## 2 Materials and Methods  
The RH used was collected from a local rice factory located at Tanjung Karang, Selangor, Malaysia, where the species of the RH is recognized as _Oryza sativa_ (Asian rice) [4]. At an earlier state, after being milled, the RH was kept indoor inside the factory to reduce the chances of contamination from the surroundings. The RH was washed numerous times by using pipe water to remove stains and impurities. By using a large basin, the RH was soaked in water and the sands and soils submerged to the bottom of the basin. After that, only the RH that floated on the surface of the water was collected. Then, the washed RH was dried in an oven at 120 \({}^{\circ}\)C for 8 h. The dried RH was then burned in the electrical furnace at 1000 \({}^{\circ}\)C for 2 h at a heating rate 10 \({}^{\circ}\)C/min to obtain the WRHA. Subsequently, the obtained WRHA was ground by using a mortar and pestle. In order to obtain the fine powder, the WRHA was then sieved into the size of 45 \(\upmu\)m. The obtained WRHA was then mixed with ZnO. A zinc silicate glass with a weight composition of (ZnO)\({}_{0.55}\)(WRHA)\({}_{0.45}\) was prepared by using the solid state method [2]. In this research, the raw material used was zinc oxide (ZnO) (99.9%, Sigma Aldrich, Subang Jaya, Malaysia) and WRHA was extracted as mentioned previously. The ZnO and WRHA were weighed by using an electronic balance for about \(\sim\)16.5 g and \(\sim\)13.5 g, respectively, to give the total amount of \(\sim\)30 g of the whole mixture. The mixture was then dry milled by using a milling machine at 80 rpm for one hour to ensure that the composition was well mixed together. Right after the mixture was milled together, it was carefully poured into a cylindrical alumina crucible of 47 mm in height and with a wall thickness of 2.5 mm, which has the ability to withstand high temperatures of up to 1600 \({}^{\circ}\)C; then, the mixture was melted in a closed electrical furnace at 1450 \({}^{\circ}\)C for 3 h. In the meantime, a pair of water with a glass collector at the bottom of the pair was prepared. After the melting process was done, a flowy molten glass was obtained inside the alumina crucible and it was poured into the pair of water. As a result, transparent glass frits were formed. The collected glass frits were left to dry at room temperature and ground by using a plunger, mortar, and pestle to obtain the fine powder, and then sieved at 45 \(\upmu\)m. In order to get the pallet for the purpose of ceramization, a palleting procedure was carried out. The powder was mixed with polyvinyl alcohol (PVA) to bind it together and later was put into the stainless-steel mould that was 13 mm in diameter and 2 mm in thickness. Lastly, the powder was pressed by using a uniaxial pressing pallet with an applied load of 3 tons for 10 min. The pallet was then subjected to the sintering process at various sintering temperatures, ranging from 700 to 950 \({}^{\circ}\)C, with an increment of 50 \({}^{\circ}\)C for each sample in a 4 h duration. The zinc silicate glass and glass-ceramics were characterized for their physical, structural and optical properties. The densities of the zinc silicate glass and glass-ceramics were measured by using an MD-300S densitometer in which Archimedes' principle was applied. The results obtained were compared with true density that was measured by using a micromerities AccuPyc II 1340 Gas Pycnometer. For bulk density by using Archimedes principle, at the beginning stage, the samples were weighed by using the weighing machine in the air, giving their weight in air (W\({}_{a}\)). Then, it was followed by the submersion of the sample into liquid, to obtain the weight of the displaced fluid.