Hello everyone. I've read lots of recommendations regarding the toning in selenium or gold that say that in order to achieve archival permanence it is necessary to "tone to completion". Since I'm mostly interested in image permanence and do not want too much color shift, I've bought a bottle of Tetenal Gold toner. How do I make sure that the toning has been taken to completion? The color shifts slightly rather quickly, and then how long should I keep the prints in toner? Does this time increase as the toner gets exhausted? I use Ilford MGIV FB. Any input would be much appreciated. Thanks a lot! Best regards - Carina.