Fadedawg, is that you, the master?? GW?? I started this thread about 3 days after getting no action at IC. I kept it going to get different opinions on the process. You have been invaluable! Still so much to learn. I'm approx 400' above sea level, so I'm hitting 29.9.
Graywolf yes, master, not so much...............
We should maybe first define the term shatter??? I define it as a scale that ranges from glass brittle at room temperature, to pull and snap, which is slightly pliable, but not tacky at room temperatures.
To be brittle at room temperature requires high levels of carboxylic acid as a percent of the whole. It is the attached COOH carboxyl group, that raises their melting point and stiffens them. Once it is removed, the melting point is closer to ambient, so they become looser and tacky at those temperatures.
Retained solvent and water also makes them looser, so both need to be purged.
High levels of C-30 plant waxes make the mixture pliable and cloudy.
Lastly, and more to my point, is that monoterpenes are alcohols, ethers, esters, aldehydes, and ketones, so are solvents themselves.
It doesn't take many monoterpenes mixed with the carboxylic acids, to turn a brittle mix to a pull and snap. As a tongue in cheek overall thought, more monoterpenes mean more aroma and flavor, so more is gooder, up to some point where it is just too, too much.
Besides the C-10 monoterpenes and C-15 sesquiterpenes, where as a general rule, more is better, there are the C30 group where mostly more is badder.
Ostensibly the only good thing in the ~C29/33 group, are the C-30 flavonoids, but with them come the plant waxes, chlorophyll, and the anthro cyanin plant pigments/glucosides.
Not only do they dilute the mixture, making the carboxylic acids a smaller percent of the whole, but they darken it. Especially the chlorophyll and anthro cyanins. The anthro cyanins not only are plant color pigments, they are plant sugars that caramelize with heat and darken.
The best way I've found to get the best product, which for me is typically a pull and snap, is to start with young material, still in the carboxylic acid state. It can be done cured or fresh frozen. Easier to get stable gem quality shatter with most of the water removed first, and I consider that after hanging until the small twigs snap, it is ready to extract.
If I'm extracting fresh frozen, I cut the buds up into about 1/2" chunks and pack the columns before freezing them, so to not expose the trichomes to atmospheric moisture, so they coat with ice.
With both, I prefer the columns at around 0F and the LPG mixture (7/30-50/50%) at around -40C. I don't soak and run approximately three column volumes of LPG through them, first from the bottom, followed by a top flush.
That isn't going to work for you passively, but if you put your lower tank in dry ice and alcohol/water mix, and use a warm vapor pressure assist tank (or N2) to exert enough pressure on the chilled tank, to push it through a heat exchanger on the way to the column, and flood from the top only, you can come close.
I like to finish in a cotton candy foam shatter, because you can't get a thinner film to purge from than the walls of a bubble, so it removes more of the butane before it leaves the Terpenator. You can achieve the same thing with an active or passive system, by switching from recovery to high vacuum as soon as the butane pool is visibly gone and only random bubbles appear. Once it inflates into a foam, I hold it there until it dries stiff and brittle.
I then back fill with N2, vacuum to -29.5" Hg again and backfill with N2 again, before opening. I like to freeze the pot to further stiffen it and then just whisk it to powder with a spatula, and pour/spread it onto parchment sheets in a stainless tray.
I preheat the oven to 115F and set the tray inside. I note the temperature that the powder turns fully liquid, and reset the oven to that temperature, before starting the vacuum and pulling until the muffin starts to foam up and holding at that level until it calms down and then continuing down to around -29.5, stopping and holding as necessary on the way.
When the bubbles slow down, I take the sheet out of the oven, place another parchment sheet over the top, and flip the patty, then peeling away the now top sheet and replacing it in the oven. Repeat that finish procedure until the solvent bubbles cease and only CO2 bubbles fizzle here and there, mostly around the edges.
Remove at that point and cool, before testing extensively.