sheet material containing micro cavities, of the type with visible signs when a liquid surface is applied to the micro cavities.the improvement is to make the liquid surface is maintained in juxtaposition of pseudo particles by a heat curable binder civil and ensure that a valueforce imaging of at least 2 g - force is reached, thus making the structure should have a marking when it is inadvertently in the heat, the pressure.one or both.
展开▼
