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Zinc Oxide / Calamine cream
Has anyone worked with this before? Just curious if there are any tips with working with ZnO/Calamine. Thank you
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18 Replies
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I have some and also experimenting with it.
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I have worked with it as I have come up through Pharmacy Compounding. If you want some guidance on working with it, look at some of the many Formulations that are posted for Pharmacy compounding as well as the USP/NF documents. Remington: The Science and Practice of Pharmacy covers it quite a bit.
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@Microformulation thanks ill look at that book. I had been attempting a petrolatum paste with ZnO at 20% with calamine. Looks smooth until it cools and then it seems gritty.
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In Pharmaceutical compounding we made small batches and honestly only when the mass produced OTC was deviated from.
Your issues are thus;
-If you are in the US, it is an OTC product. That means you must follow an OTC monograph and with the Regulatory requirements, it is not a Cosmetic nor is it feasible for a Cosmetic line to Market.
-The USP OTC percentage is 8% and that was a bear to get incorporated if I recall correctly. Why 20%? In Pharmacy Compounding we were able to deviate from the OTC monograph since I prescription was provided, there were Journal citations for the Physician to justify the higher percentage and it properly became a Prescription Drug evolution. Even so, I never made higher than 12% and that was a challenge. In the end, the sensorials were not what I would have liked. -
@Microformulation
thanks for the info, i am aware and i am fully compliant with all otc requirements. -
1-25% is in the monograph but difficult to obtain and as such, I can’t recall any products that go that high. I do recall 20% ZnO with 1% Calamine.
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If I had to guess, I’d say your ZnO was re-agglomerating. What are you using to mill this with?
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@Bobzchemist hey thanks for the reply. I am just doing lab samples right now using lab stick homogenizer. I’ll look into agglomeration. Anything you can think of to help with that issue? Thanks
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High-speed (Cowles) disperser, 3-roll mill, colloid mill or ball mill. You could even use a muller if your sample size is small enough. Stick homogenizers don’t generate nearly enough shear force.
There are also grades of ZnO and/or dispersing agents that should help.
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@Bobzchemist Thanks for the tips. Just to clarify I am using something like this and not a kitchen-aid stick blender.
https://homogenizers.net/products/d500-homogenizer?nosto=productpage-nosto-1
Is this still not enough sheer? We have a huge colloid mill but not for lab batches.
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Well, “enough” shear should be determined by results. How are your Hegman/FOG readings?
That homogenizer should probably work for batches up to 100 grams or so. Anything larger will likely take hours to grind small enough.
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Actually had some success using your tips, thank you. I just increased my sheer and mixing time with my lab homogenizer. We don’t have a hegman gauge so I can’t get any number from our plant mill. But since this is just a lab project I don’t have to worry about that for now.
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hi, Bob maybe you can help me, I post here because the problem I am trying to solve is very similar. I formulated and manufactured anti sun organic ZnO paste for a client. Got very good results in vivo , but got 11 SPF(UVB) in vitro the problem is as I understand is with dispresing ZnO in an organic oil phase. I am trying to pick up the right equipment (colloid mill) but have a problem to find one. Do you have any insights?
thank you in advance
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You could try using a premilled dispersion. I have had some very easy products lately using the G-Block products. Nailed the SPF and Spectrum right on the first try.
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Thank you very much for your reply
It seems that every zinc oxide dispersion that produced commercially will not pass my client requirements,
. Although found something interesting for another project, dow sunspheres powder. Going to do some samples with it.
I am using beeswax+jojoba+olive+coconut+cocoa butter organic mix. zinc oxide is dispersed in this faze when it is still hot. It is solid wax at 20 C. So the problem as I see it is in the dispersion of ZnO. -
If you’re making a paste, a 3-roll mill would be your best bet.
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