Offices have recently seen an increase of inkjet printing on plain paper. Two types of ink have been used for this printing: water-based ink and oil-based ink. However, there is a trade-off between the two. Although water-based ink offers sharp images, it also results in significant curling of plain paper after printing. Conversely, although oil-based ink allows curl to be suppressed, it results in poor image quality with low density. By carefully controlling the ink's absorption into and penetration of plain paper, we developed a new ink that achieves both image quality and curl suppression.