Thursday, June 9, 2016

Weekday Wonderings: How do you combine preservatives?

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In this post, Weekday Wonderings, ingenting writes: In this post you write about pairing potassium sorbate with another preservative...I was wondering (not just for this case, but in general), when pairing preservatives, how much should you add of each? Would you need to adjust the recommended usage rate in some way? Or can you use each preservative at their own recommended usage rate?

E.g. (I'm totally making this combo up, btw), if you want to combine LGP with Germaben II, would you use 0.5% LGP and 1% Germaben II, for a total of 1.5% preservative... or would you dial it down to, say, 0.3% LGP and 0.5% Germaben II?

Yes, you'd want to use their recommended usage rate for things like sorbic acid or potassium sorbate when combining them together. So you'd want to use sodium benzoate at up to 1% as your bacteria killer and potassium sorbate at up to 0.39%.

As for using two broad spectrum preservatives like Germaben II and liquid Germall Plus together, we generally wouldn't. I've combined them at their maximum usage rate in a toner than contained strawberry extract as I couldn't stop the darned stuff from going mouldy. This combination didn't help either, so I gave up on powdered strawberry extract and moved to the liquid version.

Related posts:
Organic acids & sodium benzoate

In the same post, ingenting also asks: request...I was wondering if one day you could do a post on recommended books to teach yourself diy cosmetics, or the books that have helped you get to here ( chemistry books included:) ). 

Click here to see the references I use when researching ingredients! (From the FAQ) I also have a few blogs I like, which you can find down a bit on the right hand side of this blog.

Related posts:
Where to get good information? 

1 comment:

JoeyL05 said...

I am thinking about making a lip stain - water, glycerin, carmine. What should I preserve it with? I was thinking a broad spectrum (liquid germall plus) but wasn't sure if there are any special considerations for things going on your mouth. Thanks so much!