Radial Chromatography T-shirts! The Experiment You Can Wear!

Introduction

As isopropyl alcohol is gradually squeezed out onto an area of fabric, a simple pattern made with permanent ink markers is transformed into an explosion of colors and chromatographic designs. This exciting chromatography activity is a fun way to finish a chapter on solutions, mixtures or solubility.

Concepts

• Solubility
• Separation of a mixture
• Compound vs. mixture
• Chromatography

Background

Although many materials may appear to be pure substances, some are actually mixtures of two or more different compounds that take on the appearance of one substance. One technique that scientists use to separate out mixtures of compounds is chromatography. The word chromatography is derived from two Greek words meaning “color writing.” In chromatography, compounds in a mixture are separated as they dissolve in a solvent and travel along a substrate at different rates. In paper chromatography, the substrate is a highly absorbent paper and the solvent (usually water) is allowed to seep through the paper by capillary action. The compounds in the mixture become separated as they dissolve in the water and travel up the paper at different rates, depending on their physical attraction for the paper versus the solvent.

In this activity, the substrate is cotton and the solvent is isopropyl alcohol. The mixtures to be separated are dyes found in permanent markers. Most permanent markers use a mixture of dyes to achieve a permanent and rich color. The pens selected for this activity are high quality pens with a rich selection of dyes. The result is a T-shirt with a variety of colorful chromatographs that will last for years.

Materials

Safety Precautions

Isopropyl alcohol is a flammable liquid and a fire hazard; keep away from all flames, sparks and heat sources. Isopropyl alcohol is also slightly toxic by ingestion and inhalation [LD₅₀ 5045 mg/kg]. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The excess isopropyl alcohol can be used in other laboratory activities or treated according to Flinn Suggested Disposal Method #18b.

Prelab Preparation

If a new T-shirt is used, wash and dry it first to remove the sizing and other chemical additives.

Procedure

1. Place the basin upright inside the T-shirt. Position the T-shirt so that the area to be decorated is covering the mouth of the basin.
2. Stretch the rubber band around the basin over the T-shirt, and then gently pull down on the T-shirt along the sides to draw up any slack and to tighten the T-shirt fabric slightly over the mouth of the basin. The T-shirt should be stretched taunt over the basin (see Figure 1).
   {14132_Procedure_Figure_1_Setup for T-shirt radial chromatography}
3. Use the permanent pens to make a pattern of spots somewhere on the stretched fabric. Some suggested patterns are offered in Figure 2.
   {14132_Procedure_Figure_2}
4. Fill the pipet with isopropyl alcohol.
5. Position the pipet tip over the center of the pattern and directly on the stretched fabric. Gradually squeeze the pipet bulb to deliver a slow and constant stream of isopropyl alcohol onto the fabric. Note: If the alcohol starts dripping down into the basin, the alcohol is being added too fast—faster than the T-shirt fabric can absorb it. Slow down!
6. As the isopropyl alcohol soaks in and passes through the colored spots, it will start to spread the ink spots out radially into a brilliant chromatograph.
7. When the chromatograph has grown to be several inches wide, stop adding the isopropyl alcohol. Allow the alcohol to continue to be absorbed and the chromatograph to grow for another minute or so.
8. Create a new pattern somewhere else on the stretched surface. Keep the new pattern away from the most recent pattern to avoid any contamination. Repeat steps 4–7.
9. When the stretched area has been sufficiently decorated, allow 1–2 minutes for partial drying. Then remove the rubber band, and if desired, repeat steps 1–8 to decorate another area of the shirt. Try a variety of patterns, shapes and sizes. Be creative.
10. When finished decorating the T-shirt, allow the shirt to dry completely.
11. After the T-shirt is completely dry, iron the shirt to help set the patterns. At this point the T-shirt is ready to be worn, but some of the colors tend to fade with repeated washings (especially in hot water). To reduce fading, wash in cold water.

Teacher Tips

• Patterns in the 3–10 cm range seem to work best, and the basin should be large enough that 5–6 patterns can be done at a time without having to move the fabric. Very large patterns (>15 cm) can also be made, but they tend to take considerably longer to dry. Keep in mind that the larger the desired pattern, the larger and darker the ink spots need to be.
• A dye binder may be used to allow the chromatographs to stay bright and colorful after many washings. Without the binder, the chromatographs are still impressive but the colors will fade over time. The binder will make the shirt a little stiff but this will also soften with time. Dye binder should be available at fabric or craft stores. As with all clothes and colors, washing techniques will impact the colorfastness. Washing in cool water and using gentle detergents will extend the lifetime of the colors and fabric.
• This activity is best done as a “just-for-fun” lab activity, with the emphasis on exploration and artistic creativity. Ideally each student should have his or her own T-shirt (brought in from home), basin, rubber band and pipet. This will enable them enough time to finish in a 45–55 minute period. Markers, and solvent containers can obviously be shared—one set for every 4–5 students. These additional supplies can be purchased separately from Flinn Scientific or a local craft store. Materials can also be brought in from home. Large plastic containers or dish pans make great basins.
• If the sleeves of the T-shirt are to be decorated, wide-mouth plastic cups may be used in place of the basin, and the patterns made one at a time.
• The process is not limited to T-shirts. Sweat shirts, shorts, white pants, tank tops, hats, pillow cases, socks and canvas shoes have all been used. 100% cotton fabric works best.
• The chromatographs produced in this activity do not have color separations as distinct as a paper radial chromatography. This is due to the fast rate at which the T-shirt chromatographs are run. Again, this activity is best done as a “just-for-fun” lab experiment. To slow down the chromatography and get greater separations, dilute the isopropyl alcohol with a little water to change the solvent polarity and the speed of the separations.
• Beautiful designs can be produced by using various color markers. Try to combine colors into one chromatograph design.

References

Special thanks to Bob Becker, Kirk wood High School, Kirkwood, MO, for providing us with this activity.