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  1. #1

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    RA4 baryta papers: difficulty?

    I'm wondering, how much more difficult is it to coat baryta papers with color emulsions for RA4 process, compared to coating with BW emulsion?

    Maybe it's a silly question... ?
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  2. #2
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    All color paper was on Baryta until the mid 60s, and then the conversion to RC began. This was done in the interests of decreasing pollution and processing time. Baryta absorbs a huge amount of chemicals and this must be washed out.

    The coating formula for many Baryta papers had to be adjusted with respect to RC due to the fact that Baryta absorbs chemicals from the emulsions and RC will not. Therefore, RC papers would keep better than the same formula on Baryta, and would be somewhat slower with the same formula.

    PE

  3. #3

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    Thanks!

    I'm guessing we won't see color baryta papers in the near future? :-)
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    Not unless we coat our own.

    PE

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    Many B&W printers still don't get this, but RC paper base can give greater reflectance and therefore slightly wider range of image tone. Combined with shorter storage/display life of dye image from RA-4 papers compared to properly toned silver image, I don't realy think there is a very good reason to make color paper on baryta base.

  6. #6

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    But still... the surface on an air-dried glossy baryta print would look pretty darn good on a color image...
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  7. #7
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    Current images from color RC papers are expected to last from 100 to 200 years depending on the keeping conditions and manufacturer. This has been achieved during the last 10 years or so, although overall image stability has been improving constantly for the last 50 - 60 years since the introduction of the first color imaging materials.

    This would probably not be possible on Baryta paper support. It is mainly due to the UV absorption properties of Baryta vs Titanium Dioxide used in the two products, but also in other factors involved in the RC/TiO2 base. For example, it is possible to incorporate antioxidants into RC support for stability that are impossible to add to Baryta.

    OTOH, B&W images in silver are apparently of similar stability on either Baryta paper or RC support and are limited mostly by the quality of the process and the stability of the paper. At the present time, Baryta paper images are known to survive for over 100 years.

    Early RC prints are not as stable due to the degradation of early RC due to UV and oxygen.

    Having been directly involved in the testing of these images from about 1965 - 1970, and having kept up with the studies thereafter, I am quite aware of the advantages and disadvantages of the paper, dyes and silver images.

    I might add that at normal viewing distance, you might not be able to distinguish between a color print on baryta support and a color RC print.

    PE

  8. #8

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    Quote Originally Posted by Photo Engineer View Post
    Current images from color RC papers are expected to last from 100 to 200 years depending on the keeping conditions and manufacturer.
    This depends not only on the material used, but also the test condition and interpretation of the data. It also strongly depends on the acceptable color shift or density loss used to determine the life of the image. There is no single valid set of criterion and test method, so that the published test results vary a lot even for the same material, such as Kodak Endura. Depending on the test conditon and interpretation, this same material is rated 20 years (stronger light, no UV filter, etc., used by Wilhelm) and a couple off hundred years (weak light, UV filter, etc., used by Kodak). Images on current Endura may last for 200 years in ideal refrigerated museum storage with molecular sieve, but in the storage condition of average consumers, I doubt that the image will go significantly faster.

    However, I also believe that modern RC paper base is a lot more permanent than earlier ones. I also agree that antioxidants added to the polyethylene resin are not usable in baryta sizing layer. Those antioxidants have to be nondiffusible but there is no good way to make hydrophilic nondiffusible antioxidants to add to baryta sizing, but it's easy to make nondiffusing hydrophobic antioxidants for polyethylene.

    Another consideration is that I have a final rinse solution that adds UV blocker and antioxidants to the print. (Similar idea to sunscreen protection but with extra antioxidants.) I'm not sure why Kodak or Fuji never came up with this kind of solution (perhaps cost consideration, as the ingredients are not very cheap), but this treatment is very effective with untoned silver images on RC base in my testing with UV and oxidizing agents.

  9. #9
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    Kodak used an antioxidant buffer bath for years as a stabilzer. It was sold as Kodak Ektaprint Type II stabilzer. I have a patent on a modified version which is now used by several other companies for films. The Type II stabilzer greatly enhanced the stability of color paper, sometimes by over 2 - 5x depending on conditions.

    As for dye stability, I am quite familiar with the antioxidants in both the paper support (see patents by Venor et al) or in the coupler dispersions (see patents by Lestina et al). I helped develop the first color paper to incorporate the work of both of these people and others (see patents by Edens and VanCampen). I am familiar with the methods of testing and the reporting of them (See work by Tuite or Wilhelm or Kapecki).

    The questions of testing conditions involve the use of 200 fc or 500 fc for fade tests under light, and what ingredients to add to the gas mixture and what proportions for the high temperature and humidity tests. These are under debate between Fuji, Kodak and the standards committee.

    The most recent compilation of this was by Kapecki at the ICIS conference in May and discusses all of these issues and more. RIT has a very large lab entirely devoted to research on this subject.

    I have been tracking the subject since I was first introduced to it in 1965, and I have seen data going back to the 40s showing the history of this subject as it evolves.

    It is much too complex an issue to discuss here. It is like dipping a toe into the ocean and saying you are now an expert on marine biology.

    PE

  10. #10

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    Ron, I'm very familiar with the work you mentioned, except I don't know Ektaprint Type II stabilizer. Do you have a patent number or name of compounds used in this final bath? Does it also improve the image stability of modern papers with antioxidants incorporated in the emulsion layers, or does it work on a different mechanism?

    Anyway, the main reason I brought these up is really to make a point that there's really not much point in making baryta color paper. A lot of writers from 1990s criticized photo manufacturers to make more profit from RC than baryta, saving silver from emulsions, etc. and a lot of people seem to believe that those criticisms are valid. It's always hard to fight against common misconceptions but this is the time to do so.

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