Say "Cheese!" Chemistry Article for Students | Scholastic Science World Magazine

In the 1940s, American physicist Edwin Land peered through his camera and snapped a photo of his 3-year-old daughter. The little girl asked why she couldn’t see the picture right away. Back then, all cameras used film, which had to be developed, or treated with chemicals at a lab. His daughter’s impatience inspired Land to invent a faster option: the instant camera. It contained film that developed automatically. For the first time, anyone could watch a photo image appear right before their eyes.

In the 1940s, American physicist Edwin Land looked through his camera. He snapped a photo of his 3-year-old daughter. The little girl asked a question: Why couldn’t she see the picture right away? Back then, all cameras used film. It had to be developed, or treated with chemicals at a lab. Because of his daughter’s question, Land thought up a faster method. He invented the instant camera. Its film developed automatically. For the first time, anyone could watch a photo image appear right before their eyes.

Land founded the Polaroid company, and his instant photos became an instant hit. Over the next few decades, Polaroid sold hundreds of millions of instant cameras and more than a billion packs of instant film. Other companies joined the instant photo market in the 1980s. But by the early 2000s, digital cameras had started to become popular. Instant photography soon fell by the wayside.

In recent years, instant film has made a big comeback, thanks in part to a new generation of young photographers. “People seem really interested in the experience of creating a tangible, one-of-a-kind photo,” says Stephen Herchen, chief technology adviser at Polaroid. That experience relies on a sequence of nearly 50 chemical reactions. “Instant film may be the most chemically complex product humans have ever invented,” says Herchen. Here’s a look at the sophisticated science that makes instant photos possible.

Land started the Polaroid company. His instant photos became an instant hit. Polaroid sold hundreds of millions of instant cameras over the next few decades. It also sold more than a billion packs of instant film. Other companies started making instant cameras in the 1980s. But by the early 2000s, digital cameras were becoming popular. Instant photography soon fell out of use.

In recent years, instant film has made a big comeback. That’s partly because of a new generation of young photographers. “People seem really interested in the experience of creating a tangible, one-of-a-kind photo,” says Stephen Herchen, chief technology adviser at Polaroid. That experience requires a series of nearly 50 chemical reactions. “Instant film may be the most chemically complex product humans have ever invented,” says Herchen. Advanced science makes instant photos possible.

Number 1 Pressing the button to take a photo opens the shutter, allowing light to enter the camera through the lens. Inside, the light reflects off a mirror and hits the film.

MAGICTORCH

Number 2 Each film square contains three layers of silver halide crystals. This light-sensitive compound is made of silver (Ag) plus an element from group 17 of the periodic table, such as bromine (Br) or iodine (I). Each layer darkens in response to a specific color of light: blue, green, or red.

Number 3 The film is ejected from the camera. As it slides out, rollers break open a pod of chemicals in the white band at the bottom of the frame and spread them through the interior layers. One of these chemicals blocks additional light from affecting the film, and another alters the film’s pH, or acidity. That controls the length of time it takes for the film to develop.

Number 4 In areas where silver halide crystals weren’t exposed to their target color of light during the shutter click, a chemical from the pod makes dyes in the film dissolve. They move upward to become visible at the photo’s surface. Yellow dye is released from the blue-light-sensitive layer, magenta from the green-light-sensitive layer, and cyan (blue-green) from the red-light-sensitive layer. In exposed areas, a developer chemical from the pod sets off reactions that keep the dyes locked in place, so they remain unseen.

Number 2 Each film square contains three layers of silver halide crystals. This light-sensitive compound is made of silver (Ag) plus an element from group 17 of the periodic table, such as bromine (Br) or iodine (I). Each layer darkens in response to a specific color of light: blue, green, or red.

Number 3 The film is ejected from the camera. As it slides out, rollers break open a pod of chemicals in the white band at the bottom of the frame and spread them through the interior layers. One of these chemicals blocks additional light from affecting the film, and another alters the film’s pH, or acidity. That controls the length of time it takes for the film to develop.

Number 4 In areas where silver halide crystals weren’t exposed to their target color of light during the shutter click, a chemical from the pod makes dyes in the film dissolve. They move upward to become visible at the photo’s surface. Yellow dye is released from the blue-light-sensitive layer, magenta from the green-light-sensitive layer, and cyan (blue-green) from the red-light-sensitive layer. In exposed areas, a developer chemical from the pod sets off reactions that keep the dyes locked in place, so they remain unseen.

SHUTTERSTOCK.COM (PHOTO OF FRIENDS); SAMXMEG/GETTY IMAGES (POLAROID FRAME)

DON’T SHAKE IT! There’s no need to shake instant film. The chemicals are designed to spread throughout the film on their own. Shaking too hard can actually damage the image!

Number 5 The released dyes flow upward toward the film’s surface, and an image starts to appear. Combinations of these dyes create all the colors in the final image, except white. White is supplied by a pigment called titanium dioxide (TiO2), from the pod in the frame.

Number 6 After several minutes, the film’s pH shifts, halting development. The final image is now ready to share with friends or hang on your wall!

Number 5 The released dyes flow upward toward the film’s surface, and an image starts to appear. Combinations of these dyes create all the colors in the final image, except white. White is supplied by a pigment called titanium dioxide (TiO2), from the pod in the frame.

Number 6 After several minutes, the film’s pH shifts, halting development. The final image is now ready to share with friends or hang on your wall!