Semi Permanent hair colour
Semi-permanent hair colour will last longer than a temporary colour and will fade over time with each new wash. Semi-permanent colour molecules are smaller than temporary colour molecules. Being smaller, they can get a little deeper inside the cortex of the hair. This means that the colour will last longer than temporary colour. Each wash will remove some of the colour molecules so the colour will fade slowly.
Semi-permanent colours can last for six to eight washes and can be applied in various ways using techniques such as all over colour, hi/low lights, spot colour and scrunch in colour. Semi-permanent colours are good for clients who do not wish to have permanent colour or who haven't decided on permanent colour yet.
Heat will affect the processing time. Cold temperatures will slow down the processing time and hot temperatures will speed up processing time. If atmospheric conditions appear to be cold then additional heat may be required. If conditions are hot then colour will take quicker. The method of application may be affected by hot temperatures. i.e. If temperature appears to be hot then application may need to start from mid-lengths and ends (as in virgin hair) due to the additional heat given off by the clients scalp.
If the hair is porous the processing time may be shortened due to hair damage. i.e. if ends are porous delay colour application until the last 15-30 minutes.