Litmus paper can never ever get a right PH level bacause only aqueous solutions could be tested for pH. The oil will interfere with the result.
You must use an industrial PH meter after seperating oil and water.
Even if the product itself sounds like it has only water in itself, for example, toner, it’s a mixture.
FYI, not all that’s slightly acidic is good to your skin.
The best PH level for acne treatment is usually 3~4. Not 5~6.
Most people tend to believe that a PH balanced product (Slightly acidic. Usually a PH level of 5~6 something) is best for skin.
And most brands do nothing with the comments that their products turn out to be PH balanced.
Make no mistake about it, PH paper can not get a right result.
The brands are just enjoying the compliments, even though it's not true, 'cause you said the producs were PH balanced.