Una vez que... +subjuntivo vs +indicativo

Question

I have encountered real-life examples using both indicative and subjunctive with "una vez que..." and I'm just hoping to confirm or correct my understanding of how this works, please...? For examples, In an article about animals' senses of smell, in discussing the properties of volatile scent compounds I read "Una vez que se vaporiza, puede extenderse rápidamente por el aire" and in a tutorial for making tortillas mexicanas I found "Una vez que sepas cómo hacer tortillas..." I'm thinking that the first takes the indicative because its describing something factual understood to happen routinely, whereas the second takes the subjunctive because it's referring to something that from the writer's point of view hasn't happened yet or is more a hypothetical idea. Is this an accurate way to understand this or am I missing something...? If this is accurate, does it generally hold true with other, similar constructions like those discussed in this lesson? Thanks in advance, as I appreciate the help!

Accepted Answer

Hola Sky
Yes, your assumption is spot on! 
Una vez que... can be used with both in the exact contexts that you explain. 
"Una vez que" is a conjunction that conveys more or less the same as "cuando..." - we can't make a lesson for each different conjunction, but if you look at this lesson about cuando +present indicative/subjunctive, you'll see how it also applies to other time conjunctions. We give a couple more examples at the end of the lesson with other time phrases. 
I hope it clarifies it.
Saludos cordiales
Inma