Contact sponge method
Analytical technique description:
Contact sponge method is a water absorption test by side of the studied material that can be performed also in situ.
A sponge having preset characteristics and dimensions is charged with an adequate amount of water (when it is in contact with the surface, it has not to leak). For the application on the examined surface, a circular plastic plate is used.
The amount of water absorbed by the surface is calculated by difference, weighing the sponge before and after the application. The precision of the measurements directly depends on the precision of the used balance.
Contact sponge method is easy applying in situ, unlike other water absorption methods. Water absorptions measurements are very widespread because they are useful for the evaluation of the conservation state of a surface and of the performance of conservative treatments, in particular protective ones.
Contact sponge method is based on the measurement of the amount of water absorbed by the side of a porous material. Such amount of water absorbed is determined by difference, weighing not the substrate (enhancement of weight, absorption), but the sponge (decrease of weight, desorption).
Instrumental details:
Test Kit: sponges Spontex1 Calypso type, in natural fibers,  cut by means of die cutter having 55 mm diameter (surface 23,76 cm2), circular plastic plates Falcon 1034 Rodac Plate type, portable balance (Florence Unit, Milan Unit).
Via Madonna del Piano, 10 - 50019 Sesto Fiorentino (FI)
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Institute for the Conservation and Valorization of Cultural Heritage