Thirty Something Hobbies

I picked up this gorgeous new Debbie Bliss SoHo wool rather randomly thinking "love this maybe I'll knit a hat in it?" so thought I'd do the cable pattern hat from the Rowan book that Max (http://www.noodlesanddoodles.com) sent me, as I was using a different wool to the pattern suggestion and the pattern said 8mm needles while the wool recommended 51/2mm I'd better be good and do a tension square. Having done that I settled on 10mm needles to get the right size?!? I did think that's a bit odd but the tension square's the way to do it - so how come that 12 rows up with 23 to do my hat is already over halfway up my head but shorter around the brim than previously successfully knitted hats??? it looks like my lovely hat will reach down to my chin while squeezing my head tight?! So I will persevere as I am, because I'm really no idea what to change and maybe have to roll it up a lot - I'll keep you posted!