Gum Bichromate: Can't get good results

[GuidoIlieff]

Hi everyone. I'm starting to work on gum prints by teaching myself how to. I found a video where a woman scrubs a test sheet very aggressively and the gum doesn't come off: .

In my experience the tiniest touch to the exposed gum when developing removes a big amount of the gum and leaves a very pale image of the exposed area. I'm wondering, is that always the case or exposed gum should hold on to the paper when you brush it like the example in the youtube video?


Right now I'm having problems with what I think is the size of my paper. I was trying gesso with crappy results as you will see in the photos. I just can't get white areas if I use very diluted gesso or the image is totally washed away if I use too much.
Tomorrow I'll try with unhardened gelatin.

In this image the background is supposed to be white:

Is it possible to get pure black and white images with gum prints?



Sorry for my English! I hope some one understand me.
bye

 

[GuidoIlieff]

Here is another picture. This time scanned. Everything on the border should be white except the registration marks. On this print I used gum to size the paper which gave me better results than the gesso. Also, im using photocopies as negatives because that's what I have and its fine for me.

 

[koraks]

Gum is a tricky process because there are so many variables. This is true for other alt processes like cyanotype etc. as well, but with the pigment processes (gum, carbon, intaglio etc) the number of variables really explodes. What you end up is literally a million ways a print could be made, and every practitioner having their own unique approaches.

I can only recommend studying the contemporary masters - people like Bob Carnie, who has a few videos online, and if you can, get Calvin Grier's Gum Printing eBook. That one is really good because it not just explains how he does it, but it mostly goes into a couple of relevant areas of underlying theory. For instance, paper sizing is something he dedicates a number of pages to, starting with the concept of surface energy of the paper and then exploring several ways of sizing paper.

I just can't get white areas if I use very diluted gesso or the image is totally washed away if I use too much.

What happens here is that without sizing, you've got a lot of pigment staining. It so happens that carbon black pigment (which you are likely using in one form or another) is a heavily staining pigment that embeds itself between/on the paper fibers and won't entirely go away, even with prolonged washing. Sizing the paper seals the fibers off, making the staining issue less. But in this particular case, you ended up with a sizing layer that apparently has insufficient surface energy - i.e. it doesn't have sufficient affinity with the gum layer you put on top, which consequently mostly slides off during development.

I think Calvin used a formalin-hardened gelatin size for his gum prints, but I also recall that he applied a second coat (perhaps an acrylic gesso, or it might have been albumen - I'd have to check his book). Then again, he ended up using a different approach to developing the gum layer, adding some hydroxide to the gum and sensitizer, and then using development in accordance with pH. This resulted in more or less instantaneous development that was also perfectly controllable/consistent. As far as I know, he's the only one to do it that way. Other practitioners use an unmodified gum sensitizer and a lengthy soak, followed by very gentle mechanical action, usually by pouring water onto the print (see e.g. Bob Carnie's videos).

The few times I made gum prints I sometimes ended up with an adhesion that wouldn't withstand any form of mechanical action; any form of brushing or even pouring water onto the print would wash away the image. Other times (on the more successful attempts), I found that it actually took quite some brushing to get the image to appear and the image would be rather stable/resilient, but it also tended to be rather grainy. I remember using hardened gum as a paper sizing for those prints, but the paper I use was quite textured, which likely didn't help much.

Is it possible to get pure black and white images with gum prints?

In my experience, yes, this is actually one of the easier things to do, but the results I got were quite grainy as mentioned above. But with a high pigment load, you end up with pretty much a binary image that consists of paper white (plus perhaps some pigment stain...) and near black. For smoother results, and to get a nice and solid black, multiple layers are necessary. I have to admit I never really got beyond 3 layers, at which point further layers wouldn't adhere well anymore. I didn't spend much time troubleshooting that issue back then and moved on to other processes.

