fotospeed gum bichromate kit + a few questions

Discussion in 'Alternative Processes' started by phritz phantom, Aug 27, 2007.

  1. phritz phantom

    phritz phantom Member

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    i'm on my first foray into gum printing, using the fotospeed kit.
    has anybody ever used this kit? and has any tips or bewares for using it?

    one thing i'm wondering is that there's not a single word on the dangers of gum printing. it's not even mentioned which chemicals are in the solutions.
    so, the sizing should be some kind of gelatine- harmless (although smells horrible). so is the gum arabic.
    the sensitizer is potassium or ammonium dichromate - the dangerous stuff.
    but what's in the clearing solution?

    and the exposure?
    the fotospeed manual says: up to 24minutes for sunlight; bill mabrey says: 6-7minutes in sunlight.
    and does it have to in direct sunlight or is normal daylight sufficient (not in the shadows of course)?

    if i coat the paper today (at night) and plan to do the exposure tomorrow afternoon, is it safe to store the dried, coated paper? say, in a bag which comes with photographic paper?

    and how to store the developed gum prints? is all the bichromate gone after development (the water bath)?? or are there still traces of the chemical in the emulsion?
    i somehow don't trust those images...
     
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  2. Katharine Thayer

    Katharine Thayer Member

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    I've never seen this kit, but it sounds from your description as though nothing is labeled by its real name, is that correct? Surely there must be instructions with it that tell you what things are... If not, shame on them.

    If the sizing comes premixed, it's not likely to be gelatin with a hardener; who knows what it is, if they don't say.

    The clearing agent is most probably sodium bisulfite or potassium metabisulfite; they are equally effective clearing agents. (There's a thread somewhere in this forum about that.) They give off fumes that can make you cough, so you should use it in a well-ventilated place, but other than that it's not too terrible.

    Exposure in sunlight depends on the strength of the sunlight (it's widely variable depending on location, season, and time of day) and the strength of the dichromate. With saturated ammonium dichromate, I usually figure my times in direct sunlight in seconds rather than minutes (in other words, less than a minute.) Indirect sunlight also has a lot of UV, and I've exposed prints in 3 minutes or so even in the shade, but my experience is that indirect light tends to make the image more diffuse (small details can turn into blobs rather than printing sharp) since the radiation is coming from everywhere rather than from one place.

    Gum printing really isn't all that dangerous. The only thing that's "dangerous" is the dichromate, as you say, and it's really only dangerous in industrial quantities, especially when breathed; it caused cancers of the breathing passages in people who had to spray it onto car bumpers, back in the days when car bumpers had a chrome finish. In the small quantities we use it in, it's really fairly harmless. I wouldn't recommend eating it, and some people caution that you should use a mask when weighing the powder, though I never do, and some people develop a contact dermatitis from putting their hands in dichromate-laced water, so it would be sensible to wear rubber gloves just as a precaution, though I never have.

    The issue about keeping coated paper overnight is the dark reaction, which is a reaction between the gum and the dichromate that starts when the two are mixed and coated into a film, and proceeds even in complete darkness. But the speed of this reaction is highly dependent on humidity (and is also influenced by other things such as dichromate concentration); In a very dry environment the reaction proceeds so slowly that its effect is negligible and people can leave their coated papers even for weeks without fogging; in very damp environments the reaction proceeds rapidly enough that it wouldn't be advisable to leave paper overnight, or even for a couple of hours. So it depends mostly on the humidity.

    A finished gum print should be quite inert and archival, if permanent pigments are used. The unreduced dichromate leaves the paper right away in development; there's not likely to be any left in the print after development.
    kt
     
  3. phritz phantom

    phritz phantom Member

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    thanks for the lengthy reply. you answered all my questions... and a few ones more.

    yes, there are instructions included with the kit, they seem to be quite detailed and accurate. but, as i said, what i found to be strange, was that there's not one single word on the chemicals included.
    all bottles are labeled with names, but those names are only "sensitizer" or "sizing solution",...
    so i don't even know if my sensitizer is potassium or ammonium dichromate.

    i just coated my first sheet (doesn't look that good, i have to confess) and will try exposing for 3 minutes tomorrow afternoon.
    and i will take a big look at your page asap.
    thanks again.
     
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  4. phritz phantom

    phritz phantom Member

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    ok, now my first try was a failure.
    i could see a very faint image, but even after about two hours in a waterbath - tried everything: soaking, running water, brushes and even gentle rubbing - nothing changed. the image became even more faint. i also never saw any flakes come off, the image stayed the same pretty much.

    i think the reason is because my emulsion is too thin. i expected the emulsion to have a consistency more like honey than normal watercolor. the emulsion i brewed was definitely more like watercolor and so was its color (a little uneven and not very opaque).
    i used 5ml gum solution and 5ml of sensitizer + a less than pea size portion of pigment for a 15x15cm image (appr. 6x6inch).
    should i use more pigment the next time?
     
  5. phritz phantom

    phritz phantom Member

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    i wonder, if the image was severely underexposed - i only exposed for 4,5 minutes on a sunny day, instead of 24min said in the fotospeed kit manual - wouldn't all of the emulsion come off?
     
