During recent years starch has become probably the most frequently used biopolymer in ceramic technology.~(1-17) Starch can be used as a simple pore-forming agent (PFA),~(1-7) similar to other PFAs of biological origin, such as poppy seed or lycopodium spores,~(17-19) or as a combined pore-forming and body-forming (consolidating) agent, as in the process of starch consolidation casting (SCC).~(8-17) In both cases the starch type determines the shape and size of pores in the ceramic microstructure. When traditional slip casting (TSC) is used for shaping of porous ceramics (using starch as a PFA) the resulting porosity corresponds very well to the initial PFA-to-ceramic ratio. More precisely, the nominal PFA content (volume fraction of starch related to the ceramic powder in the suspension) is approximately equal to the total porosity in the fired ceramic. The percolation threshold for ceramics prepared by TSC with PFAs is approx. 18 %, i.e. only when this porosity value is exceeded, the pore space can be considered as interconnected.~(13) With SCC the situation is different. This method can be sucessfully applied only when the nominal starch content is higher than 5 – 10 vol.%, depending on the starch type, and the maximum content is approx. 60 vol.% or slightly higher, depending on the starch type as well as ceramic powder type and content.~(8-17) For low starch contents the porosity achieved with SCC is always higher than the PFA content (nominal starch content) and the pore space is predominantly open.
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