Tom;
To answer your question;
Yes, a powder oxidizer should be added when the job requires it.
Our PowerMax contains a powder oxidizer, but on some grout cleaning jobs you will need to add more to get the grout back to original color.
We like to sprinkle it on the presprayed floor and brush it in.
It will then accumulate in the grout lines where it will have the best effect.
Larry Cobb