There are three main types of fabrics for internal window blinds. Blockout, aka dimout or blackout, Translucent also go by light filtering or sheer and Sunscreen or solar screen.
Blockout fabrics are coated or sealed with a backing to ensure no light leaks through the material weave. Blockout fabrics are an ideal choice where a high level of light block and privacy are required such as bedrooms and media rooms or provide ultimate privacy in bathrooms and public facing windows. Blockouts are great for reflecting and reducing heat in the home.
It is important to remember that even with a blockout fabric, it is hard to completely block all light coming through the window. Consideration must be given to gaps around the edges of the blind which will depend on the type of blind, and how the blind is manufactured and installed. Full light blockout is difficult to achieve however blockout fabrics when used with the appropriate blind and accessories such as a cassette roller blind can blockout nearly all light at the window making this application ideal for home theatres.
Translucent (also known as light filtering or sheer) fabrics allow light to filter through. Quite often translucent fabrics are the same as blockout before the blockout coating has been applied. Translucent blinds provide a softer look and feel than blockouts, and are ideal where filtered light is preferred sometimes avoiding the need for lighting to be turned on during the day. Translucent fabrics are an ideal choice for living rooms and other areas where privacy is not the major consideration.
Sunscreen (or solarscreen) fabric is an open weave fabric specifically designed to block heat and glare but allow good vision through the blind. Generally graded by their openness factor, typically 3% or 5%, Sunscreen fabrics are very popular in rooms featuring a scenic view and offices where heat and glare reduction is the main consideration.