Mix Color for a Predisposition Test
A: Actually, it does not matter which is added to the mixing bowl first. It would simply depend on your personal preference. Most stylists add the peroxide developer first because it is the product which must be measured usually.
The main concern in mixing your aniline derivative color formula for use is to make sure that you use equal parts of color with developer. An improper color-to-developer ratio is often the key cause of problems with a hair color service.
When doing a predisposition test (also referred to as a skin/patch test) to determine sensitivity to a color mixture, you should only use a small amount of color and developer, say perhaps a half-teaspoon (2.5 ml) of each. Measure carefully, mix well, and allow it to sit for five minutes and then apply a small dab behind the ear or on the inside of the elbow and allow it to sit for at least 30 minutes then wipe it away and wait 24-48 hours to see if there is any reaction of the skin at the test site.
ANY redness or other sign of irritation on a test location is cause to abort any planned chemical service. Even a minor irritation could be magnified when the exposure covers the entire scalp. Safety is the reason for performing a predisposition test, and a negative reaction is a sure STOP signal.
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See also:
How to color hair
What does the developer do?
Allergic reactions to hair dyes
