Adjusting pH in Shower Cream

You are right to be concerned about a shower cream with a pH of 11. This is very alkaline and can be irritating to the skin. Lowering the pH to 8-9, as you intend, is a good step, although ideally, shower products are formulated closer to the skin's natural pH (around 5.5-6.5).

To lower the pH of your shower cream, the most common and effective ingredient to use is Citric Acid. It is a mild acid widely used in cosmetics for pH adjustment.

Another option you could consider is Malic Acid, which also functions as a pH adjuster.

How to adjust the pH:

1. Prepare a small amount of the acid (e.g., Citric Acid), perhaps dissolved in a tiny amount of water if it's a powder.
2. Add a very small amount of the acid solution to your shower cream.
3. Mix thoroughly until the acid is completely dispersed. Citric Acid is easily soluble in water-based formulas.
4. Use your pH meter to measure the pH again.
5. Repeat steps 2-4, adding only small amounts at a time and mixing well, until you reach your target pH of 8-9.

Adding the acid gradually is crucial because pH can change quickly, and you want to avoid overshooting your target.

Both Citric Acid and Malic Acid are suitable for this purpose.