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Author Topic: IGFS  (Read 19261 times)

Mark D Segal

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Re: IGFS
« Reply #40 on: July 22, 2015, 08:41:14 pm »

Hi Mark MG,

I agree - my stuff is in the equivalent of dark storage. BUT that said, if I still see a difference of paper white between stock that is 7 years old and stock that is 1 year old, either it's my imagination (which I'll check with readings), or the surface colour stability may not be all that great - even in dark storage. However, the printed areas still look fine. So ink may cover "many a sin". I think the more important longevity issue for me is what happens to the colours, and less small changes in paper white provided they are even. For B&W photography however it may be a different matter.

The 4900 sensitivity issue - as I've said elsewhere - "it depends" - (a) how bad the problem is, and (b) how much it matters to you, and both factors could be correlated. In my particular case, I'd prefer not to have to bother with nozzle checks and cleaning, but none of it has been fatal, and the quality I get out of this printer is so good that for me the maintenance is not a deal-breaker. This is subjective - will vary from person to person, just speaking for my own experience and priorities. My main focus is the ink on paper - not how the paper feels, so even if these x900s are more sensitive than other models, I wouldn't be scrapping this printer on that account.

I shall check out the Hahn FA Baryta satin - thanks for the suggestion.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....."

Ernst Dinkla

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Re: IGFS
« Reply #41 on: July 23, 2015, 04:38:55 am »


 My only slight disappointment with the new HN FineArt Satin is that it's about 1 point warmer in b* value (2.4 versus 1.6) yet it's L value is also a little higher, so which one is "whiter" depends on your personal taste. You just need to look at a sample to see if it suits your needs.

best,
Mark

Hello Mark,

Yes, going along with my visual experience too, the higher the Lab L value the less it matters that a paper has a higher b value (is warmer).

An interesting question after your XRF tests is whether BaSO4 is a better companion for OBAs than TiO2 in relation with the LILIS effect. In non-RC silver halide prints, now decades old, there must a clue for this based on both combinations. It would surprise me if they all were based on the same whitening agents.

There is another reason why this may prove to be a better component for OBAs, both TiO2 and OBAs absorb UV light, TiO2 emits the energy as heat beyond infrared. If the UV absorption is in the same wavelengths then TiO2 will block UV for OBAs if they are further into the paper construction, the place normally more suited for OBAs for longeviy. As OBA UV absorption can happen at different UV wavelengths (and SpectrumViz's Eye1 Pro is not revealing all OBA types) it becomes more complex.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots


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Sbarroso

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Re: IGFS
« Reply #42 on: July 25, 2015, 07:43:21 pm »

Some forms of TiO2 are known and used to generate "HO·" radicals from water and light. These radicals are more reactive than hydrogen peroxide. They are used to convert organic material into CO2 (e.g. for cleaning residual waters).

OBAs should be quite sensitive to radicals. A small modification of their chemical structure and the fluorescence is gone.

Most probably the TiO2 used for coating papers is a not the proper one for generating radicals. But trace amounts of active forms could be always present and help to a (very) slow degradation of OBAs and, even the paper it self.

I´m not an expert on the field, so take it with a big grain of salt. But at least is the word of a chemist :P

BTW: I´m waiting for a package of A4 and A3+ of the HM Bariya Satin. I used last week the last sample I got in the photokina and I was, again, impressed. It really reminds me the baryta papers of my darkroom days. If I do a comparison it won´t be probably so close... but probably better. I do like the surface similar to IGFS, a litle bit less glossy may be. But its body it´s more "organic / natural cartoon" than IGFS. Similar to the rag baryta, but with no so much texture. I even find the surface more even than the HM rag satin.
I may keep using IGFS (actually the HM silk clone) for routine work, but I will probably use the new HM Satin in many prints where I hesitate to use the expensive HM Rag baryta, especially for BW.

Mark D Segal

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Re: IGFS
« Reply #43 on: July 26, 2015, 11:05:32 pm »

Hi Mark MG,

I agree - my stuff is in the equivalent of dark storage. BUT that said, if I still see a difference of paper white between stock that is 7 years old and stock that is 1 year old, either it's my imagination (which I'll check with readings), or the surface colour stability may not be all that great - even in dark storage. However, the printed areas still look fine. So ink may cover "many a sin". I think the more important longevity issue for me is what happens to the colours, and less small changes in paper white provided they are even. For B&W photography however it may be a different matter.

