Have you ever been confused when you requested, say, an 80# cover and were asked if that is a text weight or a cover weight? What exactly is the difference? And why can’t you just say an 80# cover?
A paper’s basis weight is determined by the weight of 500 sheets of that paper when cut to a designated dimension. But here is the thing; the dimensions are different for different categories of paper. For coated papers that are classified as cover stocks, the dimension is 20” x 26”, while the dimension for papers that are classified as text stocks is 25” x 38”. Therefore, on a square inch basis, cover stocks are heavier, thicker and more opaque than text stocks with corresponding basis weights.
When designating a text stock, the assumption is that you are using a text weight, since cover weights are rarely used for the text of a publication (so if you say “60#”, the assumption is you mean a 60# text paper). However, if you request an 80# cover, that could mean an 80# text weight for the cover, or an 80# cover weight for the cover, since both are commonly used for covers. However, the difference between the two is significant.
When designating a basis weight for your cover, the clearest means of avoiding confusion is to request your cover as follows: 80# cover, text weight or, 80# cover, cover weight.