Preferred examples of swelling reagent are N-methyl pyrrolidone, esters such as, ethyl acetate, propyl acetate, butyl acetate, ethyl lactate, butyl lactate etc., ketones such as acetone and methyl-ethyl-ketone (MEK) and cyclic ethers such as THF. The concentration of the swelling reagent in the pretreatment liquid may be suitably determined so as to attain the effect of providing a good print qual