I have a friend who knows a guy who ate a pig whose last dying effort involved innoculating some brf cakes. Well it turns out he knew this half jamaican half chinese ant eater/komodo dragon who once claimed he invented pumice...

anyway HE sent a message in a bottle saying that these BRF cakes are all colonized on the visible edges of the glass and is in the process of leaving the jars a few more days to insure full colonization of the cake. Anyway turns out the chap being part ant eater is fairly nose curious and he's been sniffing his jars. A jar that still has un-colonized substrate visible still smells of brown rice flour, jars that appear to be mostly colonized smell almost odourless and the jars that have been colonized for a little longer are starting to have that farmiliar mushroomy smell.

So I'm wondering if smell is a reliable test for finding out if jars have been adequately colonized or if this strange ant eating dragon chap should stick his nose in some place else?

Thanks in advance!

Smell is a great way to tell if you have contaminants (but watch out, if you are dealing with contams you dont want them flying up your nose!) but I would not say it is a reliable method for determining % colonization. Usually I just use my eyes, smell confirms that they're clean, once the white fuzziness is thickening and has coated the entire cake, you're about good to go. It will start to twist up after this and fully colonized jars can hang out for a little while (although you dont want to let them go too long). It should be fairly apparent, I tend to bang the jars with my hand throughout colonization to break up the myc and increase the speed of colonization. At a certain point the colony is too developed to really break up like that anymore, that's when I know they're about done colonizing.

peace
SB

smell is only a good way of determining if a jar has been infected with bacillus cereus, an anaerobic bacterial contaminant. they thrive in wet spots along the jar wall.
this becomes apparent a few days after innoculation, it will smell like rotton apples

my buddy usually does wild bird seed and he cant smell them until he shacks the jar and breaks up the giant cake. i love that smell so much lol.

I'm gonna say the "Sniff" test is not super reliable and may not be the best idea. There are some bacteria and molds that produce toxins as their waste. Some of these are extremely toxic to man (don't ask me to quote which ones). I'd stick with the visual test. Does it look fully colonized? if yes, wait another 2-4 days and then birth.