Severe staining when toning a Van Dyke Brown print in gold thiourea toner ...

[largo]

I just experienced a severe staining of my Van Dyke Brown print after I toned them in a gold thiourea toner (Clerc or Sandy King #2 formula). The toner work well in the sense that it indeed cooled the tones like expected, but all the highlights and the paper base is stained with a sepia-like color, almost like if I toned my prints with tea ! Because of the sepia tint, I suspect sulfides to be somehow involded, of silver sulfides ?

I am sure that the staining is related to the gold toning step (but maybe also related to the preceding steps) , because my tray dedicated for toning was too small for the print, so I had to bend the print so that the image part was fully submerged in the gold toner. As a consequence, the bottom part of the print is not stained at all since it was not submerged in the toner bath (see the attached pics) :

<== back of the print, see the bottom part not stained.

3 remarks before I detail my process :

1) I toned my VDB print BEFORE fixing, as recommended by many master printers : Sandy King, Donald Nelson, Dick Stevens (the later for kallitypes, but they are similar w.r.t. toning), Tim Rudman (in his Toning book)
2) the 1% gold chloride solution that I use to mix my gold toner is old (about 10 years old), but I read that it keeps very well. It looked OK, clear and yellowish.
3) I don't know much about my tap water, but I do know that it has a pH of 7.

Here is my process :

1. Sensitizer : 16 drops of ferric ammonium citrate + 16 drops of tartric acid + 16 drops of silver nitrate. The sensitizer is perfect, clear, fresh, no precipitate at all.
2. Paper (Bergger COT 320) is sensitized (single coating) and dried during 1 hour
3. Exposure : 13 minutes under UV lamp
4. Clearing in demineralized water with a teaspoon of citric acid : 5 minutes with agitation



5. Rinse : 3 minutes in a tray of running _tap_ water : note that I used tap water here, not demineralized water.
6. Toning : 8 minutes in a gold thiourea toner ("Sandy King’s Gold Toner #2"); here is its formula (CLERC Formula, with thiourea) :
- Pour 500 ml demineralized water
- Add 25 ml 1% gold chloride solution
- Add 25 ml 1% thiourea solution (1 g thiourea in 100 ml)
- Add 0.25 g tartaric acid
I observed after adding the 1% thiourea solution to the water+gold chloride that the mix took a brownish color, I don't know if this normal or not ? (see the attached pic) :

7. A short rinse in tap water before fixing
8. Fixing in weak sodium thiosulfate solution, during 2 minutes
8. Hypo-clearing in a 1% sodium sulfide solution, during 2 minutes
9 : Final wash : 30 minutes in running tap water.

I already successfully toned my VDB prints with platinum or palladium, without staining...

I read here (https://www.photrio.com/forum/threa...ixing-role-of-citric-acid.117388/post-1921485) that if gold thiourea toner is used before fixing, thiourea will cause staining. That instead alkali gold toners should be used when gold toning before fixing. The thread is about salt print, but I think it applies to VDB prints.

I see that the gold toner for VDB sold by Bostick & Sullivan does not contain thiourea, but ammonium thiocyanate, this is the one used in this video :

What do you think ? What went wrong ?

Thank you for your help !

 

[cliveh]

Then don't tone them in a gold thiourea toner.

 

[largo]

Then don't tone them in a gold thiourea toner.

Thanks, this is helpful

The gold-thiourea toner (originally from Clerc) is commonly used, for example in this video :


Also in this video (at the 6:57 mark) :


I see in these 2 videos that the gold-thiourea toner is totally clear, not brownish like mine... This might be the cause ?

 

[FotoD]

I observed after adding the 1% thiourea solution to the water+gold chloride that the mix took a brownish color, I don't know if this normal or not ?

Not normal, I would say. But can't remember for sure.

No NaCl in your toner recipe?

How many changes of water in #4? I wonder if you have washed out all unexposed silver and iron. I washed 9m, 5 changes, 2.5% H4Cit.

