I tried this last year too and dyed by hair black, but I still managed to bleach half of it to within an inch of its life, which resulted in me having to go for a bob from hair that hung over halfway down my back.
To avoid the temptation of bleach, I decided to henna my hair after having my hairdresser strip out the black dye to get my tresses to a lovely dark copper.
As I had applied it to other people's hair and used to work for Lush, I felt confident that I knew what I was doing with it.
While previously I had used a sharp knife to cut the henna up, I decided to grate it as my hair is quite fine - the curse of natural blondes. It took a while but resulted in a fine powder that melted quickly and achieved the texture of melted chocolate really easily - which is how the Lush website says it should be.
Starting from underneath by hair, I worked the henna into my roots and then through the lengths, tying my hair up as I went to stop it brushing against my skin and causing staining. It took about 45 minutes to do all my hair and go back over it with the henna I had left to make sure I didn't miss any sections.
I found that the gloves I used weren't great and actually got in the way of application as they were too loose. They also broke without me realising, resulting in a bright orange hand. I definitely recommend latex gloves for applying henna!
To bring out the red tones more, I ran a hair dryer over my head every half an hour, as the heat helps to activate the henna. If you try this, just look out for drips as the oil in the henna will melt.
Once the time was up, I rinsed out as much of the henna as I could before shampooing - it was a rinse and repeat job to get rid of all the henna grains - and conditioning.
I'm definitely going to be regularly hennaing my hair to build up the colour and shine, as it acts as a treatment as well as colour. I'm looking forward to seeing what the colour is like on my natural colour when it starts growing through, as it is likely going to be a lot brighter on blonde roots.
If you want a permanent option that has a lot of gloss and a beautiful natural-looking colour, I definitely recommend Lush's henna.