Imagine printing a photograph using nothing but flower petals, berries, or spinach leaves – and sunlight. This isn’t fantasy; it’s the anthotype process, a 19th-century photographic technique that creates images with plant-based pigments. In this comprehensive guide, we’ll dive deep into anthotype prints – what they are, the science of why they work, and how to do it yourself step by step.
The Science Behind Plant-Based Pigments and Light Sensitivity
Why do anthotypes work at all? The secret lies in the chemistry of plant pigments. Many plants contain colorful compounds (such as anthocyanins, chlorophyll, carotenoids, and curcumin) that are, to varying degrees, sensitive to light. Under prolonged exposure to sunlight – especially the high-energy ultraviolet rays – these pigment molecules break down in a process called photodegradation. In simpler terms, the sun literally bleaches the color out of them. This is the same phenomenon that causes dyed fabrics to fade in the sun or leaves to lose color when overexposed to light.
Anthocyanins, for example, are the pigments that give red cabbage, berries, and many flower petals their red, purple, or blue hues. They are notorious for being fugitive pigments – easily fading when exposed to light, high temperature, or changes in pH
Sir John Herschel found that anthocyanin-rich juices made decent light-sensitive emulsions, but some were more stable than others. He noted that Reseda luteola (Dyer’s weed, or weld), a plant used by textile dyers, produced a particularly stable yellow-green image that resisted fading longer than most (It wasn’t permanent by any means, but it faded less rapidly, indicating it had higher lightfastness than, say, rose petal juice.)
The exposure of an anthotype is essentially a selective bleaching. Wherever UV light hits the pigmented coating, it “destroys” that pigment, causing it to lighten significantly or become colorless. The areas shielded from light (under a leaf, object, or the dark areas of a transparency) retain the original color. The result is a positive image formed by the remaining color in the protected areas against a bleached background.
A fascinating observation from 19th-century researchers is that the rays of the spectrum most effective at bleaching a given color tend to be the complementary color of that pigment. For instance, a blue flower extract might bleach fastest under yellow-orange light, while a yellow pigment is most quickly faded by blue/violet light. In practice, however, anthotypes are usually just exposed to full sunlight (which contains all colors as well as UV).
Different pigments have different sensitivities: chlorophyll (the green in leaves) will also fade under intense light, though chlorophyll-based prints (sometimes called chlorophyllotypes when made directly on leaves) often require weeks of sun. Curcumin, the bright yellow compound in turmeric, degrades relatively rapidly under UV – a property exploited in turmeric anthotypes. Interestingly, curcumin also has a chemical quirk: it is a PH indicator (changes colour depending on the PH of the solution).
The key takeaway is that most plant-based dyes are not archival. In painting, they’re known as “fugitive” colors – beautiful but prone to fading. Anthotype prints will eventually vanish, because the pigments continue to slowly break down even in low light.
How to Select Plants for Pigment Extraction
Nearly any deeply colored plant matter can produce some sort of image, but some are better than others in terms of color strength and longevity. When selecting plants, consider: (1) the intensity of the pigment (how strong or dark is the juice/color), (2) the color you want, and (3) the lightfastness (how quickly it bleaches and how well the final image color holds up). Often, there’s a trade-off – very light-sensitive pigments give you faster exposures but may also fade the quickest after printing.
Beetroot – deep magenta: Beetroot is widely regarded as one of the most reliable anthotype pigments. The roots (and even the stalks) contain betanin, a vivid reddish-purple dye. Beet juice gives a rich dark coating and yields pinkish prints. It does fade under sun (requiring exposures on the order of days), but the contrast can be quite good and the initial color is strong.
Berries – blues, purples, reds: Dark berries like blackberries, blueberries, elderberries, cherries, and raspberries are excellent sources of anthocyanins. Blackberry juice, for example, can produce beautiful purplish-pink images. Blueberries give a more bluish or pale purple tone (they may need a boost with acid to get a good hue). These pigments tend to bleach in a matter of days of sun.
