Thanks for the detail!
# Issues:
- As the decoction reduced it would become thicker, splash onto the sides of the beaker and solidify. I would periodically have to scrape these solids off the sides back into the liquid. Maybe a magnetic stirrer would have prevented this?
One way I've resolved this kind of issue when reducing cactus brew, albeit a somewhat time-consuming one, is by using at least three snugly-fitting
transparent (i.e., glass) lids swapped in rotation, plus a basin of cold water.
When the liquid in the beaker (or, in my case, pan) starts simmering, place the first
cold lid on top. It will start to fog up with condensation, which subsequently forms droplets. Just before the droplets get big enough to start dripping back into the beaker, get the next cold lid ready and swap it with the condensation-covered one.
Collect the condensation into a separate container with the help of a silicone spatula if you like [it's more or less distilled water, but also might contain traces of spray from the brew], then float the lid upside-down in the basin of cold water so it will be cold enough to condense water rapidly. (It doesn't matter if it sinks, but having a lid that's only wet on one side is more convenient.)
Meanwhile, have the next cold lid ready, drying it if necessary. Less drying is better, otherwise you end up with a load of soggy towels. Using dry lids also helps to prevent contaminants from the basin water from dripping into the brew.
The cycle continues as before, replacing the hot, wet lid with a cold, dry one, scooping off condensation, placing the hot lid into the cooling basin and drying off the previously cooled lid ready to swap again. Keep an eye on the liquid level in the pan/beaker!
This process pretty much entirely stops the brew from leaving a deposit on the sides of the evaporation vessel as it reduces. The succession of lids helps to keeps humidity levels high enough such that the brew can't dry out and stick to the walls, at the cost of near constant monitoring of the lids. It's also a very crude and inefficient example of distillation, but it solved the "wall residue" problem for me.
As an illustration of time scale, it took about four hours to evaporate 2L in a 24cm pot with this method, using a gentle simmer to prevent scorching of the brew.