articles/Paper/barytaphenomenon-page1
by Mike McNamee Published
It all kicked off around 23 January 2006 with Chau Digital announcing a new inkjet paper, da Vinci Fibre Gloss, with claimed properties that were similar or even better than traditional silver halide. The claims were not misplaced and it is testament to just how good this type of technology is that the table with this article now extends to 28 variants - indeed some were added as we were compiling the list. All claim allegiance to the Fibre Base Baryta flag. Names, however, can be deceptive, some of the products are 'baryta type' and so do not contain barium sulphate, although they display 'air-dried fibre base' properties. This little nugget of intelligence came to light late in the reviewing cycle and left us with a quandry about our phrasing and terminology.
What is Baryta?
The list on the left shows the available synonyms for the mineral, barium sulphate (our favourite is Terra calcarea phlogisto et acido vitrioli mixta). Baryta is not among them, it is usually reserved for a suspension of barium sulphate in gelatine. With the chemical formula of BaSO4, barite it is a dense material; barium has more than twice the atomic weight of iron. It is extracted from mines all over the world, there being about 100 places in the UK alone. Its major use is to create thixotropic pastes to seal oil well-heads during drilling operations. Another prominent application is for the medical 'barium meal'. Here the heavy barium atom is very opaque to X-rays, so creating a quality image. It is a method pioneered in Liverpool, by Thurstan Holland, around 1896. He published more than 100 papers and was a foremost worker in the field of battlefield injury and diagnosis by X-rays.
If you are wondering why it should have ended up as a major component of photographic printing paper, it is because the pure material is very white, insoluble in water and impervious to many acids and chemicals. Originally it had a secondary purpose of keeping contaminant chemicals in the base paper from migrating into the light-sensitive silver halide layer. It is still used in the form of pressed cake as a white reference standard, as it reflects 98% of light falling upon it. Bleached, finely ground barite is prepared in a gelatine slurry form and coated onto the surface of traditional air-dried, gloss silver halide papers and it is the baryta that imparts the sought-after finish. For this reason it is slightly surprising that it has taken so long for the coating to appear on an inkjet paper. The traditional technology was slightly left in the wilderness by the rise in the use of Resin Coated silver halide papers, with their fast-drying, flat-drying characteristic. Here the original baryta layer was replaced by a layer of plastic, as well as an additional plastic layer on the bottom surface, so that water (and the chemicals of the development process) did not absorb into the fibres of the paper base and thus need long washing times. Baryta papers thus retained a premium tag in the fine art silver print market, more difficult to deal with, but with more subtle characteristics.
When used on an inkjet media, baryta imparts the look and feel of its older cousins but additionally has been shown to hold high Dmax values in the blacks and good neutrality of greys and whites. In addition, our analysis soon showed that the gamut volume was extended and that the skin tones were more accurate. This was at a time when the material was very new, indeed we had just two sheets of A4 couriered from Permajet for testing.
In Use - the basic properties
The baryta coatings confer good neutrality to the base white of the paper which may or may not be modified by the addition of optical brightening agents. If OBAs are added there is a cooling of the paper appearance along with a brightening (ie an apparently higher reflectance). These attributes come at a cost, OBAs are less stable to light over extended periods, causing a loss of brightness and yellowing of the base tone. The cooling and brightening also drags the tones towards the cooler base tone of the paper, resulting in a loss of accuracy in absolute terms (even though the image may look excellent). Skin tones, as an example, are dragged towards blue-magenta, causing a loss of saturation.
Despite these apparent downsides, the 'baryta' family of papers have consistently produced the best colour audit data that we have measured for Paper Chase. In particular, the earth tones were more accurate; in statistical terms we found an average of 9.66 ΔE Lab falling to 4.95 ΔE Lab comparing non-baryta and baryta type papers (respectively) under similar test conditions. The improvement was predominantly in the darker tones, assisted by the ability to hold higher densities, but the expanded gamut also allowed for improvements in both hue and saturation.
Baryta - The verdict!
The good news first - these papers are universally good and, of the 20 or so we examined in close detail, they all performed and looked like traditional air-dried baryta fibre based silver halide prints. The Dmaxs, gamuts, metamerism and grey neutralities are all consistently firstclass. Rather than bringing clarity to a choice our study has only served to muddy the water. The only thing that differentiates the papers greatly is cost and the level of optical brighteners present. On that basis Galerie Gold Fibre Silk is a clear winner.
Given that the colour audit data are so close, any decision about which paper to go for will depend upon just five factors:
1. A historical preference for a brand.
2. The tone of the surface (ie how creamy, how much brightener).
3. Price.
4. A coincidental match you may find between an available icc profile and your own system.
5. There are some variations in the availability of sheet and roll sizes.
Of these 1 and 4 are personal, 3 and 5 are absolute, and 2 depends on a personal preference or wariness about OBAs.
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