Can you make gum bichromate without bichromate?

Yes. Vision Picturale reformulated gum bichromate as Aquaprint by replacing potassium bichromate with the VP N°03 universal sensitizer, a proprietary non-toxic formulation. The rest of the process is identical — gum arabic + watercolor pigment + sensitizer, water development — and the polychromatic painterly result is indistinguishable from the historical version. Only the chemistry changes, enabling home practice in a kitchen without a carcinogenic oxidizer.

Is potassium bichromate dangerous?

Potassium and ammonium bichromate, used in historical gum bichromate, are oxidizers classified as irritant, skin sensitizers and potentially carcinogenic (hexavalent chromium compounds). Handling them requires a ventilated studio, protective equipment and regulated effluent disposal. This is why Vision Picturale replaced them with the VP N°03 sensitizer in Aquaprint: you get the same result without that toxicity, working on a plain kitchen countertop.

How many colors can you layer in Aquaprint?

Aquaprint lets you layer as many color coats as you like, each adding one pigment. For a four-color print, you typically layer cyan, magenta and yellow (sometimes a black), i.e. three to four successive passes. Each coat is applied, dried, exposed and developed before the next. This layering produces a chromatic richness digital printing cannot reproduce, at the cost of precise registration between passes.

Do you need a special negative for Aquaprint?

Aquaprint needs a digital negative printed on transparent film, at the final print size (contact process, no enlargement). For color, you need a per-channel separation with one negative per pigment, calibrated to each color's response curve. The ICC profiles supplied with the Vision Picturale kit compensate for these curves. A well-densified negative is decisive: the gum's exposure window being narrow, a negative too light or too dense ruins the coat.

Gomme bichromatée : réaliser son premier tirage — sans bichromate avec l'Aquaprint

Gum bichromate (or "gum print") is one of the most expressive alternative photographic processes — polychromatic prints with a painterly richness close to watercolor. The historical recipe uses potassium or ammonium bichromate, an oxidizer classified as irritant and potentially carcinogenic. Not something you want to use at home.

At Vision Picturale, we reformulated this process under the name Aquaprint. Same painterly result, same color freedom, but using our VP N°03 sensitizer — no bichromate, no toxics, safe to practice in your kitchen.

Aquaprint vs. historical gum bichromate: what's different?

Aquaprint replaces potassium bichromate with the VP N°03 universal sensitizer, a proprietary non-toxic formulation. The rest of the process is identical: gum arabic + watercolor pigment + sensitizer, developed in water. The visual result is indistinguishable — only the chemistry changes, for your safety.

Materials for your first Aquaprint

VP N°03 sensitizer — the heart of the process, available here
VP N°04 gum arabic — ready-to-use solution
Watercolor pigment — color of your choice (sanguine, black, cyan, magenta, yellow…)
Watercolor paper 300 gsm minimum, no optical brighteners
A digital negative printed on transparent film
A UV source — direct sun or Luminograph

Step 1: Prepare the Aquaprint emulsion

Mix equal parts gum arabic solution (with pigment) and VP N°03 sensitizer. Work under incandescent light — the mixture becomes UV-sensitive once prepared.

Step 2: Coat the paper

Apply a uniform coat using a flat brush or hake. Dry completely in the dark (30–45 minutes at room temperature).

Step 3: Expose to UV

Place your negative in contact with the paper under glass. Expose to UV — typically 3–8 minutes with a Luminograph, 2–5 minutes in direct summer sun.

Step 4: Develop in water

Immerse in a room-temperature water bath. Unexposed areas dissolve gradually in 10–30 minutes. Do not force — let the water work.

Step 5: Additional color passes

Once dry, re-coat with a second color. Layering cyan, magenta and yellow produces a richness that digital printing simply cannot replicate.

Learn more on the Aquaprint process page or order the VP N°03 sensitizer directly.