I found Ivory Black to be much warmer and weaker (in pigment concentration/opacity) than Lampblack. But so much depends on the brand. Good luck!

Vaughn

PS -- depending on your RH, I found I needed 48 hours to dry freshly poured tissue at general room temp (with a fan on the tissues for the first 12 hours). Our RH usually ranges from 60 to 70%. If you do sensitize and print tonight, incomplete dried tissues might give some mottleing in your prints (probably due to un-even absorption of the sensitizer).