Thursday, September 18, 2008

Knitting Math Part 2

* * * * * * * W A R N I N G * * * * * * *


The last time we talked about knitting math, I covered how to calculate proper yardage for a project. That information can be used to design a new pattern or change a current pattern into a different gauge.

The next step involves plotting the gauge to full scale. Converting an existing pattern will give you exact cast-on, decreases and bind-off stitches to match your new gauge.

(yarn shots thrown in to help you deal with the math overload)

The simplest part of this takes some measuring or pattern checking. For instance, if you have a sweater where the front is 20 inch wide by 22 inches long. Your gauge measures at 4 stitches to the inch and 3 rows to the inch, then the math would look like this:

20 x 4 = 80 stitches to cast-on

22 x 3 = 66 rows will result in proper height.

Most of the time when a pattern tells you to knit until piece measures so many inches, I don't convert that section. You'll just knit to that length whether it's for armholes or necklines.

The trickier part of pattern conversions comes when you have decreases over a defined area. For example on sleeve cap shaping. If the pattern reads decrease at edge 1 stitch every other row. This will have to be examined to your new gauge and as I had to do this just recently I will give you the sample I worked on...

Original pattern calls for this cap sleeve shaping:
BO 5 st at the begin of next 2 rows (50 st remain)
DEC 1 st at each end of every needle every other row 4 times,
Then every row 14 times
BO 14 remaining st

The Shaping of Cap on Sleeves:
Pattern schematic has the width at 17 inch at the point where the shaping begins. Shaping of cap will happen over 7.5 inches ending with a width of 4 inches to bind-off. From the above description of the original shaping we see that the first BO action is dramatic. This quick BO will create a notch on both sides which should match the bind-off for the armholes.

We then have more decreases, but at a slower pace. A total of 8 stitches decreased every other row. You'll need to look for the row gauge of the original, which is 13 rows = 3 inch (or 3.25 rows per inch). Decreasing happens over 8 rows (every other row [2] x 4 dec)... then we calculate over the row gauge (8 rows ÷ 3.25 per inch = 2.46 in). This tells us that the slower pace decrease happen over a 2.46 inch span.

We'll then match this with our row gauge... 13 rows = 3.75 in (or 3.5 rows per inch) – please note I round up when I need to. We take this number (3.5) and find how many rows we'll need to do the slower decreases.

3.5 rows per inch x 2.46 inch = 8.61 rows

This shows not much of a change or difference between the original row gauge and new row gauge. Yet my stitch count is greater and I have to decrease significantly over a shorter distance.

The remaining 5 inches would have to accommodate a larger decrease amount compared to the original gauge. Instead I take a look at an overall decrease of the full sleeve. If I calculate so see how many times per row I would need to decrease my stitch count from 70 stitches to 20 over the full cap... 50 stitches ÷ 2 (for each edge of cap) = 25. Then divide that times our row gauge: 25 ÷ 3.5 = 7.14 inches. That puts us closer to the length of cap shaping we need verses planning out each row of decrease.

To make up for the .35 remaining I'll do a non-decrease row in the beginning which will give us plenty of length on the cap.

My pattern conversion:
BO 6 st at the begin of next 2 rows (70 st remain)
K 2 row in pattern. Ending on WS row.
DEC 1 st at each end of every needle until 20 stitches remain
BO 20 remaining st

Pattern converting can become a challenge. If you break it down section by section and have your calculator, pencil and paper handy it can work out just fine. Always take notes and jot numbers down. It's a process and if you need a break, take one.

Just knowing that it is possible to end up with a garment worth knitting is huge to me. I'm sure most people would say it's just not worth it. That is totally fine too. I would rather know that it's possible then to feel like there is nothing I can do about it.

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