@ResolvableOwl I'm not sure where I've been unclear, but I have been typing responses in between dealing with screaming children, so it's possible I left something out as I've been distracted. I will try again.
On May 1, 2021 I made 4 small experimental batches of CP soap. The first 2 soap batters I made that day are numbered 18 and 22 respectively in my lab book. They are behaving just fine post-saponification (no DOS) and neither had lard in them. The 3rd and 4th soap batters I made that day are numbered 19a and b respectively. They were made as follows quoted from my lab book:
"19a: I poured melted 80g lard and 20g coconut oil into a plastic freshly washed cylindrical frosting container. I weighed out 1.4g of a 50:50 EDTA and distilled water solution and blended it into the melted oils. Then I weighed out 28g distilled water into a separate bowl that I had used for all other distilled water and lye solutions that day, then measured 13.76g NaOH (lye) crystals into my lye cup and slowly poured it into the pre-measured h2o. [So, I apparently was incorrect in previous posts where I went off memory and said 19a had 5%SF. According to my records it really had 8%SF]. Once the NaOH was fully dissolved in the water I poured it into the melted oils and EDTA mixture (I'm a rebel and decided not to wait for the NaOH solution to cool). I blended the tiny soap batter with a new stainless steel milk frother bought for the purpose of mixing small test batches. [On this 100g batch it added a ton of bubbles, but on batches 18 and 22 which were larger 300g batches it worked splendidly without incorporating extra air.] This batch took an irritatingly long time to come to trace. I think I read somewhere that lard takes a while to trace??? I'd love input if someone has experience with high-lard recipes and time to trace. Once I was satisfied that I had mixed long enough and it wasn't going to separate I poured the batter into my freshly washed rectangular cream cheese container mold. Scrape down and wipe out the cylinder frosting container in prep for the next soap batch.
19b: Methods same as 19a. Pour 80g melted lard, 20g melted coconut oil, and 1.4g EDTA solution into cylindrical frosting container. Blend. Measure 29.61g distilled water and 14.8g NaOH [makes 1%SF]. Combine. Blend hot lye solution into oils with milk frother. Wait an absurdly long time for trace. Leave 19b in frosting can mold so I can tell 19a and 19b apart by shape.
On May 26, notice orangey yellow edges on both 19a and 19b. May 27th reach out to soapmakingforum to find out if this is DOS or something else happening."
Is that clear enough? Did I leave anything out?
I have not been put off lard entirely. I see no point in discarding a perfectly good and economical triglyceride from all my recipes just because I used an older container of lard that I knew might be on its way out in the next few months and I was attempting to use it up to avoid going to the store for more. I've learned my lesson and might start storing more oils in the freezer. I have used multiple jars of multiple brands of lard in the past 2 years, and this is my first time having this DOS issue. My first ever lard bar made last year was lovely after a few months of curing. These DOS disasters were a SF preference test, a first non-goat milk soap test, and an EDTA test (as I've never used EDTA before...), not an oils test. 19a was supposed to be compared to my lard-and-milk soaps to see if I like how EDTA works with my hard water. 19b was supposed to be compared to 19a to see if I like high or low SF.
My conclusions based on further research, rereading my lab book, and y'alls input saying it looks like it looks like it could be DOS and that it is possible for very young soaps to go rancid, and even my children saying the orange soaps are starting to smell funny: I'll have to redo the test with some fresh lard next time the weather is nice enough for soaping outdoors. Also, I will look further into ROE and other (?) antioxidants...
Other wisdom/tips always appreciated.