塗模層是塗覆在發泡聚苯乙烯鑄造模型上或鑄造砂模表面上的耐火材料層，其功能是隔離澆鑄的高溫金屬液接觸砂模，其性質會影響鑄件的品質。透氣性是塗模層諸多重要性質中的一種，與選用耐火材料的特性有直接關係。
本研究利用自行建立的實驗裝置並根據達西定律，量測塗模層的透氣性，以探討耐火材料的顆粒形狀、粒徑分布及鱗狀石墨或矽酸鈣纖維的添加對塗模層透氣性的影響。研究結果顯示，陶瓷砂粒徑較大的塗模層具有較高的透氣性，而添加物的影響則視形狀與百分比而定。塗模層在電熱爐內780~810℃煆燒3 min後的透氣性會略微提高。SEM微觀形貌顯示，粒徑的大小、添加物的形狀與數量會影響塗模層內孔隙的大小。依據微觀察結果提出耐火材料添加物影響透氣性的模式。

The mould coatings is a layer of refractory applied on the surfaces of expandable polystyrene patterns or casting sand mould, to separate the casting metal liquid from contacting mould, its properties will affect the quality of castings. Ability for air or gases to pass through is one of the most important properties of the coatings, which directly related to the characteristic of refractory.
In this research an experimental set-up was used employing Darcy’s law to measure the permeability of mould coatings, to investigate the effects of granular shapes, sizes, particle distribution of refractory, and additives flake graphite or fibrous calcium silicate on the permeability. The results shows that coatings made of a larger size of ceramic sand has a higher permeability, however the effect of additives depends on the particle shape and its relative amount. The coatings after calcinations in a furnace with a temperature ranged between 780~810 ℃for 3 minutes shows a higher permeability. The micro topographies from SEM shows that the particle sizes, shapes and relatives amount of additives will affect the void size existed in the coatings. Based on this observation, a model for the permeating mechanism associated with additives has been proposed.

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