I'll alert @Andrew O'Neill since he has done a lot of gum and he usually has useful insights to share. Perhaps a few other of our resident gum printers (although they are few and far between on this forum) might also chime in.

 

[nmp]

Hi everyone. I'm starting to work on gum prints by teaching myself how to. I found a video where a woman scrubs a test sheet very aggressively and the gum doesn't come off: .

I wouldn't call it "very aggressively" - I think she is being quite gentle. But your point is valid. The problem is gum is developed from the bottom, so by definition the layer close to the surface is soluble and has to be removed. That means there is a gap produced at the pigmented-binder/paper interface, so in essence it is just floating around (only held in place by surrounding dark shadow areas if there are any) making it very delicate to touch. So in a sense it is a simple but a flawed process. Carbon transfer process on the other hand, fixes this flaw and develop from the top by flipping the binder tissue upside down. Of course, that makes it much more complicated. No free lunch in alternative processing...

:Niranjan.

 

[Andrew O'Neill]

What paper are you using? I've only gotten prints that look like that when I use inappropriate paper, or pigments (Cotman water colours for example are not good for gum... they stain the paper). I've only been using Hahnemuhle Platinum Rag, and Daniel Smith water colour pigments. It's not necessary to size the paper. When you lightly tough a wet print, the pigment will easily come off. It's very delicate when wet. You need to try a better pigment, and if that doesn't help, then change your paper. It's like what @nmp says... no free lunch in alt. processing!

 

[GuidoIlieff]

What paper are you using? I've only gotten prints that look like that when I use inappropriate paper, or pigments (Cotman water colours for example are not good for gum... they stain the paper). I've only been using Hahnemuhle Platinum Rag, and Daniel Smith water colour pigments. It's not necessary to size the paper. When you lightly tough a wet print, the pigment will easily come off. It's very delicate when wet. You need to try a better pigment, and if that doesn't help, then change your paper. It's like what @nmp says... no free lunch in alt. processing!

Well... To be honest I'm using the cheapest paper and gouache. I thought I could get a reasonable print if I size the paper correctly but Im afraid I wont be able to then. Thanks!

 

[Andrew O'Neill]

Well... To be honest I'm using the cheapest paper and gouache. I thought I could get a reasonable print if I size the paper correctly but Im afraid I wont be able to then. Thanks!

Been there, done that. Get your hands on paper that's been internally sized, and decent pigments and you'll have more success.

 

[GuidoIlieff]

I wouldn't call it "very aggressively" - I think she is being quite gentle. But your point is valid. The problem is gum is developed from the bottom, so by definition the layer close to the surface is soluble and has to be removed. That means there is a gap produced at the pigmented-binder/paper interface, so in essence it is just floating around (only held in place by surrounding dark shadow areas if there are any) making it very delicate to touch. So in a sense it is a simple but a flawed process. Carbon transfer process on the other hand, fixes this flaw and develop from the top by flipping the binder tissue upside down. Of course, that makes it much more complicated. No free lunch in alternative processing...

:Niranjan.

oh ok. So there is something wrong in what I do. If I use my brush with the lightest touch and softest brush I remove everything in the print, nothing holds on. That's why I called it aggressive. Thanks for the info!

 

[GuidoIlieff]

Been there, done that. Get your hands on paper that's been internally sized, and decent pigments and you'll have more success.

Well maybe in the future. Everything is very expensive and I cant import where I'm from. I learned a lot though. Thannkks

ps: nice youtube, I subscribed!

 

[GuidoIlieff]

Gum is a tricky process because there are so many variables. This is true for other alt processes like cyanotype etc. as well, but with the pigment processes (gum, carbon, intaglio etc) the number of variables really explodes. What you end up is literally a million ways a print could be made, and every practitioner having their own unique approaches.

I can only recommend studying the contemporary masters - people like Bob Carnie, who has a few videos online, and if you can, get Calvin Grier's Gum Printing eBook. That one is really good because it not just explains how he does it, but it mostly goes into a couple of relevant areas of underlying theory. For instance, paper sizing is something he dedicates a number of pages to, starting with the concept of surface energy of the paper and then exploring several ways of sizing paper.



