Home Frosting Kit and Missed Spots
A: If the frosting kit is simply one that uses a "pure lift" action - meaning that it simply bleaches the hair from the natural color - then the bleach will be active as long as the mixture remains wet. You can even theoretically remoisten a bleaching mixture by adding water, and it will continue to bleach the hair when applied.
There is also the fact that storing these mixtures once they're combined is dangerous. The bleaching properties use a chemical reaction that gives off heat and by sealing the container you could discover that the container bursts, leaks or causes other forms of damage if it should escape its confines.
The good news is, that the warning of waiting TWO DAYS to highlight again, refers to the attempt to lighten an area previously lightened. If you used a cap or foils to isolate locks of hair to be lightened, then you can easily get another cap (or use foils) and highlight the hair that hasn't been previously lightened whenever you are ready to do so.
Just be sure to use caution and not double expose pre-lightened hair to lightening solutions again or you could seriously damage that portion of the hair.
©Hairfinder.com
See also:
How to color and highlight hair
Highlighting with a cap
Highlighting with foils