Sunday, August 27, 2017

More on Sampling for Grist

After fooling around with trying to spin a specific number of makes in a 1 gram sample, I found I really couldn’t get the grist I wanted consistently.

So I went back to weighing.  Since I don’t have a McMorran balance, which is expensive and single purpose, my first approach was to make a balance to measure relative weight.  I took a short section of dowel rod into the end of which I stuck a sturdy pin. The dowel rod rests on the top of a vase, placed near the edge of a level table, so that the yarn samples hang freely. Then I bent a piece of stainless steel wire.  The center was bent up and this rests on the needle in the dowel rod. It took a bit of messing to get this wire to hang level, but it is important that it does. See the pictures.

Basic parts for the yarn balance - the dowel rests on a vase, glass or mug set at the edge of a level table.  The wire rests on the needle in the dowel.

To use it, I hang on one side a length of yarn that is at the grist I want (in this case a sport weight measuring about 3.36 meters/gram) and on the other side I hang a sample fresh off the wheel that is self plied. I make sure the samples are at least 18 or more inches long. I cut the commercial sample a bit longer so I can snip off bits of it until I achieve balance.  Then I compare their lengths, holding both equally taut.  Actual length doesn’t matter.  If the commercial is longer than my spun yarn then my grist is too dense, if it is short, my grist is too loose and if they are the same length, then the grists are equal.  The balance is easy to make and costs very little.  It is, however, fiddly to use.  It is also subject to my ability to discern level and other factors.  It's better than nothing and a good way to at least get a sense of what one is trying to achieve.

Comparison yarn on the left and my yarn on the right.  Comparison yarn is gets snipped off until the balance is level - in this case, I'm not quite there yet.  Then the lengths are compared.

One of my favorite tools is my weigh scale that measures to the nearest 0.1 grams.  It’s great for all sorts of things – like measuring out the fiber for each single, determining final skein weight, measuring out larger quantities of dye, etc., etc.  It is, however, not fine enough for grist sampling.  Imagine my delight to find that scales measuring in milligrams (0.001 grams) are available and about half the price of a McMorran balance.  For 20$ I bought a 50 gram scale.  It’s about the size of a simple calculator.  I will be able to more precisely measure smaller quantities of dye and chemicals as well as do quick grist measurements.  

Now came the other issue – how do I measure length?  I collected a bunch of commercial yarns from my stash in various weights and from various manufacturers.  I looked at the ball band to determine what the grist is supposed to be.  For example, a Nature Spun sport weight is supposed to measure 168 meters in a 50 gram skein – or 3.36 m/gram.  I cut a length of it and weighed it.  I divided the weight by the m/g to find out how long the sample should be.  Then I measured.  In most cases the length was somewhere between fully stretched and relaxed.  This actually makes sense, since most yarn measuring devices measure length while the yarn is under some tension.

That led me to another question – how is the WPI measured on these commercial yarns?  I prefer to use a control card rather than wrapping, although I sometimes do that, too.  In all cases again, I had to hold the yarn fairly tightly to get the WPI on the control card that yarn should have with respect to grist and Yarn Council norms.  Not at all like what most people describe for measuring WPI.  I now understand what Alden Amos was driving at when he advocated measuring WPI packed to refusal. 
I ended up making a padded box for the scale, which is big enough to include a centimeter tape, the calibration weight and a calculator.  It’s portable and quick and I am hopefully further along in being able to control the grist of my yarns, besides the diameter.  

My milligrams scale, calculator, centimeter tape and calibration weight.  All fit into the box that I padded with closed cell foam.

I’ll let you know how it goes.

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