Enamel can be transparent, opaque or opalescent (translucent). Diamond is an optically anisotropic crystal that is transparent to opaque. A hydrocolloid dressing is an opaque or transparent dressing for wounds. Various categories of OXCs include electronic ("opaque"), optical ("transparent"), and wavelength selective devices. It is often opaque or colored using pigments. Morion is a very dark brown to black opaque variety. Switchable projection screens can be switched between opaque and clear. They are also typically available in two versions&colon; colored or clear/opaque. Streak is particularly important as a diagnostic for opaque and colored materials. This makes gouache heavier and more opaque, with greater reflective qualities. The white, opaque and gray phenotypes form a tristable phenotypic switching system. It is clad in a combination of opaque and vitrolite glass. It is similar to but not as opaque as titanium white. This scattering means that crystalline PET is opaque and white in most cases. It is supposed to be thick, opaque, and loose.