This gif is showing my technique for a bubble texture effect onto unfinished veg tan leather. This bubble mix used Ajax dish soap and milk paint pigment. I use a large mason jar for the mix, lay the leather flat on the table and then blow bubbles using a straw into the mix letting it overflow the jar and fall onto the leather below. I control bubble size by the diameter of the straw and how fast I expel air. I control negative space density by how fast I move the mason jar. The ratios must be spot on for this to work well, so experiment and play. It's your process, so make it as fun as you want.