Even with expensive modern upholstery leather there is often a problem of unstable dyes which transfer to the clothing of the user. One reason is that fabric dyes may have been used. Furthermore, in order for a dye to penetrate the pores and bind with the leather fibers, the leather should be warmed, carefully fatliquored (quick-drying oils can be used which promote dye attachment) and immersed in dyebaths which are not too concentrated. A series of immersions is recommended for deeper colors. Before the leather dries, unreacted dye residue should be be removed by wiping with a soft, moist, wool cloth.