The yardages given in this chart are for 100% wool. The ratio of yards per ounce is not an exact science as there are many variables, which determine this ratio.
Spins, slubs, tweeds, quality and processes (Superwash), all alter the ratio of yards per ounce per yarn weight category. Luxurious fibers, including alpaca, silk, mohair and camel hair, as well as cotton, linen, rayon and blends of any of these fibers have their own ratios of yards per ounce per weight.
Regardless, any fiber, if it is true to a weight category, will obtain the required gauge on the given needles in Stockinette Stitch, yielding a desirable fabric – one that is not too dense (tight), or too loose (Í).
Penny Straker is now 70 years old and still working at both her knitting and gardening businesses. Please note that from April 1 through November 1, her time to respond directly about pattern-related issues is extremely limited due to the long hours of her gardening business. In an effort to assist knitters who may need help or have questions, we’ve set up a Ravelry group with a help thread. Your questions may also help others if posted publicly.