I never got good results with gold/thiourea before fixer, after fixer was Ok. Gold/H4Cit toner was Ok before fixer, but much different in color.

Thiourea tones to a yellowish tone. Maybe you just need to wash out unexposed salts better before toning?

Good luck!

 

[FotoD]

And I would mix the toner in the order: gold chloride, thiourea, water, tartaric acid, NaCl.

Check out https://unblinkingeye.com/Articles/Vandyke/vandyke.html

 

[largo]

I just found this in Louis-Philippe Clerc's book "Photography - Theory & Practice", 3rd Ed. (1954), page 396 :

"The complex salts formed by thiourea with gold and silver salts are stable only in an acid medium; moreover, the double silver salt splits up in dilute solution and gives silver sulphide, so that there is a danger of staining the prints when washing them between the toning and the fixing operations. If it is desired to keep the toned prints between toning and fixing, they should be put in water slightly acidulated with an acid (e.g. boric acid, which is without action on thiosulphate). The following formula gives excellent results. Tartaric acid should be used for gelatine P.O.P., and citric acid for collodion papers.

Sodium chloride : 20 g
Thiourea (1% solution) : 50 ml
Tartaric or citric acid : 0.5 g
Gold chloride (1% solution) : 50 ml
Water to make 1000-2000 ml

In Christina Z. Anderson's "Salted Paper Printing" book, I can read (about a possible cause for yellowish prints) :

"The print was not rinsed well enough after toning so that acidity was carried over into the fixer, which creates silver sulfide that attacks the print. Make sure to rinse a toned print well before fixing, either in an alkaline bath made with plain water and ¼ teaspoon of sodium carbonate, or after certain toners, a salted water bath."

Still in Christina's book, about the possible causes for stains on the print :

The fixer has contaminated the toner and brown patches of silver sulfide result. Keep the fixer far, far away from the toner and don’t ever cross-contaminate with fingers or tongs.

The print wasn’t washed well after toning and before fixing and silver sulfide has formed in the print, which will result in dirty yellow opaque stains. One author suggests a pound of sodium carbonate in a gallon of water for an after-toning bath to stop these stains from forming.

The after-toner alkaline bath has become contaminated, and when the toned print is put in it, instant stains result. Change this bath frequently if necessary; it’s only water and a bit of sodium carbonate. Don’t use his for gold thiourea, or you may get instant yellow-brown fog. Use a 5% salted water wash instead.

Gold thiourea is an acid gold toner. [...] Gold thiourea toner is acidified with tartaric acid, whose function is to restrain the decomposition of thiourea to hydrogen sulfide which will immediately react with unexposed silver to fog highlights. Thus after thiourea gold toning do not use an alkaline wash, but a 5% salt wash only. The moral is this: if you have these instant staining issues just after toning, look to the pH of the after-toner water bath first, and wash the print well before it enters the fixer. Your staining issues should disappear.

Again, in Christina's book :

Have a packet of litmus strips on hand to test the alkalinity of the gold toner just before use. This will ensure that you are always on target concerning the pH of the gold toning solution. There is one visual indicator for the readiness of an alkaline gold toner: it goes from yellow to colorless when it is ready.

Could this would explain the yellow-brownish color of my Clerc Gold-Thiourea toner ? Too acidic (gold chloride is acidic? Could the addition of sodium chloride fix this ? Christina mentions that the ideal pH is 7-10

Also found this comment on photrio interesting :

sodium chloride for gold thiourea toner?

I have a bit of alt-print chemistry inbound, but I managed to miss the sodium chloride used in Sandy King's gold/thiourea toner. Normally I would just sub with pickling salt with no anti-caking agent, but given the expense of gold chloride, I wanted to get some expert opinion as to whether it...

www.photrio.com

I use non-iodised cooking salt, but really it hardly matters, because so little is involved.
And a tip for you: if you use it one-shot, you don't have add the gold chloride to the whole volume at the outset. Just mix the other bulk components and store. Add gold chloride to a measured quantity at the bulk solution just before use. One drop of 1% gold chloride per ml is the correct rate. The solution will be yellow initially, then clear after 30 seconds or so. It's good to go after that.

