Scarification, regardless of type, works by speeding up the natural processes which normally make seed coats permeable to water and air.
For drupes (stone fruits), scarification also extends to weakening or removal of the hard endocarp shell around the seed.
An exception to that phenomenon is western poison oak, whose thick seed coatings provide a time delayed effect for germination, but do not require fire scarification.
[5] Chemical scarification occurs commonly in nature in the course of endozoochory—when animals consume fruits and seeds and their stomach acids soften and begin to break down testae, rendering them more permeable to water.
After the seeds have been expelled through defecation they are not only pre-packaged in plant nutrient-rich faeces but also more susceptible to imbibition—the process of water uptake essential to the initiation of germination.
[6] Artificial scarification involves human use of one or more chemicals to mimic the natural stomach acids of frugivorous animals to promote germination.
The thawing and freezing of water, fire and smoke and chemical reactions in nature are what allow seeds to germinate but the process can be sped up by using the various methods described thus far.
Finally the hairy bigleaf lupine's control group germination rate was 32% yet when treated with sulfuric acid it rose to 76.8%.