Quenching BRASS has no effect on hardness, it merely cools it, or in other words, STOPS the annealing process, which many do wrongly anyway.
BRASS can only be hardened by working it, which means moving it’s grain structure by stretching it, compressing it and pounding it.
If you anneal to ANY red colour, cherry or dull red is often coined, you have essentially ‘burned’ the metal. Burnt in this instance means that you have broken the grain structure by CHANGING the chemistry of the brass by forcing molecules to ‘gas off’. The grain structure when properly aligned through annealing run parallel and have ‘gas’ adhesion, when hardened, the grain jumbles around and loses this gas adhesion. Burning the brass destroys the gas adhesion.
If you anneal correctly, time and heat is spot on, just as the annealing temp OF THE BRASS is reached, an orange/pink flame occurs, or hue, is seen, this is the gas in the grain structure releasing, go beyond this point and you ruin the grain structure. Just as that point is reached and the case is removed from the heat, the gas resettles and annealing has taken place. If you quech at this time, as many do, it does not change the annealing that just occurred.
In my job, I am required to anneal to certain conditions of the metal in question. I make copper, aluminium and brass element windings for helical type induction, if the anneal is wrong the metal will crack as it is wound, that is unacceptable in my industry.
We manually anneal copper bar because you can SEE when it gasses off and sags, other metals are induction furnace heated, but checked by hand first for the correct temp.
It is rare to get ANY type of hardness back from ‘burnt’ brass.
Hope this helps.
Cheers.