In Giorgio Bordin video

he mentions that sodium bicarbonate should not be added to the hypo fixer after toning. I think he meant sodium carbonate. This would follow Christina Anderson's advice not to do a sodium carbonate wash after gold-thiourea toning .... ?

At this point, to summarize, here are the things I'm going to investigate :

1) I think my gold-thiourea toner might be badly prepared (bad pH ?), because of its weird color (I should be colorless from the videos) and because I did not add sodium chloride (I don't know the purpose of adding kasher salt ?), and maybe because I did not add the ingredients in the appropriate order ? Nevertheless, I think my 1% gold chloride and 1% thiourea stock solutions keep indefinitely, so they are OK.

2) I strongly suspect the formation of silver sulphide, and that the staining actually occurred _after_ the toning bath (see attached pic above : when in the gold toner bath, the print looked still OK), in the quick rinse with tap water before the fixing or in the fixer bath itself ? Sulfuring of the print due to residual acid in the print when it hit the fixer ?

 

[koraks]

? Too acidic (gold chloride is acidic? Could the addition of sodium chloride fix this ? Christina mentions that the ideal pH is 7-10

A lot of conflicting information you dug up there. I imagine that's of little help. Especially a pH7-10 mentioned for a bath that's supposed to be acidic (= ph<7).

When I make Clerc's gold toner, I mix all the ingredients except the gold chloride. This should produce a totally clear, colorless solution with no cloudiness etc. Upon addition of th gold chloride, the yellow color of the gold should diffuse nearly instantly and the toner should be colorless again within a few seconds. If this doesn't happen, something's wrong with your toner. What? I don't know. I'd start by mixing some fresh with all of the ingredients (so including the NaCl).

What's your source of tartaric acid?

I've toned plenty of VdB's before fixing with nu particular precautions. It generally works fine. However, toning after fixing is safer in terms of fogging etc, but even in compromised situations, I've rarely gotten anything nearly as bad as you've got there. The really tricky one I've never been able to get to work reliably, i.e. without any traces of fogging of masked whites, is gold toning salted paper prints before fixing. But Van Dyke is a lot easier.

How many changes of water in #4? I wonder if you have washed out all unexposed silver and iron

Good question.
I generally wash in 2-3 changes of water, acidified with a tiny pinch of citric acid, which takes 4-5 minutes. The final change of water should remain virtually clear. The water of the initial wash will be very cloudy with unexposed silver salts.

I strongly suspect the formation of silver sulphide

Indeed. The question is where the sulfur comes from. Is it the thiourea, the thiosulfate or something else? It surely isn't the tap water, as that generally doesn't contain much sulfur at all (if it does, it's time to pack up and move out).

8. Fixing in weak sodium thiosulfate solution, during 2 minutes

That's virtually guaranteed to be a grossly insufficient fix.
I always use C41 color fixer, diluted 1+10 or so, for at least 2 minutes, but preferably longer. This fixer is far stronger and faster than your weak sodium thiosulfate fixer. I can't imagine that a natural paper base with silver salts permeated throughout the base will fix at all the way you're doing it. I think at least part of your problem is that your fixing bath mostly serves to create some poorly soluble silver salts that are then nicely spread out through the paper base, where they can then dry up in a fairly even, yellow to tan colored stain.

 

[largo]

A lot of conflicting information you dug up there. I imagine that's of little help. Especially a pH7-10 mentioned for a bath that's supposed to be acidic (= ph<7).

Yes I realized after that I dug info for salter paper print process that might not be relevant for VDB. I think abumen / salted paper processes require alkaline toners because the albumen or gelatin do not like acids, right ?

When I make Clerc's gold toner, I mix all the ingredients except the gold chloride. This should produce a totally clear, colorless solution with no cloudiness etc. Upon addition of th gold chloride, the yellow color of the gold should diffuse nearly instantly and the toner should be colorless again within a few seconds. If this doesn't happen, something's wrong with your toner. What? I don't know. I'd start by mixing some fresh with all of the ingredients (so including the NaCl).