Flower petals – various colors: Since “anthotype” literally means flower print, it’s fitting to use flowers. Traditionally recommended are petals of richly colored flowers like violets (Viola odorata) which yield a “rich blue” dye, roses (pinks/reds), hibiscus or poppies (deep reds), marigolds (Tagetes, “Studentenblume”) for yellows, and coreopsis or dahlia for warm tones. Petals usually macerate easily and often have strong dye, but the resulting color can sometimes be lighter on paper than you expect (many petals give pastels). Still, florals are fun to try – just avoid any that are very pale to begin with.
Vegetables & leaves – greens, yellows, etc.: Don’t overlook foliage and veggies. Spinach leaves (and other dark leafy greens) contain chlorophyll that yields a green emulsion – our Example 2 below uses spinach which gave a “deep green juice”. Green anthotypes are usually quite light-sensitive (bright sun will bleach them to a yellowish-brown in a few days). Red cabbage leaves can be blended to get a reddish-purple juice (anthocyanin again). Onion skins (especially red onion skins) boiled in water produce a dye – yellow from yellow onions, orangey from red onions – that can be used, though these may be lighter in tone.
Turmeric (though not a plant to pick fresh – we use the spice powder) yields an incredibly bright yellow coating and very fast exposure times (hours).
Coffee and tea have been tried by some, but those are fairly light-brown to start with and not very sensitive – they might produce a faint print after a long exposure.
Dye plants – special mentions: Some traditional natural dye plants from the fabric world carry over to anthotypes. As Herschel found, weld (Reseda luteola) gives a vibrant yellow-green that is somewhat more resistant to fading
. Madder root (red dye) or indigo (blue) are famous dyes, but their color might not easily extract just with water/alcohol (madder needs a hot process; indigo requires reduction, so those are advanced). If you’re an adventurous chemist, you might try them, but most people stick to simpler kitchen botanicals.
Binding Agents: What They Are and Why They’re Needed
Before we jump into the extraction process, we need to talk about binding agents. In anthotype context, a binding agent refers to a substance mixed with the plant pigment that helps it adhere to the paper and coat more evenly. Many plant juices by themselves can be used straight, especially if they are very watery and stain the paper well. However, some pigments are more like tiny insoluble particles suspended in liquid, and when they dry, they might dust off or look powdery. Adding a binder can improve the image quality and consistency.
Do you always need a binder? Not necessarily. If your plant extract is very watery and strongly colored (like blackberry juice or beet juice), it may soak into the paper fibers and stain them permanently enough without any additive. In fact, some anthotypists forego binders for a more “pure” process, especially if they’re using high-quality watercolor paper that absorbs well. However, adding a binder can be helpful if: (a) your emulsion is rubbing off or flaking when dry, (b) you want to apply multiple coats and not lift the previous layer, or (c) the pigment is very granular (e.g. turmeric or flower petals that don’t fully dissolve).
A small amount of binder goes a long way.
Great binders are: Ethanol, distilled water, high proof alcohol, isopropyl alcohol, vodka
Step-by-Step Guide to Extracting Pigments for Anthotypes
Step 1: Gather your plant material and equipment.Decide on the plant you’ll use (see the section above for ideas). You’ll generally need 1 to 2 cups of fresh plant material for a small batch of emulsion (enough to coat a few sheets of paper), but this varies with the pigment concentration. For example, one medium beet or a cup of berries can yield a few tablespoons of potent juice
Equipment-wise, prepare a cutting board and knife (for chopping), a mortar and pestle or blender/food processor for grinding, and a container (jar or bowl) to collect the juice. You’ll also need a fine sieve or cheesecloth for straining the liquid and a spoon or spatula.
Step 2: Chop or crush the plant matter.Cut your plant material into small pieces to increase surface area. Remove non-colored parts (for instance, with a bunch of flowers, you’d use the petals and maybe colorful sepals, but not the green stems). For leaves, tear them up; for things like red cabbage, slice it into shreds. If you’re using a mortar and pestle, work in small batches, adding a few drops of solvent (water or alcohol) if needed. Grind the material firmly in a circular motion to break down the cells and release the juice. If using a blender or food processor, you might add a little solvent to help it puree – just enough to get it going. Aim for a pulpy, soup-like consistency. Some soft fruits (like berries) will practically liquefy on their own; tougher roots (like beet) might need a blender.
