Does Aquaprint give the same look as dichromate gum bichromate?

Yes. Dichromate is only a hardening trigger and plays no part in the final image: the matte surface, pigment grain and the ability to stack layers are identical. Only the sensitizer changes (VP N°03, dichromate-free).

Why is traditional gum bichromate dangerous?

Because its light-sensitive salt, potassium or ammonium bichromate (dichromate), contains hexavalent chromium, classified CMR (a proven carcinogen and mutagen), toxic by inhalation and a skin sensitizer.

Can you make colour gum (four-colour) without dichromate?

Yes. You superimpose several pigmented passes (cyan, magenta, yellow, black) as in traditional gum, using the dichromate-free N°03 sensitizer.

Gomme bichromatée sans dichromate

Gum bichromate is a pigment-based photographic printing process: you mix a pigment, gum arabic and a light-sensitive salt, brush it on, expose it under a negative, then develop in water. The result — velvety matte surface, pigment grain, a painter's touch — made it the weapon of the Pictorialists in the late 19^th century. Its only flaw fits in one word: the salt used, dichromate, is carcinogenic.

A process invented in 1855, revealed by Demachy

The principle — bichromated gum hardens in light — was established by Alphonse Poitevin in 1855. It stayed marginal until the 1890s, when Robert Demachy, in Paris, turned it into a genuine artistic medium. In 1895 his first gum prints, shown in Paris, London and Brussels, were received as a revolution: at last a photograph that looked like a drawing, where the hand intervenes. Demachy became its "apostle".

Robert Demachy, Contrasts (1904), monochrome dichromate gum bichromate print — Robert Demachy, Contrasts, 1904 — public domain

same process · different chemistry

Monochrome Aquaprint gum print by Vision Picturale, dichromate-free — Vision Picturale — monochrome Aquaprint gum, N°03 sensitizer

Two monochrome gum bichromate prints a century apart: same matte surface, same pigment grain, radically safer chemistry. We don't recreate Demachy's image — we carry on his process.

The masters who carried it

Gum bichromate is not a laboratory curiosity: it was the process of a whole generation of artist-photographers. Almost every Pictorialist master practised it — and all of them are in the Maison Picturale library.

From the inventor to the great Pictorialists — each name links to their prints.

Gum, by those who made it

A few period prints, monochrome and sanguine, from the masters' archive. Each links to its page in the Maison Picturale library.

Robert Demachy, Study in Red (1898), sanguine — Robert Demachy, *Study in Red*, 1898
Voir le maître →

Robert Demachy, Contrasts (1904), monochrome — Robert Demachy, *Study in Red*, 1898
Voir le maître →

The truth: dichromate

What makes historical gum problematic is neither the pigment nor the gum arabic — it is the potassium or ammonium bichromate (dichromate) that makes it light-sensitive. The hexavalent chromium it contains is a proven carcinogen and mutagen (CMR), toxic by inhalation and a skin sensitizer. You can admire the genius of the process without wanting to handle that salt at home.

Aquaprint: gum, reformulated without dichromate

Aquaprint is our reformulation of gum bichromate. The gesture, the gum arabic, the pigment, the water development, the look: all preserved. Only the sensitizer changes — our N°03 contains no dichromate. Same Pictorialist beauty, practised safely, at home.

Gum, without the poison

Same process, same look, different chemistry. Aquaprint lets you practise gum bichromate — including in sanguine, like Demachy — with no CMR salt at all.

Sensitizer: VP N°03 — dichromate-free
Classification: No CMR
Look: Matte surface, pigment grain, multiple layers
Practice: Cotton paper, at home, in daylight

Aquaprint Sanguine kit· €79 Or acquire a master print →

The three Aquaprint gums

Gum bichromate is not a single colour: it is a family. Aquaprint offers three — all with the N°03 sensitizer, dichromate-free.

Sanguine

Sanguine is a precise gum variant: a red-brown pigment evoking the red chalk of Old Master drawings. Demachy made it famous, his red gums recalling Renaissance sanguine drawings. Aquaprint Sanguine follows exactly that path.

same sanguine · different chemistry

Aquaprint sanguine gum print by Vision Picturale, dichromate-free — Vision Picturale — Aquaprint Sanguine, N°03 sensitizer

Demachy's sanguine (1898) and today's Aquaprint Sanguine: the same red chalk, without the dichromate.

Aquaprint sanguine gum portrait — Aquaprint Sanguine: prints and material details. Click to enlarge.

Sanguine gum Aquaprint print on cotton paper — Aquaprint Sanguine: prints and material details. Click to enlarge.

Four-colour

Where Pictorialists mostly stayed monochrome, gum also lends itself to colour: several pigmented passes (cyan, magenta, yellow, black) are stacked. Aquaprint Quadrichromie takes gum all the way to a full colour image — still dichromate-free.

Colour gum bichromate Aquaprint print — Aquaprint Quadrichromie: layered colour gum. Click to enlarge.

Colour Aquaprint gum, still life — Aquaprint Quadrichromie: layered colour gum. Click to enlarge.

FAQ

Does Aquaprint really give the same look as dichromate gum?
Yes. Dichromate is only a hardening trigger; it plays no part in the final image. The matte surface, the grain and the ability to stack layers are identical.

Can you work in colour, like four-colour gum?
Yes: you superimpose several pigmented passes (cyan, magenta, yellow, black), exactly as in traditional gum — without dichromate.

Is it really safe at home?
The N°03 sensitizer contains no CMR salt. As with any studio practice you work tidily, but without the carcinogenic risk of dichromate.

For the full panorama of non-toxic processes, see our guide to alternative processes or the glossary.

Gomme bichromatée : le procédé des pictorialistes, sans le dichromate