Water Absorption (Ceramic)
Compute the water absorption of a ceramic piece, WA = (wet mass − dry mass)/dry mass·100%, the amount of water the open pores absorb by immersion. It is the property that classifies ceramic tiles: porcelain (WA ≤ 0.5%, very dense and strong), stoneware, semi-stoneware, semi-porous and porous (wall tile, WA > 10%). The lower the absorption, the more sintered and resistant the piece. Enter the wet mass and the dry mass.
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Water absorption (ceramic tile)
Water absorption, WA = (wet mass − dry mass)/dry mass·100%, is the single most important property in the classification of ceramic tiles — and it says everything about how far the body has been sintered. It is measured by weighing the dry piece, boiling it (or pulling a vacuum on it) in water so the open pores saturate, and weighing it again: the water taken up reveals how much open porosity the body has. The scale set by ISO 13006 / NBR (the Brazilian standard) defines the groups: porcelain tile (WA ≤ 0.5% — all but impervious, dense, extremely hard, fit for outdoor areas and heavy traffic); stoneware (0.5–3%); semi-stoneware (3–6%); semi-porous (6–10%); and porous (WA > 10% — the light wall tiles, easy to cut, but which take neither frost nor heavy traffic). The lower the absorption, the more the body has vitrified, and the better it resists mechanical load, staining and freezing (water sitting in the pores expands as it freezes and cracks the piece — which is why outdoor floors in cold climates call for a low WA). It is also what separates vitreous tableware (WA close to zero) from an earthenware pot (porous, it 'breathes'). Enter the wet mass and the dry mass.
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Vitrification Degree (Ceramic)
Estimate the vitrification degree of a ceramic, VD = (1 − WA/WA_green)·100%, comparing the current water absorption with that of the green (non-vitrified) material, as a measure of how much the glassy phase filled the pores during firing. Vitrification — the formation of molten glass that seals the pores — densifies the piece, lowers absorption and raises strength and impermeability. It is what turns porous clay into vitreous porcelain. Enter the current and green water absorptions.
Knoop Hardness (HK)
Calculate the Knoop hardness, HK = 14.229 × F ÷ d², from the load F (kgf) and the long diagonal d (mm) of the elongated rhombic indentation left by a Knoop diamond indenter. The result, in kgf/mm² (HK), is used mainly for microhardness of brittle materials, coatings, glass and ceramics, and thin samples: the Knoop's elongated, shallow indentation measures narrow layers and hardness gradients better than Vickers and is less sensitive to microcracking. Enter the load and the long diagonal of the indentation.
Cobb (Paper Water Absorption)
Compute the Cobb value of a paper, Cobb = mass gain (g) / area (m²), in g/m², the amount of water absorbed by one face of the paper in a standardized time (usually 60 s). It measures resistance to water penetration, crucial in packaging papers, printing (glue/ink control) and products that contact liquids. A low Cobb indicates good sizing. Enter the mass gain and the tested area.
Sintering Relative Density
Compute the relative density of a sintered body, RD = (bulk density/theoretical density)·100%, the fraction of the maximum density (of the fully dense, pore-free material) the piece reached. It is the central measure of the degree of sintering: advanced ceramics aim for RD above 99% (almost pore-free) for maximum strength and properties. The residual porosity is 100% − RD. Enter the bulk (sintered) density and the theoretical density.
Apparent Porosity (Ceramic)
Compute a ceramic's apparent porosity, AP = (wet mass − dry mass)/(wet mass − immersed mass)·100%, the volume fraction occupied by open pores (accessible to water), measured by Archimedes' method. Unlike water absorption (relative to mass), apparent porosity is relative to volume. Open pores reduce mechanical strength and increase permeability. Enter the wet, dry and immersed masses (hydrostatic weighing).
Firing Shrinkage (Ceramic)
Compute the linear firing shrinkage of a ceramic piece, FS = (L_dry − L_fired)/L_dry·100%, the size reduction during sintering in the kiln, when pores close and particles draw together. It is a critical dimensional-control parameter: porcelain tiles shrink a lot (~7%), while porous ceramics shrink little. Variations in shrinkage cause product miscalibration. Enter the dry and fired lengths.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.