Confused about gold chloride toning baths

HandleyPhoto · Oct 3, 2025

Currently in between darkrooms so I'm doing a lot of reading to study up before I begin constructing my new darkroom. I'm reading a lot about toners, and my question relates to the gold toners. Search results for gold chloride( Au(I)Cl or Au(III)Cl3 ) often bring up results for chloroauric acid (HAuCl4), even on suppliers sites such as ArtCraft chemicals, does this compound work as a gold toner? Though I haven't tested it from what I've read in Modern Photographic Processing(Haist) the gold toning reaction works via free Au ions reacting with metallic silver, where chloroauric acid would dissolve into [AUCl4]- ions. Has anyone tested chloroauric acid, the salt produced by the dissolution of gold metal in aqua regia, in print toning?

My second question is which gold chloride salt is preferred the Au(I) or the Au(III). Haist mentions that the Au3+ would displace 3Ag atoms, requiring less gold so I'm assuming this would be desirable? I'm just confused because the name Gold Chloride seem to be used rather interchangeably.

Screenshot is from Modern Photographic Processing Vol 2 (Haist p122)
Any insight at all into either of these questions would be greatly appreciated
-Jacob

retina_restoration · Oct 3, 2025

The Gold chloride sold by ArtCraft is appropriate for Gold toning of prints. I've been buying it from them for years and making my own Gold toner for toning Kallitype and Salt prints.

DREW WILEY · Oct 3, 2025

I use 1% gold chloride from Photog Formulary highly dilute for cold toning ordinary silver papers. My own preference is similar to the classic GP1 prescription, but about a fourth the strength, mixing up just enough from A&B concentrates right before toning. It's quite economical in that manner. No exotic ingredients needed.

HandleyPhoto · Oct 3, 2025

So I called ArtCraft and he confirmed that it is chloroauric acid not gold chloride. So my next question is why does every formulation list gold chloride as the reagent needed when it is actually chloroauric acid that is used. Additionally if anyone knows the mechanism of this reaction I would love to know.

retina_restoration · Oct 3, 2025

HandleyPhoto said:
So I called ArtCraft and he confirmed that it is chloroauric acid not gold chloride.

ArtCraft lists it under both names, undoubtedly speaking to the incorrect naming history (see below). It is what I have been buying for years, to make the gold toner that uses Ammonium thiocyanate as the second component (It's a two stock solution toner, diluted to make a working solution). I've used this for ages to tone Kallitypes and Salt prints. I know that the version ArtCraft sells is perfectly suitable for making a Gold toner.

A quick search gave me this: In solution, chloroauric acid behaves as a source of Au(III), and it is often used in gold plating, nanoparticle synthesis, and photographic processes.

Also: In the photographic literature, HAuCl₄ was frequently called “gold chloride” or “chloride of gold” even though chemically it was the acid, not the neutral chloride (AuCl₃).

So I gather that technical manuals from years ago started calling HAuCl₄ "Gold chloride" when in fact it was not. True Gold chloride isn't nearly as soluble in water, so we use HAuCl₄ for our processes.

HandleyPhoto · Oct 3, 2025

retina_restoration said:
ArtCraft lists it under both names, undoubtedly speaking to the incorrect naming history (see below). It is what I have been buying for years, to make the gold toner that uses Ammonium thiocyanate as the second component (It's a two stock solution toner, diluted to make a working solution). I've used this for ages to tone Kallitypes and Salt prints. I know that the version ArtCraft sells is perfectly suitable for making a Gold toner.

A quick search gave me this: In solution, chloroauric acid behaves as a source of Au(III), and it is often used in gold plating, nanoparticle synthesis, and photographic processes.

Also: In the photographic literature, HAuCl₄ was frequently called “gold chloride” or “chloride of gold” even though chemically it was the acid, not the neutral chloride (AuCl₃).

So I gather that technical manuals from years ago started calling HAuCl₄ "Gold chloride" when in fact it was not. True Gold chloride isn't nearly as soluble in water, so we use HAuCl₄ for our processes.

That’s interesting that it’s used with thiocyanates, I thought acids weren’t supposed to be mixed with thiocyanates to prevent cyanide gases ? Is it because the concentration of the acid is so low ?

Chloroauric acid is relatively easy to make from metallic gold which is why I wanted to clarify all of this. Thank you so much !

mshchem · Oct 3, 2025

HandleyPhoto said:
That’s interesting that it’s used with thiocyanates, I thought acids weren’t supposed to be mixed with thiocyanates to prevent cyanide gases ? Is it because the concentration of the acid is so low ?

Chloroauric acid is relatively easy to make from metallic gold which is why I wanted to clarify all of this. Thank you so much !

Gold dissolved in aqua regia, stand upwind. Re-crystalizing is tricky, I've made silver nitrate, it's a pain too. I've always heard this referred to as auric tri-chloride

retina_restoration · Oct 3, 2025

HandleyPhoto said:
That’s interesting that it’s used with thiocyanates, I thought acids weren’t supposed to be mixed with thiocyanates to prevent cyanide gases ? Is it because the concentration of the acid is so low ?

