Pigments

**Drew Wiley** · 12-Nov-2022, 12:36

Hi Bob. Can't talk much at the moment. But I do own a set of some extraordinary watercolor pigments sought out all over Europe and Africa by my late aunt, an expert on the subject, hand-ground by her, and of the highest permanence, better than any art store unless you're talking about just a couple speciality suppliers in Europe who might charge more per gram than gold for certain ingredients. But many of even those aren't impervious to the long-term effects of UV. That's why she only used them for sake of watercolor paintings etc, and never for her legacy public fresco murals, which mainly involved natural oxides. Even the concept of permanence is relative. Color which seems fresh in cave painting 40,000 years old, or in Egyptians tombs 3,000 years old, can quickly deteriorate once exposed to humidity shifts and UV-rich lighting. So try not to outlive your own prints, or you might be disappointed. When I'm done illustrating my own cave, I'll seal it off well.

**Vaughn** · 12-Nov-2022, 16:17

That's the danger of carbon prints -- make a bad one and it can be around for a looooong time! Gelatin and carbon -- pretty tough stuff!

**Drew Wiley** · 12-Nov-2022, 16:31

A few prints were actually recovered from the Titanic and a few other deep wrecks. Platinum prints, where the image is in the fiber itself, did a lot better than carbon, where the coating lifted off. One more reason not to display your prints on the walls of a sinking ship unless they're Pt/Pd.

**koraks** · 13-Nov-2022, 01:10

Originally Posted by bob carnie

Hi Koraks

thanks so much I will look into Bruce MacEvoy as you list.
I do plan some tests myself to leave pigments in the outdoors for months on end and do LAB readings at time of printing and over time to see which of the pigments I use lose density.
I hope that the dichromates are removed with the wash process, as well one can do a metabisulfite bath at the end but I have no idea how to read the levels of AD in my finished gum prints
I use Calvins Cyan now , I am talking pre The Wet Print , Christina A and others recommended Thaylo Blue Green shade for cyan but it is a high staining pigment so I started custom mixing Viridian Green with a blue to get my cyan.
It was a PIA and am very happy with Calvins.

On a FB Gum page I have seen people use many types of colourant to make the colour and I think they have good possibilities.

Bob

Hey Bob,

Great, thanks for the follow-up. Yes, many colorants would work and there are many ways to create a workable gamut. See e.g. Calvin's more recent work using natural pigments; it's a much more subdued, neutral palette than you'd get with high-chroma industrial pigments, but still (or perhaps, even more so) offers a very natural looking outcome. The creative possibilities are infinite. This is one of the things that has always drawn me to pigment processes.

As to the dichromate remnants: I've done some testing lately with carbon and my results were somewhat disconcerting. I noticed some color and chroma problems in my test prints, reached out to Calvin, who was extremely helpful, and he put me on the right track by pointing out dichromate stain might be the issue. I looked into it further using pointers he gave and did some testing of pure gelatin prints (without any pigment) at low and high dichromate concentrations to get an impression of the stain and how to manage it. Turns out that the stain is virtually impossible to remove, at least from my test prints onto Yupo. With just a wash, the stain remains of a yellow-orange hue, which implies it's still chromium-VI based and quite probably detrimental to print stability (not just the pigment, but possibly the gelatin and the support as well!) in the long term. Extended washing of several hours removes some of it, but not all...Reduction with bisulfite or ascorbic acid does effectively reduce the chromium-VI to chromium-III as evidenced by the hue shift towards a near neutral grey with a hint of lime. But there's still chromium metal left in the print and I'm not sure how problematic it is. The one thing that really 'helped' was to just use as low a dichromate concentration as possible...but evidently this has implications for tonal scale, pigment loading etc.
Here's the blog post I wrote about it a few days ago: https://tinker.koraks.nl/photography...rbon-printing/
This is an illustration of the dichromate stain on some carbon-without-carbon (gelatin only) prints:

From top to bottom:
Print with 1% dichromate sensitizer; no substantial washing or clearing of the print. Note low level of stain; there's just not much chromium in there to begin with
Print with 16% sensitizer; note heavy staining. Unwashed and uncleared print.
Print with 16% sensitizer after soaking in water for a few hours. Note reduced but still present stain.
Print with 16% sensitizer after vitamin-C clearing bath (bisulfite does the same thing). Note reduced stain that has shifted to neutral hue.

When doing these tests my interests were more in the hue & chroma problems that come with stain and not so much the print longevity issue, so that's what I focused on.

PS: take he Lab* measurements on that blog page with a huge grain of salt as they were made with uncalibrated equipment. If you want I can give you some more accurate measurements made with the i1Pro I received recently.

**koraks** · 13-Nov-2022, 01:27

Originally Posted by Vaughn

Good you have found a good black! I have stayed away from using dry pigments...too lazy (and very happy with what I am using).

It is almost impossible to compare pigment loading of different pigment types usefully. I use 5 grams of Grahams lampblack per 750ml of water, which is 0.7%...ca 0.6 grams pigment per 10 grams of gelatin. The weight of my pigment also includes the binder (gum arabic, water and honey) and thus the tissue is very low contrast.

