Japanese American Scientist Satori Kato invented instant coffee back in the early 1900s, and the first mass-produced instant coffee company did business in England by 1909. By 1938, Nescafe invented freeze-drying technology and instant coffee became a staple convenience food. (See reference 2). Transforming water and coffee grounds into instant powder requires large industrial spray or freeze-drying facilities.
Make large amounts of coffee using extraction cells, large industrial machines that mix ground coffee and water. Extraction cells work much like percolating coffee machines, only on a much larger scale.
Pump coffee into a tall tower for spray drying. Liquid coffee sprays through hot air, causing water to evaporate. The coffee residue that remains settles at the bottom of the tower as a fine powder. Adding hot water reconstitutes the coffee. Spray drying coffee results in a loss of flavour.
Retain more coffee flavour by freeze drying coffee. Freeze thin layers of liquid coffee to --40 Fahrenheit. Break the frozen layer of coffee into small pieces and place in a vacuum. The airless environment lowers the boiling point of water so far that the water boils off, leaving a powder used for better quality instant coffees.
Both freeze-drying and spray-drying coffee results in loss of flavour. Some instant coffee mixes make up for this loss by adding other flavours.
Mass production of instant coffee requires training and large-scale industrial equipment unavailable to most people.