I think that part of my problem first comes from my brownish gold toner... :

Maybe I did not mix the ingredients in the appropriate order ? Or this happened because I did not add the sodium chloride ?

By the way, what is the purpose of NaCl in Clerc's Gold Tiourea formula ? I can't find this information...

What's your source of tartaric acid?

Bought here : https://www.disactis-photochimie.fr/acide-tartrique-50gr-c2x38711669

French supplier of chemicals for photography, top quality.

Good question.
I generally wash in 2-3 changes of water, acidified with a tiny pinch of citric acid, which takes 4-5 minutes. The final change of water should remain virtually clear. The water of the initial wash will be very cloudy with unexposed silver salts.

I think I'll change my process to use 2-3 2 minutes baths of acidified demineralized water instead of a single 5 minutes bath in acidified demineralized water... This should improve the clearing...

The question is where the sulfur comes from. Is it the thiourea, the thiosulfate or something else? It surely isn't the tap water, as that generally doesn't contain much sulfur at all (if it does, it's time to pack up and move out).

I don't know where the sulfur comes from either...

I also came across these explanations & formula in Donald Nelson book "A Step by Step Manual of iron-silver processes" :

The tartaric acid restrains the decomposition of the thiourea to hydrogen sulfide, so it keeps well. (The hydrogen sulfide that occurs if the tartaric acid is not added will react with unexposed silver to fog highlights.) Immediately after toning, use a wash of distilled water with a teaspoon of citric acid and avoid alkaline washes or staining will occur.​

​

12 ml gold chloride 1%​

12 ml thiourea 1% solution​

12 ml tartaric acid 10% solution​

5 g sodium chloride​

Distilled water to make up to 500 ml​

​

To make the stock solutions:​

​

1. Make the 1% gold chloride solution by adding 1 g gold chloride to 100 ml of distilled water. Store in a 100 ml bottle.​

2. Make the 1% thiourea solution by adding 1 g thiourea to 100 ml of distilled water. Store in a 100 ml bottle.​

3. Make the 10% tartaric acid solution by adding 10 g tartaric acid to 100 ml of distilled water. Store in a 100 ml bottle.​

​

To make the toner:​

​

1. Measure 12 ml of 1% gold chloride solution​

2. Add 12 ml 1% thiourea solution while stirring. Stir until a resulting yellow/orange precipitate is redissolved.​

3. Add 12 ml 10% tartaric acid solution to 150 ml of distilled water.​

4. Add the gold/thiourea solution to the tartaric acid/distilled water while stirring.​

5. Add 5 g sodium chloride, stirring to dissolve completely.​

6. Make up to 500 ml by adding distilled water.​

​

Stir well, you should eventually obtain a clear and colorless solution.​

What do you think of this formula ?

That's virtually guaranteed to be a grossly insufficient fix.
I always use C41 color fixer, diluted 1+10 or so, for at least 2 minutes, but preferably longer. This fixer is far stronger and faster than your weak sodium thiosulfate fixer. I can't imagine that a natural paper base with silver salts permeated throughout the base will fix at all the way you're doing it. I think at least part of your problem is that your fixing bath mostly serves to create some poorly soluble silver salts that are then nicely spread out through the paper base, where they can then dry up in a fairly even, yellow to tan colored stain.

Here is how I prepare my fixer :

First I prepare the stock solution :

sodium thiosulfate : 150 g
sodium carbonate : 10 g
1 liter of warm tap water

1. In 1 liter of hot tap water, add sodium thiosulfate and stir until completely dissolved.
2. Add sodium carbonate.
3 Store in a hermetically sealed glass bottle.

Then when I want to fix a print, I dilute 1 part of this concentrated product with 4 parts of tap water at room temperature (1+4 dilution).

Eventually, this is basically a 3% hypo solution when used, this is why I call it a weak solution...