Step 3: Optional – soak or heat (if needed).Some pigments come out better with a little time or warmth. If you have sturdy plant parts (woody or dried items, or something like marigold petals that release more color with heat), you can soak them in hot water or a solvent. For instance, onion skins or dried hibiscus flowers could be simmered in a small pot of water for 10–15 minutes to create a dye bath, just as if you were making natural fabric dye. If you do this, use minimal water to keep it strong, and remember to let it cool. Alcohol (like denatured alcohol or high-proof isopropyl) can be used at room temperature to tincture certain pigments – for example, pouring alcohol over crushed petals and letting them steep for a few hours or days can pull out color (Herschel often used alcohol for his flower extracts).
Step 4: Strain the pigment: separating the liquid dye from the solids. Place a fine metal strainer over a bowl, or stretch a piece of muslin/cheesecloth over a bowl (secure with a rubber band). Pour or scoop your plant mash into the strainer or cloth and press it to squeeze out the juice. If using cloth, gather the edges and wring it like a sponge to extract every drop of color. You may need to strain twice – first through a coarse sieve to remove big chunks, then through a cloth to catch finer pulp. The goal is to get a clean, particle-free dye solution. Any “juicy bits” left in the liquid could cause spotting or uneven coating on your paper.
Step 5: (Optional) Adjust the mixture – add solvent or additives.Evaluate your extracted liquid. Is it very thick like a paste, or is it very dark and opaque? If it’s too thick to brush on paper, you can dilute it slightly with distilled water or alcohol. If it’s very pale or thin, you might want to concentrate it (by evaporation or by starting over with more plant material). At this point, some people choose to add a bit of alcohol and/or vinegar. For example, in a blackberry anthotype test, the creator added 1 tablespoon of isopropyl alcohol and 1 tablespoon of white vinegar to ~3 tablespoons of blackberry juice. The alcohol dilutes the mixture and can help it soak into the paper more evenly (it also acts as a preservative to discourage mold), and the vinegar can enhance the pigment’s color intensity (in that case, making the purple more vibrant). If you plan to store the liquid for a day or two before use, a splash of alcohol will keep it from spoiling.
Preparing the Paper for Printing (Coating & Drying)
Choosing the right paper: Select a paper that can handle wet coating and won’t deteriorate under long sunlight exposure. Watercolor papers (100% cotton rag if possible) are excellent – they are designed to handle washes of liquid. A medium weight (140 lb / 300 gsm) cold-press watercolor paper is a safe bet. Acid-free, neutral pH paper is ideal.
Coating technique: Work away from direct sunlight when coating). Lay your paper on a flat, non-absorbent surface. Using a brush, apply the plant emulsion evenly across the paper. Foam brushes are great because they give a smooth coat and hold a lot of liquid
Apply enough coats to get a good solid coloration. Often one coat of pigment will look much lighter after it dries. It’s common to repeat the coating and drying process 2 or 3 times to build up a strong color on the paper. Do note: each additional coat will increase the exposure time needed, because the color is denser (and thus takes more sun to bleach). But it will also yield a richer final image (darker shadows). If you do multiple coats, try alternating brush directions each layer for uniformity, and ensure the prior layer is absolutely dry so you don’t disturb it (a binder in the emulsion helps the first layer stay put for the second).Between coats – or if only doing one – you need to dry the paper in the dark.
Do not rush to exposure until the sheets are bone dry; if they’re even slightly damp, two things can go wrong: the negative/object might stick to the paper, and evaporation under the glass during exposure could cause condensation or blurring.
The Exposure Process: Printing Your Anthotype
Setting up the contact print: Anthotypes are typically contact printed, meaning the object or image is placed directly on the coated paper. If you want a photograph, you’ll need a transparent positive (on acetate or transparency film). This is essentially a clear sheet with a black-and-white positive image printed on it. (Remember, anthotypes produce a positive image from a positive – the areas under dark opacity will remain colored, forming the shadows of your image.)
For non-photographic prints, you can use objects: leaves, flowers, lace, feathers, cut-out shapes, etc. These will make photogram silhouettes. Fresh leaves might bleed moisture, so pressing them in advance to flatten and dry slightly can help.
