Wednesday, April 22, 2009

Calculating Handspun For Weaving

By Leigh

I decided I would start this series the way I ordinarily would, by looking what I will need for the final product. In the next post, I will show you how I measure my handspun.

If you are a weaver, then you are already familiar with how to measure warp and weft for your projects. If you don't weave, then all of this may be quite foreign to you. My goal is to explain this so that non-weavers can get the gist of what goes into the process. I will try not to get too technical, but I may get long winded!

I've already mentioned that I have my eye on the Folkwear Turkish Coat pattern for the pol-paca I've been spinning. The obvious question is, how much yarn will I need to spin for this coat? As with any sewing project, the first thing I need to know how much fabric is required. Below is the information I found on the back of the package:

Click on above for a better look-see.

I have a 59 inch width loom, but only the first two measurements are possible for me. Why? Because of several factors that aren't apparent at first glance. Besides planning for finished fabric length and width, I also need to allow for loom waste, take-up, draw in, and shrinkage.

Loom waste - the part of the warp that is tied to the front and back of the loom and doesn't get woven. This can be anywhere from 18 to 36 inches depending upon one's loom.

Take-up - the result of the over and under path of the yarn as it is woven. Usually 10% is added to the project length to allow for this.

Draw-in - the pulling in of the selvedges during weaving. Usually 1 to 2 inches is allowed for this.

Shrinkage - From wet finishing (washing and drying) the fabric after it's off the loom. While this varies with the type of yarn, typically 10% is added. However, if the weaver is unsure, it is imperative that a sample is woven, washed, and dried!

Consider too, that the fabric is stretched tightly on the loom during weaving Simply cutting it off the loom causes it to relax and "shrink" somewhat. All these things must be accounted for when planning how much yarn will be needed for any project.

Let's say I plan to go with the second measurement, for a width of 45 inches, and length of 3 and 7/8 yards. I need to consider several things in order to plan the amount of yarn I will need. The formula I need to use looks like this:

Desired finished project length
+ fringe or hem (none here as it is yardage for sewing)
+ take-up (about 10%)
+ shrinkage (another 10%)
+ loom waste (I allow 24")
= total warp length.

I usually calculate in inches, and then convert to yards for measuring. Without boring you with all the math, I can tell you that to weave 3 and 7/8 yards of fabric, I will need a warp length of a tad over five yards. I will round this up to a minimum of 5.5 yards for the project.

What about weft? The formula for that is:

Desired finished width
+ draw-in (10%)
+ shrinkage (I'm allowing 2")
= total warp width

Taking all that into account, I need to plan on a width of about 52 inches on the loom, to end up with 45 inch wide fabric. If I wanted to weave the 54 inch fabric mentioned on the pattern, I would need to plan on a 62 inch width on the loom. With my loom only accommodating a 59 inch width, you can see why this isn't a possibility for me.

However, this doesn't tell me how many warp threads I'm going to need in order to put a 52 inch width of warp on my loom. For that, I need to decide how many threads per inch I want my fabric to be. Here are a few more terms to help explain that:

EPI - Ends Per Inch, i.e. threads per inch

Sett (noun), Set (verb) - referring to ends per inch.

Obviously, the more ends per inch, the thicker and heavier the fabric will be.

Calculating sett is a science in itself. I often use charts, such as these. Or methods such as these or this. But for this example, I'm going to rely on experience, and choose a sett of 8 epi. This is based on my working similar size acrylic knitting yarns for twill afghans. I will weave a sample before actually warping for the pol-paca cloth, and this will let me know if adjustments need to be made. If the sample is too thick or too heavy for a coat, I will try a lower sett. If it isn't thick enough, I will increase the sett.

Armed with that number (8 epi), I can figure out how many warp ends I will need.

52 inch width on loom
x 8 epi
= 416 ends

Multiply this by the 5.5 yard length I need to warp, and I come up with a total of 2288 yards of handspun required for the warp.

And for the weft? First, a few more terms:

Pick - term for individual weft threads

Shot - same as pick

PPI - Picks Per Inch

If I plan to make a "balanced" cloth, i.e. with as many weft picks per inch as warp ends per inch, then I will use 8 (the EPI), to multiply by the number of inches in 3 and 7/8 yards.

52 inch width on loom
x 8 PPI
x 140 inches in 3 and 7/8 yards
= 58,240 inches, which rounds up to 1618 yards needed for the weft

Assuming I've calculated correctly then, I will need approximately 3906 yards of handspun yarn to weave the fabric for this coat. Plus a little more for the sampling.

So, how much handspun do I have so far? We'll look at that next time.

Posted 23 April 2009 at http://leighsfiberjournal.blogspot.com

Related Posts:
Spinning For Weaving, Knitting, Crochet, Etc. An Introduction
Calculating Sett
Another Way to Calculate Sett

12 comments:

  1. Great explanation Leigh. I'm so eager to get my loom set up again and to have access to so many weaving possibilities. Plans are afoot to make this possible.

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  2. I am very interested in this as a new spinner! but I don't think I am spinning warp yet...

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  3. Oh what a great pattern for that lovely yarn you've spun! Such a thorough and understandable tutorial too.

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  4. thanks for this - I know I'll come back to it at some stage! though I think weaving for a coat might not be feasible just yet for me:)) it sounds like you still have a lot of spinning in front of you, before you can start to weave...

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  5. Really enjoyed your lucid descriptions :) I had to do the math myself for a handspun project in the works recently -- it was a bit surprising to think of things in yards rather than my knitter's-brain ounce thinking.

    One question -- why is there no allowance for take-up in the weft? or is that handled by the draw-in calculations done for the warp width (52 in.)?

    Thanks! Amelia.

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  6. Thank you one and all for the feedback! I always wonder how well I explain the technical stuff and hope it makes sense.

    Janet, I can't wait to see some weaving content on your blog!

    Bettina, actually I figure if I can just get the warp spun, I can spin as I weave the weft. :)

    Amelia, good question. One term, "take up" refers to warp, the other, "draw-in" refers to the weft. They are both describing the same thing basically, but one refers to length and the other to width.

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  7. Weaving the full 60" of your loom would get very very tiring and be hard on your body. So you are very wise to weave a narrower width fabric. Your yarn should full beautifully and that is going to be as important to the look of your coat as the weaving itself. So you might want to weave more than one sample and try two different setts, one a bit looser than you think appropriate, and then run fulling tests on each of them. You might end up recalculating the length and width you need to weave depending on the fulling results. I assume these will be small narrow samples so I would weave a bit extra so that when you are done, you can practice fulling (keeping records, of course---grin!) on the larger sample.

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  8. Math was always a weak subject for me but I had enough under my belt to manage our finances. I didn't realize how weak my math was until I started weaving. It's not a one size fits all formula. You've got epi, loom waste, shrinkage and whatever I have forgotten.

    I think East Coast weavers have a better time of it. You've got the time-worn tradition of weavingfrom the historic mills. We on the West Coast thankfully have Deb Chandler's book and blogs like yours. The more I weave, the more I want to weave and the more I weave, the more I know that I don't know enough.

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  9. You are like having a online class but yours is free! Thanks!

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  10. Thank you for this in-depth post. Now I know finally what picks per inch means!

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  11. Wow--wonderful information here...so MUCH to learn from! Thanks Leigh, for explaining it all!

    I think I have to print this post out...and the links...and keep it handy for future use! You make things easy to understand!

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  12. Leigh.... You are so GOOD! I have reccomended your site to several students and I know that you have at least one lurker who is learning so much! Thank you!

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