> RC based papers are likely to develop problems similar to those of
> photographic RC papers.
>
> Receptor Coatings (43)
>
> [Typical single layer coatings include a number of ingredients.  These can
> be complex mixes, which, of course, means that the interactions with inks
> and other chemicals might also be very complex and unpredictable in the
long
> run.]
>
> Some matte coatings are almost entirely silica particles.
>
> Some silica coatings might be slightly acidic. (44)
>
> Laminates and Coatings (45)
>
> It is generally recommended not to laminate or coat valuable prints, since
> the danger of unwanted interaction between the laminate and the image
> forming dyes is present and as yet widely untested.  Coatings are
> practically non-reversible.
>
> Varnishes are vegetable oil formulations that air-dry.  Lacquers are
> solvent-based and dry to a high gloss, but they often lack good adhesion
and
> flexibility.
>
> Lamination of Longevity?
>
> Lamination at one time was used to preserve papers, but has fallen out of
> favor.  Although lamination was controversial for the beginning, later
> critics mainly only attacked the use of insufficient deacidification
rather
> than the lamination itself. (46)
>
> Some documents had become brittle inside of the lamination, perhaps a
result
> of cellulose acetate [the film used] deterioration.
>
> Lamination of Ink Jet Prints
>
> For advertising banners, etc., the benefits of laminates or coatings are
> well suited to the purpose -- short term protection.
>
> A fin art hardcopy that will either be exhibited in controlled lighting or
> be carefully housed will not necessarily need the brute protection of a
> laminate.  In order to avoid any as yet unforeseen complications that
might
> arise with the long term intimate contact between a plastic and the ink,
not
> to mention the largely irreversible character of the physical fusion, it
> might be wise to avoid laminates or coatings altogether.
>
> If protection against physical damage is needed, then it might be
> appropriate.
>
> Preservation Issues (48)
>
> The main concern in long term stability of ink jet prints is their
> relatively weak light-fastness.
>
> Light and UV-Fastness
>
> Dyes will not only fade due to UV, but also due to the effects of visible
> light. (52)
>
> UV radiation in the 200 - 400 nm range is primarily what causes
> photochemical reactions and bond ruptures in organic compounds.
>
> Reactions between the colorants and the substances in the coatings are
> typically of reductive and oxidative nature.
>
> Colorant Fading
>
> The photolytic deterioration of organic colorants is the main factor.
>
> If a double bond is broken, the conjugation length of the molecule is
> reduced, and the color absorption capabilities are disturbed, either
leading
> to a loss of its absorptive and reflective capabilities which is perceived
> as fading, or leading to a shift in wavelength absorption which results in
a
> color shift.  The complete rupture of a bond (cleavage), such as  is
> possible with azo groups (-N=N-) leads to the division of the molecule
into
> two smaller ones, which will each have shorter conjugation lengths. (53)
>
> [This color shift may be part of the warming we see with most dyes and
> pirments used in B&W pritning.]
>
> Magenta dyes have continued to be the least light stable. [My recent
> UltraChrome and MIS color pigment test seems consistent with this.]
>
> Magenta and black dyes have long posed stability problems.
>
> The size of the pigment stacks assist in dissipating the energy.   Also,
> already faded surface molecules can act as light barriers for the internal
> molecules of the pigment crystal. (54)  [Perhaps this is part of the
reason
> there seems to be faster fading of pigments at first.]
>
> Pigments vary in their lightfastness depending on the internal structure
of
> their particles.  Large crystals free from defects will probably have a
> higher lightfastness.
>
> Substrates and Coatings
>
> When the presence of the ink receptor coating with its complex mixture of
> binders and additives is taken into account, the prospect of permanence
> testing and research becomes daunting.  It is partly for this reason that
it
> is largely recommended to print documents that are to be valued in the
long
> term on thorough tested, well known, high quality, and uncoated substrates
> such as 100% rag content artists' paper.
>
> An alkaline environment might increase the lightfastness of a print, but
it
> could also reduce the color gamut.  As the image quality is the current
> driving force in sales, manufacturers are reluctant to trade off color for
> permanence.  [So, it might be that we would be better off with a more
> alkaline surface -- contrary to the color printers.]
>
> Little is known of interactions between the coating and the substrate in
> environments of high humidity and temperature.  Problems have arisen with
> the structural stability of coated vinyl substrates; due to the smooth
> surface of the vinyl and the tendency for integrated plasticisers to
migrate
> to the film surface, the coating can partially fail to adhere, which can
> lead to flaking. (54-55)
>
> Laminates
>
> For advertising, laminates will greatly enhance weatherability.
>
> Water vapor and oxygen will diffuse through the plastic in small amounts
> over a long period.
>
> Lamination can only be recommended for prints that have no high monetary
or
> artistic value.
>
> The overall understanding is that, thought the protective coatings may
> enhance the durability in the short run and in extreme environments, the
> long term consequences cannot be completely predicted.
>
> One-sided coating can be problematic in that substances access the reverse
> side and diffuse through the substrate to form stains that are visible on
> the front, but inaccessible due to the plastic coating.
>
> If a print is to be sealed, be sure it is completely dry -- 24 hours.
>
> De-lamination has been successful. (56)
>
> Spray-on lacquer used in photography consists of cellulose nitrate and
> introduces all the aging related problems associated with that chemical,
> including yellowing and production of nitric acid gases.
>
> UV absorbers integrated into the lacquers and the cellulose nitrate were
> also responsible for these reactions.
>
> Recommendations (57)
>
> Inkjet hardcopies can be extremely complex objects.
>
> As inks become more and more light stable, the generation of hardcopies
from
> the last ten years will become one know to be condemned to rapid fading,
but
> it would seem that this is a phase that well eventually come to an end.
> [But will any of us live long enough to see it?]
>
> Paul
> http://www.PaulRoark.com
>
>
>
>
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