This is very educational and useful, and this is the right forum for the info. Thank you, and Merry Christmas!
You are absolutely right, that the purpose of scarification, in all its methods, is to allow water to penetrate through an otherwise impermeable seed coat. And especially, that one needs not remove to the entire depth of the seed coat to achieve the goal. Only enough to allow adequate water penetration. The part of the seed inside the seed coat is delicate and usually quite susceptible to pathogens, especially if damaged. If you expose the inside part, you are providing an easy way for pathogens to enter. When hot water treatments work, the temperature gradient creates tiny (microsopic) fissures in the seed coat through which water can penetrate.
I have never attempted acid stratification, either. The application time needed has so many variables: species of seed and geographical source of that seed, when the seed was harvested, temperature, concentration of acid, type and form of acid, etc., etc. And useful data sources are very limited, not to mention (as you say) where to obtain said acids.
For me, any seed needing scarification large enough to grab I will do it with a file, or individually sand with sandpaper. Any smaller seed I carefully rub between sandpaper. It is very easy to overdo it, especially with the small seed, so I always recommend prudence.
The graph you composed could be quite useful, but in its present form it is very misleading. The time scale is enormously variable, with eight increments equaling one hour at first, then one increment equaling an hour, then eleven. Could I ask you to redo it with a consistent time scale? The result will be much more dramatic, and true to what is actually happening.
Again, thanks so much for the time spent putting that post together for us. Hard data and unambiguous writing is rare among the chit chat of forums across the internet. Bravo!