  6. Katharine Thayer

    Katharine Thayer Member

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    Yes.
    kt
     
  7. phritz phantom

    phritz phantom Member

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    thanks,
    one more question:
    how thick is your layer of emulsion? can you still see the paper through or is it completely opaque?

    sorry, about stealing your time with all that questions.
    thanks once more. and great homepage. very informative.
     
  8. Katharine Thayer

    Katharine Thayer Member

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    No problem; I enjoy doing what I can to help people who are struggling with gum.

    I'm really curious about your sensitizer, what type and concentration it is, if the kit instructions recommend a 24-minute exposure in direct sun. That's awfully long, for gum even with saturated potassium dichromate, so I wonder if they've diluted it. Did it come premixed?

    My layers really vary depending on what look I'm after. If I'm doing a one-coat gum with a dark DMax, or a dark layer to fill in just the deepest shadows on a multicoat gum, then chances are the coating will be heavy enough to look completely opaque as it's brushed on. Otherwise, my layers tend to be more transparent. Some gum teachers teach that the layer should be thin enough that you should be able to read text through it, if you coated it on a newspaper page, and I think that's fairly good advice to keep beginners from overpigmenting, but I don't look at it as a hard and fast rule.

    A less than pea-sized ball of pigment in 10 ml of gum/dichromate isn't excessive at all (to make the heavy, stiff emulsion of iron oxide black that I described in a thread on black pigments, I emptied an entire tube of paint into 15 ml gum) and if it's a weak pigment or a chintzy brand, might be less than adequate. It's really impossible to give a general rule about this.

    Not sure any of this is as helpful as just varying the variables one at a time (exposure, pigment load, etc) and seeing for yourself what happens. But feel free to continue to ask questions as you go along.
    kt
     
  9. phritz phantom

    phritz phantom Member

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    i really can't say anything about the sensitizer. also nothing on the fotospeed hp: no datasheet etc. i can only say that's an orange liquid (with a little bit residue on the bottom) and they recommend mixing it 1+1 with the gum solution. and yes, everything was pre-mixed.

    there seems to be something fundamentally wrong with the emulsion. there is only one pigment included (looks like i got the cheap version of the kit), which is "payne's grey". it did look grey - in dim light - when i painted it on, but turned blue after exposure and a long, long time of washing.

    i will size and pre-shrink a few more papers today and will try again tomorrow, without the over-night storage period.
    hopefully, because the weather forecast isn't too good...!
     
  10. Katharine Thayer

    Katharine Thayer Member

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    Don't give up yet! There's probably nothing wrong with the materials; you just need to figure out how this particular combination of materials works together. If the instructions say 24 minutes in the sun, then the sensitizer must be diluted enough to make that a reasonable exposure, and I'd follow the instructions.

    Payne's grey is an interesting choice for a kit. Monochrome kits always used to use lamp black, but that's a difficult pigment for beginners to use without staining, and I suppose Payne's grey seemed safer. It's not a specific pigment in itself, but a convenience mixture of black and blue. Most manufacturers use lamp black for the mixture, but they use different blues.
    kt
     
  11. argus

    argus Member

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    Thanks for the comments, Katherine. They are helpfull for me too when I shall pick up my efforts in gum printing again.

    Greetings,
    G
     
  12. phritz phantom

    phritz phantom Member

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    hi,
    unfortunately i wasn't able to do more tests today, because it has been pouring all day. hopefully tomorrow will be more lucky...

    but i thought of another possible source of error. since i don't have a proper register, i sandwiched the paper and the negative between two pieces of plexiglass (about 5mm thick) and fixated it with screw clamps.
    i have just read that normal glass is a pretty good uv-filter and i read in another thread that plexiglass is an even better one (or not... both opinions were present in that thread).
    i could use normal glass (about 3mm thick, from a cheap picture frame) instead of the plexi.
    or should i completely avoid putting the negative and paper under any kind of glass? in this case, i'd have to build something...
     
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  13. phritz phantom

    phritz phantom Member

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    finally an image!
    [​IMG]

    i got an old sunlamp, which was made in the 70ies or so, and it worked fine. exposure of 5 minutes, negative and paper under a sheet of glass, the lamp was about 60cm above the negative.
    how does that look for a first try?

    so, if i wanted to put a second layer of gum on it? how do i get the negative in exactely the same position as before? is there some kind of trick?
    and is it necessary to clean the negative after exposure? since it was in direct contact with the dichromate-emulsion. i don't think my inkjet negatives can be washed.
     
  14. smieglitz

    smieglitz Member

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    You also mention coating under dim light. The gum emulsion actually isn't very sensitive, especially when wet, so coating under average incandescent or fluorescent light conditions should be fine. Just be sure to dry it in dim light or the dark. If the correct viscosity, the emulsion should start to set while you are smoothing the coat. You will feel it start to get tacky and at that point, you should stop blending and either set it aside to dry or force dry it with a hair dryer set to cool (no heat). The emulsion should never be wet or thin enough to come off on your negative.

    You may wish to continue your discussion on the hybridphoto.com website for tips on the negative making and registration for additional layers.

