I was expecting to come out of the shower with hair as greasy as when I went in. But this week's revelation is: bicarbonate of soda does actually clean my hair.
I've used it twice so far and my hair feels pretty much normal. However I have two things going in my favour:
a) I only washed my hair every two days anyway, and I didn't use much shampoo; and
b) We have really soft water.
For anyone interested, I read around a few websites and decided to use a softly-softly approach to begin with. So I am only using one teaspoon of bicarbonate of soda mixed with a cupful of water (200ml to be precise). I pour about half of that on my head, massage it into the scalp for a couple of minutes then rinse. I thought I would gradually increase the dosage if it wasn't working, but so far it seems to be cleaning my hair well enough.
I still have a bit of conditioner left in a bottle so I've been using that after the wash. When it has run out I'll start experimenting with cider vinegar.
I keep wondering why I've been using shampoo for thirty years when that bicarbonate of soda sitting in the kitchen cupboard would do the job just as well. It's quite amazing.