Longevity of anthotypes: Comparing dried petals and stored emulsion

Ready to take your anthotype practice to the next level? Gabriele Coassin shares three years of in-depth experimentation, revealing little-known tips, seasonal tricks, and personal discoveries that go far beyond the basics. His shares findings from unexpected plant emulsions to innovative winter conservation methods.

Writer and photography / Gabriele Coassin

This article is for those who already know the basics of anthotypes. For beginners, read this article and there is much more here on AlternativePhotography.com

The anthotype process is based on the sensitivity of plant colours to sunlight and UV in particular. Ancient fabric dyers understood this: curtains lost colour over time, even without washing. Decorators and painters also knew this, preferring mineral over vegetable colours, which were especially unstable when exposed outdoors. From these observations came the idea of obtaining beautiful photographic prints without a camera: place an object in contact with a sheet sensitized with the coloured juice of plants that discolour more rapidly when exposed to light.

The natural materials we use are not highly sensitive and take what seems like biblical times to produce an image. And even then, it fades – because light continues to act even after the work is complete, with no final fixing process like that in silver-based photography.

At the time of its invention, the impermanence of these plant-based photographs was a tragedy; works had to be displayed in dim light and quickly returned to drawers. Since World War II, the widespread use of colour photography has allowed for the reproduction and exhibition of anthotypes with greater longevity when proper safeguards are used. Today, digital fine art reproduction changes everything, allowing for exhibitions of vibrant anthotype artworks, scanned and printed, while preserving the originals in the dark, like archival prints.

In recent years, an international art movement has revived ancient photographic techniques as new creative opportunities. Among these, the anthotype stands out as the most colourful, inexpensive, and full of untapped potential. It is precisely these unpublished experiments – conducted over more than three years – that I share here for the first time outside my workshops. This is not a scientific study, but it follows a consistent method.

Four of the twelve trials, October 2022: comparison of single or double layering, exposed under glass, 40-50 hours

Seven of the fourteen 50-hour tests, October 2023: comparison of exposure under glass or under Crylex — Seven of the fourteen 50-hour tests, October 2023: comparison of exposure under glass or Crylex

This is just a part of the juices in the fridge, of which I experiment with durability, time effectiveness, alcoholic exaggerations, different concentrations and imaginative mixes suggested in the Latin American forums, which are very active in this nice photo game. — Some of the juices in the fridge, of which I experiment with durability, time effectiveness, alcoholic exaggerations, different concentrations and imaginative mixes suggested in the Latin American forums, which are very active in this nice photo game.

Extracting colour from plants with alcohol allows the preservation of liquid emulsions

Extracting colour from plants can be done with alcohol (a common spirit available at home, such as vodka, gin or rum) or spirit vinegar (cheap, used for cleaning), which is more stable over time compared to wine or apple cider vinegar, which tend to decompose, even in the refrigerator, within a few weeks. Extracting colour with vinegar also generates completely different tones compared to using water or alcohol.

The mix of blended plant matter and alcohol can be left to infuse for 30-60 minutes with 40° vodka or gin, half a day with 25-30° light liquor, or a full day in 12-14° wine. For quick demonstrations, I use denatured 90° alcohol for 10-15 minutes, depending on room temperature.

In school settings, I use liquid extracts as they are, selecting juicy natural products. If the mixture is too thick, I add a little water. For powdered materials like paprika, turmeric, or spirulina, blending with alcohol works fast and well.

Using high-proof alcohol has several benefits: faster evaporation when coating the paper, longer preservation of the emulsion in sealed dark glass bottles, and reduced risk of mould or pests. The alcoholic base also helps extend the visibility of the image, though anthotypes will fade over time. Unlike cyanotypes, anthotypes remain impermanent, so reproductions are typically displayed while originals are kept in the dark unless fading is part of the artistic intent.

After preparing the colour extracts, properly filtered with a paper coffee filter, they should be placed in glass or plastic bottles - preferably dark - tightly closed, with as little air as possible, labeled with the date and precise information on the natural essences and diluent used, and finally sealed with a few turns of food-grade film. — After preparing the colour extracts, properly filtered with a paper coffee filter, they should be placed in glass or plastic bottles – preferably dark – tightly closed, with as little air as possible, labeled with the date and precise information on the natural essences and diluent used, and finally sealed with a few turns of food-grade plastic film.

The new trials with unseen natural essence: Phlox paniculata

Tests using Phlox paniculata: October 2022, extraction, drafting and immediate exposure – excellent contrast.

