Oxides and ultramarines

[Vicki C]

Hi all, in my “off season” I have been experimenting with oxides and ultramarines for soap colorants. My goal is to create reproducible colors by recording proportions of colorants instead of my usual less systematic method of winging it. I’ll post some pics later, but I am seeking hive mind wisdom on using iron oxide pigments that are made for paint in soap. I have purchased yellow and red iron oxides from TKB, Brambleberry, and WSP, and while these are reliable, the yellow is more of a mustard and the red more of a brick red, including a red iron oxide I recently purchased from WSP that looked much brighter on screen than IRL.
But. There is a company called Kremer Pigmente that sells pigments for artists. (Other companies too of course.) Some pigments are obvious NOs! for soap because of toxicity. Looking at the MSDS sheets for the iron oxides there is nothing that would exclude them from use in soap that I can see, and their pigments look brighter and truer than what is available elsewhere.
I do use micas, but there are some questions I have about them. Some micas are a blend of mica and polyurethane 11, and neon colorants are all polyurethane 11, as far as I can tell. I’m not a chemist but I wonder if polyurethane 11 contributes to microplastics, or micro persistent-manmade-stuff. (Polyurethane is not technically a plastic, but it does hang around in the environment.) At a practical level micas are pretty expensive, and if I can create my own colors at a lower cost then that has obvious appeal.
Anyone else been down this road? @Mobjack Bay I know you have experience with oxides and ultramarines. @DeeAnna I'm curious about your take on soap colorants with polyurethane in them.
TIA

 

[Mobjack Bay]

I've drooled over those same pigments but never had enough time to figure out if they would meet the guidelines for use in soap.

If you haven't already, you probably to want to get more familiar with the regulations on use of color additives in cosmetics. @paradisi - is this an area you can weigh in on?

Here's what I am aware of - These two pages provide summaries of color additives allowed in cosmetics:

https://www.fda.gov/industry/color-...s-drugs-cosmetics-and-medical-devices#table3A
https://www.fda.gov/cosmetics/cosmetic-ingredient-names/color-additives-permitted-use-cosmetics

You can link through to specific information for each permitted colorant, which for oxides specifies "synthetically prepared" and lists thresholds for metals:

§ 73.2250 Iron oxides.​

(a) Identity. The color additives iron oxides consist of any one or any combination of synthetically prepared iron oxides, including the hydrated forms. It is free from admixture with other substances.
(b) Specifications. Iron oxides shall conform to the following specifications, all on an “as is” basis:
Arsenic (as As), not more than 3 parts per million.
Lead (as Pb), not more than 10 parts per million.
Mercury (as Hg), not more than 3 parts per million.
(c) Uses and restrictions. Iron oxides are safe for use in coloring cosmetics generally, including cosmetics applied to the area of the eye, in amounts consistent with good manufacturing practice.
(d) Labeling. The color additive and any mixture prepared therefrom intended solely or in part for coloring purposes shall bear, in addition to any information required by law, labeling in accordance with § 70.25 of this chapter.
(e) Exemption from certification. Certification of this color additive is not necessary for the protection of the public health, and therefore batches thereof are exempt from certification pursuant to section 721(c) of the act.

And, yes, unfortunately, polyurethanes contribute to microplastics.

 

[ScentimentallyYours]

And, yes, unfortunately, polyurethanes contribute to microplastics.

After reading the recent articles about finding microplastics in our brains, I’ve been thinking about all the lipstick I’ve chewed off my lips through the decades. Now I have one more thing to blame for my faulty memory!

 

[paradisi]

Where did you get the idea that all micas contain polyurethane-11?

I read the INCI before I buy, and *none* of the ones I've used contain it.

 

[Vicki C]

Where did you get the idea that all micas contain polyurethane-11?

I read the INCI before I buy, and *none* of the ones I've used contain it.

Sorry, I misspoke - I meant to say all NEON pigments contain polyurethane 11. I’ll edit that now.

I've drooled over those same pigments but never had enough time to figure out if they would meet the guidelines for use in soap.

If you haven't already, you probably to want to get more familiar with the regulations on use of color additives in cosmetics. @paradisi - is this an area you can weigh in on?

Here's what I am aware of - These two pages provide summaries of color additives allowed in cosmetics:

https://www.fda.gov/industry/color-...s-drugs-cosmetics-and-medical-devices#table3A
https://www.fda.gov/cosmetics/cosmetic-ingredient-names/color-additives-permitted-use-cosmetics

You can link through to specific information for each permitted colorant, which for oxides specifies "synthetically prepared" and lists thresholds for metals:

§ 73.2250 Iron oxides.​

(a) Identity. The color additives iron oxides consist of any one or any combination of synthetically prepared iron oxides, including the hydrated forms. It is free from admixture with other substances.
(b) Specifications. Iron oxides shall conform to the following specifications, all on an “as is” basis:
Arsenic (as As), not more than 3 parts per million.
Lead (as Pb), not more than 10 parts per million.
Mercury (as Hg), not more than 3 parts per million.
(c) Uses and restrictions. Iron oxides are safe for use in coloring cosmetics generally, including cosmetics applied to the area of the eye, in amounts consistent with good manufacturing practice.
(d) Labeling. The color additive and any mixture prepared therefrom intended solely or in part for coloring purposes shall bear, in addition to any information required by law, labeling in accordance with § 70.25 of this chapter.
(e) Exemption from certification. Certification of this color additive is not necessary for the protection of the public health, and therefore batches thereof are exempt from certification pursuant to section 721(c) of the act.

