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  1. #1

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    Optical Brightener for RA-4 Chemistry

    I have been mixing my own RA-4 print developer with reasonable results. However, I find that an awful lot of papers tend to have a cream base because of base fog. It seems that because RA-4 paper is so much more sensitive than the old RC-74 stuff, it does tend to pick up a bit of base fog. The formula I am using calls for an optical brightener, Tinopal SFP, but I understand there are also many alternatives to this. I don't have such a chemical, and I believe it would make my prints more "punchy" by whitening the base.

    My question is: Does anyone have any idea where a modest or small quantity of such a brightener may be obtained? I am completely stumped.....hours spent on Google have not helped, unless I want to order a truckload from China.

  2. #2

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    wow- 5 months, no replies!

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    Ok, here is one.

    Brighteners tend to decompose in the paper and turn yellow! So, the one selected is the one less likely to do this! In addition, brighteners tend to make the blacks turn bluish. Again, they have selected one that minimizes this.

    PE

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    Quote Originally Posted by newcan1 View Post
    I have been mixing my own RA-4 print developer with reasonable results. However, I find that an awful lot of papers tend to have a cream base because of base fog. It seems that because RA-4 paper is so much more sensitive than the old RC-74 stuff, it does tend to pick up a bit of base fog. The formula I am using calls for an optical brightener, Tinopal SFP, but I understand there are also many alternatives to this. I don't have such a chemical, and I believe it would make my prints more "punchy" by whitening the base.

    My question is: Does anyone have any idea where a modest or small quantity of such a brightener may be obtained? I am completely stumped.....hours spent on Google have not helped, unless I want to order a truckload from China.
    First of all, no, I don't know where you could get the optical brightener (OB).

    However, there are some things about OB use in color developer and color papers that might be of general interest.

    The Kodak color developer has contained an OB since 1959. However, the material was not chosen for optical properties but its ability as a large, water soluble molecule to form complexes with freed sensitizing dyes so that they could be more easily washed out. As PE commented, a disadvantage of this use of an OB is that whatever is not washed out contributes to a bluing of the blacks (a more neutral black was preferred). Therefore, an OB was chosen that was relatively inefficient for brightening power. PE also mentioned the use of OB in the support so here's some info on that. An OB (an efficient one) has been used in the raw base paper of Kodak color papers since 1974. A different OB has been used in the face side RC layer since 1988.

  5. #5

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    Fotospeed for one does a combined optical brightener/stabiliser liquid which is said to brighten the print's colours. Would it remove the off white colour you have in the paper? I have no idea unfortunately.

    pentaxuser

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    Thanks all for this interesting information. I didn't realize that Kodak papers incorporate a brightener. I suppose I could just buy Kodak developer, but I rather like mixing my own from dry chemicals given my sporadic use.

    I came across some stuff made by Sprint Systems, but for black and white papers. I tried it with some RA paper and it did seem to brighten the print up a bit, but from what Photo Engineer is saying above, I'll probably regret it later when it breaks down!

    I am aware of the Fotospeed product, but have found it impossible to acquire here in the US. Freestyle had some for a while, but then it disappeared mysteriously. I hate it when things like that happen.

  7. #7

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    Nova Darkroom does similar stuff. It might even be Fotospeed stuff since as far as I am aware Nova doesn't make its own chemicals. I don't know if it can export directly to the U.S.

    pentaxuser

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    To add to what Papermaker said, Kodak removed the optical brightener from the Ektaprint C and Ektaprint 3 developers and then put it back into the RA4 developer. It was causing too much bluing, too much yellowing due to retention of the dye, and it was just not good enough for all of the purposes it was intended for.

    In addition, the sensitizing dye in the green (magenta) layer was replaced in 1970 with a new dye that washed out differently and the brightener did not work properly. I believe that it has been changed several times since then.

    PE

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    mts
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    It has been my understanding that optical brighteners work by converting UV (in sunlight) to white light, and are therefore ordinarily used in washing detergents to yield "whiter whites." I wonder how they might be able to improve whites in photo papers that are normally viewed under artificial light with negligible UV, although there is no doubt a bit of UV emitted by florescent bulbs. If the intent is to remove residual dyes, then we aren't talking about the same sort of OBs that are used in detergents....
    By denying the facts, any paradox can be sustained--Galileo

  10. #10
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    Optical brighteners make prints less archival. Correct me if I'm wrong but I think adding in your own/extra would also cause this to happen.


    Eg; is why the inkjet papers without any brighteners are popular.

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