What happens here is that without sizing, you've got a lot of pigment staining. It so happens that carbon black pigment (which you are likely using in one form or another) is a heavily staining pigment that embeds itself between/on the paper fibers and won't entirely go away, even with prolonged washing. Sizing the paper seals the fibers off, making the staining issue less. But in this particular case, you ended up with a sizing layer that apparently has insufficient surface energy - i.e. it doesn't have sufficient affinity with the gum layer you put on top, which consequently mostly slides off during development.

I think Calvin used a formalin-hardened gelatin size for his gum prints, but I also recall that he applied a second coat (perhaps an acrylic gesso, or it might have been albumen - I'd have to check his book). Then again, he ended up using a different approach to developing the gum layer, adding some hydroxide to the gum and sensitizer, and then using development in accordance with pH. This resulted in more or less instantaneous development that was also perfectly controllable/consistent. As far as I know, he's the only one to do it that way. Other practitioners use an unmodified gum sensitizer and a lengthy soak, followed by very gentle mechanical action, usually by pouring water onto the print (see e.g. Bob Carnie's videos).

The few times I made gum prints I sometimes ended up with an adhesion that wouldn't withstand any form of mechanical action; any form of brushing or even pouring water onto the print would wash away the image. Other times (on the more successful attempts), I found that it actually took quite some brushing to get the image to appear and the image would be rather stable/resilient, but it also tended to be rather grainy. I remember using hardened gum as a paper sizing for those prints, but the paper I use was quite textured, which likely didn't help much.



In my experience, yes, this is actually one of the easier things to do, but the results I got were quite grainy as mentioned above. But with a high pigment load, you end up with pretty much a binary image that consists of paper white (plus perhaps some pigment stain...) and near black. For smoother results, and to get a nice and solid black, multiple layers are necessary. I have to admit I never really got beyond 3 layers, at which point further layers wouldn't adhere well anymore. I didn't spend much time troubleshooting that issue back then and moved on to other processes.

I'll alert @Andrew O'Neill since he has done a lot of gum and he usually has useful insights to share. Perhaps a few other of our resident gum printers (although they are few and far between on this forum) might also chime in.

Thanks for all the info! Bob Carnie youtube is the reason why im doing this and Calvin Grier's book looks like everything I want, but I cant buy something online with my country's money (im from Argentina, its complicated...)

I read someone using gesso AND gelatin for the coat, maybe I'll try that if plain gelatin doesn't work and also change my pigment.

 

[Andrew O'Neill]

Well maybe in the future. Everything is very expensive and I cant import where I'm from. I learned a lot though. Thannkks

ps: nice youtube, I subscribed!

Thank you for your support! Gum is fun once you get it to work for you. Don't give up! I also like to do Gum-Over Kallitypes, Cyanotypes, tri-colour... Loads of fun! By the way, one of my best buddies over in Japan (where I met him) is from Argentina. Looking forward to visiting him this Summer! Cheers!

 

[nmp]

oh ok. So there is something wrong in what I do. If I use my brush with the lightest touch and softest brush I remove everything in the print, nothing holds on. That's why I called it aggressive. Thanks for the info!

I was not able to understand what was said about the process in the video. But perhaps the kind of negative also matters. If you have a image-setter type of negative, presumably the image is pretty close to on or off - dots stay and the rest gets washed out. In such a scenario, I would think brushing out the non-dot areas would be easy to do as the dots pretty much stay anchored to the paper. Otherwise, you have to resort to something like what Bob Carnie does, I believe. I think he leaves the print facing down and then occasionally gives it tap or two with his fingers or a brush to dislodge those stragglers off the paper on the other side - so never really touching the print side of the paper.