Yes Vaughn, it sure is difficult to make a meaningful comparison between pigments. So many factors influence the outcome. And there's always the question to what extent a comparison is necessary. Although there are two reasons why I do sometimes try. The first is to try and place my experiences into a broader context. If e.g. you mention a certain pigment loading or Sandy does in one of his writings, it's helpful for me to know what that actually means in practice. By having a bit of a reference in pigment loading, it's possible to estimate things like the kind of negatives you must be working with, what kind of relief you might be getting, what kind of exposure times etc. It's one of those parameters that indirectly says a lot about someone's process.

The other reason is just for consistency, which in my case is mostly about saving time. If I know that my 1% India ink to 8% gelatin tissue behaves in a certain way, it's nice to be able to translate that experience to a new pigment without having to do many test prints to figure out how strong the new pigment is.

Sadly, it's very difficult to do a good comparison, but it's possible to get in the ballpark nonetheless. What I generally do is make a 1% w/v solution of a pigment or a paint in water for the pigments/paints I want to compare. Then take two identical beakers with let's say 100ml water in each, and place 10 drops or so of the reference pigment solution into it. I then try to match the same tint by placing drops of the other pigment solution into the other beaker until they look more or less the same. In practice this gives a huge error, but the differences between pigments and paints are often so much huger still! For instance, the ivory black I trialed recently has perhaps 5% or 10% the tinting strength (if I'm generous!) of the lamp black that's in India ink or that constitutes the Kremer dry pigment I talked about earlier. That's such a huge difference that even with a large margin of error, a visual comparison as described above gives a useful insight.

**bob carnie** · 13-Nov-2022, 07:06

Originally Posted by koraks

Hey Bob,

Great, thanks for the follow-up. Yes, many colorants would work and there are many ways to create a workable gamut. See e.g. Calvin's more recent work using natural pigments; it's a much more subdued, neutral palette than you'd get with high-chroma industrial pigments, but still (or perhaps, even more so) offers a very natural looking outcome. The creative possibilities are infinite. This is one of the things that has always drawn me to pigment processes.

As to the dichromate remnants: I've done some testing lately with carbon and my results were somewhat disconcerting. I noticed some color and chroma problems in my test prints, reached out to Calvin, who was extremely helpful, and he put me on the right track by pointing out dichromate stain might be the issue. I looked into it further using pointers he gave and did some testing of pure gelatin prints (without any pigment) at low and high dichromate concentrations to get an impression of the stain and how to manage it. Turns out that the stain is virtually impossible to remove, at least from my test prints onto Yupo. With just a wash, the stain remains of a yellow-orange hue, which implies it's still chromium-VI based and quite probably detrimental to print stability (not just the pigment, but possibly the gelatin and the support as well!) in the long term. Extended washing of several hours removes some of it, but not all...Reduction with bisulfite or ascorbic acid does effectively reduce the chromium-VI to chromium-III as evidenced by the hue shift towards a near neutral grey with a hint of lime. But there's still chromium metal left in the print and I'm not sure how problematic it is. The one thing that really 'helped' was to just use as low a dichromate concentration as possible...but evidently this has implications for tonal scale, pigment loading etc.
Here's the blog post I wrote about it a few days ago: https://tinker.koraks.nl/photography...rbon-printing/
This is an illustration of the dichromate stain on some carbon-without-carbon (gelatin only) prints:

From top to bottom:
Print with 1% dichromate sensitizer; no substantial washing or clearing of the print. Note low level of stain; there's just not much chromium in there to begin with
Print with 16% sensitizer; note heavy staining. Unwashed and uncleared print.
Print with 16% sensitizer after soaking in water for a few hours. Note reduced but still present stain.
Print with 16% sensitizer after vitamin-C clearing bath (bisulfite does the same thing). Note reduced stain that has shifted to neutral hue.

When doing these tests my interests were more in the hue & chroma problems that come with stain and not so much the print longevity issue, so that's what I focused on.

PS: take he Lab* measurements on that blog page with a huge grain of salt as they were made with uncalibrated equipment. If you want I can give you some more accurate measurements made with the i1Pro I received recently.

Very interesting... when you use dichromate with carbon where is it applied at the tissue making stage ? Its been so long since I did one I am embarrassed to say I forget the steps in a carbon transfer print.
I too am good friends with calvin I am in the middle of a big purchase from him, I tried the earth pigments for him with various success and will do more tests when I get through this busy period

**koraks** · 13-Nov-2022, 08:04

I sensitize the tissue with dichromate just before exposing, using a foam roller, diluted with ethanol. It then needs to be exposed as soon as possible when dry, which is between around 45 minutes and a few hours for me.
Technically it's also possible to add dichromate to the glop when making the tissue but there are several drawbacks to this, so I don't bother.

I've only been in touch with Calvin briefly, but he's been really helpful indeed. I noticed your name in the acknowledgements of his Gum printing manual!

**bob carnie** · 13-Nov-2022, 08:45

Originally Posted by koraks

I sensitize the tissue with dichromate just before exposing, using a foam roller, diluted with ethanol. It then needs to be exposed as soon as possible when dry, which is between around 45 minutes and a few hours for me.
Technically it's also possible to add dichromate to the glop when making the tissue but there are several drawbacks to this, so I don't bother.

I've only been in touch with Calvin briefly, but he's been really helpful indeed. I noticed your name in the acknowledgements of his Gum printing manual!

I am a fan of Calvin , he is young and enthusiastic about materials I use...All I really did was look at his notes and made suggestions, some he took others not but its all good as far as I am concerned.