Final answer:
When mixing less than 1oz of bleach powder for foil highlights, a proportional amount of Olaplex No.1 should be added according to the manufacturer's instructions, typically less than 1/8oz. Mass percentages like those used for liquid bleach active ingredients do not apply to Olaplex No.1.
Step-by-step explanation:
When applying foil highlights and mixing less than 1oz of bleach powder, the amount of Olaplex No.1 to be added to the mixture is not fixed by mass percentages like the active ingredient in liquid bleach, sodium hypochlorite, which has a mass percentage concentration. Instead, Olaplex No.1 is mixed in according to the manufactuer's instructions. For professional treatments like bleaching, it's essential to follow the specific guidance provided by the Olaplex system, which typically would be a small dose corresponding to the manufacturer's ratio, often measured in milliliters rather than ounces.
If you are mixing less than 1oz of bleach powder, the general recommendation for Olaplex No.1 is to add 1/8oz (3.75ml) of Olaplex for every 1oz of bleach powder. Therefore, for less than 1oz, you would use a proportional amount of Olaplex, less than 1/8oz. As this amount could be difficult to measure accurately, it's always recommended to check the guidelines provided by Olaplex for small quantity measurements to ensure the correct ratio is maintained for the safety and effectiveness of the product.