Wednesday, October 17, 2012

The Fudge Factor Part 3

Part 3 of a series explaining how to convert gauge in knitting patterns.
The adjustment of the sleeve increases and decreases need to be carefully reviewed as the rounding off of fractional numbers in the original source pattern can lead to some odd shaping. Patterns are written to be easily interpreted across multiple sizes, in ways not necessarily consistent when you work with only a single size. When doing the calculations for the decreases of an underarm or a neckline, check your results by validating your numbers on both the individual decrease steps, as well as the sum of the decreases added together. Adjust the decreases accordingly. Sleeve increases can be more easily and accurately calculated using knitters’ graph paper. Knitters’ graph paper accurately reflects stitch and row gauges as rectangles rather than squares in the manner of regular graph paper. A more accurate angle is calculated using this paper, even if the decreases are not evenly spaced, as they are when calculated mathematically. Graphing also offers the option of creating a contoured sleeve shape which more closely aligns with arm shape as opposed to the often used simple straight angle. Round any fractional numbers off to the nearest whole number. End the increases at least an inch before the rows are completed.
To determine the cast on, multiply the cuff measurement by the stitch gauge.
Example: 9 inches x 4.5 stitches per inch = 40.5 stitches.
Adjust this number if a stitch pattern has to be taken into consideration and if adding selvage stitches for seaming.
On a 6 stitch pattern repeat with 2 seaming stitches,
6 stitches x 6 repeats = 36 + 2 selvage stitches = 38.
36 stitches ÷ by gauge = 8 inches
6 stitches x 7 repeats = 42 + 2 selvage stitches = 44.
42 stitches ÷ by gauge = 9.3 inches
Choose the stitch number best for the project.
Calculate the wider top part of the sleeve. 15 inches x 4.5 stitches = 67.5 stitches.
This number should match the first as being either odd or even. In this case the closest even number is 68. The numbers should match, as all increases will be done in pairs.
Using the desired sleeve length measurement, multiply the length by row gauge.
Example: 16 inches x 6 rows = 96.
(Don’t forget to adjust the measurement if there is a band to take into consideration).
The number of stitches to increase is the difference between the top numbers and the bottom: 68 – 38 = 30. Divide the number in half since we will be making an increase at each end of the needle.
The result means we need to increase 15 times.
On the graph paper, draw in a short straight section at the top where no increases will be worked. Draw in the diagonal line and mark in the 15 stair steps increases. Remember the increases are normally worked on right sides only so work in two row increments.
If the garment being converting has picked up bands, you will be able to fudge factor the stitch counts provided.
If you made length adjustments, it is better to use stitch pick up rates. The stitch pickup rate is a stitch for a stitch on horizontals; three stitches for every four rows on vertical edges; one stitch for every cast off step on curves and diagonals. Some diagonals advise a pickup for every row depending on the angle. The closer the angle moves to the horizontal the higher the number of stitches required. 
These ratios assume a standard stitch to row gauge ratio and are approximate. Often knitters work towards stitch gauge and completely ignore row gauge while swatching. This can lead to abnormal ratios and will impact the band results. It is for this reason some references quote the ratio as five stitches for every seven rows or two stitches for every three rows. Some change the ratio according to the stitch gauge and use the two to three ratio for gauges less than four stitches per inch. The ratios are based on stocking stitch. For garter stitch the ratio is one pickup for every ridge (two rows). On rare occasions, a pattern might change the ratio as the band pickups cross over a different main body stitch pattern.

Yarn requirements can be recalculated by comparing your gauge to the original gauge. There are three error factors with this calculation. The first is created by the individual knitter. Since the knitter is unable to swatch with the original yarn there is no way to know if the stitch and row gauge ratio would have matched the gauge of the original yarn. The second error factor comes from the standard industry practice of increasing yarn amounts by 10 to 20% to account for row gauge differences. The third error factor is caused by the yardage being calculated to match the numbers for the skein or ball yardage of the original yarn. Designers always round up in this situation. Use a similar existing pattern for the yarn substitute or a generic yardage chart whenever possible as a comparative verification.
Example 1: Converting to DK (Yarn Weight Number 3) from Worsted weight yarn (Yarn Weight Number 4)
Your Gauge DK: 22 stitches, 28 rows = 4 inches
or 5.5 stitches, 7 rows = 1 square inch
5.5 x 7 = 38.5 stitches/square inch
Original Gauge (the pattern) Worsted: 18 stitches, 24 rows = 4 inches.
or 4.5 stitches, 6 rows = 1 square inch
4.5 x 6 = 27 stitches/square inch
Fudge Factor
38.5 ÷ 27 = 1.42
Your yardage is the unknown number; apply the fudge factor.
The pattern calls for 1600 yards
1600 yards x 1.42 = 2272 yards
Example 2: Converting to Worsted weight yarn (Yarn Weight Number 4) from DK (Yarn Weight Number 3).
Your Gauge in Worsted: 18 stitches, 24 rows = 4 inches.
or 4.5 stitches, 6 rows = 1 square inch
4.5 x 6 = 27 stitches/square inch
Original Gauge (the pattern) DK: 22 stitches, 28 rows = 4 inches.
or 5.5 stitches, 7 rows = 1 square inch
5.5 x 7 = 38.5 stitches/square inch
Fudge Factor
27 ÷ 38.5 = .70
Your yardage is the unknown number; apply the fudge factor.
The pattern calls for 1950 yards
1950 yards x .70 = 1365 yards                              
I would recommend you photocopy your pattern, highlight all the numbers pertinent to your size then go through applying your conversion ratio to each number.
Use the schematic if your pattern has one, as a check for each of your numbers, by multiplying your gauge by the measurements provided.
To be sure the garment will fit the way you envision it, measure a similar sweater which fits well and compare the measurements to those you are about to knit. The amount of ease (the difference between your measurements and the garments measurements) is a very personal choice. There is no guarantee the original pattern included the amount of ease you would have been happy with.
It is often best to stay within the same fiber type when choosing a different yarn. The properties of, for example, cotton versus wool vary greatly, so look carefully at your chosen design when substituting. A heavy cabled garment may work well in wool but is far too heavy in cotton. A straightforward stocking stitch design will usually work in both fibers. Some stitches easily produced in a wool with good elasticity may be difficult to work in inelastic linen or hemp. Some fibers like silk or rayon have drape and will grow in length. Experience is the best teacher in these cases.

 Part 1 can be found here.

Part 2 is here.

1 comment:

  1. Thanks a lot for this serie on conversions. It has clarified this issue for me very much!