Think carefully before you answer, revisited

This is the same sketch, shown a few pictures back, with acrylics added.

I've been doing a lot of playing lately putting acrylic washes atop charcoal sketches. I've found if I 'fix' the charcoal using cheap hair spray as a fixative, I can lay acrylic over it without smearing the charcoal.

Most charcoal artists will tell you only archival commercial fixatives work, that hair spray will yellow your paper over time.

Well, maybe so, but I've many charcoal sketches well over 5 years old, that I've fixed with hair spray, that have been hanging in indirect sunlight all that time, that show absolutely no signs of yellowing.