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  1. #21

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    BTW, as a last note: I use foam brushes for sizing, not good synthetic bristle ones... The brush absorbs a good amnt. of sizing and if that doesn't suffice while coating, you dip it in the solution once more. Keep the brush in the warm solution (while working) and wash it well as soon as the job's done. If not, it will be useless for the next time. (Due to the hardened gelatin left inside.) Clean the vessel by first rinsing it with water and then filling it up to the top using 1+5 diluted household chlorine bleach. A couple of hours is enough, you'll be surprised how much gelatin stays in the container - even after a good wash. (It will show up as clumps clouding the solution, after some time...)

  2. #22

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    Brownman, I know this place via the Internet but never went there yet, we have however a very old drugstore in the center where they have a lot of chemicals, potassium dichromate, pigments, formol, metabisulfite, alum and whatnot. ppl come from all across belgium to go get their stuff there : http://www.le-lion.be/

    Loris, yep thats what I am doing already. I'm surprised though that such a small amount of formalin is able to harden all that gelatin. I just applied a single coating of size using this technique, same paper and same proportions but three different gelatins (first test).

  3. #23
    holmburgers's Avatar
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    What kind of alum is this? Is it pure enough to use for all the aforementioned purposes?

    http://www.amazon.com/Dragon-88-Bran.../dp/B002B5QWBI

    I saw this at a Chinese Market in my town and was quite surprised, but I guess I didn't have a good idea of what alum really was.

  4. #24
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    Quote Originally Posted by holmburgers View Post
    What kind of alum is this? Is it pure enough to use for all the aforementioned purposes?

    http://www.amazon.com/Dragon-88-Bran.../dp/B002B5QWBI

    I saw this at a Chinese Market in my town and was quite surprised, but I guess I didn't have a good idea of what alum really was.
    If it's for food use, it's most likely potassium aluminum sulphate - not 'chrome' alum.
    K Alum will harden gelatin, but not to the extent that chrome does. Both perform better with the addition of some acid.
    - Ian

  5. #25
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    Quote Originally Posted by Hexavalent View Post
    If it's for food use, it's most likely potassium aluminum sulphate - not 'chrome' alum.
    K Alum will harden gelatin, but not to the extent that chrome does. Both perform better with the addition of some acid.
    Well, there goes that money down the drain - I bought the wrong kind, Pot Alum. Does the bloom of the gelatin make any difference to the hardening properties?
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  6. #26
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    Quote Originally Posted by Jerevan View Post
    Well, there goes that money down the drain - I bought the wrong kind, Pot Alum. Does the bloom of the gelatin make any difference to the hardening properties?
    Not necessarily money down the drain!
    Potassium Aluminum Sulphate DOES harden gelatin, just not to the same degree as chrome alum, it's quite usable. There are many factors at play when it comes to 'hardening' gelatin besides the 'bloom' (bone/skin, porcine,bovine, extraction method, pH, time, temperature etc.,). Try out some different formulae to discover what works for you.
    - Ian

  7. #27
    holmburgers's Avatar
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    Well that's good to know.

    Thanks!

  8. #28
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    Quote Originally Posted by Hexavalent View Post
    Not necessarily money down the drain!
    Potassium Aluminum Sulphate DOES harden gelatin, just not to the same degree as chrome alum, it's quite usable.
    Thanks, then I can sleep well at night again.
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  9. #29
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    Quote Originally Posted by Ian Grant View Post
    There's two alums used in hardening gelatin, plain Alum a generic term usually means Potassium Aluminium Sulphate and it's used mainly in hardening fixers but only works in acid solution lower than about pH5.

    The other, Chrome alum, is Potassium Chrome Sulphate which has greater hardening properties and is used in commercial film & paper emulsions as well as for Gelatin subbing layers.

    Both Formaldehyde & Chrome alum work well when sizing with gelatin but the choice may depend on what the papers going to be used for.

    Ian
    Further evidence.... jeez, I guess I just should've read closer.

  10. #30
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    Quick question;

    I'm going to size some cold press watercolor paper with gelatin. I have in my possession and want to use chrome alum, not formalin or glyoxal.

    Is it necessry to include the alum in the gelatin, or can I soak the sized paper in it after the fact. How severe is the staining, as mentioned above by R Shaffer?
    If you are the big tree, we are the small axe

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