Actually, in my computer the right image looks more pink than in real life. I really am happy with my new reds! There will be a bit of tweaking still, to get the right deep reds, but this is definitely a huge improvement! There were a few things which I think I was doing wrong. I had switched to prewashing my fabric in cold water rather than on the hottest setting as advised in my dyeing book (not for any particular reason, just because I always wash with cold water). I suspect that this wasn't doing a good enough job of washing any pre-existing substances out of the fabric. I think my pre-soak solution of washing soda in water had also gradually become weaker (out of habit - Phil blames it on my slap-dash approach to cooking, learnt from my mum!).
I was also surprised to notice what a big difference the quality of the fabric made to the final colour. When I first started dyeing my own fabric I used a reasonable quality homespun, but then found a cheaper one which I buy by the bolt. However, this week I tried some better homespun (more even weave) from our local craft shop and was surprised to see how much better this took the dye. I wonder if that is due simply to the weave of the fabric, or to something else?
Anyway, I am now looking forward to cutting out my next quilt, with a healthy dose of reds!