From: lah@Cadence.COM (Lin A. Hendrix)
Subject: Pre-shrinking was Re: Washing hanks of wool
Reply-To: lah@cadence.com
Organization: Cadence Design Systems, Inc.
Distribution: na
Date: Sun, 3 Jan 1993 22:57:17 GMT

Hi fellow textile maniacs,

It makes sense to pre-shrink some fibers such as cotton and silk.  
Other fibers don't behave as nicely after such treatment.  Linen, 
wool, and rayon are typically fibers that need to be dry-cleaned or 
hand-cold-washed.  Retaining certain dyes and finishes on all fabrics 
is one reason that manufacturers insist on dry-cleaning.  Personally,
I never pre-shrink yarns.  I can't imagine dealing with a skein coming
undone.  Besides, most of the shrinkage in garments occurs from the 
dryer and I'm *definitely* not putting skeins of yarn in that!  I make
test swatches and then wash and dry them differently to see what the 
shrinkage is.  I adjust my gauge to the swatch that turned out best.

Linen:  When preshrunk loses it's hand and can become quite rough to 
the touch.  Often dyes are not as colorfast on linens and fading 
becomes a problem if you don't want the "worn" look.

Rayon can be hand washed if it's high quality (not neccessarily high-
priced).  Best results are still dry cleaning.  Rayon is not that sturdy 
a fiber and looks "worn" very soon. 

Notes on washing wool:  Two things cause wool to shrink, one is rubbing 
or friction, the other is heat/hot water.

On the hot water idea:
Wool's "natural" form is somewhat convoluted and wrinkled.  When 
commercially washed, dyed, carded, spun, and plyed, it gets un-convoluted.  
Both friction and heat cause wool to return to it's natural form, i.e. shrink.  
Depending on the treatment of the original yarn it could shrink *a lot*.  So 
much so that you have maybe 30% of the yarn you started with.  Sometimes, 
because your water isn't that hot or the friction is reduced, it shrinks 
unevenly.  This is why you can't wash the yarn in hot water and expect to 
wash the completed sweater too.  You sweater will probably keep shrinking and 
shrinking a bit more with each washing.

Many yarn manufacturers treat their yarn chemically with softeners, 
deticklers, and sizers.  Since the yarn was never meant to be washed in 
hot water (or even cold water) they take no precautions about this stuff 
washing out.  If you don't follow the manufacturer's instructions, you run 
the risk of an itchy and coarse result.

The best way to wash wool?  Natural soap flakes dissolved in small amount 
of hot water then the yarn gently lowered into a cold water bath, swished 
gently, squeezed gently, then rinsed in the same manner.  You can't expect
wool to come out of a washing machine even if cold water was used without
shrinking due to the friction involved.

Sometimes you may get lucky and get a wool that's naturally non-shrink prone
but you can't expect all wools to behave the same.  An exception is the newer
washable wools that have come onto the market in the last few years.  The 
manufacturers use chemicals and heat to force the wool into shape.


Cotton:   Many cottons are pre-shrunk.  Mercerization is a type of pre-
shrinking that you'll find on many of the better quality cotton yarns.  Look
for Mercerized or Scott's (Ecosse in French) when you buy the fiber.  You'll
need to be cautious of "flaked" cottons (both in yarns and fabrics).  Although
still quite durable, the flakes are cotton ends that get plyed as part of the
yarn, you'll find these tend to "flake-off" with each washing, rough treatment
in a washing machine will doom these yarns to an early death.

Silk does shrink a bit, roughly 2% in length.  But at the cost of silk yarn
would you really want to take the chance of the dye running?  Silk fabrics
can be pre-shrunk if, again, you don't mind the "worn" look.  


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+++++ Your friendly midnite, manic, textile artist, lin hendrix +++++
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