Riot Foam was a foam developed to cover any disturbance and solidify around everything in it. It was new in 2099 when Judge Joe Dredd called in the Riot Squad to smother the voices of Ma 'Green Fingers' Mahaffy's brainblooms, as they were singing the Humming Song. It was used by the Riot Squad in 2103. In 2105 / 2106, contraband Riot Foam could be purchased for 1,000 creds a gallon.