The short answer is that if you formulate mild shampoos with gentle to mild surfactants and ensure the pH is below 6, you can be assured your product is colour safe.
Almost all the surfactants we use in our products are considered gentle to mild. Some of my favourites - sodium cocoyl isethionate (SCI), which I use for shampoo bars to create big, fluffy, "elegant" foam and lather; C14-16 olefin sulfonate (Bioterge AS-40), which is great for oily skin and hair; SMC taurate, which is great for dry to normal hair and skin; and foaming silk, oat, amaranth, and other proteins, which are super mild and great for really dry hair or any skin type.
Sodium lauryl sulfate isn't considered mild, so if you're looking to make something colour safe, this is the one to avoid. Some people avoid sodium laureth sulfate, but it's considered mild, and is good for all hair and skin types.
Choosing the right surfactants is vital, but there are two other things to consider - incorporating mildness and ensuring the product has the right pH.
cocamidopropyl betaine, cocamidopropyl hydroxysultaine, or disodium cocoamphodiacetate in my products is that they bring mildness to the product. I generally add around 10% to thicken and increase mildness. (I leave it out when I want to make a clarifying shampoo for my really oily hair.)
Ensuring the shampoo or conditioner has the right pH is vital. An alkaline product with a pH of 8 or higher can lead to some serious damage as the cuticle won't lay flat, and this leads to dull looking hair that tangles easily. When hair tangles too much, it can strip the cuticle from the hair, leaving it weak.
This is the reason that most people can't use CP soap as a shampoo as the alkaline pH can really damage our hair.
We want a pH of 6 or lower, and, as you'll see with the new conditioners I'm using like stearamidopropyl dimethylamine and Varisoft EQ65, we have to alter the pH to make sure they are positively charged and conditioning to our hair. If you're using something like decyl glucoside, which can have a pH as high as 11, or sodium lauryl sarcosinate, you have to ensure your pH gets down below 6 by adding citric acid or another acid to the mix.
I have been playing with at least 10 new surfactants and quite a number of new conditioners, which I'll be sharing with you soon. I'm so excited about this!!!
pH of shampoo
pH of conditioner
Adjusting the pH of our products
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