Here goes!
For 40 4 oz vegetable shampoo bars:
3 lb cold distilled water
510g sodium hydroxide
3 lb 1 oz olive oil
2 lb 4 oz oz castor oil
8 oz jojoba oil
2 lb 4 oz coconut oil
30g grapefruit seed extract (as preservative, optional)
15-18 teaspoons essential oil (as fragrance, optional)
There are loads of potential add in nutrients eg shea butter, sweet almond oil but I thought this would give you an idea of the least complicated recipe I have (I think) for solid shampoo bars.
You then follow normal soap making procedure including important safety precautions like goggles etc. which you can get from somewhere like Soapkitchen online. Although it's easy enough once you get the hang of it there's loads that can go wrong so you need proper instructions and it would take pages to write it all here, but to give you a flavour of it:
The basic idea is you mix the sodium hydroxide & water which reacts and heats up. You leave it to cool while heating up the oils. Add grapefruit seed extract to oils and mix thoroughly.
When oils an dsodium hydroxide solution are both are at 80 degrees farenheit you add lye to oils and mix for a very long time until the mixture 'traces' (maybe 10-40 mins)
Mix in essential oils thoroughly and pour into lined mould eg loaf tin fully lined with heavy duty greaseproof paper. Cover and keep warm eg wrapped in a towel, for 24 hours. Cut the bars then leave to cure for 4-6 weeks (they are still caustic).
OR!!!
You can make some 'soap shampoo' by mixing 10 oz herbal water with 1-2 oz liquid castile soap, 1 tsp glycerine & 20-35 drops essential oil
Also have recipes for various hair rinses, liquorice root, nettle & vinegar, glycerine hair conditioner, birch water shampoo, soap bark shampoo, allsorts really! If there's anything you like the sound of, I'm happy to type them out
xx