Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,872   Posts: 1,583,450   Online: 1148
      
Page 14 of 24 FirstFirst ... 4891011121314151617181920 ... LastLast
Results 131 to 140 of 238
  1. #131

    Join Date
    Oct 2010
    Location
    wonderful new jersey
    Shooter
    Medium Format
    Posts
    107

    how much chrome alum?

    Hello

    When I made Lippmann plates, I would add 2 ml of a 1% solution of chrome alum to about 100 ml of emulsion just before I was ready to make the plates. The glycerin was used in a 1-2 % solution to soak the plates in after processing. It would swell up the gelatin to bring the colors where they should be. If you left it too long the whole plate would go off,and the reflection would be godawful. But soaking it in distilled water and letting it dry would bring it back to what it was before. I started with 1% and maybe a 30sec dip

    Glad to see someone else tilting at the windmill too. I spent about two years of making Lippmann plates before I got two that actually gave me something close to the actual colors in the scene. How are you developing your plates? Did you know you can produce holograms with these plates as well?

    hope this helps
    rob

  2. #132
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,542
    Images
    65
    Rob;

    For your formula, one needs the percentage of gelatin. Can you give that?

    Thanks.

    PE

  3. #133

    Join Date
    Oct 2006
    Shooter
    Medium Format
    Posts
    131
    Quote Originally Posted by R Shaffer View Post
    I would think that chrom alum would work, however you'll need to figure out what dilution and time to get sufficient hardening.

    I believe that the idea of the glycerin is to re-swell the emulsion. I don't know what sorbitol is, so I can't help there.

    Both of these steps are an attempt to keep the developed & dried emulsion the same thickness as the exposed emulsion. The shrinking emulsion will cause color shift or loss color image all together.

    There may be better ways of post-swelling the emulsion. A while ago Jeff Blyth put some interesting posts on the now no longer existing holographyforum.org. Fortunately, two of them can be found here again: http://holoforum.org/forum/viewtopic...7&t=67&start=0
    (Incidentally, all former holographyforum.org posts will soon become available on http://holoforum.org/ as well.)

    The new swelling agents Jeff Blyth advocated for, are citric acid and succinic acid. They require a well hardened layer. Keep in mind that their efficiency may depend on the kind of hardening agents involved: aldehyde hardening seems to do better with these acids than say, chrome alum.

  4. #134

    Join Date
    Oct 2010
    Location
    wonderful new jersey
    Shooter
    Medium Format
    Posts
    107
    to PE

    I started with 4g of gelatin (Knox ) per 107ml emulsion. That is after the dyes and chrome alum are added; without that, the starting volume is 102ml .
    I liked the results best with 6g of gelatin-with everything else the same.

    rob

  5. #135

    Join Date
    Apr 2008
    Location
    Santa Cruz, CA
    Shooter
    Multi Format
    Posts
    167
    Images
    17
    Quote Originally Posted by Hologram View Post
    There may be better ways of post-swelling the emulsion. A while ago Jeff Blyth put some interesting posts on the now no longer existing holographyforum.org. Fortunately, two of them can be found here again: http://holoforum.org/forum/viewtopic...7&t=67&start=0
    (Incidentally, all former holographyforum.org posts will soon become available on http://holoforum.org/ as well.)

    The new swelling agents Jeff Blyth advocated for, are citric acid and succinic acid. They require a well hardened layer. Keep in mind that their efficiency may depend on the kind of hardening agents involved: aldehyde hardening seems to do better with these acids than say, chrome alum.
    I got an email last week that the forum had moved. I have not tried any new Lippmans since my remaining plates are slightly smaller and do not fit my holder. So I need to devise a way to modify my holder.

    But that is interesting about citric acid. How is it that citric acid will swell the emulsion? I guess I should go and poke around the new forum. Thanks for the update.

  6. #136
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,542
    Images
    65
    Rob;

    Your level of chrome alum is a little low but in the ball park.

    As for swell, you might try Urea.

