Anthotypes are images created by coating paper with plant-based dyes and then using sunlight to bleach the pigment where it’s exposed. They’re eco-friendly but require patience – exposure times can range from hours to weeks, and the resulting prints are ephemeral (they will fade over time)
Pigment Extraction in Avocado Anthotypes
Using Avocado Peels: Collect the skins from ripe avocados. It’s fine if some flesh is attached, but scrape off the excess fruit. You can use them fresh or dry them for later. To extract pigment, cover the peels with water in a pot and simmer for 30–60 minutes
. The water will turn a deep peachy-orange or tea-brown as the tannins leach out. Let it cool, then strain well (through a fine mesh or cheesecloth) to remove slimy bits. This simmer method is effective because heat helps release the color compounds from the thick skins.
Including Pits (Optional): Avocado pits also contain pigment and can be added for a stronger dye. If using pits, chop or grate them (carefully – they are hard) before boiling, to expose more surface area. I've noticed that using peels only yields a brighter pink / reddish colour, when you include pits the colour turns more brown / orange.
Alternate Cold Extraction: It’s possible to extract with a longer cold soak: soak chopped peels in water (or a water/alcohol mix) for several days. The solution will color, but there’s a higher risk of mold or fermentation. Adding a bit of alcohol can act as a preservative if doing a cold extract. Still, heat extraction is faster and sterilizes the mix, so it’s generally preferred for avocado.
Aim for a rich tea-like color intensity in the liquid. If it looks very pale, boil longer or use more peels. A stronger starting emulsion will give a darker initial coating on paper and potentially better contrast.
Best Paper Types
Avocado-based emulsions contain tannins, which, like pomegranate, bind to cellulose. The choice of paper can influence how well the image forms: if the dye soaks in too deeply, it may not bleach out easily Use a high-quality watercolor or printmaking paper (cotton rag preferred).
Regular watercolor papers (Fabriano, Arches) also work, but heavily “dyed-through” sheets may retain color stubbornly. One tip is to “stain” the paper surface rather than fully immersing the paper. Brushing on multiple coats (letting each dry) deposits plenty of pigment on the surface fibers, which UV can then reach and fade. In comparison, soaking the paper in a dye bath (immersing it) will dye all the fibers, possibly requiring longer exposure for the core to fade
If you do want to try immersive dyeing (to get a very uniform color), consider thinner papers or those without too much internal sizing, so the dye takes evenly. After dyeing, rinse and dry the paper thoroughly (untreated avocado dye can be a bit prone to oxidation spots). While brushed coatings are simpler and effective, I much prefer to immerse the paper in the tray, it yields a much deeper, more vibrant and uniform colour, just needs a longer exposure.
Exposure
Exposure Duration: Avocado emulsions are on the slower end of the spectrum. You should anticipate multiple days to several weeks of strong sunlight for a full exposure. My experiments happened during august, some of the hottest days with high UV index, and it took 4 full days to expose.
Factors: The needed time depends on initial density of the coat (more pigment = more time), number of coats, and sun intensity. If you applied only a thin single coat (light pink color paper), a few hours in august might yield a faint image. With a rich coat (multiple layers), expect longer.
Recommended Approach: As with others, expose until the background of the print (exposed areas) has lost most of its color. Avocado prints, like many others often don’t bleach to pure white; the exposed zones might become a pale yellowish or pink or off-white at best. When you see a clear difference between the masked image (still pink/brown) and the background (significantly lighter), you’ve reached a good endpoint.
Color Stability & Fading
After Exposure: Once you “develop” an avocado anthotype (i.e. remove the mask/negative), the image you see is temporary. Without fixing, the dye remains light-sensitive Any continued exposure to light will keep bleaching the remaining pigment. Therefore, handle the finished print in dim light. Over time, expect the image to fade overall. The brown/pink colors may also shift in hue. For example, the vibrant rosy-brown might dull to a beige if anthocyanin components (if any) fade, leaving just tannin.
Relative Stability: Avocado dye on paper is somewhat more durable than many anthotype emulsions. Tannins have modest inherent lightfastness and even act as a mild mordant, anchoring themselves to paper fibers. This means if kept in darkness or low light situation, an avocado anthotype can last a long time with little change. I am storing some in the dark, while some I have hanging on my wall to assess how fast they fade. As of now, they are holding up pretty well in moderate natural light, showing little to no fading over the course of 4 months, which is great compared to emulsions like berries, turmeric and petals that over the same time have almost completely faded.
