In many of the classes I taught on tentmaking, somebody would ask me to explain what terms like "canvas," "duck," and "seconds" mean. I would have a strong temptation to point toward the window and say "Look! There! Out the window!" and make my escape in the ensuing pandemonium. This is because the explanation of any of these terms tend to be a lot more complicated than I can easily deal with in a few words, even words as succinct and apt as you know mine to be. However, when you buy cloth, salespeople are going to come at you with all sorts of different terms to describe their wares. You end up wondering what these terms mean at all, and whether it makes any difference in choosing fabric. Hence, this month's column.
Let's start with the word "canvas." Originally, it meant cloth woven from hemp fibers. The similarity between the word "canvas" and the word "cannabis" betrays its origin. Yes, it's the same species of plant that produces Willie Nelson's favorite agricultural product, although the industrial version bears as much relation to wacky tobaccy as a Great Dane bears to a Chihuahua,
It wasn't too long before canvas came mean what it does today ... any cloth weighing more than, say, eight or nine ounces per square yard. It could be woven loosely or tightly, and could be made from anything from hemp to cotton to synthetic yarns, or a combination of any two or three of them. Nowadays, cotton is what most of it is woven from, although cotton/synthetic blends (usually polyester) are popular in applications that require more resistance to stretching.
Another term you hear a lot is "duck" or "army duck." "Duck" is from the Dutch word "doek" meaning cloth. Any kind of cloth. But for English-speaking people, it has a slightly more specific meaning: a closely woven, heavy fabric. How heavy? Again, it's generally taken to mean nine ounces or more, although the range is broad enough to include fabric up to twenty ounces or more. "Army duck" is duck that is used by the army for things like tents, truck covers, and the like. It doesn't specify any particular type of weave, weight, or application, so when people toss the term around as though it really means something, beware.
Before we delve much further into this subject, I'll have to explain some weaving terms, because the types of duck vary mainly in how they are woven. We'll start with some definitions.
A "yarn" is simply a bunch of fibers that are twisted together to form a single continuous strand. Most are "single-ply" meaning that the fibers have gone through a single twisting operation, although some are "plied" yarns, meaning that two separate pre-twisted yarns are twisted together to form a single fatter yarn that is more stable, since the second twisting operation is in the opposite direction from the twisting operation used in making the original yarns. Almost all manila and sisal rope is plied.
There are two ways a yarn can run when woven into cloth. It can either go along the the length of the roll, in which case it's called the warp, or end yarn, or it could go back and forth across the width of the roll, in which case it's called the fill, or filling, or weft. When these cross in a simple, uncomplicated over-and-under pattern, the result is what we call a "plain" weave.
Note that the creative weaver can control how much the cloth stretches, and along which dimension, by varying the thicknesses of the two yarns, or the amount of tension given each yarn in the weaving process, or both. (To get a visual impression of what a cloth looks like when it's woven with different tensions in the yarns, go get a package of spaghetti. Boil up half of it to "al dente." Lay some of the uncooked strands on a table, parallel to each other. Now take a strand of the cooked stuff, which is now soft, and weave it over and under the hard, uncooked strands. Repeat with another strand of the cooked stuff, reversing the over-and-under pattern. Keep on doing this until you get bored or hungry for some of that spaghetti, and wish you had some marinara sauce to go with it. What you've just built is a model of what a cloth might look like if some of yarns (usually the fill yarns) are woven under high tension -- those are the uncooked strands -- and the crossing yarns (usually the warp yarns) are woven with low tension -- the cooked strands. The cloth manufacturer might want to weave a such a cloth for an application that requires an absolute minimum of stretch along one axis, such as conveyor belts or sails.
If both the warp and the fill yarns are roughly the same size, and are under roughly the same tension, the result is a "square weave" cloth.
If we want to get fancy, we could arrange it the fill yarn goes over one warp yarn, and then under two of them. Then, on the way back, we run our fill yarn over two of them, and then under one. On the next row, the same over-under-under pattern is repeated, only shifted over one yarn. That's what we call a "drill" cloth.
Similarly, we could run our fill yarn so that it goes under one warp yarn, then over the next three yarns. Again, on the next pass of the shuttle, the pattern is staggered over one yarn. That produces a weave called a "twill" cloth.
(At this point, I thought I was detecting a pattern. If "drill" means dwo, or two, and "twill" means three, what would four yarns be? "Quadrill?" With great expectation, I went to my unabridged dictionary and found out that "quadrille" was either a French square dance or a Spanish card game. Rats. Another brilliant theory down the drain.)
