A technique used to decorate hard, white bodied earthenware from roughly 1835 to the first quarter of the 20th c. The decorations were underglaze blue patterns (most often transfer printed but also applied by hand by brush stroke), the ink of which was caused to bleed or "flow" into the undecorated portions of earthenware vessels during the glaze firing. The desired "flow" was produced when lime or chloride of ammonia was added into the protective shell of the fire-clay sagger surrounding the wares during the glaze firing.

a type of blue and white pottery on which the blue pattern deliberately flows into the white background

Transferware produced in numerous patterns in which the cobalt blue ink flowed, or smeared, during firing. The resulting out-of-focus look was colorful and popular, and flow blue was widely produced in England and the Netherlands from 1830 to 1900. Its popularity was welcomed by the manufacturers, because the flowing disguised the smudges that were made if the transfer was moved slightly as it was laid on the item: this enabled them to deskill the decorating process even more, and thus to pay even lower wages to the women and girls who did the job.