Place your dried, coated paper on a flat surface. Lay the transparency or objects on top of the coated side. Align as needed. Now, press it down with glass. Good contact is crucial for sharp images: glass ensures the negative or objects stay flush against the paper, preventing blurriness from any gap.Also, clipping it tight keeps things from shifting if you have to move the setup.
The sun is by far the most common “exposure unit” for anthotypes. You’ll want direct sunlight hitting the print, as UV is what does the bleaching. A sunny outdoor spot from late morning to mid-afternoon works best. Some artists use UV lamps or tanning lights to expose anthotypes, which can be useful in winter or if you lack direct sun.
Exposure time: Here’s where anthotypes are very different from other processes – the exposure can range from a couple of hours to several weeks! It all depends on the pigment’s sensitivity and the intensity of your light. For a very reactive pigment like turmeric in strong sun, you might see a result in 1–3 hours. For an average anthocyanin pigment (berry, beet, petal) under midsummer sun, think in terms of days – often 1 to 3 days of good sun will do it.
Monitoring and finishing the exposure: It’s generally best not to disassemble the frame to peek until you think it’s done – any slight movement will cause a registration error (a ghost image). If you must check, do it in low indoor light and carefully lift one corner of the object/negative to see the paper.
Once you’re satisfied that the exposure is complete, bring the print indoors still under the glass. The areas that were hidden from light will show the original pigment color (these form the “shadows” or dark parts of the image), and the exposed areas will be near-white or much lighter (these are the “highlights”).
Fixing and Preserving Anthotype Prints
One of the biggest challenges with anthotypes is that the prints are inherently unstable. By the nature of the process, an anthotype image is simply the leftover pigment, which is still prone to bleaching. Anthotype prints are unable to be fixed and will continue to fade over time – the same light that creates the image will eventually erase it
So, how can we preserve our hard-won print?
Firstly, minimize light exposure after printing. Display it only under low lighting and never in direct sun. If you want to show it, frame it behind glass that has UV protection (many modern acrylic or glass options can filter 90+% of UV). This won’t stop fading entirely, but it will significantly slow the process. Ideally, store the print in a dark portfolio, drawer, or light-tight box when not viewing it.
Many artists will scan or photograph the anthotype immediately upon completion – this way they have a high-quality digital copy that captures the colors at their peak. You could make prints of this digital image if you wanted a permanent record, allowing you to tuck away the original safely.
Mordants and toners: In fabric dyeing, mordants (like alum, iron, tannins) bind dyes to fibers to improve lightfastness. Some artists have experimented with gently toning anthotypes in alum solution or using vinegar/iron to shift colors. There is no published consensus on a mordant that “fixes” an anthotype without also altering its color. Alum might help bind pigment to paper fibers a bit more, but it likely won’t stop photodegradation – it’s worth researching if you’re adventurous, but proceed cautiously.
Waxing the print: An old practice with salt prints and cyanotypes is waxing – applying a thin coat of beeswax or Renaissance wax to the finished print. This can deepen the paper’s translucency and arguably provide some protection from moisture and airborne pollutants. For anthotypes, waxing (with something like microcrystalline wax or natural wax) has been suggested as a way to block some UV light and seal the surface
It won’t make it fully stable, but it could slow fading and give the print a nice finish. To do this, the print must be bone dry; then you gently rub a small amount of melted wax or wax polish over it and buff it. Be aware it may also slightly change the visual tone (usually making colors appear more saturated).
Resin encapsulation: One unconventional method to preserve the exact state of an anthotype is to embed it in resin. As one guide noted, you could pour a clear epoxy resin over the print (or sandwich it between resin layers) to completely seal it off from air and UV
This essentially laminates the piece. It’s a bit extreme and experimental – resin could darken the paper or cause the pigment to bleed if not done carefully – but some people have had success preserving botanical art in resin. If you try this, use art-grade clear resin and follow all safety and technique guidelines (resin work is a whole art of its own!).
Despite all these, the most practical “fix” is dark storage. Many anthotype artists accept that the print will eventually fade. In fact, some incorporate that into the meaning of the work – the ephemeral nature of the image can symbolize memory, decay, or the passage of time. For example, artist Christine Elfman made anthotype portraits with lichen dye that deliberately fade like memories, becoming “ghost images” over time
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