一旦提到『密度』就立即让人想到阿基米得这位科学家，他应用水中置换法、浮力法让我们了解『密度』等于重量除以体积的基础观念。但由于市场的需求，新的复合材料陆续被发展，代替传统的制造方法。由于新材料的替代，也改变了对材料和产品的密度量测方法的改变。根据ASTM已将材料和产品分为：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(ImpermeableDensity)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(ApparentDensity)。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(PermeableDensity)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(BulkDensity)。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。Oncewereferredtothe『density』willputweinmindoftheArchimedesscientistimmediately.Heappliedthewaterdisplacementmethodandbuoyancymethodletusknowbasicconcepts.Thatis『density』equalsweightdividedbythevolume.However,asmarketdemand,thenewcompositematerialsh***ebeendevelopedoneafteranother,insteadofthetraditionalmanufacturingmethods.Asthenewmaterialsubstitution,butalsochangedthemeasurementmethodsofdensityfornewmaterialsandproducts.AccordingtoASTMstanda***formaterialsandproductshasbeendividedinto：1、Non-absorbentorporousmaterialsandproductscontaininglessthan2%porosity.2、Absorbentorporousmaterialsandproductsmorethan2%porosity.OpenporesCloseporesTherefore,formaterialsorproductsmadeatthisstageofthedensitymeasurementisalsoanewclassification.Wewillbedividedintotwomeasurementmethod:1、Apparentdensity：Thedensityofimpermeableproductasdefinedbythevolumecontainedclosedpores,oropenporeswillnotbewaterinfiltrationwhocalledapparentdensity.Measuringrange:Themeasureddensitycontainsthesamplewithintheclosedpores.Typicalproducts:rubber,plastic,hardalloy,preciousmetals,etc.,oranexternalliquidcannotpenetrateintotheporoussinteredproductsofpowdermetallurgyorthe***allporosityofthematerialsandporousproducts.)