AT HOME · 45–60 MINUTES · AGES 8+ · ADULT LEADS

The 45-Minute Fall Leaf Pigment Lab: Separate the Colors Safely

Crushing a red leaf does not guarantee a perfect red stripe. That is the lesson: prepare the sample, control the solvent line, observe what separates and report the result you actually got.

What this experiment can—and cannot—show

Paper chromatography can separate some pigments because the solvent moves through paper and carries compounds at different rates. The U.S. Forest Service explains that leaves contain green chlorophyll as well as yellow and orange carotenoids; as chlorophyll breaks down in fall, other colors become visible. The American Chemical Society uses paper chromatography to separate pigments and emphasizes using only a small amount of isopropyl alcohol with safety planning.

Your result will not identify a tree, measure exact pigment concentration or prove why a particular leaf turned red. Species, leaf condition, solvent, paper, sample strength, temperature and technique all matter. A weak smear, one dominant band or no visible separation is still data. Do not add stronger solvents or heat to force a prettier result.

Supplies and setup

• Three known, clean leaves collected lawfully from the ground or your own property: one green, one yellow and one red or orange works well for comparison. Avoid poison ivy, unknown irritating plants, moldy leaves and roadside contamination.
• Plain white basket-style coffee filters cut into strips, pencil, ruler, three stable clear jars and binder clips or pencils to suspend strips.
• Separate small cups or bowls, spoon or mortar and pestle, paper towels and a tray to contain drips.
• 70% isopropyl rubbing alcohol in its original labeled container; adult handles it.
• Safety goggles for everyone at the table and adult-appropriate gloves if the label or risk review calls for them.
• A timer, notebook and colored pencils for recording observations.

Use a washable, uncluttered surface away from food preparation, medication, candles, pilot lights, heaters, outlets that spark and direct sun. Keep food and drinks out of the work zone. Tie back long hair. Set the jars where they cannot be knocked over and use only a shallow solvent level. If ventilation, supervision or spill control is uncertain, do not use alcohol.

Prepare comparable samples

Tear or cut similar-size pieces from each leaf and keep them separate. Crush the first sample until the tissue is broken down. The adult adds a small amount of alcohol—enough to wet the crushed material, not fill the cup—and continues mixing according to the activity plan. Let the pigment extract become visibly colored. Clean and dry the tools or use separate tools before the next leaf so one sample does not contaminate another.

Make a pencil line about 2 centimeters from the bottom of each strip. Place a small concentrated drop of extract on the line. Let it dry and repeat several times on the same spot to build color without creating a wide puddle. Mark the sample name in pencil at the top, never at the solvent end. Ordinary marker ink is a mixture that can separate and confuse the leaf result; the shadow lab offers a chemical-free science night when materials are limited.

Run the paper without drowning the evidence

The adult pours a shallow layer of alcohol into each stable jar. Suspend the strip so its bottom edge touches the solvent while the pigment spot remains above the liquid. If the spot sits underwater, pigment can dissolve into the jar instead of moving up the paper; reset with a dry strip rather than pretending the run worked. Keep the paper from pressing against the jar wall if that distorts the path.

Watch the solvent front rise. Do not seal a setup in a way that conflicts with the alcohol label or creates pressure. Do not warm it. When the solvent front approaches the upper portion of the paper or the planned time ends, the adult removes the strip with appropriate protection, immediately marks the solvent front in pencil and places the paper on the prepared tray to dry in the controlled ventilated area.

Read the result without certainty theater

Count visible bands and describe color, width and relative distance. A green sample may show more than one green or yellow band; a yellow leaf may yield a faint result; a red leaf may smear rather than produce a clean red line. The Forest Service source supports the presence of chlorophyll and carotenoids in leaves, but your kitchen result does not chemically identify every band. Use cautious language: “a yellow band traveled farther than the dark green band,” not “this proves it is carotene.”

Create three columns: observed / inferred / still unknown. “Two bands” is observed. “The sample contains more than one mobile pigment” is an inference. Exact compound identity is still unknown without validated standards and methods. This same habit appears in the trail-map explain-back game: separate what the source says from what the family assumes.

Troubleshooting the common failures

• No color moved: the sample spot may be too weak, leaf too dry, paper unsuitable or run too short. Repeat with a more concentrated spot only if the adult can do so within the same safety plan.
• Everything dissolved into the jar: the pigment spot was likely below the solvent line. Start again with less solvent or a higher spot.
• One broad smear: the spot may be too large or wet. Use smaller dried layers rather than one puddle.
• Strips lean or touch: stabilize the suspension. Do not hold a strip by hand over an open solvent jar for the whole run.
• Colors do not match the leaf: record that. Visible leaf color and extract behavior are not identical measurements.
• Child loses interest: adult ends the chemical work safely. Do not leave an open setup running unattended.

Cleanup and storage

The adult caps the original alcohol container promptly and stores it exactly as labeled, out of children’s reach. Handle remaining liquid, wet paper, crushed plant material, gloves and cleanup towels according to the product label and local household-hazard guidance; do not pour or mix chemicals based on an internet shortcut. Wash hands after cleanup. Wipe the work surface and keep the area ventilated until vapors are gone. If alcohol gets in eyes, is swallowed, is inhaled in a concerning amount or causes symptoms, use the label’s first-aid directions and contact Poison Help in the United States at 1-800-222-1222 or emergency services as appropriate.

No-solvent and low-energy versions

No-solvent version: place green, yellow and red leaves on white paper. Compare vein pattern, patches, edge color and light transmission near a window. Draw each leaf and label only observed colors. Use the Forest Service explanation afterward to discuss chlorophyll and carotenoids. It will not separate pigments, but it preserves the evidence habit.

Low-energy version: prepare one green-leaf strip only, with the adult doing every chemical step while the child makes a before-and-after sketch. Younger-sibling version: keep the sibling outside the chemical zone and give them dry leaves for sorting by size or color. Bad-weather follow-up: build the paper bridge or use the no-posting photo hunt.

Who should skip it

Skip the alcohol version if children cannot stay outside a clearly marked adult zone, ventilation is poor, the household has no safe storage, anyone is likely to mouth materials, or an open flame or ignition source cannot be controlled. Skip unknown plant material and leaves from places where collecting is prohibited. Choose the observation version if chemistry cleanup will outlast the family’s patience. The experiment is optional; safe boundaries are not.

Sources checked October 11, 2026

• U.S. Forest Service: why leaves change color; chlorophyll and carotenoids
• American Chemical Society: paper chromatography of plant pigments and safety planning
• American Chemical Society: chromatography activity and coffee-filter method
• American Chemical Society: isopropyl alcohol activity and label-first safety
• Poison Control: contact routes for case-specific exposure guidance