In spite of it all

I finished another hat - strange I used 2 50g balls of Debbie Bliss Merino aran then weighed the hat - I had about 18" of yarn left and the hat weighs 91g - I'm fairly sure my scales aren't THAT inaccurate, the cheap acrylic yarn weighs in correctly, so why has every Debbie Bliss ball of yarn I've used appeared to be so light? Still, I count it as 100g off my stash and a degree of stress knitted away although this yarn was so short I had to remove several rows in between the decrease rounds so that I could finish it, it makes it a bit rippled and it will need blocking hard. I suspect that my normally tight tension has been a touch tighter yesterday and today as well!

I'm experimenting with the stitch pattern I fell in love with this week, this is aran weight on 4.5mm needles which seems OK, 5mm made the texture too loose for a sweater.