Basic wettability tests of the samples with disk geometry constructed without using bonding materials. Distilled water droplet (in color blue) and mineral oil droplet (in color orange) contact angle measurement at times 0 and 10 s (after placing these droplets on the flat surface of the samples) of the samples with disk geometry composed by: the same quantity of base material (5 g), same weight fraction of combined particle size (50% w/w of <20 μm, 50% w/w of 20–74 μm), same quantity of pH 3 hydrochloric acid solution (6% w/w relative to 5 g of base material) and different weight fractions of bonding materials (5% w/w or 10% w/w relative to 5 g of base material).