And, yes, unfortunately, polyurethanes contribute to microplastics.

Thank you, this is super helpful.
The product information sheet for yellow-orange 943 says that it is in conformance with CFR 21 §178.3297 which are the regs for “food contact polymers.” Under this regulation iron oxide is listed as an approved colorant for food contact polymers with no restrictions and unfortunately no specifications about levels of heavy metals allowed. (If it did have those restrictions then it could be assumed that the pigment complied.)
I could ask the vendor if they have certificates of analysis for their pigments.

 

[paradisi]

There are separate regs about individual limits for heavy metals in cosmetics. I've seen clays and other colors sold online for soap that were above those limits, I'd tread carefully.

 

[paradisi]

I've drooled over those same pigments but never had enough time to figure out if they would meet the guidelines for use in soap.

If you haven't already, you probably to want to get more familiar with the regulations on use of color additives in cosmetics. @paradisi - is this an area you can weigh in on?

Here's what I am aware of - These two pages provide summaries of color additives allowed in cosmetics:

https://www.fda.gov/industry/color-...s-drugs-cosmetics-and-medical-devices#table3A
https://www.fda.gov/cosmetics/cosmetic-ingredient-names/color-additives-permitted-use-cosmetics

You can link through to specific information for each permitted colorant, which for oxides specifies "synthetically prepared" and lists thresholds for metals:

§ 73.2250 Iron oxides.​

(a) Identity. The color additives iron oxides consist of any one or any combination of synthetically prepared iron oxides, including the hydrated forms. It is free from admixture with other substances.
(b) Specifications. Iron oxides shall conform to the following specifications, all on an “as is” basis:
Arsenic (as As), not more than 3 parts per million.
Lead (as Pb), not more than 10 parts per million.
Mercury (as Hg), not more than 3 parts per million.
(c) Uses and restrictions. Iron oxides are safe for use in coloring cosmetics generally, including cosmetics applied to the area of the eye, in amounts consistent with good manufacturing practice.
(d) Labeling. The color additive and any mixture prepared therefrom intended solely or in part for coloring purposes shall bear, in addition to any information required by law, labeling in accordance with § 70.25 of this chapter.
(e) Exemption from certification. Certification of this color additive is not necessary for the protection of the public health, and therefore batches thereof are exempt from certification pursuant to section 721(c) of the act.

And, yes, unfortunately, polyurethanes contribute to microplastics.

Strictly speaking, if one is not making or selling cosmetic soap (avoiding all cosmetic or drug claims), then one *can* use anything to color soap. (Should is another story).

The FDA approved lists for colors are I think a great place to go, for the soaper's sake and the end user.

Relatedly... there are many different tints and tones of oxides and ultramarines available, shopping around can widen our choices while keeping on the approved lists.

 

[Mobjack Bay]

Thanks @paradisi. In particular, I should’ve mentioned the stricter regulations for cosmetics vs. generic soap, which I’m sure @Vicki C is aware of although others may not be.

 

[Vicki C]

Thanks - I typed out a response saying exactly that, that they aren’t cosmetics so I could use them without breaking any laws, but deleted it. Yes understood that there are limits for heavy metals. If the pigment vendor has COAs for their pigments I might give them a try. I have been looking for different tones of cosmetic oxides but coming up dry. Any ideas for sources?

 

[Vicki C]

I have fallen down my merry rabbit hole (as one does) of researching pigments… I discovered a very cool website, https://artistpigments.org/, that has color info and spectral analyses on a billion artist pigments. Well, not a billion, but a lot.
I think my dream of finding a brighter non-mustard yellow iron oxide might be difficult to realize. The pigments I am looking at look different on the vendor’s website and the website I just linked - here’s an example:

The graphic on the left is from the pigment vendor’s website, on the right from the artistpigments.org website. I think they look brighter on the left.

So, my next quest is to find brighter iron oxides. I don’t know if they exist. What I can’t figure out is how they get such bright colors in micas from just titanium dioxide and iron oxide. I know they don’t just stir them together, and mica colorants are made by layering the pigments on the mica particles. Still. A lot of the micas also use tin oxide, which is white but (I think) changes how the color is reflected.

I know, I know. Just support the mica manufacturers and stop trying to reinvent the wheel. (I do support them.)

 

[Tammyfarms]

I have fallen down my merry rabbit hole (as one does) of researching pigments… I discovered a very cool website, https://artistpigments.org/, that has color info and spectral analyses on a billion artist pigments. Well, not a billion, but a lot.
I think my dream of finding a brighter non-mustard yellow iron oxide might be difficult to realize. The pigments I am looking at look different on the vendor’s website and the website I just linked - here’s an example:

View attachment 81082
The graphic on the left is from the pigment vendor’s website, on the right from the artistpigments.org website. I think they look brighter on the left.

So, my next quest is to find brighter iron oxides. I don’t know if they exist. What I can’t figure out is how they get such bright colors in micas from just titanium dioxide and iron oxide. I know they don’t just stir them together, and mica colorants are made by layering the pigments on the mica particles. Still. A lot of the micas also use tin oxide, which is white but (I think) changes how the color is reflected.

I know, I know. Just support the mica manufacturers and stop trying to reinvent the wheel. (I do support them.)

I can’t add anything to the conversation except to say that I love your curiosity.