[Zink]

Other interesting ingredients, PEG-8 beeswax (natural enough?), Cholesterol (reduced TEWL 10% alone at 1% in one study!), Hemp Seed or Cocoa butter or other butters that might be superior to Shea.

[Zink]

Thanks Mark, I’ll try 1% Sodium Citrate first!

[Zink]

Belassi: You are probably correct, will test. Any issue with just adding more propylene glycol btw?

MarkB: Correct pH is 2.5. I was not aware of this. Any advantages for Methyl Gluceth-20 over propylene glycol or hexandiol? How much sodium citrate do you suggest I add?

Thanks for the very useful feedback so far! 

[Zink]

Mike_M: it is heated in propylene glycol to 60C under stirring, at which point I can’t see any crystals. It’s possible this is inadequate. 

Belassi: Over time = overnight, It’s in a sealed container so I doubt evaporation is the cause.

Bill_Toge: Good point. I have not measured to see if crystallization is more severe at lower temperature.

[Zink]

Hi Robert,

It’s for a gentle face / body cleanser. Doesn’t need to foam at all.

[Zink]

Thanks will do, any lead is helpful!

[Zink]

“As for Silicone-coated Zinc Oxide, the API Fee for this is $160.00 because we outsource this.” no development needed.

[Zink]

@bobzchemist I’ll talk to my CMOs about this, for previous OTC formulas there were no method development/validation costs, presumably because the API tests/formulas were standard enough to be handled without any method development specific to the project.

[Zink]

@bobzchemist I’m fully aware and I’m not a production facility, already working with a couple of contract manufacturers set up to do OTC drugs. It adds some expense, but API active ingredient testing, depending on the ingredient, is typically only in the low hundreds pr. ingredient, in my case using silicone coated zinc oxide exclusively should help keep the cost down, I’ve contacted my manufacturers to verify cost. Thanks for the rec of Allied Analytical

[Zink]

Here’s what I’ve found so far: Amalabs one of the top Google results will do SPF30, 80 min waterproof and broad spectrum testing for $4633. If you only need SPF testing, not making any waterproof or broad spectrum claims that number goes down to $2167. 

@bobzchemist I’m not sure what you mean by active ingredient assay, I didn’t see any mention of it in the FDA final sunscreen monograph. You only need 10 subjects for the SPF test.

 

@pma: makes sense, I wonder if there are labs that do this though? I can’t find any through searching on Google, what search strategy would you use?

[Zink]

Yes formulas and packaging is ready. Sent you a message!

[Zink]

Bobz you should really do an article on colour cosmetics / pigments for Chemistcorner! 

How does reflective wavelength work? Is there some sort of coefficient you multiply particle size with to see what parts of the visible spectrum it reflects? Allegedly USP-1 with a 110 nm avg particle size is less opaque and less suited for this use.

In my case I have a oil/hydrocarbon based formula, I’m going to try a TiO2 and perhaps Boron Nitride combo, but perhaps you could comment on these strategies to ensure good opacity without excessive agglomeration:

Ideas to get around ZnO agglomeration

1. Switch to TiO2 exclusively.
2. Use coated ZnO; Are there oil soluble coatings?
3. Use a pre milled ZnO/TiO2 slurry.
4. Mill minerals with Lortone ball mill using 1/4″ stainless steel balls
5. Lapidation of the ZnO/TiO2 in paste form
6. Outsourcing of the milling?

Thanks!

[Zink]

15000 units over 3 products, non-drug moisturizers.

[Zink]

Thanks for the information. Before getting to that point I’m interested to see if the formula is at all possible, if it is, passes accelerated stability and it looks promising, SPF testing cost will not be a problem.

[Zink]

i’d be open to pay for consulting on this formula.

[Zink]

To clarify further, what I’m looking for is a minimal good-bet starting point.

[Zink]

I was wondering if this was the case, but there are a few spray on mineral-only spray sunscreens out there that get good reviews, e.g. http://www.amazon.com/Goddess-Garden-Natural-Sunscreen-Trigger/dp/B00KBXP44I/ref=pd_sim_194_7?ie=UTF8&refRID=0N1KG7TWKNDA7XYAWXJH

Active Ingredients: Titanium Dioxide 6.4%, Zinc Oxide 6.0% Inactive Ingredients: Aloe Vera, Glycerin, Glyceryl Caprylate, Glyceryl Stearate, Glyceryl Stearate Citrate, Glyceryl Undecylenate, Glycine Soja (Soybean) Oil, Helianthus Annus (Sunflower) Oil, Iron Oxide, Lavandula Angustifolia (Lavender) Oil, Lecithin, Polyhydroxystearic Acid, Radish Root Ferment Filtrate, Stearic Acid, Tocopherol (Vitamin E), Xanthan Gum Certified Organic

[Zink]

What made me ask the question is that I want to make the best possible products for the skin, products that enhance skin barrier function over time without making you dependent on the product (i.e. you can stop using it without suffering from significant side-effects). That doesn’t imply there is something wrong with traditional emulsifiers at all, but it asks whether we know if some are better for the skin than others.

I guess you could boil the question down to: What emulsifier has the best long term effects on skin barrier functioning and skin inflammation?

[Zink]

Anyone?

[Zink]

Still looking!

[Zink]

Think I’ll make an overview and share it here later.

[Zink]

Could you tell us more about what your lipstick cases are like? Are they made out of wood? Plastic? What shape? You could try to find people on e.g. Etsy who make similar items and partner with them for small volume work.

[Zink]

That article is just a very basic overview of what’s available, I’m looking for things that are specifically water-soluble and low pH compatible, and ideally evidence that they’re helpful at reducing TEWL or improving some other moisturize related property.

E.g. 1.5x10e6 MW Sodium Hyaluronate gets hydrolyzed at pH 1.6 - 3, see:
2008 Effect of pH on the Behavior of Hyaluronic Acid in Dilute and Semidilute Aqueous Solutions
2005 Role of the pH on Hyaluronan Behavior in Aqueous Solution

[Zink]

I’m definitely aware of low pH giving a lot of common emulsifiers a problem, creating cottage cheese in some cases.

Exclusively water based moisturizers are in general a new topic to me, so curious as to what people have found effective. I see some products for instance use hyaluronic acid and even derivatives of it that will reduce tewl.

[Zink]

Not decided, it could go to the professional market or the consumer market if adjusting pH to 3.5. In both cases it’d need to be weak enough to not need any post use neutralization or washing off, yet potent enough to cause significant exfoliation. 

In any case interested in what kind of humectants and skin protectants would work well in a low pH formula.