In this post, Question: Why would you leave preservatives out for sensitive skin?, Mariena asks: I use Phenonip in my lotions and emulsified scrubs and was wondering about the 0.5 to 1% usage rate. How do I know when to use just 0.5 and when to use 1.0% Perhaps in an anhydrous product, I could use 0.5 and in a lotion containing water, use 1%? What do you think?
When it comes to preservatives, I tend to err on the side of caution and use the maximum allowed because I can't be sterile in my workshop (but I do my best to be very clean). You'll notice in my recipes I always use the maximum allowed for Liquid Germall Plus because I don't know how you will make the products at home, and I'm hoping that using the maximum will cover you for all possible problems.
Having said this, like Liquid Germall Plus, Phenonip is a very good broad spectrum preservative, so it will do a great job at protecting your products at lower levels. If you're using hard to preserve ingredients - like our botanicals - then I'd go with the higher levels. If you aren't using a lot of botanical ingredients, then consider using a lower level. It really is up to your judgement how much you wish to use.
As an aside, you do not need to preserve products that are anhydrous - meaning they don't contain water - that won't be coming into contact with water. Products like whipped butters, lip balms, balms, sera, and so on don't need preservatives. You could use an anti-oxidant like Vitamin E to retard the rancidity of the oils, if you wish. Sugar and salt scrubs require preservatives because they are coming into contact with water when you put your wet hand into them when using them at the sink or in the tub or shower.
Preservatives section of the blog
Water activity and sugar or salt scrubs
In the same post, La Prairie Lady asks: I saw a lot of recipes with citric acid in water. that help ?? or just a light preservative for 1 month in the fridge.
Citric acid (or 2-hydroxy-1, 2, 3-propanetricarboxylic acid) is a chelating, anti-oxidizing, and pH altering ingredient that can bind metal ions, help prevent rancidity, and alter the pH of our lotions and surfactant mixtures. It is not a preservative that can prevent contamination from mold, yeast, and bacteria in our products.
Rancidity is a natural process in which our oil based ingredients degrade over time by being exposed to heat, light, and oxygen. It is inevitable, and while we can add anti-oxidants to our products to slow down the process, but we can't stop it completely. Citric acid can behave as a water soluble anti-oxidant in our products.
When citric acid is used as a chelating ingredient, it binds metal ions like calcium, magnesium, copper, zinc, nickel, and cobalt to keep our products from experiencing auto-oxidation. By binding these metals, it also keeps surfactant mixes nice and clear, and it helps to boost the efficacy of your preservative.
As an aside, you may see citric acid listed as a "natural preservative" for foods. This does not mean it is an effective preservative for cosmetics, and it is not approved as a broad spectrum preservative for our products. You might see it in combination with other preservatives, but generally it's being used as a chelating or anti-oxidizing ingredient.
If you're going to use a preservative, use it at the proper usage levels. As you can see from Liquid Germall Plus, the suggested usage rate ranges from 0.1% to 0.5%. Find something like this and use the lower level. If you use the lower level, you don't need to put it in the fridge - you can leave it out and use it like you would any other product.
HOW MUCH PRESERVATIVE SHOULD I USE IN A SUGAR SCRUB?
In this post, Formulating for your skin type: Emulsified scrubs for dry skin, Candice asks: When calculating the amount of preservative, should the weight of the sugar be included? If I make 100gr of scrub and add 140gr of sugar, do I include my preservative (1% optiphen in my case) as 1% of 240gr or 1% of 100% (only the emsulsion part, pre-sugar)?
You don't need to preserve the sugar or salt in a scrub, just the base of oils and other ingredients.
Join me tomorrow for more formulating fun!