"Cadimum" was written by Pinegrove's frontman, Evan Stephens Hall, who also sings, plays the guitar and adds percussion to the track.
Hall at that time was sending letters to a friend on the West Coast, and they eventually began exchanging shapes instead of words.
[3] The cover art of Cardinal, as well as several lyrics on the album, refere to the color ,either directly or by metaphor, most notably in "Cadmium".
[3] Ian Cohen at Pitchfork considered "Cadmium" as indicative of the album's overarching themes, specifically, "the failure of words to express what [Hall's character] really wants".
[5] James Rettig at Stereogum was positive in his impression of the single, writing, "Hall's revelations about communication are met with crisp affirmations from the rest of his band; each time the music drops out sounds like a step on the path to aligning what you say and how you feel.