I've seen you answer your readers questions on your blog before and wondered if you would answer mine.
My question is: What do you think is more important, buying yarn by the weight, or by the yardage?
I am new to crochet and want to make sure I buy enough for my projects!
You have a great question there!
I think it would be ideal to say to go with the yardage, but since yarn is not sold that way, I cannot recommend it. I hear what you're thinking -- but Dee, my label says it's X amount of ounces and X amount of yardage! Yes, that is what the label says. And if you pick up another ball of yarn by the same manufacturer, of the same line, but is a darker color, and then read that label -- it will say the exact same thing!
So I ask, if a darker color yarn weighs more due to the dye, how is it possible that you'll get the exact same yardage as that of the lighter colored yarn without having to pay more money for it? You won't. And that is because of the dye that makes their weight, and thus their yardage unequal! The yarn manufacturer is using the exact same labels for that particular line, only changing the colorway/dye lot information.
Why do they use the same labels?This is because the majority of the time yarn is sold by weight. Else the manufacturer would be lose money that they had to lay out for the dyes! Think of the yardage listed on the label as more of a guesstimate. This is why, when looking at labels you will see "Approx / Approx / Aprox XX m / XX yrds" printed on the label as shown in the picture on the right.
(And if you ever swatched the same brand yarn -- light vs. dark -- you'll notice that the darker yarn is usually slightly thicker. Again, this is due to the dye!)
So, what is one to do to ensure they purchase enough yarn? I recommend buying extra -- a ball or two more. Not only will doing so ensure you have enough, but you can also work up that swatch (I really recommend creating two swatches so you can beat one up with laundering and have something to compare it to prior to staring the project. After all, why should we spend our valuable time crocheting up beautiful projects if the yarn ends up looking junky after washing?!). Buying extra yarn will also ensure you will also have enough yarn to leave the needed long tails for beginning & ending projects, cutting out the manufacturers knots (& properly rejoining the yarn), and possibly enough to go "off roading," the act of adding a bit of individual flavoring/designing to your project.
I hope this helps, & thanks for the great question! :)