Shrinkage drying methods

Drying methods and conditions, sample size, and shape have been shown to influence various physical characteristics including structure, density, porosity, shrinkage, and rehydration of dried potato products. These are important properties characterizing the texture and the quality of the dried potato product. 

After obtaining the wet gel, it follows a solvent extraction process to dry it. When a gel with low mechanical strength is dried by simple evaporation, capillary forces created at the curved hquid-vapour interface can produce the shrinkage of the pore stmcture. Therefore, a carbon without appreciable surface area (closed pores) is obtained. For this reason, the drying method has a decisive effect in the structure of material. There are several routes to dry the carbon precursor and each of them produces different change in the properties of material. 

Drying determines the nature of the final product and it is governed by surface tension of the gel. Volume shrinkage is most evident in this step as the pressure and temperature play important roles. Three types of drying method have been employed by researchers supercritical drying (SCD), ambient pressure rying (APD) and freeze drying (FD). 

Current research related to biological additives is focused particularly on their influence on the properties of mortars, namely on porosity, tensile strength, compressive strength, drying shrinkage, etc. [23, 24, 26], The identification of proteinaceous additives used in historical buildings has been marginal for many years and no reliable methods are properly described in the literature. 

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