Congratulations! You're ditching the synthetic chemicals and going for natural colour!
But now you're wondering what you need, right?
Here's your quick start guide:
1 . What colour is your hair now?
Natural plant dye can only add colour on top of your original colour. This means that hair colour can't be lightened. Ex: if you have dark brown hair, you can't become a redhead (although henna over brown hair will shine red highlights in the sun).
Natural plant dye for hair is translucent. This means that your original hair colour will affect the tone and shade of your final colour. Ex: a golden blond using only henna will have a very different looking red than a light brown using only henna.
2. What colour do you want to be?
Different plant powder combinations will be used to try to achieve the final colour you want. As implied above, no specific final colour can be guaranteed because it's dependent on the original colour, but here is a general guideline:
light blond = 100% cassia
bright strawberry blonde = 80% cassia : 20% henna (4:1 ratio)
light red = 50% cassia : 50% henna
ash blond = 80% cassia : 10% henna : 10% indigo
red = 100% henna
reddish auburn = 90% henna : 10% indigo
brownish auburn = 75% henna : 25% indigo
medium brunette = 50% henna : 50% indigo
cool medium brunette = 50% henna : 50% indigo + amla
dark brunette = 25% henna : 75% indigo
cool dark brunette = 25% henna : 75% indigo + amla
almost black = 10% henna : 90% indigo
Black: 100% henna first, rinse out, then 100% indigo
3. How much powder do you need?
It's wise to colour all of your hair the first time. After that, you can just colour your roots or continue to cover all of your hair for the strength & glossy effects of the powders. So here is an approximation of how much powder you need per application to be able to thoroughly cover all of you hair:
100g = short hair
200g = collar length hair.
300g = shoulder length hair.
500g = waist length hair.
* If you have very thick hair or curly hair or if you are tall, you'll need more powder than estimated above.
It's a good idea to make a little more than you think you'll need the first time so that you don't run out.
4. Buying your powders.
You can buy solo powder packages in bulk amounts or you can buy a henna hair colour kit. There are also sample sizes available if you just want enough to colour your hair-brush-harvested test hair. Have fun experimenting with different ratios of powders - just make sure to always test first!
*Remember, organic powders that permanently stain the hair are translucent, so if you're hennaing your hair for the first time when there has been some grown out after synthetic chemical dying, there might be a colour change line, but hopefully you've gotten a close enough colour match that it won't be too obvious