Some of you may not know, but I was a hairdresser and had both Certificate of Hairdressing and Diploma of hairdressing Management.
So a lot of you may have a question:
Why do my hair colour fade so quickly after I went to my hairdresser? Its already professionally done but the colour does not stay or maintain well.
Ask yourself a question:
Did you wait for a full 72 hours before shampooing?
If not, then this may be one of the reason your hair colour come off so fast.
When colouring hair, your cuticle layer open which makes it easy for the chemical to penetrate to the hair shaft.
However if you wash your hair too early while your cuticle layer still opens, the colour will come off. Thus we always recommend to wait for a few days before washing your hair at home so the pigment has time to soak into the hair cuticle before your first wash.
Also, if you are asian and doing ash hair colour, please purchase a purple based shampoo to maintain the ash undertone of your hair. You may wonder why and a lot of hairdresser didn't explain to you.
So human hair has a lot of pigment including red, blue and yellow and asian hair has a lot of red which takes the longest to bleach to get rid of this undertone. Once the hair is bleached, you will find out your hair turning reddish brown (refer to #5 light brown of the above picture) and then yellowish (#6 and #7) but its a very concentrated yellow which you need to further bleach it to reach a neutral blonde (#8) and then your hairdresser can apply the ash tone hair dye on your hair. However blue undertone hair dye is the easiest to be washed off, thats why we always recommend client to buy a purple based shampoo to neutralise the yellow for maintenance.
Most western have blue undertone hair thats why its much easier for them to reach platinum/ash blonde. On the other hand, there is no doubt that we always have to sit in the salon for 8 hours just to bleach the hair to achieve the ash hair colour.
Photo Reference
Hair shaft structure: https://www.dreamstime.com/illustration/cortex-layer.html