Different rules for different colour houses abound, although all of them keep to the universal level /number system, each house has a different approach to colour developers and that can vary country to country.
Often in the UK and Europe, I feel 10 volume is under used in permanent hair colour. I love it for it’s versatility and would like to see more colour houses allow us to use it. I have seen it used by some American product companies and love it.
1. When pulling a colour through I hate using 20 volume developers as I feel we shouldn’t need to use something this strong on already coloured hair. Mixing my target shade with 10 volume would give me the deposit but not the lift and leave the hair in better condition. More often than not I have to use Demi colour but the colour selection in Demi colours don’t always have enough cooler shades when I’m fighting brassy tones.
2. When using Balayage to to create super soft tones on darker tinted hair I quite often mix my lightener with 10 volume. It’s very gentle and gives a beautiful sun-kissed feel.
3. Although I love INOA I don’t use it as much as I would if it had a 10 volume developer, as it has in the USA . The thought of Pulling 20 volume developer through the hair just makes me shudder. This can’t be as good as using a 10 volume developer.
4. For great coverage without the one to two shades lift a permanent hair colour with 10 volume instead of 20 volume can give great coverage and have longevity.
5. The permanent hair colour ranges have many more shades than the semi and Demi ranges and be able to use 10 volume I believe would make it even more flexible.