Potato starch grains are an ideal for observation in polarized light and in dark-field. Sample preparation is simple and straight-forward.
Materials: a potato, kitchen knife, slides, cover slips, water, iodine.
- Cut the potato in half and scrape a little of the potato onto the microscope glass slide. This can be done either with a knife or with the fingernails. There should not be any large potato pieces on the glass.
- Place a small drop of water on the “potato juice” and then place the glass cover slip on top.
- Observe using the microscope. The starch grains will be visible as oval structures.
- Now dilute a small amount of iodine in some water. The water should only turn slightly yellow. Place a drop of the dilute iodine next to the glass cover glass, so that some of the solution is able to flow between the cover glass and the slide.
- You should be able to see how the starch grains change color. The iodine will react with the starch and turn it blue-black.
- Alternatively, you can observe the starch grains in dark field or in polarized light (without adding iodine): Darkfield Microscopy | Simple Polarization Microscopy | Potato Starch Grains