How candy-coated chocolates are made

The first big customer for M&M's was the U.S. Army, which wanted chocolate that would survive the tropics.

stations: 10
things upstream: 49
raw sources: 20
steps from the ground: 8

The short version

Candy-coated chocolates start as small centers tumbling in a rotating drum. Cold sugar syrup goes on, spreads over the rolling mass and dries under moving air, again and again, until a crystal shell has built up one thin coat at a time. Colored syrups go on near the end, and a ribbed pan buffs the pieces with wax.

Form the small centers

Chocolate is shaped into small buttons, or a nut or other filling becomes the core. These centers would melt in warm weather without a shell.

Goes in
Chocolate
Prepare the surface

Some cores first get gum-rich syrup alternated with fine sugar, which fills ridges and gives later coats something smooth to grip. A film of gelatin or gum can also block fat and water from moving between core and shell.

Goes in
Sugar
Spray on cold syrup

Centers roll in a drum while spray guns wet them with sugar dissolved in water. Chocolate cannot take heat, so one panning patent gives about 27 °C for this stage. The mass keeps tumbling until the syrup has spread evenly.

layers of 10 to 14 µm

Goes in
Water
Blow each coat dry

Conditioned air flows through the drum and carries off the water, leaving a skin of tiny crystals. Every coat must dry fully before the next, since rushing makes the shell fail, so the work runs slowly.
Lay down color

Titanium dioxide has long gone into precoat layers, giving an opaque white base so the colors above read true. Syrups carrying colorant then go on over it. One patent replaces the white pigment with sucrose esters.

Goes in
Titanium dioxide
Finish with thin syrup

Last coats use a weaker syrup, which dries more slowly and forms smaller, finer crystals. That is what makes the surface smooth enough to shine.
Rest on trays

Pieces usually spend a night on trays in a climate-controlled room before polishing, though the syrup used can change that.
Polish with wax

A ribbed pan works dry or liquid blends of carnauba and beeswax over the pieces. A confectioner's glaze can follow for protection, and glazed candy then airs for 18 to 24 hours so the solvent can leave.

Goes in
Carnauba palm wax Beeswax
Print the trademark

Each piece gets a letter printed on one side in edible ink. The printed mark has been part of M&M's since the early 1950s, first black and then white.

Goes in
Ink
Send to packing

Finished pieces leave the coating room and go to the packaging line.

End of the lineCandy-coated chocolate

Worth repeating

M&M's were likely inspired by Smarties, a British candy with a chocolate center and a hard sugar shell, which Forrest Mars may have seen soldiers eating in the Spanish Civil War.
During World War II the candies were sold only to the military.