I fix during 2 minutes. Weak solution + shorter times to prevent bleaching of the print (which should be prevented here in my case by the gold toning...). Because of the relatively thin layer of silver metal that forms the image, VDB prints are more vulnerable to attack (bleaching) by hypo fixers stronger than 5%.
Also there is no gelatin or other substrate that require a stronger fixer, like in traditional b&w paper. The non-exposed silver to be removed is directly accessible to the fixer.

Dick Stevens in "Making Kallitypes, the definitive guide" recommends 5 to 10 minutes in a 2,5-5% hypo fixer. All authors agree on a concentration between 2,5 and 5%, but they recommend usually 5 minutes in such a fixer... So I could go for a longer fix time.

Now I am wondering if my fixer stock solutions keeps well ? ....

 

[koraks]

I think abumen / salted paper processes require alkaline toners because the albumen or gelatin do not like acids, right ?

No, not really. Clerc's toner will tone albumen and gelatin prints just fine. Salted paper prints as such don't necessarily use albumen or gelatin or any other colloid; I always make them without.

By the way, what is the purpose of NaCl in Clerc's Gold Tiourea formula ? I can't find this information...

Me neither! Copying @nmp because he probably knows.

Bought here

Yeah, I know them. I just use food grade tartaric acid, btw.
Reason I asked is because of the apparently crucial role it plays in preventing decomposition of the thiourea. There was talk recently on here about tartaric acid being a poorly defined substance; I'm no chemist, but AFAIK it's pretty well-defined with the only tricky bit being that it occurs in different isomers. I don't know if this relates in any way to its function in this toner.

Which reminds me - if you're going to mix fresh toner, please also mix some fresh thiourea. In my experience, solutions of a few percent thiourea should be stable (I've used them many times, and with ages up to over a year, easily), but maybe something funny has happened with yours. Sounds unlikely, but it's worth a shot to eliminate the possibility.

What do you think of this formula ?

Looks similar to the other formulas, just a different order of dissolving. Which suggests the order doesn't matter all that much.

Eventually, this is basically a 3% hypo solution when used, this is why I call it a weak solution...

Yup, that's weak and there's nothing in there that will prevent the thiosulfate from being attacked by oxygen. It's also alkaline, which I suspect may have something to do with your staining problems.
I know about the general advice to use some kind of archaic 'plain hypo' fixer with alt. processes, but I myself have stopped doing so because of the unnecessarily long fixing times and risk of incomplete fixing. Problems with highlight bleaching in my own printing were *always* due to insufficient exposure of the print combined with an inadequate negative. Making negatives with a longer tonal scale and exposing the prints longer always proved to be the solution.

Also there is no gelatin or other substrate that require a stronger fixer, like in traditional b&w paper.

Unlike in regular B&W paper, you have no baryta or RC coating to prevent silver complexes from embedding themselves between the paper fibers, from where they are notoriously difficult to fix out.

I've got the stained and faded prints that I fixed so cautiously with weak plain hypo fixer because of the reasons you mentioned to prove that these arguments should be treated with a thorough amount of distrust. Silver-based alt. process prints require very thorough fixing in my experience, and failing to do so results in catastrophic failure of the prints over time. Insufficient fixing is far too often used as a workaround for insufficiently exposed prints, resulting in one problem being used to mask another. The net effect is poor print longevity. Especially Van Dyke prints tend to both fade (loss of image density) and yellow (staining highlights). This can happen within a few weeks, months or years. I've got a 'nice' Van Dyke in our downstairs bathroom to remind me of the risk of poor processing practices. Here it is:

The print, when fresh, was punchy with good dmax and clean masked whites. The now visible brush marks show how much fogging has occurred and there is also severe loss of density in the image. All this is entirely due to grossly insufficient fixing in ways very similar to what you're currently doing.

Plain hypo fixer can work, but I'd recommend mixing it fresh, or at least adding sulfite to protect against oxidation, and also to use two-bath fixing for at least 5 minutes per bath, so a total of 10 minutes.

