Porous ceramics materials are widely used in various fields of science and engineering due to their high heat resistance, dielectric properties, and chemical resistance at low temperatures. Due to the high porosity of the quartz ceramic surface, moisture can be absorbed and retained, resulting in the deterioration of the above-mentioned properties. Therefore, the ceramic surface requires protection from moisture, which is achieved by using water-resistant coatings that also provide wear-resistance, stability to heating, solar radiation, and erosion. This paper exhibits the results of testing coatings based on new experimental organosilicon and commercially available organic coating materials on porous quartz ceramic plates. All the coatings were found to be resistant to solar radiation in accordance with the requirements. Data on the dielectric properties and gas permeability coefficients of the commercial and experimental systems were obtained. It was determined that the experimental coating based on the pigmented organosilicon binder KAST-2 has the lowest gas permeability coefficient at the highest pressure gradient.