Regarding staining, both paper and as well as the pigment contribute to it. There are staining pigments and non-staining pigments that water-colorists are very familiar with. I recently did a test on several papers that I had on hand with cheap store brand pigment, while playing with the Chiba process. Sure enough, the best was HPR that Andrew mentions which is also the most expensive, but the surprise close second was a very cheap student water color paper called Canson XL. So it is good to test out different papers and see you can find a gem in one the cheap pile. Same goes for the pigments.

For sizing the surface, have you considered a layer of gum itself - just use the gum dichromate mixture without the pigment, expose, clear. That should have better affinity to the layer above than gesso.

Anyway, good luck in your gummy pursuit.

:Niranjan.

 

[koraks]

Get your hands on paper that's been internally sized

Ah, but you'd be hard-pressed to find a paper that isn't internally sized...maybe toilet paper, but I'm not even sure on that! All papers are internally sized. It's what holds the fibers together. But there are several ways in which papers are being sized, and even more variables when it comes to type, size, shape and length of fibers, how they're arranged, what kind of buffering agents and fillers may be present, surface treatments, etc. etc. All combined it's a massively complex product and in my experience it's nearly unpredictable which paper will work for which process and with what kind of optional pre-treatments. Test, experiment, buy more papers, test again....

 

[Andrew O'Neill]

Ah, but you'd be hard-pressed to find a paper that isn't internally sized...maybe toilet paper, but I'm not even sure on that! All papers are internally sized. It's what holds the fibers together. But there are several ways in which papers are being sized, and even more variables when it comes to type, size, shape and length of fibers, how they're arranged, what kind of buffering agents and fillers may be present, surface treatments, etc. etc. All combined it's a massively complex product and in my experience it's nearly unpredictable which paper will work for which process and with what kind of optional pre-treatments. Test, experiment, buy more papers, test again....

I only use internally sized toilet paper...
But of course you are right!
We have this cheapy paper I bring in for my students. We can only get decent results if we use the more expensive Daniel Smith Lamp Black with it. Cheap, student grade water colours...like Cotman...stain terribly...
Another characteristic that makes for a good gum paper, is its ability to stand up to repeated water baths... especially the hot bath I give the paper to shrink it when negatives need to be registered for tri-colour...

 

[koraks]

Cheap, student grade water colours...like Cotman...stain terribly...

I suspect this has to do with the quality of the pigment dispersion itself, and possibly with associated factors like pigment particle size distribution. But it's kind of odd, if you think about it, since with many pigments, there's a negative correlation between tinting strength (usually regarded as desirable) and staining, and the mechanism that ties them together is pigment particle size. If you take a very finely divided carbon black pigment (e.g. Pbk7 from a reputable brand - lamp black) it will have a very high tinting strength, since it takes only a tiny amount of pigment to disperse evenly across a really large volume. If you have much larger pigment grains floating around, it takes a lot more of them to get the same tinting strength.

However, what also happens with very tiny pigment particles, is that they are kind of persistent if they stick to something - and they are pretty likely to do so. So finely 'ground' pigments with high tinting strength tend to stain. Whereas lower-tinting strength pigments that consist of lower-grade (larger) pigment clumps don't stain as badly.

I guess where the comparison goes off is the dispersants used in lower grade paints. I think there's something on this on handprint.com and if anyone's interested, I'd sure recommend reading up on it. I think the dispersing agents used in lower grade paints also promote staining - they basically make it easier for the pigment to bind with other molecules (including water, which is kind of the point with pigment dispersing agents).

Sorry about that; got carried away a little. But yes, paint does matter, and paints differ for sure in terms of staining behavior, and there are several reasons for this. It's mighty interesting stuff!

 

[GuidoIlieff]

I was not able to understand what was said about the process in the video. But perhaps the kind of negative also matters. If you have a image-setter type of negative, presumably the image is pretty close to on or off - dots stay and the rest gets washed out. In such a scenario, I would think brushing out the non-dot areas would be easy to do as the dots pretty much stay anchored to the paper. Otherwise, you have to resort to something like what Bob Carnie does, I believe. I think he leaves the print facing down and then occasionally gives it tap or two with his fingers or a brush to dislodge those stragglers off the paper on the other side - so never really touching the print side of the paper.

Regarding staining, both paper and as well as the pigment contribute to it. There are staining pigments and non-staining pigments that water-colorists are very familiar with. I recently did a test on several papers that I had on hand with cheap store brand pigment, while playing with the Chiba process. Sure enough, the best was HPR that Andrew mentions which is also the most expensive, but the surprise close second was a very cheap student water color paper called Canson XL. So it is good to test out different papers and see you can find a gem in one the cheap pile. Same goes for the pigments.

For sizing the surface, have you considered a layer of gum itself - just use the gum dichromate mixture without the pigment, expose, clear. That should have better affinity to the layer above than gesso.

Anyway, good luck in your gummy pursuit.

:Niranjan.

Wow, thanks. Seems like the Canson XL is what I need.

In some boos I read they describe gouche as something you can use so I tried with that. Today I did more experiments and sizing my actual paper with gelatin makes the development easier but I think I used too much of it.

I tried with exposed gum and had good results but I forgot I was exposing and it seems like I burned the dichromate because it stained the paper orange. But you are right, seeing the results now it looks like the exposed gum is my best shot.

Tomorrow I'll try again!

 

[GuidoIlieff]

I suspect this has to do with the quality of the pigment dispersion itself, and possibly with associated factors like pigment particle size distribution. But it's kind of odd, if you think about it, since with many pigments, there's a negative correlation between tinting strength (usually regarded as desirable) and staining, and the mechanism that ties them together is pigment particle size. If you take a very finely divided carbon black pigment (e.g. Pbk7 from a reputable brand - lamp black) it will have a very high tinting strength, since it takes only a tiny amount of pigment to disperse evenly across a really large volume. If you have much larger pigment grains floating around, it takes a lot more of them to get the same tinting strength.

However, what also happens with very tiny pigment particles, is that they are kind of persistent if they stick to something - and they are pretty likely to do so. So finely 'ground' pigments with high tinting strength tend to stain. Whereas lower-tinting strength pigments that consist of lower-grade (larger) pigment clumps don't stain as badly.

I guess where the comparison goes off is the dispersants used in lower grade paints. I think there's something on this on handprint.com and if anyone's interested, I'd sure recommend reading up on it. I think the dispersing agents used in lower grade paints also promote staining - they basically make it easier for the pigment to bind with other molecules (including water, which is kind of the point with pigment dispersing agents).

Sorry about that; got carried away a little. But yes, paint does matter, and paints differ for sure in terms of staining behavior, and there are several reasons for this. It's mighty interesting stuff!

Hi. This is a technical question related to physics: Do you know why tiny particles tend to stick to surfaces?

 

[GuidoIlieff]

I only use internally sized toilet paper...
But of course you are right!
We have this cheapy paper I bring in for my students. We can only get decent results if we use the more expensive Daniel Smith Lamp Black with it. Cheap, student grade water colours...like Cotman...stain terribly...
Another characteristic that makes for a good gum paper, is its ability to stand up to repeated water baths... especially the hot bath I give the paper to shrink it when negatives need to be registered for tri-colour...

I agree, gelatin sized toilet paper is the way to go.

Do you have a recommendation for other pigments that may work? I cant afford Daniel Smith.


One more question. Can you recommend the floating paper technique for putting the emulsion onto the paper for gum print?

 

[koraks]

Hi. This is a technical question related to physics: Do you know why tiny particles tend to stick to surfaces?

You got me there - no, I don't! I'd be curious to know, though!

 

[nmp]

You got me there - no, I don't! I'd be curious to know, though!

For that you might have to thank one of your countrymen - Van der Waals, for something called Van der Waals forces that govern the affinity of objects at very short distances in absence of other relatively stronger intermolecular forces like ionic, hydrogen bonding, etc.

In the current context of watercolor pigment staining in gum, I am sure it is further complicated by many other factors.

:Niranjan.

 

[koraks]

Well, funny you should mention it,.because the only thing I could come up with is Van der Waals forces ending up stronger than the force of e.g. water washing between the paper fibers for smaller particles. Larger particles may present not all that bigger contact surfaces with the paper fibers (and hence similarly dimensioned Van der Waals forces), but given their bulk they will would be less aerodynamic and hence get dislodged easier. But that's a bit of offhanded theorizing on my part; I don't really have a background in physics.

 

[nmp]

Well, funny you should mention it,.because the only thing I could come up with is Van der Waals forces ending up stronger than the force of e.g. water washing between the paper fibers for smaller particles. Larger particles may present not all that bigger contact surfaces with the paper fibers (and hence similarly dimensioned Van der Waals forces), but given their bulk they will would be less aerodynamic and hence get dislodged easier. But that's a bit of offhanded theorizing on my part; I don't really have a background in physics.

Finer particles are also more likely to get sucked into the paper fibers with capillary action which then are less accessible to the mechanical action. I guess the viscosity of the gum mixture also plays a role in how much gets into the paper vs stays on the surface. Or even brushing - how vigorous. Perhaps that's why I see those master gummists like Carney, Grier, etc spend barely any time at all brushing the stuff. I am OCD, so I keep trying to fix those streaks and make it even worse with every stroke.


:Niranjan.

 

[nmp]

Wow, thanks. Seems like the Canson XL is what I need.

In some boos I read they describe gouche as something you can use so I tried with that. Today I did more experiments and sizing my actual paper with gelatin makes the development easier but I think I used too much of it.

I tried with exposed gum and had good results but I forgot I was exposing and it seems like I burned the dichromate because it stained the paper orange. But you are right, seeing the results now it looks like the exposed gum is my best shot.

Tomorrow I'll try again!

Canson XL is kind of a miracle paper - so far it has worked well with cyanotypes, cuprotypes and now perhaps with a pigment process or two. It does stain more with the photosensitizer (ferric ammonium oxalate) I am using in the Chiba process, but clears up with citric acid. Good thing about cheaper papers is you can experiment with heart's content and not worry about the cost - so they can be great at learning the mechanics of the process.


:Niranjan.

 

[koraks]

Perhaps that's why I see those master gummists like Carney, Grier, etc spend barely any time at all brushing the stuff.

Maybe; I think other factors play a role as well, mostly related to emulsion rheology and especially viscosity. If viscosity is too low, you can basically only coat a very thin emulsion, which limits optical density (pigment load could be raised, but at some point you'll run into problems with tonality and emulsion stability). A lot of brushing won't help much in that scenario; you'll just be pushing watery goo around until it starts to dry - and streak badly. If the emulsion is too viscous, it's neigh impossible to spread it out evenly to begin with, and again, no amount of brushing is going to help solve things. If the viscosity is just right, it's not too difficult to spread it out and it'll just take a couple of quick wipes with a soft, clean brush to even out the surface.

So I think regardless of the scenario, you always end up with the conclusion that a lot of brushing doesn't help anyway. It would be trying to fix a problem that is likely better fixed at the emulsion mixing stage.

 

[Andrew O'Neill]

I agree, gelatin sized toilet paper is the way to go.

Do you have a recommendation for other pigments that may work? I cant afford Daniel Smith.


One more question. Can you recommend the floating paper technique for putting the emulsion onto the paper for gum print?

I only have experience with Cotman (garbage), and Daniel Smith. Sorry. I'm not familiar with the floating technique... is that for paper sizing? If it is, I only have experience (when I was sizing paper) with pouring warm gelatin (with hardener added) on paper, spreading it around, then squeegeeing it off.