1、无吸水性或孔隙小于2%的材料和产品。
2、吸水性或孔隙大于2%的材料和多孔性产品。
故使得现阶段对于材料或产品的密度测量也有了新的分类。我们将其分为二大类：
1、不具渗透性产品的密度 (Impermeable Density) 所定义之体积不含开放孔，或开放孔不会被水渗入者，在精密陶瓷学中称为视密度( Apparent Density)。
量测范围：包含样品物体内封闭孔隙所测得之密度。
代表性产品：橡胶、塑料产品、硬质合金、***等或外部液体不能渗入之粉末烧结产品或孔隙小之材料和多孔性产品。
2：具渗透性产品的密度 (Permeable Density) 所定义之体积含开放孔及封闭孔，粉末冶金中一般所称之烧结密度即属此，在精密陶瓷学中称为体密度(Bulk Density)。
量测范围：包含样品物体内封闭孔隙与开放孔隙所测得之密度。
代表性产品：粉末冶金、精密陶瓷、氧化磁铁、土壤、吸水性材料…等或外部液
体可渗入之粉末烧结产品或孔隙大之材料和多孔性产品。
Once we referred to the『density』will put we in mind of the Archimedes scientist immediately. He applied the water displacement method and buoyancy method let us know basic concepts. That is 『 density』 equals weight divided by the volume.
However, as market demand, the new composite materials h***e been developed one after another, instead of the traditional manufacturing methods. As the new material substitution, but also changed the measurement methods of density for new materials and products. According to ASTM standa*** for materials and products has been divided into：
1、Non-absorbent or porous materials and products containing less than 2% porosity .
2、Absorbent or porous materials and products more than 2% porosity.
Open pores
Therefore, for materials or products made at this stage of the density measurement is also a new classification. We will be divided into two measurement method:
1、Apparent density： The density of impermeable product as defined by the volume contained closed pores, or open pores will not be water infiltration who called apparent density.
Measuring range: The measured density contains the sample within the closed pores.
Typical products: rubber, plastic, hard alloy, precious metals, etc., or an external liquid can not penetrate into the porous sintered products of powder metallurgy or the ***all porosity of the materials and porous products.