This study was undertaken to observe the porcelain porosity exerted by the contamination of the alloy and liquid. The alloy used in this study was Jelstar; liquids were Ceramco Sta-Wet liquid, distilled water and tap water; and Ceramco vacuum porcelain powder was used. The measurements with photomicroscope (x200, Olympus) were made on the porosity, the diameter (mm) of the pores and the numbers of the pores ($No/mm^2$) The results of this study were obtained as follows: 1. In the porosity, the opaque layer contained over 70% of the total porosity, and the porosity was increased about twice in every porcelain layer by the tap water. 2. The contamination of the alloy and liquid caused porosity to increase markedly at the interface of the metal-porcelain. 3. The diameter of the pores were increased about 1.5 times larger by the contaimination of the liquid, and only a slight increase in the opaque layer due to the contamination of the alloy. 4. In the numbers of the pores, there were significant differences according to the contamination of the alloy and the porcelain layer. And the contamination of the liquid caused significant differences only in the opaque layer.