‘Blind’ refers to a print feature that is applied without the addition of any other print feature. In most cases, this will have the blind feature show as the same colour as the cardstock, but manipulated in some other way. For example, blind deboss would press a design into a cardstock without changing the colour of the cardstock, whereas deboss + foil stamping would press a design into a cardstock as well as apply foil to that design. In some cases, a blind feature may be applied over another print feature, but still be considered blind – for example, if the whole front face of a white card is printed with an image, but a logo is being embossed without any other print feature directly over that printed image, that emboss is still blind as it is not directly applied with its own corresponding additional print feature (such as a foil).
