Tag Archives: Preshrinking

It Is Not Worth It To Pre-shrink Size 4, 85% Cotton Yarn, Part 2

Crochet, Experiments, Proportion, , ,

DSC07418 The top row was made with preshrunk Premier Home,  85% cotton yarn, and the bottom row was made with the same yarn, but  unshrunk.  Hook sizes for the columns were G, H, and I, in order of increasing size.  The coasters were washed  in hot water and dried in a hot dryer.  Before and after this washing, the coasters in each row were weighed in ounces on my kitchen scale, and the average diameter was taken.

  1. The preshunk row before washing weighed 0.60 ounces, and had an average diameter of 3.62 inches.   After washing it weighed 0.55 ounces, and had an average diameter of 3.27 inches.
  2. The unshrunk row  before washing weighed 0.55 ounces, and had an average diameter of 3.31 inches.  After washing it weighed 0.55 ounces,  and had an average diameter of 3.31 inches.

After washing the preshrunk coasters felt a bit softer and thicker.

Thus the weight of the pre-shrunk coasters  may have gone down a little with washing;  this was not noticeable in the unwashed coasters.  The average diameter of the unwashed coasters declined 0.35 inches, as opposed to the decline of 0.17 inches in the unshrunk group.  So the preshrunk coasters had a 2 fold greater shrinkage compared to the unshrunk coasters, according to the diameter.  This was 9.6 % by diameter as opposed to a 4.9% decline in diameter for the coasters made with the unshrunk yarn.

The area of the coasters is proportional to the radius squared, percentage is a proportion as well, and the radius is directly proportional to the diameter in all cases , to compare the change in area associated with washing and drying the different sets of coasters, I squared the respective diameters.

The results came out:

The preshrunk yarn coasters started out with an 8.2% larger area than the unshrunk yarn coasters before washing.

The preshrunk yarn coasters came out to have a 2.4 % smaller area than the unshrunk yarn coasters after washing.

The preshrunk yarn coasters came out to have  an 18.4% smaller area after washing than before washing

The unshrunk yarn coasters had a 9.5 % smaller area after washing than before washing.

It surprised me that the preshrunk yarn shrank with respect to itself  more than the unshrunk yarn shrank with respect to itself after washing and hot drying.

 

Did the preshrunk coasters  actually get thicker after washing?  To test this, I stacked the two rows.

DSC07417 The coasters on the left were unshrunk, and the coasters on the right were preshrunk.  I positioned them on each side of a line in the table parallel to the camera, so I can use the image to measure them on the source photograph.  On two different print outs of this photo, I determined the thickness of each coaster stack at the inner edge, close to the middle near the camera and at the out edge, and I added them up, took the difference and related it to the sum of the unshrunk height.   The results were:

  1. The sum of the six preshrunk yarn coaster height determinations was  7.812 inches
  2. The sum of the six unshrunk yarn coaster height determinations was 7.562 inches

The difference of these sums is 0.25 inches, which means that the preshrunk yarn coasters are about 3.3% thicker than the unshrunk yarn coasters.

Thus, preshrinking the yarn made the washed coasters 2.4 % smaller area, and 3.3% thicker.  These small measures are equal, considering the uncertainties of all these direct and indirect measurements.  Thus the smaller area is probably due to an increase in thickness, caused by the prewashing.   The volume of the yarn is conserved (area times height).  This 85% cotton yarn is quite durable, with little of it washing out.   It makes little difference if we prewash the yarn or not, and it is a lot of extra work.

With harsh washing and drying the unshrunk yarn resulted in coasters that shrank in :

  1. Diameter by about 5%
  2. Area by about 9.5%

These results are internally consistent.

It Is Not Worth It To Pre-shrink Size 4, 85% Cotton Yarn

Crochet, Science, , , , , ,

DSC07404 The yarn on left  is an entire skein of the same Premier Home 85% cotton, 15% polyester, size 4 yarn, except, I boiled it, and dried it in the clothes dryer on hot, in order to preshrink it.  The entire skein on the right is in its original, unshrunk condition.

DSC07402 I boiled this yarn in the pot for 15 minutes, and let it sit in the hot water for another 30 minutes, after which I squeezed it out, and placed it in the clothes dryer on a hot setting.  (Its confining thread came off, resulting in the jumbled yarn that you can see above.  I dried it about three more times on hot confining the yarn in a sock, and after this placed it in the sun for two more hours.

It took me an hour in front of the TV to untangle it, and make it into a ball of yarn.  I wondered if rolling it into a ball would undo any shrinkage, because of a very slight residual dampness in the yarn.

I wanted to test at least two things:

  1. Did boiling the  yarn make any difference in the crocheted outcome as seen in these coasters?
  2. How much difference did the crochet hook size have on the coaster size?

To test the shrunk yarn against the pre-shrunk yarn, I made six simple double crochet coasters, three with the preshrunk yarn, and three with the pre-shrunk yarn.  For each treatment of yarn I crocheted one coaster, in order of increasing hook size, a G hook, an H hook, and an I hook.  Two yarns times three hooks, gives the six coasters.

I measured and weighed the coasters, after which I washed them in hot water, and dried them several times on hot, until they were dry.  The coasters ended up looking like this.

DSC07418 The top row of coasters is made with the pre-shrunk yarn, and the bottom row is made with the unshrunk yarn. The first column is made with the G (red) hook, the second column is made with the H (orange) hook, and the third column is made with the I (yellow) hook.  It is clear that the hook size made more of a difference in diameter than did preshrinking.  (Other observations and figures bore this out.)