.....................

Well, the readings are done, and the bad news is that this paper white does seem to yellow ever so slightly over the years. The attached graphic is self-explanatory, but a few added words may help. Focus on the Lab readouts. b* is the critical one - the blue-yellow axis. The most recent stock of Swiss paper I have still boxed unused from just before the bankruptcy last year is measured in the top box of four readouts. This is two each on different places of the same sheet. The center box contains readings from various pages of two albums. These are bound volumes with no light shining on them (exactly like closed books, because that is what they are). The b* readings range from about 1 to 1.6. This is over a period of 7 years. The bottom box contains 4 readings of the paper back. The first two from the more recent stock, and the bottom two from the old stock. Perhaps b*4 is the worse the yellowing can get? And over what time period?
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Mark D Segal (formerly MarkDS)
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Alan Goldhammer

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Re: IGFS
« Reply #44 on: July 27, 2015, 04:54:11 pm »

Some forms of TiO2 are known and used to generate "HO·" radicals from water and light. These radicals are more reactive than hydrogen peroxide. They are used to convert organic material into CO2 (e.g. for cleaning residual waters).

OBAs should be quite sensitive to radicals. A small modification of their chemical structure and the fluorescence is gone.

Most probably the TiO2 used for coating papers is a not the proper one for generating radicals. But trace amounts of active forms could be always present and help to a (very) slow degradation of OBAs and, even the paper it self.

I´m not an expert on the field, so take it with a big grain of salt. But at least is the word of a chemist :P

Well I am a chemist and "HO-" radical is the same as generated from hydrogen peroxide.  Hydrogen peroxide because of it's strength would be far more reactive than small amounts of radicals produced from TiO2 (and I'll have to check the literature to see about this).  Remember that TiO2 is heavily used in the paint and coatings industry.  Exterior paints face sunlight and moisture every day and one doesn't see really dramatic fading in the short term.

It's interesting that photo paper manufacturers are using mixtures of titanium dioxide and barium sulfate these days and call them baryta papers.  I guess there is no truth in advertising.  It may be that the price point of TiO2 is much lower than barium sulfate and they have gone to a mixture as a cost control.
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MHMG

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Re: IGFS
« Reply #45 on: July 27, 2015, 06:17:33 pm »

...  Remember that TiO2 is heavily used in the paint and coatings industry.  Exterior paints face sunlight and moisture every day and one doesn't see really dramatic fading in the short term.


Yes, agreed, but one has to keep in mind the total bulk volume of pigments and binders as applied in typical artists' paintings or when applied to interior and exterior walls on homes as compared to the ultra thin dispersions of both ink pigments and media coating layers in inkjet prints. Thus, one can have significant amounts of fading, chalking, and binder break down in a typical house paint, yet there is still plenty of bulk binder and pigment volume left on the siding of the house to retain a significant degree of initial product quality appearance over several years in intense outdoor weathering conditions.  Not so with the very thin layers of pigment and binder in inkjet media. I see this issue played out over and over again when considering the surface chemistry reactions that affect image quality in prints and photographs in relationship to expectations of stability we would surmise when comparing the same chemistry in bulk volume reactions.

My first experience with surface corrosion chemistry versus bulk chemistry kinetics occurred when I was researching the degradation of some wet plate negatives made in the Matthew Brady Studios during the 19th century. It turned out that the degraded plates had poor stability glass substrates. It was not the expected cellulose nitrate coating degradation, but the corrosion of the glass substrates leaching sodium hydroxide into the image coatings and thus saponifying the natural resin varnishes, turning them into a sticky hygroscopic mess that could then attack the silver particles in the image.  From a bulk chemistry perspective, these poor quality glass substrates were still 99.999% in perfect condition, but that several hundred angstroms of glass corrosion at the glass/coating interface was enough to deliver the lethal amount of sodium hydroxide into the varnish coating layer which was only about 1 micron thick.

best,
Mark
http://www.aardenburg-imaging.com
« Last Edit: July 27, 2015, 10:42:13 pm by MHMG »
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