    PE

  7. #137

    Join Date
    Apr 2008
    Location
    Santa Cruz, CA
    Shooter
    Multi Format
    Posts
    167
    Images
    17
    Quote Originally Posted by R Paul View Post
    Hello

    When I made Lippmann plates, I would add 2 ml of a 1% solution of chrome alum to about 100 ml of emulsion just before I was ready to make the plates. The glycerin was used in a 1-2 % solution to soak the plates in after processing. It would swell up the gelatin to bring the colors where they should be. If you left it too long the whole plate would go off,and the reflection would be godawful. But soaking it in distilled water and letting it dry would bring it back to what it was before. I started with 1% and maybe a 30sec dip

    Glad to see someone else tilting at the windmill too. I spent about two years of making Lippmann plates before I got two that actually gave me something close to the actual colors in the scene. How are you developing your plates? Did you know you can produce holograms with these plates as well?

    hope this helps
    rob

    Very cool. You poured your own plates. I used the PFG-03C plates and tried both the Pyro developer and the P.F. GP-2 developers. Got color images with both, but the GP-2 had truer colors. When I go back to it I still need to make adjustments as my whites appeared blue.

    Do you have more complete instructions on how you made your emulsion?

  8. #138

    Join Date
    Oct 2010
    Location
    wonderful new jersey
    Shooter
    Medium Format
    Posts
    107
    to PE
    Is the action of urea reversible? That is if I overdo it, can I wash the plate and start over ? It is nice to be able to do that, believe me. As for the chrome I was afraid if I added any more I would ruin the plates

    to R Shaffer
    Yes I liked gp-2 myself. Ascobate developers worked but the images faded out after 2-4 months. Also found that two isopropyl alcohol baths one at 70% and one at 90+% for two minutes each after developing really helped bring out the image.
    The recipe I use came from Darran Green, who is really great about helping curious but clueless people like myself get a handle on this. I can PM it to you if you like.
    There are modern papers written on Lippman photography, naturally I can't recall any now except the SPIE (society of photonics ,imaging and light) had a few. I would have to go and dig them up to see what I have

    rob

  9. #139
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,542
    Images
    65
    The action of Urea is reversible, but it depends on hardness, hardening (type of hardener) and a number of other conditions.

    Now, type of hardener is important as chrome and alum type hardeners can be undone but aldehyde hardeners generally cannot be undone. So, you see my point I hope. (it depends)

    Sorry I cannot be more specific.

    PE

  10. #140

    Join Date
    Oct 2006
    Shooter
    Medium Format
    Posts
    131
    Quote Originally Posted by R Shaffer View Post
    But that is interesting about citric acid. How is it that citric acid will swell the emulsion?
    Here's Jeff' Blyth's explanation (http://holoforum.org/forum/viewtopic...t=67&start=0):

    However in the case of hologram treated with citric acid and then blow dried at room temperature we are left with a swollen gelatin which is different from the case of one swollen with water plus sorbitol or glycerol. In citric acid we have in effect the line of 3 carbons ins glycerol now with their alcohol groups (-OH) replaced by carboxylic acid groups (-COOH) except for the central carbon which has the (-COOH) added in place of H leaving one alcohol OH still there (mor on this later). These -COOH groups introduce a different effect to cause the swelling of the gelatin. This time the citric acid (-COOH) groups can partially displace the original internal (-COOH) groups from their attraction to the amino groups. Thse displaced (-COOH) groups are still firmly attached to the gelatin biopolymer of course and are not free to wander off in solution so the rest of the citric acid molecules is forced to be accomodated into the gelatin structureas most of the surrounding water is now evaporated off thus leaving the gelatin in a swollen state when it is left to equilibrate with ambient humidity.-- Fortunately it is a chemically weak arrangement easily completely reversed by plenty of fresh water so that it becomes energetically more favourable for all the ions involved to go back to surrounding themselves with water-molecule clouds again. The upshot of this is that if you are not satisified with the color of your treated hologram you can go back to square one without any difficulty.

    One might add that the citric/succinic acid treatment is muss less aggressive to the emulsion than chemicals like urea for example.



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin