Gum Bichromate: Can't get good results

[GuidoIlieff]

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.

I found an article that explain a few methods https://www.alternativephotography.com/coating-paper-by-floating-rod-or-brush/

I saw people use the floating technique but it seems it is only used for silver emulsions. Maybe you get a coat that is too thick with gum if you do it like that. idk

 

[koraks]

For sizing, any number of methods tends to work OK - brushing, rolling with a foam roller, a puddle pusher, floating, dipping, pouring, etc. etc. etc. Whatever rocks your boat. I'd personally start with brushing since it's straightforward and efficient. If that doesn't work, try a foam roller.

 

[nmp]

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.

True. I didn't mean to imply that staining was the sole reason for quick brushing. I should have said it doesn't hurt. Like everything, it's needs to be goldi-locks, not too hot, not too cold. Just right....

:Niranjan.

 

[koraks]

Like everything, it's needs to be goldi-locks

The arrogant little tw*t

 

[nmp]

I found an article that explain a few methods https://www.alternativephotography.com/coating-paper-by-floating-rod-or-brush/

I saw people use the floating technique but it seems it is only used for silver emulsions. Maybe you get a coat that is too thick with gum if you do it like that. idk

Floating works if the solution is very dilute and not too viscous and you are basically trying to saturate the paper surface and sub-surface. Like a salt or silver solution in salted paper process. You can probably do the same with sizing if it is not very viscous like a diluted PVA type size. But the problem is it requires a large quantity of liquid as a reservoir so it is not cost-effective if the active ingredient is expensive. Fine with salt, but silver nitrate is expensive enough to direct most people towards using a coating rod, cotton ball, brush etc.

There are a couple of non-brush techniques that I could think of that might work for gum. One is the so-called Mayer rods (expensive!) which are basically metal rods with wire wound around them, the diameter of which determines the thickness of the material deposited. The other is the foam paint roller - as illustrated in this video on gum. I bought a set myself recently as it seems to be more controllable procedure for someone like me whose brushing technique is atrocious.


:Niranjan.

 

[Andrew O'Neill]

Floating works if the solution is very dilute and not too viscous and you are basically trying to saturate the paper surface and sub-surface. Like a salt or silver solution in salted paper process. You can probably do the same with sizing if it is not very viscous like a diluted PVA type size. But the problem is it requires a large quantity of liquid as a reservoir so it is not cost-effective if the active ingredient is expensive. Fine with salt, but silver nitrate is expensive enough to direct most people towards using a coating rod, cotton ball, brush etc.

There are a couple of non-brush techniques that I could think of that might work for gum. One is the so-called Mayer rods (expensive!) which are basically metal rods with wire wound around them, the diameter of which determines the thickness of the material deposited. The other is the foam paint roller - as illustrated in this video on gum. I bought a set myself recently as it seems to be more controllable procedure for someone like me whose brushing technique is atrocious.


:Niranjan.

I have one of those rods. Expensive and a waste of money, if you ask me. I used it once and didn't like the results. It sits in a drawer... A foam brush and squeegee...items that I already had on hand...did the job.

 

[GuidoIlieff]

Floating works if the solution is very dilute and not too viscous and you are basically trying to saturate the paper surface and sub-surface. Like a salt or silver solution in salted paper process. You can probably do the same with sizing if it is not very viscous like a diluted PVA type size. But the problem is it requires a large quantity of liquid as a reservoir so it is not cost-effective if the active ingredient is expensive. Fine with salt, but silver nitrate is expensive enough to direct most people towards using a coating rod, cotton ball, brush etc.

There are a couple of non-brush techniques that I could think of that might work for gum. One is the so-called Mayer rods (expensive!) which are basically metal rods with wire wound around them, the diameter of which determines the thickness of the material deposited. The other is the foam paint roller - as illustrated in this video on gum. I bought a set myself recently as it seems to be more controllable procedure for someone like me whose brushing technique is atrocious.


:Niranjan.

THANKS! I'll buy a foam roller today

 

[Andrew O'Neill]

The thing with a foam roller is that you have to put a lot of gelatin on the paper, and roll quickly. Make sure there are no bubbles on the surface, so that last few rolls are done very lightly... all you need is the weight of the roller to do the job. Scrape up excess gelatin (I coated on large piece of plate glass) and stick back in container to use again...making sure it doesn't get mixed in with gelatin that doesn't have hardener in it!)

 

[GuidoIlieff]

I write to say thanks to everyone that helped me with this technique. I finally figure out this cheap paper and I'm getting results... maybe not the best results but I'm happy with my progress.


One thing I found out is that if you put citric acid in the emulsion the result is the same as the negative. Here is an example with and without citric acid:

I screwed the one that came out as a negative with a brush. Tomorrow I'll try to expose with a positive image and see what happens.

 

[Andrew O'Neill]

 

[nmp]

I write to say thanks to everyone that helped me with this technique. I finally figure out this cheap paper and I'm getting results... maybe not the best results but I'm happy with my progress.


One thing I found out is that if you put citric acid in the emulsion the result is the same as the negative. Here is an example with and without citric acid:
View attachment 341631 View attachment 341632

I screwed the one that came out as a negative with a brush. Tomorrow I'll try to expose with a positive image and see what happens.

So the top one is normal and the bottom one contained citric acid? Do you mean to say, the coating becomes insoluble after applying and drying and then on exposure it becomes soluble (and not just detaching and washing away?). If you can reproduce this, you have a positive process on your hand.

:Niranjan.

 

[GuidoIlieff]

So the top one is normal and the bottom one contained citric acid? Do you mean to say, the coating becomes insoluble after applying and drying and then on exposure it becomes soluble (and not just detaching and washing away?). If you can reproduce this, you have a positive process on your hand.

:Niranjan.

Well I don't know whats the chemistry but thats what happened. I want to do it again but its been cloudy and will be for the next week and a half so I'll have to wait to find out.

 

[nmp]

Well I don't know whats the chemistry but thats what happened. I want to do it again but its been cloudy and will be for the next week and a half so I'll have to wait to find out.

Check out the last paragraph on this long post from Chris Anderson - she talks about adding lemon juice and how it can harden gum. May be that's what you are observing on addition of citric acid.

Re: Paper and ink preparation

groups.io

Also the whole thread regrading staining, sizing etc in gum printing would be of interest and worthwhile reading through.

:Niranjan.

 

[GuidoIlieff]

Check out the last paragraph on this long post from Chris Anderson - she talks about adding lemon juice and how it can harden gum. May be that's what you are observing on addition of citric acid.

Re: Paper and ink preparation

groups.io

Also the whole thread regrading staining, sizing etc in gum printing would be of interest and worthwhile reading through.

:Niranjan.

Thank you very much! I'm reading everything!

 

[PGum]

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.

I will chime in on Canson XL- It is rather inexpensive, cold pressed and rougher on one side but both sides work. This is a good test paper for gum. The sizing strength is very slightly more than HPR, so a little less staining with increased loss of highlights. Multiple coats work fine, as the factory sizing stays put with numerous soaks. Slightly more mottling than HPR likely because of this more aggressive size. I use it for testing only, saving me the more expensive papers. It cockles quite badly on dry down and contains optical brighteners. HPR works best for me when making a final print.

 

[nmp]

contains optical brighteners.

Thanks. Didn't know about that. I guess over time that would cause the paper to turn warmer.

:Niranjan.

 

[PGum]

Niranjan,

It isn’t a lot but it is clearly fluorescing under UV. Not anything like you would see with office paper however.

 

[GuidoIlieff]

Hi, i'm back!

I finally got my hands on some formaldehyde and finally my papers aren't staining. Today I tried doing a color picture. The first two layers are fine but the third (cyan) wont stick to the print. I'm guessing its because the paper is oversized at that point. As I painted the cyan layer I could see the first layers repelling the emulsion. I didn't find any tips on what to do if you get to that point.
I read some people get the same results as me so it must be a common thing but I don't know what im doing wrong. Any ideas?

(The pictures are quite faded because I tried 2 times in each and I didn't print the black)

 

[GuidoIlieff]

I will chime in on Canson XL- It is rather inexpensive, cold pressed and rougher on one side but both sides work. This is a good test paper for gum. The sizing strength is very slightly more than HPR, so a little less staining with increased loss of highlights. Multiple coats work fine, as the factory sizing stays put with numerous soaks. Slightly more mottling than HPR likely because of this more aggressive size. I use it for testing only, saving me the more expensive papers. It cockles quite badly on dry down and contains optical brighteners. HPR works best for me when making a final print.

Thanks. Do you size the paper with gelatin or use it as it is?

 

[koraks]

The first two layers are fine but the third (cyan) wont stick to the print.

Yup, that's about the point where I threw the towel into the ring

the paper is oversized at that point

I don't think there's such a thing as 'oversized' (unless you mean it won't fit into your development tray!)
In principle, a layer of hardened gum will be a good surface to adhere additional layers of gum to.

I really recommend (again) Calvin Grier's Gum Printing e-book. It's in-depth but still fairly easy to read, and it goes through all the issues you're now running into and that are still coming your way. It's well worth the modest investment.

 

[nmp]

Hi, i'm back!

I finally got my hands on some formaldehyde and finally my papers aren't staining. Today I tried doing a color picture. The first two layers are fine but the third (cyan) wont stick to the print. I'm guessing its because the paper is oversized at that point. As I painted the cyan layer I could see the first layers repelling the emulsion. I didn't find any tips on what to do if you get to that point.
I read some people get the same results as me so it must be a common thing but I don't know what im doing wrong. Any ideas?

(The pictures are quite faded because I tried 2 times in each and I didn't print the black)

So I take it you are sizing the paper first with gelatin, hardened with formaldehyde. Did it also solve your non-adhering delicate film problem? Regarding the cyan layer, perhaps you can try what many do - put in a cyanotype layer at the base first instead of a cyan gum layer and then build the rest of the colors on top.

:Niranjan.

 

[GuidoIlieff]

Yup, that's about the point where I threw the towel into the ring


I don't think there's such a thing as 'oversized' (unless you mean it won't fit into your development tray!)
In principle, a layer of hardened gum will be a good surface to adhere additional layers of gum to.

I really recommend (again) Calvin Grier's Gum Printing e-book. It's in-depth but still fairly easy to read, and it goes through all the issues you're now running into and that are still coming your way. It's well worth the modest investment.

Oh sorry, I meant this: "Over-sized paper will not "take" the coating of emulsion well. Imagine painting water onto a sheet of glass. The water will bead up. This is what will happen to varying degrees with oversized paper." Norman Breslow. 1977.

There is nothing more that I want in this world than Calvin's e-book but its impossible for me. The US dollar and Euro are 500 and 600 times more expensive in my country (My currency is devaluated), and even if I had the money is a pain in the ass to buy something in dollars.

 

[koraks]

Have you tried reaching out to Calvin? He's a very approachable guy. He might be able to work something out with you.

 

[GuidoIlieff]

So I take it you are sizing the paper first with gelatin, hardened with formaldehyde. Did it also solve your non-adhering delicate film problem? Regarding the cyan layer, perhaps you can try what many do - put in a cyanotype layer at the base first instead of a cyan gum layer and then build the rest of the colors on top.

:Niranjan.

Well I'm trying to go full gum, but even if I add a cyanotype I'd still have the problem with the missing black layer

 

[GuidoIlieff]

Have you tried reaching out to Calvin? He's a very approachable guy. He might be able to work something out with you.

I have not. I didn't want to disrespect all the work he has done with that book because 50 dollars seems like a very fair price. But if you say hes approachable I'll try. Is he active in this forum or should I try to contact him on his business mail?