Display Considerations: If you want to display an avocado anthotype, use a frame with UV-filtering glass or acrylic. Place it out of direct sun. The image may still slowly lose contrast. This process can be slowed but not stopped. Some artists embrace the transience – they might re-scan or re-print the anthotype as it fades, or simply let it age.
Colour Tweaks
Avocado tannins are pH-sensitive in terms of shade. An alkaline addition (like a pinch of baking soda) can push the color towards deeper pink; an acid (lemon juice) might make it more orange. Natural dye guides often use a bit of alkali to get the classic pink from avocado. Altering pH could change how fast it fades. If you experiment, do so in small batches and note the results. Generally, the dye from plain water extraction yields a pleasant dusty pink/brown without modification.
Avoiding Mould
Avocado dye can ferment – it contains sugars and starches. Add a splash of 70% isopropanol (rubbing alcohol) to the liquid as you coat, or use fresh and then discard any leftover in the tray. If you notice any mildew smell on coated paper, don’t use it (it can stain or create spots). Always let coated papers dry in a well-ventilated area; drying in direct sun or with gentle heat can also prevent mold (but do it before adding your negative for the actual exposure!).
Pigment & Light Interaction (Scientific Notes)
Chemical Nature: Avocado skins and pits are loaded with condensed tannins (proanthocyanidins). These are large polyphenolic molecules. When you boil the skins, the tannins oxidize slightly, often giving that pinkish tone (fresh cut avocado flesh or pit turns reddish-brown due to polyphenol oxidase enzymes reacting with these compounds). The resulting dye has some anthocyanidin-like chromophores, but technically it’s tannin-based, not an anthocyanin from a plant’s petals or berries. The color comes from complex phenolics that form quinones and other chromophores upon oxidation.
Light Sensitivity: Tannins serve as antioxidants in plants, and they are generally more UV-stable than anthocyanins. They absorb a broad range of light (hence their brown color, which is essentially absorbing most visible wavelengths). Under prolonged UV, tannins will slowly undergo further chemical changes – they can break down into smaller molecules or bleach out. The process is slower because the chromophores in tannins are not as easily destroyed; they often require significant energy or radical reactions to break apart. In an anthotype exposure, UV initiates these breakdowns. It might break some chemical bonds in the tannin structure, lightening the color. Also, photo-oxidation is at play: UV can generate peroxides or free radicals in the moist organic matrix, which then attack the dye molecules.
Color Changes: You may notice the avocado emulsion color shifts over time even without light – for example, fresh dye is more pink, old dye turns brown. This is a form of oxidation (the same process that makes a cut avocado turn brown in air). So even during a long exposure (weeks), the parts under the mask are not in complete darkness – they’re in dim light and also exposed to oxygen. They might oxidize a bit too, which could darken them slightly or change hue, even as the exposed parts are lightening. The interplay of these factors can result in an image that might have, say, a slightly different tone in the shadows than the original coating color. It’s not just light destroying pigment; it’s also oxygen reacting with it.
UV Spectrum: Avocado pigment appears brown, meaning it likely absorbs UV and blue light significantly (brown is essentially a combination of absorption across the spectrum). According to principles similar to other dyes, the wavelengths that the dye absorbs most will be the ones that most effectively cause its breakdown. It’s plausible that UV-B and UV-A are doing a lot of work here. Normal window glass blocks UV-B but allows some UV-A; direct outdoor exposure gives full spectrum. This might be why direct sun is much more effective for these dyes.
Bottom line: The science explains why avocado anthotypes need patience. The pigment’s molecular sturdiness and bonding mean it resists photochemical destruction longer than, say, a delicate flower pigment. But given enough UV, those bonds will break. The result is a gentle image created by differential photobleaching. Understanding that the “best” anthotype pigments are those that fade the fastest, one can see that avocado’s challenge (and charm) is that it doesn’t fade fast – making it a bit of a slow performer in anthotype, but producing uniquely soft brown images when it finally yields to the sun.
Comments