I can settle this argument between you. The answer is that you are
both right.
It totally depends on the method of crystallization. Gradual cooling is recommended, since it takes less time and gives bigger crystals.
To understand why this happens, people need to understand what actually happens to a solute (DMT in this case) when placed in a solvent.
What is heat and why does hot solvent pull more DMT?First, people need to know why hot solvents dissolve particles better than cold solvents: Heat-energy is what breaks apart the molecular bonds in the crystal lattice of the
solute (in this case DMT), so that the crystals break down into their individual molecules, which then become light enough to bond to the
solvent instead. This is why hotter solvent can hold more solute (DMT), and why hot pulls are
much, much better than cold pulls.
In fact, heat
itself is nothing more than the
kinetic energy of vibrating (dancing) molecules. The faster/more forcefully they vibrate, the "hotter" it is. But the atoms themselves don't "know" that they're "hot" or "cold". They're simply vibrating. "Hotter" is actually just a word for "vibrating so forcefully that they collide into and rip apart any other molecular structures they come into contact with". When we touch something "hot", its interaction with our body is what we perceive as the feeling of "heat".
And that interaction is simple: Collisions! The high vibrational energy of a heated material will cause it to smash into the atoms of a lower-temperature material (or vice versa), and that's what you feel as the pain of "hot" things. It's just the atoms smashing into each other and ripping each other's structural integrity apart.
This can be seen if you lower hot iron into cold water. There will be violent bubbling. But as soon as the atoms in the two different-temperature materials have reached the same vibrational speed (the same temperature), the reaction stops.
These vibrational collisions don't just happen from material-to-material. It happens internally too. The hotter something is, the more violent its internal vibration, which of course causes
its own atoms to smash into each other too. That is why heat destroys many materials. For instance, melting a metal like iron is simply the act of bringing it to a temperature where the vibrations are so violent that the inter-molecular bonds of the iron finally break apart its own crystal lattice and it dissolves and becomes a liquid instead. Sure, we might
think that things like iron are "solid" materials, but many people will probably be surprised to hear that you can even bring something as solid as
iron to temperatures where it's
melting (1535*C), and finally actually
boiling (2750*C).
That is why heated pulls are better. The heat-vibrations break apart the inter-molecular bonds of the DMT molecules, thus dissolving the big and heavy crystal lattices (structures), and allowing the
individual DMT molecules to bond to the solvent instead. As long as the heat is maintained, the particles will stay dissolved. The DMT molecules will either stay bonded to solvent molecules, or they'll stay "vibrating" and free-flowing in the solvent. But as soon as the temperature drops, the super-saturated ( meaning "more saturated than normally possible at room temperature" ) solvent will slow down its internal vibrations, thus allowing the DMT molecules to form undisturbed crystal lattices again (which will no longer be ripped apart by heat-vibrations), and they then become heavier and heavier until they begin dropping out of the solvent. We therefore need to
maintain the solvent's heat of a heated pull until the pull is done.
And that brings us to a very related side-note, where it's time to clear up a very common mistake: If you put hot solvent into cold water, you are
actually doing a
totally cold pull, since the water will rapidly cool down the solvent
within seconds and return it to room temperature. The cold water and cold solvent will not be able to heat up the DMT crystals and won't break them apart; so putting hot solvent in cold water is a
totally pointless idea and is
the same as a cold pull. To get a
real hot pull, you
must have
both hot water
and hot solvent, so that the non-polar solvent maintains its heat and the DMT crystals
stay dissolved in it.
Onto the topic of freeze precipitation, and why colder solvent can no longer "carry" as much DMT:When the temperature drops, the vibrations slow down and the DMT molecules have a chance to re-join each other to form crystals again, without constantly being ripped apart by heat-energy anymore. When those crystals become big enough, they become too heavy and they sink out of the solvent. That is how you freeze-precipitate.
If you put solvent straight into the freezer, you
immediately remove the heat-energy and cause the "heat-dancing" molecules to calm down and you slow down their vibrations almost instantly. This of course means that they are now free to re-join each other and build new crystals
without being constantly broken-apart by heat-energy.
But, when their vibrations are extremely slow, they will have
much fewer chances to dance around and travel throughout the solvent to bump into each other and form crystals. So when you go straight to freezer, you
need about 48 hours for
most of them to have a chance to bump into each other. You will also get much smaller crystals (mostly sediment at the bottom of the jar), since the molecules will only bond to their closest neighbors and won't have a chance to "dance all around the jar" to meet bigger crystals and join them.
