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Thread: How is shrinkage amount calculated?

  1. #1
    Power Poster
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    How is the shrinkage amount calculated?

    I've had some things shrink lengthwise,
    some crosswise,
    and some things have shrunk both lengthwise and crosswise.

    I'm fairly sure that is has something to do with the difference between the original size of the piece and the shrunken size -

    but beyond that, I'm stuck.

    For example - if I start out with a piece of fabric that is 36 x 42 before washing (1512 square inches) and after washing it would be 35 x 41 (1435) -> the difference is 77 inches.

    77 divided by 1512 is approximately .0496 inches ->
    to get from a decimal number to a percentage - I move the decimal two places to the right -> which would be 4.97% (rounded to two decimal places)

    ETA: (MTS has the correct number - it should be 0.0509...)

    So then would my shrinkage have been approximately 5% ??

    Are the calculations the same if the shrinkage is only in one direction?

  2. #2
    MTS
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    Quote Originally Posted by bearisgray
    77 divided by 1512 is approximately .0496 inches ->
    to get from a decimal number to a percentage - I move the decimal two places to the right -> which would be 4.97% (rounded to two decimal places)

    So then would my shrinkage have been approximately 5% ??
    :thumbup: :thumbup:

    You're calculating the shrinkage in terms of the area.
    Your method was correct, but the numbers not: ;-)

    77 divided by 1512 = 5.1% (it's expressed as a %, not inches).

    So the area of the washed fabric is 5.1% smaller than the unwashed fabric.

    or

    77 INCHES sqin = 5.1% of the size of the unwashed fabric


    If you want to do see the % shrinkage in each direction (width vs. length), then you'd just use those numbers.

    So it would be 1 divided by 36 (2.7%) or 1 divided by 42 (2.4%) (respectively for W or L shrinkage).

    With these numbers, the shrinkage by length and width now total the overall shrinkage.

    I guess there are fabrics that might shrink substantially more one way than the other....I'm not sure if LQS cotton is one of them

  3. #3
    Super Member AlwaysQuilting's Avatar
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    I'm so glad you started this thread.
    I've never been able to figure it out either so I'll be watching the answers you get.

  4. #4
    MTS
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    deleted - combined in previous post

  5. #5
    Google Goddess craftybear's Avatar
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    wow, thanks for all of your great information

    I just love this board I learn something new every day.

  6. #6
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    Some LQS fabrics do shrink. Some more than others.
    (I've measured "before" and "after")

    Thanks for the corrected numbers.

  7. #7
    MTS
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    Quote Originally Posted by bearisgray
    Some LQS fabrics do shrink. Some more than others.
    (I've measured "before" and "after")
    I was questioning it more in terms of L vs. W.
    Like, would you lose 2" in the width and only 1" in the length because of the way the cotton was made?

    I don't prewash (yeah, yeah, I know) so I never measure. :mrgreen:

  8. #8
    Moderator QuiltnNan's Avatar
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    interesting to see the numbers in a percentage. thanks for starting this topic

  9. #9
    Power Poster QuiltE's Avatar
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    On the labels for Warm & Natural (and the others in that series) they show % shrinkage.

    ..... it'd be interesting to see how they answer your question. Why don't you email them and see what they come back with?? :)

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