[Sibech]

@doaner12, Does it get darker before going bright or is it just the light in the image?

FD&C Blue #1 (Brilliant Blue FCF) isn’t particularly light stable but much more stable in anhydrous formulations than aqueous.

Have you considered using lakes instead of the dyes?

[Sibech]

If in doubt, knock it out!

Do multiple variations, removing an ingredient from each to see which of them that does not discolor - by the looks you have no water added, and if kept dry you shouldn’t worry about the preservatives for the knock-out

Another thing, approximately how long does it take for the color to change significantly? Days, weeks, months?

[Sibech]

Come to think of it, there is a chance that the discoloration of the saturated solution was due to complexing with metal ions in the water (it was for pH correction in cooking, not cosmetics).

[Sibech]

@doreen When dissolved in water (no stabilizers) the oxidation occurs relatively slowly but after a month or two on the shelf (I had satd. L-AA) then it was suddenly orange/brownish.

Are you sure it wasn’t spray-tan in serum form? (Because dehydroascorbic acid (DHAA) was at least considered for use as a sunless tanner (patent) due to the reductive capacity of DHAA.

[Sibech]

@vanne The T-resveratrol you use in your whitening lotion is from making-cosmetics.com? I presume? in which case it also contains PEG-7 Glyceryl Cocoate and Propylene glycol (not that either of those should be particularly irritating).

The “emulsifying wax” you use, could you specify which? (some of them contain SLS which can be irritating if left on the skin, even though the concentration is low some people are more susceptible.

Regarding the ascorbic acid, you would be better off removing it or substituting with a stabilized version (Magnesium Ascorbyl Phosphate for example) as ascorbic acid is extremely unstable and will auto-oxidize into dehydroascorbic acid (with a yucky brown/orange color).

The percentages used of the potential irritants mentioned would be beneficial to assist.

[Sibech]

While for the most part agree that it is highly unlikely that a change in perfume will affect the PCT it is important to mention that a several of the organoleptic compounds in perfumes have a distinct impact on microbes.

Therefore the concentration of fragrance you use (which in rinse-off can become significant proportion) and the actual composition of the fragrance makes could impact it.

Rule of thumb: If in doubt, err on the side of caution and do a PCT. Depending on the company they will gladly give you a preliminary result after the first 2 weeks, and in my experience, they seldom fail after 28 days if they passed the first two weeks.

[Sibech]

I think @Doreen is right…

The BAS effect in all references I could find it was Biologically Active Substance, didn’t matter if the subject was food-science, water processing, ethnobotany or something fourth. The references don’t give a much of a clue by titles either as they reference a book chapter and an article, one on preservatives and one on hydrocolloids, respectively.

The article @maria mentioned also states:

In combination with hyaluronic acid and plant extracts, the polymer ensures deep and efficient cleaning of skin, toning, and waste removal and affects the intensity and duration of BAS effect.

Which goes well with the mention of both the micellar formation of low-concentration some copolymers along with delayed-release drug delivery in regard to block polymers. (http://dx.doi.org/10.1039/B208503H).

With that said, someone should tell the authors that is it is poor style to write an article without adding a list of abbreviations!

[Sibech]

@doreen I don’t use a lot of eyeshadow, but if memory serves me correctly “fallout” when not as mentioned by @bill_Toge is the amount of eyeshadow that drops from the brush/sponge during application.

[Sibech]

A quick caveat, I am not based in the US and can’t guarantee my suggestion necessarily comply with those regulations.

Personally, I would definitely outsource the actual microbial challenge testing. For new developments in a small company, I would find a microbial testing kit to use during development and then get the challenge test of a seemingly microbially stable formulation completed elsewhere.

If you use an external safety assessor they are also more likely to immediately accept an approved report from an accredited lab than in-house testing (where the methodology will be looked more into).

Also, when doing challenge testing on a new product consider sending multiple samples with different preservation systems - you’ll save yourself a lot of waiting time this way if some are rejected.

What if I just wanted to do stability testing?

As for general stability testing, in general, you should get equipment for measuring your stability endpoints (these vary depending on the product but can include a viscometer, refractometer, colourimeter (particularly for colour cosmetics), microscope and ). A centrifuge for a quick and dirty stability test and an oven + freezer for accelerated and freeze-thaw stress tests.