If you instead slowly cool it; first to room temperature, then to the refrigerator, and finally the freezer, then you'll gradually slow down the molecular vibrations. The heat-energy will calm down enough to stop ripping-apart the crystal lattices (it will stop re-dissolving the DMT crystals into individual molecules), but will
still be hot enough to provide enough energy to make the molecules dance wildly. And when they dance; they travel around in the solvent and meet each other and form bigger crystals in less time.
People who are going straight-to-freezer need to wait for the whole 48 hours. People who are gradually cooling need to wait for around 12-15 hours.
If you gradually cool the solution, you don't actually need to monitor your times. It's fine to keep it at room temperature for as long as you want, and the refrigerator for as long as you want, and the freezer for as long as you want. The principle is the same, and there's even a benefit to waiting a bit longer. So people doing gradual cooling should probably spend 1-2 hours at room temperature**, about 2-3 in the refrigerator, and the rest of the time in the freezer. Remember: The
slower you cool it, the
bigger the crystals. And there's no such thing as "too slow". In lab settings, things can be cooled even more precisely and will sometimes be allowed to cool one degree at a time, over a long period of time.
** About the room temperature step: If you did a
cold pull, you should
skip the room-temperature step. The reason is simple:
Hot solvent is supersaturated thanks to the heat, and when it's allowed to cool to room temperature the carrying-capacity decreases and it becomes
even more supersaturated. But
cold solvent was
already at room-temperature when you pulled, and will therefore
not become supersaturated by sitting at room temperature. The only way to get cold solvent to become supersaturated at room temperature is to pre-evaporate some of it. Cold pulls are therefore
never recommended,
unless you
also have access to vacuum distillation to evaporate and supersaturate the solvent without
losing any of the solvent,
or if you simply don't care about evaporating a large amount of your solvent into the air and losing it forever. People using Naphtha and doing cold pulls usually evaporate some of it, since Naphtha is so cheap that it doesn't matter. But people using
Heptane know how expensive
that is, and should use hot pulls instead, so that they don't have to evaporate anything.
Here are some more tips that help crystallization:
* Supersaturating the solvent via heated pulls and/or pre-evaporation will ensure that you have
lots of DMT molecules in as little solvent as possible. This maximizes the chances of heat-dancing DMT molecules randomly bumping into each other and forming crystals. To help understand this; imagine that you and your brother are in two random places in America. The continent itself is "solvent". The chances of you two finding each other on that
vast landmass are
extremely small, since there's so much "solvent". So,
with too much solvent you won't get any freeze precipitation. But, if you and your brother instead went into the same
Supermarket building, meaning a "smaller amount of solvent", then the chances of you two finding each other in the same supermarket is very high. And, if you two went into the
same room of a building, meaning a "very very super-saturated, small amount of solvent", then you will pretty much instantly find each other. This is how solvents work and it's the reason why hot pulls are super useful for achieving supersaturation. With hot pulls,
less solvent is capable of holding
more DMT, thus allowing you to just use a
tiny amount of solvent for your pulls, and therefore you won't need to pre-evaporate anything, since the liquid volume will
already be tiny.
* If you drop in one or more pre-made DMT crystals from a previous extraction, then you will seed the reaction. This is called a "seed crystal" and its size will attract molecules from the solution, thus growing a big crystal. Just make sure that your solvent has cooled a little bit closer to room-temperature
before you drop them in, otherwise the heat-energy will just rip them apart and dissolve
them too.
* Some people move the jar back and forth between the freezer and refrigerator every 30 minutes or so. It's a bit crazy and I don't recommend it since it provides almost no benefit. Their idea is that the liquid cools down a bit in the freezer (which might be at -18*C), then heats up a bit again in the refrigerator (which might be at +1.6*C). This constant cycling means that the solvent will spend a lot of time at temperatures
between the freezer and refrigerator values, which helps crystallization a
tiny bit. But it
doesn't help as much as you might
believe; because the re-heating process in the fridge is
very slow and won't really cause much difference, and because the fridge is already just around +1.6*C which
itself isn't very much at all (and will only cause a
minor increase in heat-dancing). If you want a hassle-free method of letting the molecules dance, then
don't waste your time juggling the bottle between fridge and freezer like this. Instead, just leave it
longer in the room and the fridge before putting it in the final freezer. The times I listed earlier are a good starting point.