Dick Stevens in "Making Kallitypes, the definitive guide" recommends 5 to 10 minutes in a 2,5-5% hypo fixer.

For VdB 5 minutes may juuuust be enough in play hypo. For salted paper, it damn sure isn't on heavier papers (>250gsm); maybe maybe maybe on very thin Japanese papers...maybe.

 

[largo]

Looks similar to the other formulas, just a different order of dissolving. Which suggests the order doesn't matter all that much.

There is much more tartaric acid in this other formula, right ? This could help in preventing decomposition of the thiourea...

Yup, that's weak and there's nothing in there that will prevent the thiosulfate from being attacked by oxygen. It's also alkaline, which I suspect may have something to do with your staining problems.
I know about the general advice to use some kind of archaic 'plain hypo' fixer with alt. processes, but I myself have stopped doing so because of the unnecessarily long fixing times and risk of incomplete fixing. Problems with highlight bleaching in my own printing were *always* due to insufficient exposure of the print combined with an inadequate negative. Making negatives with a longer tonal scale and exposing the prints longer always proved to be the solution.

Interesting. My kallitypes or VDBs are not old enough to see any fading or yellowing... So what would be your recommended fixer formula, concentration & time in fixer for a proper fixing of iron-silver processes ?

 

[koraks]

So what would be your recommended fixer formula, concentration & time in fixer for a proper fixing of iron-silver processes ?

I prefer to use C41 fixer because it's near-neutral, fast and works for just about everything, so I don't have to think about which fixer goes where etc. 1+10 for 4 minutes or so, or even 2-bath with 2 minutes per bath.

If I were to make something myself, I'd just start with standard 60% w/w ammonium thiosulfate solution (maybe sold as fertilizer) and dilute that 1+10 or so, see how it goes. Adjust to taste in case of any trouble. Maybe acidify it very slightly with a small dash of vinegar or something until the ammonium smell subsides; that usually gets you close to pH6-7-ish.

Or any normal acid rapid fixer and add ammonia to neutralize the pH, bringing it up to 6-7.

Or any commercial pH neutral rapid fixer sold for B&W work. There's a few around, I think. Moersch probably has something.

 

[NedL]

I've toned plenty of VdB's before fixing with nu particular precautions. It generally works fine. However, toning after fixing is safer in terms of fogging etc, but even in compromised situations, I've rarely gotten anything nearly as bad as you've got there. The really tricky one I've never been able to get to work reliably, i.e. without any traces of fogging of masked whites, is gold toning salted paper prints before fixing. But Van Dyke is a lot easier.

This made me chuckle. Alt stuff can be mystifying. My experience is completely the opposite. I've had good luck and results toning salt prints prior to fixing ( and I'm fanatical about highlights, not just clean borders but delicate highlights ). After quite a bit of fussing with various gold and platinum toners before fixing VDB or Sepia prints, I finally gave up and now always tone those after fixing. I particularly like gold-thiocyante toner for VDB/sepia.

Who knows? We probably use different papers and other things.

 

[largo]

I think I first encounter a problem when preparing the thiourea gold thiourea formula (Clerc formula).

As a reminder, the formula is as follows:

- Gold chloride 1%: 5 ml
- 1% thiourea: 5 ml
- tartaric acid: 50 mg
- demineralized water to make 100 ml
- sodium chloride: 2 g

I already have a 1% gold chloride solution, which is at least 10 years old, but stored in a brown bottle, I don't think it has any problems. This 1% gold chloride solution was supplied to me by a fellow photographer for the Namias formula, so it's normally a 1% gold chloride solution (I'm waiting for confirmation from the person who prepared it for me, but I'm 95% sure it's 1% gold chloride).

I start by pouring 5 ml of this solution into the beaker, its color is yellow, I think it's normal.


I then add the 5 ml of 1% thiourea solution. A precipitate forms, as expected. The solution should then be stirred and perhaps a little more thiourea added so that the precipitate dissolves. Problem for me, it doesn't dissolve at all!