Phlox Paniculata in pots, blooms from April to October in central Europe

Cleaning of faded petals collected during the summer

Macerated in cheap 28° vodka for 15 hours, then kneaded with a mortar and pestle

Juice obtained by squeezing the pulp with a cotton cloth

Phlox, left single, right double layering dye, 16 October 2022

Phlox under glass after 25 hours of sun exposure, November 2, 2022

Anthotypes after 50 hours of sun, 100% cotton paper 200 gsm

The same Phlox extract as used on 16 October 2022 was stored in the fridge for one year; layering and exposure were postponed to October 2023. The two tests used the same juice, but the first, applied and exposed immediately, yielded a more contrasted and saturated image, even with a single application. While the color saturation was lower after a year, the extract remained usable.

Double layering on Tyger Akvarel 300g/m October 2023 — Double layering on Akvarel 300g/m October 2023

Test composition under Crylex plastic glass — Test composition under Crylex plastic

Test composition after 40-50 hours: Withered leaves

Final anthotype: Poor Crylex pressure = blurring of the impression

A couple of extreme experiments to make anthotypes even when we don’t have fresh seasonal plants, flowers, or berries

Reuse the alcoholic extract of Phlox paniculata stored in the refrigerator for three years
Reuse the dried petals of Phlox paniculata stored in a glass jar in the dark for three years.

If this works, what’s the best solution?

I take the glass jar with petals dried three years ago out of the cupboard. I place half of them in a bronze mortar with a little 90% denatured alcohol.

From time to time, I crush the mixture vigorously with the pestle. After 12 hours, I dip a cotton bud into the moistened mixture to check the color. — From time to time, I crush the mixture vigorously with the pestle. After 12 hours, I dip a cotton bud into the moistened mixture to check the colour.

The color intensity (left) is weaker than the alcoholic extract prepared three years ago (right), and the mixture has partly dried out.

I add a little 42% rum, stir the mixture every 3–4 hours, and grind it finely with a garlic grinder.

After 12 hours, the new mixture is ready and can be squeezed vigorously through a cotton cloth.

The juice shows a beautiful, intense color, identical to the one from three years ago, and looks very promising.

Now I can begin experimenting. I have one bottle of juice refrigerated for three years and one freshly extracted from the old petals.

For both extracts, I’ll run two tests: brushing a single and a double layer of liquid onto paper, exposed for 25 and 50 hours.

On the left, the exposure begins for two NEW ANTHOTYPES (single and double layer) made with juice macerated from petals dried three years ago. The color is much more intense than the panel on the right, created with the refrigerated extract.

After only 7 hours of June sun, the difference in intensity between the two panels is minimal. In fact, the three-year-old refrigerated juice (right) appears slightly more saturated.

Anthotype from the juice of three-year-old petals, extracted after 24 hours of alcoholic maceration. Exposed for 25 hours in full summer sun. Both single and double layers show medium contrast, but the outcome is satisfactory.

Finally, I compare the results of the three-year-old refrigerated juice with the fresh juice from dried petals stored for three years. Let’s see the anthotypes after 50 hours of exposure.

The refrigerated juice, even after three years, is still usable if you prefer soft hues and gentle contrasts. Single layer on the left, double layer on the right.

The juice freshly extracted from the three-year-old dried petals is the clear winner. Excellent contrast and color saturation! Single layer on the left, double layer on the right. — The juice freshly extracted from the three-year-old dried petals is the clear winner. Excellent contrast and colour saturation! Single layer on the left, double layer on the right.

The experiment shows that both storage methods—refrigerated juice and dried petals—remain viable after three years, but with different qualities. The refrigerated juice produces softer tones with delicate contrasts, while freshly extracted juice from dried petals delivers stronger saturation and contrast. Depending on whether you prefer subtle or vivid anthotypes, both approaches can be valuable. This highlights the flexibility of anthotype materials and encourages further exploration of long-term preservation methods. I’ve carried out similar tests with other natural products, with results ranging from good to average. Now I look forward to seeing your results in this fascinating challenge!

Gabriele Coassin is an artisan photographer and reporter in his youth, he was included in the first Bolaffi volume/catalogue of Italian photographers, an award-winning video maker and author of professional texts, professor in Italian universities and academies. Now, in retirement, he has returned to his old photographic passion, a tireless experimenter of alchemies to be re-proposed in targeted workshops or in educational-experiential digital detox courses for the new generations, leading to the rediscovery of the slow, manual processes of proto-photography and ancient pre-cinema practices.