Most of the ceilings in this house were not taped when they were repaired. I'm assuming this untaped drywall (aka sheetrock, wallboard, gypsum board) job was a repair, because I can't imagine the ceilings in this 50+ year old house are original.
Anyway, after reading a zillion web sites and buying the recommended Black and Decker Home Repair and Improvement books (these books are a great investment if you are a DIYer), I decided I could improve the repair. So, after a run to Lowes to buy joint tape and joint compound, I was ready to begin.
I spread a thin layer of mud (aka joint compound) along a 5 foot section of the ceiling where two sheets of drywall came together (the untaped joint). Then I put the joint tape on and smoothed it out, working from the center out to get excess mud out from under the tape.
After 2 more days of putting thin layers of mud over the tape, feathering it out to blend with the surrounding ceiling, and waiting overnight for each layer to dry, the joint looked pretty good.
But then, I had an "bright" idea. I'd read about a drywall repair online in which the DIYer had cut the tape in half horizontally, effectively reducing the amount of mud needed and time spent feathering the mud.
So, I figured that if I cut the tape in half before I laid it on the joint, it would take less time and less mud to feather it out.
Boy was that a bad idea. In the first place, trying to keep the 2" wide tape straight was hard enough, but when I cut it down to 1" it was nearly impossible to tell where the joint was and keep it straight.
That didn't stop me though. I kept cutting the tape in half and eventually finished the first room. Once again, I applied (what I thought was) thin layers of mud over the tape and waited overnight for them to dry.
After buying the Kilz primer, I inspected the ceiling. I wanted to make sure it was an actual improvement before I painted it. The ceiling looked a little humpy where I'd applied the cut tape, but I thought (hoped) it would blend in once it was primed. (HA!)
With the primer on, the "humpiness" is even more noticeable. So, now I have to mud and feather over all the areas where I'd cut the tape in half.
The 5 foot section I did with the 2" tape blends in just fine.
Lesson Learned: Feathering the mud is actually harder to do on a more narrow path (1" taped joints) than it is on a wider (2" taped) path.