I had to add a further 5 ml of thiourea (i.e. double the amount of thiourea) so that the solution became completely translucent (no more precipitate or color) :


The 1% thiourea solution should be OK : I did dissolve 1g of thiourea in 100 ml of demineralized water (fresh, a few days ago). Thiourea purchased from Disactis.

I have to investigate more to determine if the problem comes from the concentration of my solutions? From the formula itself? From the stock 1% solutions ?

 

[largo]

I made a new batch of 1% gold chloride, and now mixing N drops of AuCl 1% with N drops of 1% thiourea does not yield any precipitate.

So I suspect my initial older AuCl solution bottle to contain a ~2% AuCl solution, but I'm waiting for my dealer to answer ...

 

[koraks]

So I suspect my initial older AuCl solution bottle to contain a ~2% AuCl solution

Don't think so; sounds like it was something else entirely.
The fact that your new gold chloride solution seems to be working (so far) is promising!

 

[largo]

Don't think so; sounds like it was something else entirely.
The fact that your new gold chloride solution seems to be working (so far) is promising!

My dealer confirmed that it can be a 2% gold chloride solution, that he indeed sometimes prepared 1% or 2% solutions.

 

[nmp]

Me neither! Copying @nmp because he probably knows.

Sorry I missed the alert. Sometimes it takes days for the alert to show up. Unfortunately I haven't been following the thread as much.

Regarding the NaCl, I don't have any insight except to make a guess (that can be way off) - which is: it must play some sort of a role in pushing the equilibrium towards the right, i.e. take up Ag+ created and precipitate it out of the solution as AgCl so more can be oxidized and replaced with Au. In other words, NaCl allows more complete replacement toning of silver with gold.

:Niranjan.

 

[nmp]

My dealer confirmed that it can be a 2% gold chloride solution, that he indeed sometimes prepared 1% or 2% solutions.

Looks like in the first case, you were not redissolving the precipitates completely. Perhaps instead of using a set amount of thiourea solution for an equivalent gold chloride solution, add it till the solution clears might be a better method as you did above. Wynn White suggests it so here.

:Niranjan

 

[largo]

Looks like in the first case, you were not redissolving the precipitates completely. Perhaps instead of using a set amount of thiourea solution for an equivalent gold chloride solution, add it till the solution clears might be a better method as you did above. Wynn White suggests it so here.

:Niranjan

Thanks Niranjan !

I think my Clerc's gold thiourea toner is now OK... But I have a couple of extra questions for you now that you've joined the thread :

- Are there any precautions I can take to prevent silver sulfides from being formed and staining the paper? (The thiourea and hypo in my fixer are sources of sulfur).

- I wonder if I should remove sodium carbonate from my fixer formula when I fix after a gold-thiourea toning ? I haven't measured the pH of my fixer but I imagine it's neutral or even alkaline because of the sodium carbonate... I've read here and there that I risk having an instant yellow-brown fog/stain if a gold-thiourea toned print goes into a solution that's too alkaline... Is that right ? What happens with alkaline washes after a gold-thiourea toning ?

Thanks for your helpful insights !

 

[FotoD]

Are there any precautions I can take to prevent silver sulfides from being formed and staining the paper?

Wash thoroughly. Changing the acidified water several times before toning is critical.

I haven't tested how little washing you can get away with between toner and fixer. 3 min with agitation in 3 changes of alkaline tap water seemed to do it for me.

Silver-sulfur compounds isn't necessarily a bad thing. The sulfur toning that occurs when fixing an Argyrotype is suspected to increase the permanence of the final print.

What happens with alkaline washes after a gold-thiourea toning ?

Washing in alkaline water is no problem.

Make sure you also try toning after fixing and drying the print. Maybe you'll prefer it.

 

[nmp]

Thanks Niranjan !

I think my Clerc's gold thiourea toner is now OK... But I have a couple of extra questions for you now that you've joined the thread :

- Are there any precautions I can take to prevent silver sulfides from being formed and staining the paper? (The thiourea and hypo in my fixer are sources of sulfur).

