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Wasn’t sure if this post should go here or under the ingredients section so I apologize if this isn’t the place. I have a question about measuring preservative amounts. I’m going to make up some numbers so don’t get hung up on this but if my preservative has a maximum usage rate of 2% is that with the preservative included in the ingredients or without? Not sure if I’m being very clear in my question. If I have a recipe that totals 100g do I then add 2 g of preservative on top of the 100g of other ingredients or do I calculate things to come up to 100g including the preservative? Reading this I feel like I’m being clear as mud but hopefully someone will understand. As of now I’m just sticking with Marie’s recipes but in the future would like to make my own and don’t want to skimp or overdo it on the preservative.
It doesn’t really matter if you calculate it one way or the other.
If you have a 100g product, and the usage rate of your preservative is 1-2%, you add 2g of preservative to your product. You then have a 102g product. You divide 2 (grams of preservative) by 102 (final weight of your product), which equals 0.0196, or 1.96%, which is almost 2% and effectively within your usage rate of 1-2%. Hope this helps!Let’s convert % to g, so say you have 100g of ingredients, then add 2g of preservatives, you won’t have 2%, you’ll have 1.96%. As Maggie said, you’ll typically still be within the recommended usage rate, but most people include it in the recipe, because otherwise, all the other ingredients are diluted and it can affect the stability of your product. For example, if you have an ingredient that is effective at 5%, and you put 5g to make a 100g lotion, by adding the preservative to the 100g, giving you 102g, the 5grams are no longer 5%. Also, certain things can affect the stability of the lotion, and diluting them isn’t good. I always calculate the preservative into the 100% ingredient list, except occasionally if I’m making something like a room spray and don’t feel like calculating it, since I know it’s in the correct % range and won’t affect the product.
Great. This was exactly what I was trying to figure out, calculate with other ingredients or after & it sounds like it should be calculated with the other ingredients. Makes sense, not sure why my brain was having trouble with that. Your explanation is very helpful.
I know there is some lye calculation for soap makers (not a soap maker so I might be misinformed on what it calculates) but if anyone wants to make a preservative calculator I’d be all for it. I know if you make batches in grams & stick to multiples of 100 it makes life easier but punching some numbers into an online formula would be nice.
Anyone have tips for how they figure their preservative amounts? Does everyone just do it longhand or do you have tips? I’m not at the point where I’m formulating any of my own recipes yet but hope to get there once I learn a bit more. Maybe when I’m making my own recipes calculating preservatives won’t be as difficult as it is seeming now.
What I do, is write down the % of each ingredient that I know won’t change. For example, the emulsifier, or active ingredients, and preservative. Then, I add the oils in the concentration I want depending on texture, and fill the rest with water.
For example, for a lotion, I would maybe use:
1.5% preservative
5% active ingredient
5% emulsifier
25% oils
63.6% water or other water-soluble liquidThen, if I want 543g of lotion, I just do 1.5% of 543g = 8.15g preservative, etc.
If you are using an already made recipe, like those from Marie’s blog, just change the water % to allow the preservative. Ie. If she uses 70% water and 0.5% preservative, but yours uses 2%, then use 68.5% water and 2% preservative to still get 100%.
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http://www.humblebeeandme.com/faqs/search/preservativeIt’s awesome.
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