Optical Brightener for RA-4 Chemistry

Discussion in 'Color: Film, Paper, and Chemistry' started by newcan1, Jan 8, 2012.

  1. newcan1

    newcan1 Subscriber

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    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. newcan1

    newcan1 Subscriber

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    wow- 5 months, no replies!
     
  3. Photo Engineer

    Photo Engineer Subscriber

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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
     
  4. papermaker

    papermaker Member

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    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. pentaxuser

    pentaxuser Subscriber

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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
     
  6. newcan1

    newcan1 Subscriber

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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. pentaxuser

    pentaxuser Subscriber

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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
     
  8. Photo Engineer

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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
     
  9. mts

    mts Subscriber

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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....
     
  10. Athiril

    Athiril Subscriber

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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.
     
  11. frotog

    frotog Member

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    Before searching for an OB for your developer might I suggest you run some ra4 control strips? If you're using fresh paper and your chem. is adequate you should have a baseline for dmin to work with. The current kodak vc paper has an excellent, bright paper white. Any paper that's slightly out of date or corked chem. will show significant increases in dmin.
     
  12. Photo Engineer

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    OBs will NOT affect archival qualities of prints. They can affect the yellowing of prints with long term exposure to sunlight due to degradation of the OB, but the OB in the developer has been selected to minimize this problem by leaving behind no yellow fragments and thus the brightening effect fades with time.

    The OB is specific to the paper and can have several functions. The wrong one will have the wrong (or no) effect.

    PE
     
  13. papermaker

    papermaker Member

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    Optical brighteners work by absorbing in the UV part of the spectrum and re-emiting in the blue (visible) spectrum. The re-emited blue is an increase in the total light reflected and serves to decrease the influence of yellow so that the material appears to be more blue (more blue-white). As you pointed out, if there is no UV in the incident light, then the OB doesn't do anything. However, there are many cases in which there is sufficient UV to excite the OB and provide the increased appearance of whiteness -- that's why manufactures of many different types of paper and fabrics use OBs.

    In the case of Kodak use of an OB in color developer, it is the same type of OB (stilbene derivative) as is used in detergents. Many materials have more than one function. The particular OB chosen by Kodak had the ability to help remove freed sensitizing dyes. The optical brightening effect was not wanted so an OB was chosen that performed the desired removal of sensitizing dyes but did not provide very much brightening (and most of it was washed out) so as to avoid a bluing of the blacks which was not desirable.
     
  14. newcan1

    newcan1 Subscriber

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    Yes -- when I first asked my question, I had been using some Ektacolor Edge paper that may not have been stored properly, and it did have a yellowish (or actually, more greenish) tinge to the developed base. I have since been using paper that seems much better.

    As a point of curiosity, I have some almost 20 year old RC-74 paper that has always been refrigerated, that is almost as good as new, in terms of the base whiteness! I suspect that those older papers may have stored better because they were less sensitive?

    Finally - I do have some Sprint Systems optical brightener designed for use with black and white papers (although I don't think I've ever seen a b&w paper that would need this). I may try it with the RA4 paper for fun.
     
  15. Photo Engineer

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    I have some 74 and some Plus papers that even frozen kept poorly. OTOH, I have some Endura and Supra kept at room temp and they are just fine. IDK what is up.

    PE