Chloroauric acid is relatively easy to make from metallic gold which is why I wanted to clarify all of this. Thank you so much !

When you mix HAuCl₄ with NH₄SCN, the classic reaction is the formation of auric thiocyanate complexes, which are often used for colorimetric gold tests. You get deep orange/red colors from complexes such as Au(SCN)₄⁻.
This reaction is well known in analytical chemistry and does not directly produce free cyanide.

Thiocyante (SCN⁻) is not cyanide (CN⁻). It has a C≡N group attached to sulfur, which changes its reactivity.

Under strong acid + heat, thiocyanates can hydrolyze to release H₂S and HCN in some conditions, but this generally requires concentrated strong acids and elevated temperature — much harsher than just mixing HAuCl₄ and NH₄SCN at room temperature.

HandleyPhoto · Oct 3, 2025

Thank you everyone for the info, I’ll try and update it when I successfully make some toning solution. Although I’m probably still a few months out from building my darkroom

I really enjoy learning new stuff about photo especially when I can’t be in the darkroom

mshchem · Oct 3, 2025

Gold is amazing. Why does the best always cost so much?

DREW WILEY · Oct 3, 2025

Most gold toning recipes waste gold like crazy. It doesn't really take all that much. But the commodity of gold itself is at an all time high, as is silver - a pretty tough financial reality for photograhers. I remember running a sluice box for gold as a teenager, back when it was $24 an ounce - a hard day's work for 2 of us to get half an ounce, $6 apiece. Today it's at $3900 an ounce, which would amount to almost $1000 apiece, in other words, two boxes of 16X20 FB printing paper, spending one's gold on overpriced silver.

mshchem · Oct 3, 2025

DREW WILEY said:
Most gold toning recipes waste gold like crazy. It doesn't really take all that much. But the commodity of gold itself is at an all time high, as is silver - a pretty tough financial reality for photograhers. I remember running a sluice box for gold as a teenager, back when it was $24 an ounce - a hard day's work for 2 of us to get half an ounce, $6 apiece. Today it's at $3900 an ounce, which would amount to almost $1000 apiece, in other words, two boxes of 16X20 FB printing paper, spending one's gold on overpriced silver.

It hasn't been $24/ozt since Roosevelt recalled all domestic gold. 1933.

I picked up several 1 gram glass ampules of Mallinckrodt Gold Chloride from someone who was getting rid of it.

I remember when you could buy Kodak Blue Toner, it was probably $2.25/qt kit, outrageous!

Sepia toner was probably 39 cents. The good old days. The 'ol dollar ain't what it once was. Nothing is

Except for McDonald's French fries

DREW WILEY · Oct 4, 2025

French Fries are a good deal because they get cooked in recycled crankcase oil, which next becomes biodiesel. I don't know which smells worse, driving down the freeway past a Golden Arches franchise, or driving behind a biodiesel vehicle burning leftover french fry oil.

Even after the California gold rush was long over, there was still a lot of it being recovered from the giant tungsten mining operations, back when that was exceptionally in demand for the budding nuke industry, and briefly, even more expensive than gold. The world's biggest tungsten mine at that time was on Mt Morgan in the eastern Sierra. After the tungsten was separated, the slurry went to another stage where the gold was extracted, the finally, the last of the sludge was recovered and shipped to a special facility where the platinum and palladium were extracted. Simpler older gold mines were like woodpecker holes all over the cliffs across the canyon. Massive silver mines were further north.

mshchem · Oct 4, 2025

I want a creek full of nuggets (gold not chicken). Makes me wonder what may be found beneath the sea. Bezos is probably using robots to get the goodies right now.

koraks · Oct 4, 2025

HandleyPhoto said:
Has anyone tested chloroauric acid

Yes, it's what I presently use because I got a gram or so relatively cheap. Works fine.

retina_restoration · Oct 4, 2025

DREW WILEY said:
Most gold toning recipes waste gold like crazy. It doesn't really take all that much.

I use a simple recipe for Gold toning Salt and Kallitype prints, using a 0.2% stock solution of HAuCl₄ and a 2.0% stock solution of NH₄SCN. To make a working solution toner, I add 5ml of stock A and 5ml of B to 100ml of water. This 110ml of toner will tone one 8x10 (or 11x14) print to completion in 8 to 15 minutes and is then discarded, since it’s pretty much exhausted at that point.

So, from 1g of HAuCl₄ I have enough toner to Gold tone 100 8x10 prints. The current price of HAuCl₄ at ArtCraft is $87 per gram, and the Ammonium thiocyanate adds only pennies to the price. At a cost of approximately 90 cents per print, I consider Gold toning done this way to be quite inexpensive. The paper you’re printing on is undoubtedly more costly than the tiny amount of gold you’re using for toning.

Confused about gold chloride toning baths

Thiocyante (SCN⁻) is not cyanide (CN⁻). It has a C≡N group attached to sulfur, which changes its reactivity.​

Moderator

Privacy & Transparency

Privacy & Transparency

Thiocyante (SCN⁻) is not cyanide (CN⁻). It has a C≡N group attached to sulfur, which changes its reactivity.