Reader Question – Percentages

In regard to preservatives, I know there is a certain percentage
required to add to a product, but how do I determine the amount? (is
there a mathematical formula?) For example, if I make a 16 ounce batch
of lotion how do I determine the amount/percentage of preservative to
add? ~ Charlene

Hi Charlene,

Thanks for another very good question!  Most
Preservatives should have a recommended usage rate.  At From Nature We
Love, we post these rates in each Preservative's product description. 
If you can't find the usage rate online, contact the manufacturer or
supplier to find out what it is.  Usage rates are also used with many
other kinds of additives and ingredients.  Once you know the rate,
you'll need to determine how much of your recipe works out to that
rate.  I'll use an example of 5% as a usage rate to show you a simple
way to do this.

Let's say you were making a 16 ounce batch of lotion.  The easiest
way to work with that amount is to first convert it into metric terms. 
Using an online conversion calculator, convert 16 ounces into grams. 
It should work out to about 456 grams.  Now, use a regular calculator to determine what 5% of 456 grams is.  You should come up
with a result of about 23 grams.  You can either measure your
Preservative or additive in grams, or you can convert it back to
ounces.  In this case, 23 grams would work out to about 0.8 ounces.

Do you have any tips on how Charlene can easily determine a percentage?  If so, please share them with us in the comments below.

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