Great helm The great helm or heaume , also called " pot helm " , " bucket helm " and " barrel helm " , of the High Middle Ages arose in the late twelfth century in the context of the crusade s and remained in use until the fourteenth century . They were used by knights and heavy infantry in most European armies between about 1220 to 1540 AD . Evolution . In its simplest form , the great helm was a flat - topped cylinder of steel that completely covered the head and had only very small openings for the eyes and mouth . Later designs gained more of a curved design , particularly on the top , to deflect or lessen the impact of blows . The great helm ultimately evolved from the nasal helmet , which had been produced in a flat - topped variant with a square profile by about 1180 . From this type of helmet an intermediate type , called an ' enclosed helmet ' or ' primitive great helm ' , developed near the end of 12th century . In this helmet the expansion of the nasal produced a full face - plate , pierced for sight and breathing . This helmet was largely superseded by the true great helm by c . 1240 . A later variant with a more conical top is known as a ' sugarloaf helm ' . In Spanish they are called " yelmo de Zaragoza " , referring to Zaragoza where they were introduced for the first time in the Iberian peninsula . Although the great helm offered vastly superior protection than previous helmets , such as the nasal helm and spangenhelm , it limited the wearer ' s peripheral vision , and in addition to being heavy , the mass - produced form ( flat - topped without ventilation holes ) provided little ventilation and could quickly overheat in hot weather . Knights usually wore the great helm over a mail coif ( hood ) sometimes in conjunction with a close - fitting iron skull cap known as a cervelliere . The later development of the cervelliere , the bascinet , was also worn beneath the great helm ; men - at - arms would often remove the great helm after the first clash of lances , for greater vision and freedom of movement in melee combat . The bascinet had a mail curtain attached , a camail or aventail , which superseded the coif . Mail throat and neck defences such as these were made obsolete when plate gorget s were introduced , around 1400 . The bascinet evolved from its early skull cap form to supersede the great helm for combat . The great helm fell into disuse during the 15th century , however it was used commonly in tournaments where a version of the great helm , the frog - mouthed tilting helm , evolved . Decoration . The Great Helm was often blackened , lacquered or painted , and frequently bore decorations such as : Contemporary reenactors . The great helm is today especially popular amongst live - action role players and in medieval re - enactment such as the Society for Creative Anachronism . It is inexpensive , easy to manufacture with even rudimentary equipment ( metal scissors , drill , rudimentary anvil , rivets and hammer ) , and provides good protection for the head against both sharp and blunt weapons . Its biggest drawbacks are poor ventilation and air circulation , especially if worn with closed - cell foam padding , making it very hot in warm weather . Modern reenactment versions of great helms weigh 1 . 5 to 3 kg . For safety reasons , they are made from thicker steel than medieval originals but are not overly heavy , cumbersome , or uncomfortable . Although visor slits are usually only some 20 – 30 mm wide , they do not greatly restrict the field of vision as they are very close to the wearer ' s eyes .