Understanding AHA Percentage in Your Formulation

It's great that you're getting started with making your own formulations! Calculating percentages is a fundamental skill.

How to Calculate Percentage Concentration

The percentage concentration of an ingredient in a formulation is calculated based on the weight of the ingredient relative to the total weight of the final product. The formula is:

(Weight of Ingredient / Total Weight of Formulation) * 100%

Your Example: 20g Glycolic Acid in 100g Total

Yes, you are correct! If you use 20 grams of Glycolic Acid (AHA) 100% Powder in a total formulation weighing 100 grams (which includes the water, gel maker, and the glycolic acid), the concentration of Glycolic Acid is indeed 20%.

Calculation: (20g / 100g) * 100% = 20%

Making 150g of 20% AHA Gel

If you want to make 150 grams of a 20% AHA gel using Glycolic Acid (AHA) 100% Powder, you need to find out what 20% of 150 grams is.

Calculation: 20% of 150g = 0.20 * 150g = 30 grams

You would need 30 grams of Glycolic Acid (AHA) 100% Powder for a 150-gram formulation at a 20% concentration.

Reducing Viscosity

If your gel formulation is too thick (high viscosity), the easiest way to reduce it is by adding more of the liquid phase, which in your case is likely water. However, be mindful of the next point.

Effect of Adding Water on Concentration

Yes, adding more water (or any other solvent/base) to a finished formulation will dilute all the ingredients, including your AHA. This means the percentage concentration of the AHA will decrease. For example, if you have 100g of 20% AHA gel (which contains 20g of AHA) and you add 50g of water, your new total weight is 150g, but you still only have 20g of AHA. The new concentration would be (20g / 150g) * 100% = 13.33%.

Therefore, if you need to adjust viscosity by adding water, you are also reducing the active ingredient concentration. To maintain the desired concentration while adjusting viscosity, you would need to reformulate or potentially use a different type or amount of gel maker.

Remember to always consider the recommended usage rates and pH requirements for Glycolic Acid (AHA) 100% Powder, especially for consumer products (typically not exceeding 5% AHA and pH not lower than 3.5).