You'll Never Believe the Maths Involved.....
Over the years I have met many 'beginner' weavers who have been disappointed in their first project results and sometimes they have been completely 'put off' the craft of weaving. I'm still working towards encouraging these and new weavers to continue and enjoy this rewarding craft. When you follow a knitting pattern you use the thickness of yarn and size of needles recommended in the pattern instructions. Weaving is similar but you are likely to need to work out, for yourself, the size of rigid heddle in the case of Rigid Heddle weavers, or, in the case of table and floor loom weavers, the reed needed to 'spread' the warp threads on your loom.
Weaving yarn is not always sold in the small quantities of knitting yarns - 50 -100g.
You may have to buy a cone weighing 500g. Does your intended project need more than this? You need to know before starting, especially if your yarn supplier is not close by!
Recently, one of our daughters in law decided she'd like to learn to weave and of course I have encouraged her. I own a portable folding floor loom which I have mainly used for demonstrations at events where I have been selling my wares. So she has no need to buy her own equipment, at least until she is sure she wants to continue. I thought this the perfect opportunity to document the process from beginning to end.
A length of tweed for a shawl is the chosen project.
How much yarn do we need to buy? The chosen yarn is a Shetland type from Uppingham yarns. One that I had worked with before and had success.
Their colour chart with small sample skeins was ordered and 4 colours chosen, flannel grey and donkey being the main warp and weft colours, with heron and robin's egg chosen to create a square/check design. BUT how much would we need of each colour, especially the main 'ground' colours of flannel and Donkey? Thank fully I had some 'peacock' left on a cone, wraps per inch 24. A balanced 2/2 twill weave decided upon meant 16 ends to the inch warp and weft.
Now to exercise our brains:-
How long a piece of fabric you we need?
The piece I was to weave, on my Harris 4 shaft floor loom, was going to use the yarns in my last post 'Yarn De-stash 2019'.
I required 4 yards of finished cloth, 27" wide.
As you weave there will be 10% take up of the fabric width as well as on the length. This is because neither warp nor weft actually take a straight path across or along the length of woven piece, they 'wiggle' up and down as they interact with the yarn at right angles.
So, calculate to weave a length of 4 yards + 10%. i.e. 144" + 15" - for easy calculations 160" long.
BUT, the length you weave will shrink up to 15% in the wet finishing, so you need to weave fabric 160" plus 15% i.e 24" = 184" length weaving.
Hold on!!!! you have to add on your 'loom waste'. That is the length of warp needed to tie onto the front of your loom and the unwoven warp at the end of your weaving when you can't get a shuttle through the 'shed' (space) created when you go to weave another row. In my experience this is 30 to 36 inches in total.
So your warp needs to be 184 + 36 = 220" or 6 yards long.
N.B. These pictures are not of the project being calculate in this post.
HOW MANY WARP THREADS DO YOU NEED?
Warp width needs to be:-
To get finished fabric 24 " wide - add 10% for take up- i.e. 2.4 " = 26.4"
Now add 15% shrinkage = 30.3". For safety 31" wide warp
Therefore, the number of warp ends needed is 16(for each inch width) x 31 = 496 warp ends.
HOW MUCH WARP YARN DO YOU NEED?
Each warp end needs to be 6 yards.
So, you need 6 x 496 yards of warp thread = 2,976 yards
BUT to create a selvedge you need 8 extra threads- 1/2" - on each side of your warp i.e 16 x 6 yards of yarn = 96 yards.
Total warp needed 2,976 + 96 = 3,072 yards. 2,835.6 meters.
Uppingham Yarns say there are 2,875m in 500g of their Shetland style yarn!!!!!!!!!!!!!
Given there are 2 colours in the warp then a 500g cone of the main colour is sufficient for this projects warp.
WHAT ABOUT THE WEFT?
We have already calculated that we need to weave 31" width having taken shrinkage and take up into account and a length of 184".
For a 'balanced' twill weave there will be 16 weft threads across each inch of fabric.
16 threads of 31 inches in each of 184 inches of fabric = 91,264 inches of weft yarn =2,340 meters. So a cone of 500g/2,875m is sufficient for this project.
Again, 2 colours are being used in the weft so a cone of each is sufficient.
