Info is VERY scarce about this, but when you cook canabinoids in the presence of fat, it not only is disolved, but it undergoes a chemical change as well. IIRC is is decarboxylated or something similar. this is the reason for the difference in acute effects in cooked vs smoked pot.
consumed cannabinoids are not just uptaken differently, they are actually utilized in a slightly different and more efficient manner in the body.
if anyone could back me up on this, id love to re-read whatever it was that i read this out of at some point in the past.
WMM is correct, the density of the baked good will trap and condense the evaporating cannabinoids. This leads me to believe that the cannabinoids undergo an oldschool under-investigated proccess called isomerization. It can be done at low temps in a large unit, or most correctly in a sohxlet extraction device.
I have looked into this extensivly. when the extraction liquid is evaporated and condensed thousands of times, as such the case with isomerization is, it undergoes a chemical change where the cannabinoids reduce and become very similar to eachother. i have altho never foudn a scientific explanation of what chemical change takes place.
I know anecdotally that the isomerized thc product is orally viable, smokable, vapable. it resembles a very fine black fluff opium. when several grams are consumed orally it is highly halucenogenic in nature.
NOW, this is a total stretch, buuuuut i find it conceivable!
What if the repeated evaporation and condensation within the dense brownie batter simulates a low key for or natural isomerization. this could be tested but i have no means to identify or isolate cannabinoid isomers.
also cannabinoids dont breakdown until 400-500f, so none will be straight destroyed either.
Also, Does anyone have an accurate measurement of the solubility limit of clarified, unclarified butter, and olive oil? I know the alkaloid saturation point for iso, naphtha, and acetone, but not eatable solvents
ALSO, i happen to be a chef and can tell you this if you are still worried about evaporative loss. Brush the top with a small amount of water part way thru baking, or, coat the top with a layer of sugar or bakable icing(the best way), OR if you dont mind the taste mix egg whites with powdered sugar and whip into a good slurry. brush the top with this once it is a little firm and settled.
The way bakers get a nice crust on a loaf of bread is by placing balls of ice on the oven racks with a pan below it. it ice melts, drips, hits the hot pan and vaporized. this makes a really hot high humidity environment which causes the outside of any baked good to crust without getting HARD and crunchy. all these are methods to use for other things in the kitchen so some adaptation and experimentation is required.
all ove these methodes will add a rather inpermiable layer to the top to help retain moisture.