Well it may look great, Donald, but I've not had much success in rusting with it using acid fumes.
Strangely, using hydrochloric brick cleaning acid the metal struck black in the cabinet but never actually produced red rust.
--- This black never got any thicker over ten sessions in the fume cabinet.
So today I changed tack and gave up with the fume bluing and changed to rust bluing, by turning the heat up in the cabinet and putting a pellet tin full of water inside it became a damp box.
I'm now using a saturated water/Ammonium Chloride solution to coat the metal before placing in the fume cabinet to rust --- instant success.