The question: How does my $2.99 thrift find compare to its digital cousins?
Since my test skein didn't seem big enough to settle the issue, I took the entire batch of recycled wool to the post office to use the digital scales.
The first trip, I used a table-top digital scale in the lobby. I was short on time, so I weighed the entire batch then each skein individually, noting the numbers, and headed out. When I got home, I realized the numbers from the individual weighings did not add up to the total amount I'd gotten on the same scale. The total had been 7.8 ounces, but the total from each individual weighing was just 5.8 ounces. Further investigation was required.
The second trip, I went for the big guns: The Automated Postage Center.
Ready for a surprise?
Not only did the APC weigh my wool differently (8.10 ounces), but when I re-weighed it all on the same table-top digital from the previous day, I got a different number (8.10 ounces)!
That's right, the smaller digital scale registered a different weight on two different days! I'm pleased that it and the APC were calibrated to give the same weight the second time I went in. However, I'm seriously wondering about the accuracy of all sorts of postage I've paid for other things!
In the end, I have learned a couple of useful things:
1. On both the digital and my kitchen scale, I'll get a more accurate reading if I weigh like skeins together rather than individually.
2. My $2.99 kitchen scale isn't perfect, but it's not horrible, either. It had given a total weight of 9 ounces. The APC gave 8.1, for a difference of 0.9 ounces. That's about a 10-percent variable. Definitely close enough for most of what I do. If that changes, I'll probably cave and get a digital scale.
How much yarn, finally, do I think I salvaged in my first thrifted-sweater attempt? Something between 1,180 and 1,360 yards.
Pretty good no matter how you weigh it — and if I need more precision, I can always go postal!