[karlyip]

Bill_Toge said:

given that castile soap is alkaline, I’d suspect it’s due to a dye that’s coloured in alkaline conditions and colourless in neutral to acidic conditions; as the soap is lathered more and more, it becomes increasingly diluted and neutralised, therefore losing its colour

the most likely candidate for the pink variant is phenolphthalein, and the most likely candidate for the blue variant is thymolphthalein

not sure about the green though, it may well be a mixture of 3-nitrophenol (yellow/red) and thymolphthalein (blue)

the one that goes from white to blue is almost certainly due to an encapsulated pigment; Daito Kasei, among others, specialise in this kind of technology

I searched pigments you mentioned on the ECHA, it seems that none of them could be used in rising products… I still believe that they use some optical trick like you described, as the soap is lathered more and more, the pigment becomes diluted and nearly invisible. 

BTW, I found another foaming hand wash claiming “color-changing” in Japan. 

https://pop.inquirer.net/88723/this-pokemon-themed-hand-soap-changes-its-color-everytime-you-wash-your-hands

Actually, I got one in hand and found the blue color is… very pale at all and hardly found any color change after lathering… 

I also noticed that, in both AD, they all show the color changing effect of the purple or reddish foam rather than blue foam… I think purple and red are “warmer” than blue, so it can easily create an illusion when it turns very very pale, conceiving the user that the foam turned into white. But for blue, we can still recognize it when it turns very very pale after lathering, so the color changing effect is not good at all. 

https://pop.inquirer.net/88723/this-pokemon-themed-hand-soap-changes-its-color-everytime-you-wash-your-hands 

Please correct me if I have something incorrect. 

[karlyip]

em88 said:

There is a small problem with phenolphthalein. It is carcinogenic and it is prohibited in cosmetic products in the EU. 

Yea, it isn’t on the list of FDA-approved pigments list as well, so it is supposed can’t be sold in the US. 

[karlyip]

MarkBroussard said:

Without the list of ingredients, it is not possible to get any insight into how they may have achieved this effect.

I finally found the ingredients on the internet! It just playing a trick using optical illusion. However, I can’t make the color as deep as it. 

I tried mixing Decyl Glucoside and SLS in around 1:1 to make it generate more foam by scrubbing action. Pale blue is okay, the foam could turn into nearly white, but it cannot deeper than that kind of pale blue.   :#

[karlyip]

jemolian said:

I guess the only way is to look at the ingredients list if any is available online or i guess someone will have to look at it in stores or purchase it. Makes me curious as well. 

I’m assuming the Itzazu® Color Changing Hand Soap is similar but the actives are encapsulated in a bead form? 

https://www.tropicalseas.com/products/itzazu-color-changing-hand-soap

Yea, I also saw that on the internet, it obviously contains some pigment beads but I’m not sure if we can apply it into a foam soap

[karlyip]

AuroraBorealis said:

My guess is something encapsulated. Reminds me of the color changing toothpastes for kids. 

I am still wondering is there any foaming dispenser allowing the microcapsule passing through without clotting it?

[karlyip]

jemolian said:

Looking at the website, the marketing message mentions Hypercolor technology? The color seems to change to white due to heat. 

https://en.wikipedia.org/wiki/Hypercolor

I also thought about that kind of technology.
I had gone through the EPA regulation and found that should not be utilized in this kind of product. My friend told me that the hypercolor actually is kind of very small particle and I’m not sure it can pass through the mesh of the foaming dispenser without clotting it. 

[karlyip]

MarkBroussard said:

Ha! … It’s a really cool idea to get children to wash their hands for a long enough period of time.

Do you happen to have a list of ingredients?

Hi Sir, I don’t have it in my hand…

[karlyip]

Perry said:

If you are putting the blueberry extract in your formula to for the color, then that would be illegal as it isn’t an approved colorant. You can say it is an antioxidant but if the color of your formula is in any way important for your marketing, then it would still be illegal (in my opinion).

Thanks, Perry, so if I don’t sell the product by emphasizing the color, then it probably not illegal right?