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  1. #91
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    You will have to test alternatives yourself. I have no idea what will work well. See the other similar train of posts.

    PE

  2. #92

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    Quote Originally Posted by gmikol View Post
    If one of the goals is to come up with a carbon process with fewer potential risks to human health and the environment, it seems like an alternative [to a permangante] clearing solution should also be investigated. Would a strong hydrogen peroxide solution (say, 10%) serve a similar role?
    I'm cross-posting this from the UltraStable thread, since it's relevant here, too:

    I just tried hydrogen peroxide. Some web reading suggested that it's oxidizing ability was enhanced in acid solutions. I only had 3% stuff around (drug-store H2O2), so here's what I tried:

    100mL 3% H2O2
    ~1mL 40% citric acid solution (this is about 0.4g).

    It created a just-noticeable lightening of the dye stain in an all-white area (drop test) after about 90 seconds contact. Perhaps if you can easily get your hands on 10% or stronger H2O2, it might be a viable option, and one that eliminates the need for potassium permanganate.

    --Greg

  3. #93
    CMB
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    Exposure Times

    Quote Originally Posted by gmikol View Post

    --It's about 1/2 to 1 stop slower than the comparable dichromate-sensitized tissue, but with a much longer exposure scale (about log 3.0). This is 600-800 units on my NuArc. 800 units is about 20-25 minutes, which gets to be a little hot.

    Geg
    Typical exposure times for the UltraStable Color pigment films in a 26-1K plate burner ranged between 3 to 5 minutes. The need for a 25 minute (or more) exposure time baffles me. The Hardener No.3 absorption peak is 335nm and perhaps your light is emitting little energy of that nature. Alternately, the problem may be sensitizer (concentration, mixing technique or ?) related. Here's an example of how the sensitizer was incorporated into the UltraStable materials:

    To make 250 ml of emulsion:

    1. Add 1.5 g of Hardener #3 to 50 ml of water at 85F and QS to 60ml.

    2. Slowly add sensitizer prep to 190 ml of a 13% pigmented gelatin prep at 105F.

    Hope this helps..

    Charles

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    335nm peak? Really? That's not a typo? I thought that soda lime glass didn't transmit much below 350nm.

    A couple other observations on my part:

    -- My NuArc NL22 uses the same bulb as the newer 26-1KS (NP80). This is different from the bulb that the 26-1K uses (GW114). Not sure exactly what the difference in terms of output spectrum is.

    -- My NuArc bulb is pretty old.

    -- I only used 250 mg of hardener, to make ~160 mL of emulsion, about 11% final gelatin solution. Sounds like I could quadruple sensitiser strength.

    What was the typical density range of a negative for use with UltraStable?

    --Greg
    Last edited by gmikol; 08-27-2011 at 01:07 AM. Click to view previous post history.

  5. #95
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    The 335nm absorption peak description is from the Hardener #3 spec sheet. As you state, glass cuts off most of the UV transmissions at this level. Metal halide or mercury vapor lamps used in graphic arts platemakers typically have a peak of 365nm and so there is still quite a bit of usable energy reaching the films within the spectral region to which they are most sensitive. I have found that while an old lamp may seem to burn brightly, much of its actinic light output can be severely degraded.

    Typical con-tone separation negatives have a density range of 1.20 - 1.60 and are developed to a gamma of .75

    I suspect that increasing the amount of sensitizer may go a long way towards reducing your exposure times.

  6. #96
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    Two UV ranges are recognized in photography. UVA and UVB radiation are their common designations. One is from about 350 - 400 nm and the other is shorter than 350. UV lamps are often sold in these two categories. You would have to match the lamp to the peak sensitivity of the light sensitive material.

    PE

  7. #97

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    I found the 4,4'-DIAZIDOSTILBENE-2,2'-DISULFONIC ACID DISODIUM SALT tetrahydrate, 99%
    CAS: 2718-90-3 available at my supplier in the Netherlands.
    Does anybody know what the keeping conditions and shelf life of these diazo salts are? They are rather expensive, compared with dichromates and ordering more makes them a little bit cheaper. But still around 1Ä per gram.

    Kees

  8. #98

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    I'm away from my notes for a few days, but if I remember correctly, the info I got from my supplier in the US had a 1-year storage life at 20C, and 5 years at 5C. It came shipped in a vacuum-sealed foil packet, so I transferred it into a glass jar which I keep inside a black photo-paper bag inside the refrigerator (labeled, of course). The powder is sensitive to light, though I have not tested how sensitive it is.

    It also seems to be a bit hygroscopic (absorbs water vapor from the air), so I'm going to get a silica gel packet to put in the jar for the next time I open it.

    1 euro per gram is pretty good. The other EU supplier I had found was > 2 euro per gram.

    --Greg

  9. #99

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    Quote Originally Posted by gmikol View Post
    1 euro per gram is pretty good. The other EU supplier I had found was > 2 euro per gram.

    I received my first order CAS: 2718-90-3 today! I will try to coat some transfer sheets next week.

    Charles if you read this, does the original Ultrastable recipe contain other special ingrediŽnts like surfactants or conservation agents?
    And how about sugar/glycerin/alcohol (amounts) or other plasticizers in the pigmented gelatin?

    Kees

  10. #100
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    Quote Originally Posted by keesbran View Post

    does the original Ultrastable recipe contain other special ingrediŽnts like surfactants or conservation agents?
    And how about sugar/glycerin/alcohol (amounts) or other plasticizers in the pigmented gelatin?

    Kees
    The "recipe" for the UltraStable pigment films is based on (except for the sensitizer) the formulation published in "The Home Manufacture of Materials for Carbon Printing" ( Wm. D. Fleming, American Photography, Vol 32, 1938, August, No. 8) :

    Gelatin (20%) 100 ml
    Sugar 5 g
    Glycerin 1.5 ml
    Pigment 1-5 - 2.5 g
    Thymol (10% solution in 95% alcohol) 5 ml

    Water (to make) 200 ml Total

    Surfactants were added to the emulsion to facilitate machine coating but are not necessary for hand-made materials.



 

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