The next terms used to describe canvas are "single-filling" and "double-filling." These terms tell whether one fill yarn alone, or multiple fill yarns plied together, are passed through the warp of the cloth with each pass made by the shuttle through the warp yarns. While 8-ounce duck generally has two fill yarns plied together, 10-ounce duck has three yarns, and 12-ounce has four yarns, all of them are designated as "double-filling" duck. The cloth industry seldom passes up any opportunity to confuse us.
Anyway, we are now armed with enough information to resume our analysis of what (if anything) the various labels mean.
There are a few generally recognized subsets of duck cloth. They are:
Flat duck is duck that is woven with a flat weave. That really doesn't tell you much, does it? Would it help if you knew that it was also called "Wagon Cover" duck, "enameling" duck, "single-fill" duck, or "double-fill" duck? I didn't think so. My Astrup catalog helpfully adds that "Wagon Cover" duck is a "single or double filling flat, or ounce duck, woven in standard widths for 48, 50,60, 66, 72, 84 and 90 inch widths" and include weights of 8 ounce, 10 ounce, and 12 ounce.
The Astrup catalog says that "ounce duck" is "a term applied to single and filling ounce ducks, or flat ducks, produced in the basic widths of 36, 48, and 60." So an ounce duck is an ounce duck. And a flat duck is a flat duck. Or maybe an ounce duck is a flat duck, and vice versa. Excuse me while I let out a groan of frustration.
This is a plain-weave duck, using plied yarn in both the warp and the fill. It comes in widths from 22 inches to 150 inches, last time I checked, and in weights from 7 to 30 ounces per yard. (The "yard" in this case referring to a piece with dimensions of 22" x 22" -- don't ask me why). The "number" refers to a designation given each each category of weight and construction (the number of plies used in the yarn); the numbers range from 2/0 to 12. So for once, we get a cloth specification that actually means something, although you'll need a specification chart to know what it means. Fortunately, such a chart can be found at the web site of the Texas Building and Procurment Commission.
There are a few more terms that your cloth salesperson may throw at you. Here's what they mean:
This is a native American cotton, with long fibers that make it easier to spin then the Old World varieties. It also goes by the name "Egyptian" cotton, which may confuse you until you realize that the British introduced it to Egypt (then a British colony) in the nineteenth century when the American Civil War made it difficult to obtain the desirable long-staple cotton from the temporarily dis-united United States.
This is a catch-all term for cloth that, for various reasons, can't be sold as top-quality cloth. The method for determining whether the cloth is first-quality, second-quality, or worse is usually a matter of degree. The cloth is subjected to a grading system, and if it exhibits more than a given number of flaws, it is down-graded to second-quality. There's a limit to what they can sell as seconds; if it exceeds that limit, the manufacturer must describe exactly what it was that caused the cloth to be down-graded.
Seconds can be real bargains, if you can work around the flaws. It really helps here if you have a good relationship with your cloth salesperson, because he or she will sometimes take the trouble to find out exactly what it was that made the cloth second-quality rather than first quality.
These flaws typically fall into the following categories:
Color flaws or irregular color. Most cloth customers are pretty picky about the color, and won't tolerate any variation in shade, or in variations in the depth of the color from one part of the roll to the other. Rather than junk the cloth, they dyer can either sell the roll off at a discount or attempt to re-dye it black. Obviously, there's a finite market for black cloth, and if they already have a lot in stock, they are willing to sell the mis-dyed cloth instead.
Irregular Selvage. "Selvage" is the name given to the side border of the cloth as it comes off the roll. The term comes from the phrase "self edge" -- the edge formed as the fill yarns wrap around the outer warp yarn as it reverses direction. Nowadays, it's used to refer to the side edge, even if the cloth is a canvas that's been woven over-wide and then trimmed to a specified width.
Sometimes the selvage of the cloth is a bit ragged, wavy, or tighter than the rest of the roll, so it can't be used as an edge. This raises hell with factory production, as the selvage has to be trimmed by hand before the cloth can be used. And if too much of the cloth has to be cut away, the factory may not be able to lay out their patterns in the most efficient way.
Yarn, weave or finishing irregularities. This can be open areas left when the fill or warp yarns have been improperly spliced, or weirdnesses that result in the finished cloth not wanting to lay flat or straight as it comes off the roll.
Oil or Dirt Stains.Occasionally, you see cloth that got soiled as it went through the finishing process, leaving minor discolorations. You see this most often along the selvage of the cloth. Again, you might be able to work around it, particularly if you're making a round pavilion with tapered panels and you're going to end up cutting off and discarding most of the selvage anyway.
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