The spelling of the word "art up up" can be explained using IPA phonetic transcription. The first part of the word, "art," is pronounced as /ɑːt/, with a long "a" sound followed by a voiced "r" sound and a voiceless "t" sound. The second part of the word, "up," is pronounced as /ʌp/, with a short "u" sound and a voiceless "p" sound. The final "up" in the word is added for emphasis and does not affect the pronunciation of the word as a whole.