Barry
Now that it's established that the fat came from a donner right there on the farm, let's consider it from that perspective, or your grandmother perspective.
The butchering of the hog (common in the fall) was sometimes timed by the almanac and sometimes according to the moon. Some belived that this timing affected the taste, as well as the odor of the fat. At the time of butchering, fat was sometimes sorted... meaning, separated from back fat and "leaf lard" The leaf lard is considerd the best for baking, and has less taste or odor than the back fat. After that chore came the rendering of the lard. Another process that could go wrong if not careful, and if not done under controled temps..too hot could release a odor. Most likely the rendering was your grandmothers chore. This may explain greasy door handles ect.
Once the lard was "put up" it was ready for use.
So..Later..maybe that month..when she was ready, she picked her day for the soap making.
Sounds like your grandmother used what was called pot ash for her lye solution. And that's where the "fussing" starts!
She had managed to raise the hog, go through the butchering process, and cleaned up all that mess, then the rendering process
(possibly separating the best of the fat) and putting it up for storing. All of which could have taken a turn, and gone wrong. When she decided to make the soap, she was aware that this also could go off the rails, but I'm sure she took a deep breath and powered through the last of what needed to be done with that damn hog!
For the soap making she may have done as explained above for checking her lye solution strength..a crude "Baume" method
(floating egg, or chicken feather) and also adding salt to this solution to make sure she ended up with harder bar soap instead of soft soap.
She melteted the lard (that she worked so hard to get) and if it got a little too hot, it could release a odor.
(wasn't like she had a thermostatically controlled element to work work with or a controlled environment)
Once the lard was melted she probably slowly added her lye solution and started stirring. Hopefully the kids and chickens stayed out of it and didn't distract her too much.
She may have reduced the fire as best as possible but keept "a strin" She had already prepared her molds and had them ready for the pour.
As she watched the greasy mess inside the pot slowly change into a thick gravy like substance, she wondered "what I'm I dong this for" Oh ya.. Soap!
When the soap began to sheet off the paddle, she had reached what's called trace, this would be the time that if she was gong to add scent.. this is the time to do it, but never mind..keep stirring..before it gets too thick! Hurry and pour it.
Once that was done, she could kill the fire, and leave things to rest a spell. (Grandma needed a rest too)
The next day sometime between her other chores, and after the soap had set up, she un molded and or cut into bars. She most likely had rigged up some kind of drying rack somewhere for the bars to continue to cure.
Oh but what about that damn pot outside, and the paddle? Well, not to worry, what was left is now soap and will wash out easy!
Thank God something was easy!
In a couple of months, she had a clear idea as to how this batched turned out. And if she was happy with the results.. of course she'd be proud off it. Now, see why she was! No small task given ALL considered.
Now was her soap lye heavy? Or not heavy enough? Who knows! It cleans good and didn't burn skin, so all good!
Hope I've jogged good memory's of her for you, I'm glad you got a bar of her soap back. Next time you look at it, you remember this story! LOL