Railway companies generally use a prepared sheet dressing for yellow tarpaulins. For a yellow dressing use boiled linseed oil coloured with yellow ochre ; if it does not dry quick enough, add a little patent driers. First give the canvas a good dressing with plain boiled oil; when that is dry, coat both sides with the coloured dressing. The dressing should take several days to dry; if it dries quickly it will be liable to crack.