Can you make gum bichromate without bichromate?

Yes. Vision Picturale reformulated gum bichromate as Aquaprint in a formulation without bichromate. The gesture combines gum arabic, pigment, sensitization, and water development for a polychromatic painterly result. That difference does not replace precautions: the VP N°03 developer is harmful if swallowed and skin contact must be avoided. Consult each component's safety information and the relevant SDS when available before use.

Is potassium bichromate dangerous?

Potassium and ammonium bichromate belong to the historical gum recipe. VP Aquaprint is formulated without bichromate, but it remains a photographic-chemistry process. Consult each component's safety information and the relevant SDS when available, wear the indicated protection, and do not improvise mixtures or disposal of working baths.

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.

Gum Bichromate: Beginner's Tutorial

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. The same painterly result and color freedom, in a bichromate-free formulation. Consult each product's safety information and the relevant safety data sheet (SDS) when available before handling.

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

Aquaprint replaces potassium bichromate with a VP sensitizing system without bichromate. It remains a photographic-chemistry process: the VP N°03 developer is harmful if swallowed and skin contact must be avoided. Wear the indicated protection and consult the safety information, then the relevant SDS when available, before use.

Materials for your first Aquaprint

An Aquaprint pouch — gum, pigment and sensitiser already mixed, 350 ml, in the Aquaprint CMYK kit
VP N°03 Developer — the bath that reveals and fixes the print
The colour of your choice — one pouch per hue (black, cyan, magenta, yellow, ochre, red…)
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

Pour the pouch into a bowl: gum, pigment and sensitiser are already mixed, there is nothing to measure out. Work under incandescent light — the emulsion is UV-sensitive.

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 Aquaprint CMYK kit directly.

Further reading: the history and chemistry of Aquaprint · fixing a failed print · the guide to alternative processes

Gum Bichromate: Making Your First Print — Without Bichromate, With Aquaprint