- I wonder if I should remove sodium carbonate from my fixer formula when I fix after a gold-thiourea toning ? I haven't measured the pH of my fixer but I imagine it's neutral or even alkaline because of the sodium carbonate... I've read here and there that I risk having an instant yellow-brown fog/stain if a gold-thiourea toned print goes into a solution that's too alkaline... Is that right ? What happens with alkaline washes after a gold-thiourea toning ?

Thanks for your helpful insights !

Here is a thread on altphotolist, where there is some discussion on use of thiourea based toner, that might be useful - it is salt print related but I think basic principles would apply.

https://groups.io/g/altphotolist/topic/88609331#6850

Basically for thiourea based toners, either the fixer needs to be acidic or thiourea needs to be washed out thoroughly before an alkaline fixer as @FotoD mentioned above. Your fixer is actually quite a bit alkaline: pH of 10-11 for 1% Na carb. So I would wash the print more diligently before fixer.

You can remove the carb from the fixer to make it neutral but it will also tend to bleach the silver image (again translating from salt printing as I have no direct experience with VDB) and it will not keep well so it would be better to make it fresh every time. I also add some sodium sulfite to my fixer in order to extend its longevity by keeping thiosulfate from disassociating in presence of oxygen

:Niranjan.

EDIT: Realizing since since you are toning the print replacing Ag with Au, bleaching may not be a big problem, although I don't have first hand experience with fixing toned prints.

 

[largo]

Here is a thread on altphotolist, where there is some discussion on use of thiourea based toner, that might be useful - it is salt print related but I think basic principles would apply.

https://groups.io/g/altphotolist/topic/88609331#6850

Basically for thiourea based toners, either the fixer needs to be acidic or thiourea needs to be washed out thoroughly before an alkaline fixer as @FotoD mentioned above. Your fixer is actually quite a bit alkaline: pH of 10-11 for 1% Na carb. So I would wash the print more diligently before fixer.

You can remove the carb from the fixer to make it neutral but it will also tend to bleach the silver image (again translating from salt printing as I have no direct experience with VDB) and it will not keep well so it would be better to make it fresh every time. I also add some sodium sulfite to my fixer in order to extend its longevity by keeping thiosulfate from disassociating in presence of oxygen

:Niranjan.

EDIT: Realizing since since you are toning the print replacing Ag with Au, bleaching may not be a big problem, although I don't have first hand experience with fixing toned prints.

Thanks Niranjan once again for your helpful answer !

I actually just made a new VDB print, toned with gold-thiourea Clerc toner before fixing it. Everything went well this time !! Things that I changed compared to my previous stained print :

1) the new batch of fresh gold-thiourea (Clerc’s formula) was crystal-clear this time and quickly & entirely toned the print towards a cold/neutral black just like expected. I added the NaCl to the toner, just like recommended in Clerc’s formula.

2) prior to fixing, I washed the toned print in slightly acidic demineralized water

3) I eventually fixed it during 2 minutes in a 3% hypo solution. No sodium carbonate, no sodium sulfite, just plain hypo. I guess the fixer had a neutral pH (I’ll check this tonight)

Just out of curiosity, do you have any background in chemistry ? I’m asking because your answers are detailed and very useful !

 

[largo]

Here are some pictures of my latest gold toned VDB print….

 

[koraks]

Looks great!

I eventually fixed it during 2 minutes in a 3% hypo solution.

They're your prints, but you've been warned...

 

[largo]

Looks great!



They're your prints, but you've been warned...

Correct me if I’m wrong, but silver halides are way more difficult to remove by the fixer than the silver compounds that must be removed from VDB/Kallitype prints (no silver halides in these processes ) , right ?

I read this in Dick Stevens ‘ book « making kallitypes the definitive guide »

That would explain the shorter fix times and weaker fixers used ?

Since I usually tone my prints I could fix them longer in a stronger fixer without experiencing any bleaching…