    Joe
     
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  15. Katharine Thayer

    Katharine Thayer Member

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    Sorry, I missed some of these posts when they came in, so I'm a little behind.

    Thanks for posting your first image, pp; that must have been quite a thrill to see it come up at last.

    I don't know that it makes sense to talk about stain or overexposure with regard to this image, just because there's some tone in the highlights. This would be a concern only if you intended all the lightest parts of the image to be paper white, which would make it a rather contrasty image in spite of the somewhat weak nature of Payne's grey.

    It's interesting; five or ten years ago everyone was printing their test images to have some white in them, as a way of showing off the fact that there was no pigment stain in their gum prints; now I gather many people feel that there should be some tone even in the lightest areas. Whatever floats your boat, as they say here in the USA. But it wouldn't be for me to say that because there's some tone in your highlights, that automatically means there's something that needs fixing. If you said you meant the lightest areas to be white, and they didn't turn white, then we could go on to talk about stain or overexposure being the cause of the tone where there should be paper white.

    Katharine
     
  16. Katharine Thayer

    Katharine Thayer Member

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    When using a film negative, I just line up the negative with the image on the paper before coating subsequent coats (sometimes, as I've said before, my coating is so opaque that it's impossible to aline the negative after coating) and mark around the corners with pencil. Then after coating and drying, I simply fit the corners of the negative into the corner marks. When using paper negatives, I just mark around the corners of the negative before the first exposure, and keep fitting the negative into the same corner marks each time. It's not as precise as aligning the negative with the image, as you can do with film negatives, but it works surprisingly well.

    The coating should be dry enough before you expose that it shouldn't stick to the negative or get any emulsion on it; if you do, you're probably not drying the coating long enough.
    Katharine
     
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  17. Katharine Thayer

    Katharine Thayer Member

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    Joe is right; if you've got crystals settling out, then it's a saturated solution, and my surmise that maybe they diluted it is no doubt in error. But then I would question the 24 minutes in direct sun recommendation; that would be hugely overexposed even with potassium dichromate, as I said before.

    I've always used a 1:1 mix, and it works quite well for me. But you'd need to decide for yourself which is the best mix or mixes for you (depending on the goal of the particular layer).
    kt
     
  18. Katharine Thayer

    Katharine Thayer Member

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    Below I've run a quick test to show how an actual gum coating using quinacridone gold pigment looks when the recommendation to reduce dichromate as a proportion of coating mix is followed. I didn't calibrate the beginning exposure exactly for today's humidity, so it may not be perfect, but the absolute number of steps printed under any condition isn't relevant for this demonstration; what's relevant is the relative number of steps printed under the various conditions. (And try to overlook the streaks of blue; that's left over from that experiment with Prussian blue I did for a different thread last week. No matter that I cleaned up carefully afterward, there are still grains of blue pigment here and there to get onto things, which is why I don't work with powdered pigment as a rule).

    On top is a mix containing 1:1 gum/pigment: saturated ammonium dichromate, exposed for 3 minutes. In the middle is a mix containing 2:1 gum/pigment: saturated ammonium dichromate, exposed for 3 minutes. It should be apparent that, though there's no dichromate stain in paper white areas of either strip, the second one printed significantly fewer steps. But that's more a function of not properly adjusting the exposure time to the decrease in dichromate; when the exposure time was doubled in the third strip to compensate for the reduction in dichromate, then the number of steps printed was similar to the number of steps printed with a 1:1 mix. Note that there is neither pigment stain, nor dichromate stain, with either the 1:1 mix, or the 2:1 mix.

    Katharine
     

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  19. smieglitz

    smieglitz Member

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    My bad. I did mix up the color test with the dichromate stain test scans. Sorry.

    However, I never inferred anything about dichromate stain in my original response and I'll stick to my suggestion that too much dichromate solution may thin the emulsion (because of the water content, not the total dichromate concentration) to the point that a specific pigment may be able to stain the paper (especially one given inadequate sizing or hardening) since it takes longer to set and the emulsion has a better chance then to soak into the paper rather than setting on the surface.

    I'll remove the example to avoid further confusion. Sorry.

    Joe
     
  20. Katharine Thayer

    Katharine Thayer Member

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    Okay, since you're removing the example, I edited my post (while I was still in the editing time window) so that it no longer refers to the example. No problem.
    kt
     
  21. phritz phantom

    phritz phantom Member

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    i just wanted to bump that thread to thank you all, especially katharine and her webpage, for your help.
    after a long hiatus i took up gum printing again and after some time i a, getting pretty good results.
    i love this process. while being a little bored with classic silver photography (and also not having an enlarger right now),exploring the sheer endless possibilities of variarion in gum printing was a real delight.

    thanks a lot.
     
  22. Mike Wilde

    Mike Wilde Member

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    envious here

    I have always wanted to do gum, and having read a bunch of Judy Siegel's publications, don't think that it should be impossible. But right now my shortage is time. Ahh perhaps once the kids are teens and want nothing to do with me, and can drive themselves somewhere I will finally get gumming. Some decade or so in the future...
     
  23. Katharine Thayer

    Katharine Thayer Member

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    You're welcome!
    Katharine