-
100% Perfect Formulation
For the last sixteen plus years I have be researching and delving into all sorts of topics in the Cosmetic Chemistry area. I have learned a great deal from great chemists like Perry and Maurice Hevey and others in crafting and soapmaking message boards as well as Cosmetic Chemistry boards. It was impressed upon me that working with a formula based on 100% was crucial and that in making sample batches you may find the need to add an ingredient to the formula and that you must recalculate the formula to include the ingredient so that it again equals 100% which I try to do hence the question about the calculator. However, sometimes I have seen posts on other boards that say “Oh, just take it out of the water phase” which I didn’t think was the correct way to do things.
So, after looking at Perry’s Excel sheet video, I am seeing that when each ingredient is added, the water percentage lowered. So, now I have to admit that I am confused and I should would like to hear from Perry or anyone else (with a serious reply) so that I make sure that I am understanding this correctly. Sometimes you have to go backward a little to go forward!
Thanks!
David -
13 Replies
-
I’m not sure I understand your question but I’ll take a stab at an answer.
First, every formula always adds up to 100%.
It is convenient to assume that one of your ingredients is the main solvent, and then whenever you add a new ingredient you just subtract that amount from the main solvent (usually water).
So if you start with water and add 1% citric acid, you know have 99% water and 1% citric acid. For each subsequent ingredient added you can reduce your main solvent level accordingly.
When you need to recalculate.
Recalculating is only required when you make a batch of something and then add an ingredient afterwards. So, suppose you have a formula with 99% water and 1% citric acid. But say you want to add some functionality like 1% tetrasodium EDTA. Well, you can’t just add that ingredient to the finished product because now your total formula volume is greater than 100%.99% water
1% citric acid
1% EDTAIn this case, all the ingredients would have to be recalculated to get their actual percentages. The total amount is 99+1+1 = 101. So the actual percentages are
water = 99/101
citric acid = 1/101
EDTA = 1/101I’m not sure if that answers your question but hopefully it does.
-
So Perry,
In the last paragraph you are saying that your formula now equals 101%
Don’t you have to recalculate to get your actual new formula that is 100%?
If so wouldn’t it be:
water=98.02
citric acid = .99009
EDTA = .99009now totally 100%???
-
Now if I wanted to change one of my formulas to increase the amount of one ingredient which is currently at 10% by say another 10%. (Doubling it) Wouldn’t I take the current formula minus the ingredient and recalculate it down using 80% as my total so all the current ingredients keep their proper percentages and relationship to one another and now equal 80% of the formula and the other 20% is the ingredient that I doubled is then added to the 80% to equal 100%?
-
“Don’t you have to recalculate to get your actual new formula that is 100%?
If so wouldn’t it be:
water=98.02
citric acid = .99009
EDTA = .99009now totally 100%???”
YES, that is correct.
-
Now if I wanted to change one of my formulas to increase the amount of one ingredient which is currently at 10% by say another 10%. (Doubling it) Wouldn’t I take the current formula minus the ingredient and recalculate it down using 80% as my total so all the current ingredients keep their proper percentages and relationship to one another and now equal 80% of the formula and the other 20% is the ingredient that I doubled is then added to the 80% to equal 100%?
In this case, you would simply reduce the water (or solvent) amount by 10%. You don’t recalculate all the other ingredients. Just the solvent.
For example, if you have a formula that is…
Water = 80
Citric acid = 10
EDTA = 10and you wanted to double the amount of citric acid. The formula would then become…
Water = 70
Citric acid = 20
EDTA = 10 -
I think I understand but it appears from what you said that you have different “cases” dependent upon the ingredients and their purposes?
If you are starting “from scratch” you would do it as it was done using your Excel file in the video, in that you kept the water as a “constant” at the top which then would reduce percentage as each new ingredient is added?
If you have a formula you have already made, decide to add something to the batch thereby increasing the total amount you would do as I suggest above in my post where I recalculated it back to 100%
Am I understanding this correctly?
-
It’s a ratio that changes and is expressed in %.
-
????
-
David, the point is how do you want to change the formula. If you want to increase an ingredient you have to decide (it depends of many factors) between at least 2 options:
1- To add an amount of your ingredient and do not change the rest of your formula. In this case % of the rest of ingredients are reduce proportionally to his initial % because “you can not have” more than 100%. That would be this example:
water=98.02
citric acid = .99009
EDTA = .99009
2- to increase your ingredient reducing another/s (for example reducing the solvent) but not the rest. That would be Perry´s example (he reduced just the solvent):FROM
Water = 80
Citric acid = 10
EDTA = 10TO
Water = 70
Citric acid = 20
EDTA = 10Look the finals % to try to figure out how is going to impact the formula.
-
@David08848 - “Am I understanding this correctly?”
I think you’ve got it now. Before you make a batch you can make all adjustments by changing the amount of water (or main solvent).
After you’ve made a batch and you want to increase the level of an ingredient, you have to recalculate all the ingredients. In fact, I don’t think it’s possible for you to add an ingredient to a finished formula without affecting the levels of all the other ingredients in the batch.
-
PharmaSpain, that helps to clear things up a bit, thanks! It appears that there are several options to choose from and limiting it to one may not be your best choice.
Now to throw another aspect into changing a formulation, I want to add a larger amount of the humectant to one of my formulas that has three bases which are saponifying fatty acids and oils but I don’t want to change the water amount because I am concerned about speeding up the saponification process because using less water makes a stronger base solution.
If I am upping the humectant by a small percentage it may not make much of a difference so it makes sense to me that I have to use “Try-chemistry” and just try a sample batch to see how it turns out!
Thanks Perry for your replies and clarifications and PharmaSpain for your post proving the old adage that the first day you learn the rules and the second day you learn the exceptions to the rules and there appear to be several acceptions in this case!
-
@PharmaSpain It is actually an interesting point that you never can vary only one ingredient in a formula - you have to vary at least 2 or more
Log in to reply.