A tip on decarbing/purging

I own a plain jane lab microscope from years back. It is a three lense and can zoom down to cell level.

If you want to know when precisely extract is decarbed fully, or when exactly the solvent is purged, then here is what I do when in doubt. I place the extract in a petri dish and heat it nearly too hot to pick up with bare fingers and place it on the microscope. I sometime use a butane torch to do this or more gently on the stove. My microscope has a light underneath and shines up through the extract. When it is melted the extract forms a very nice flat surface that allows a lens to get in focus range.

If you have never done this I encourage you to try it. If you see bubbles in the extract under magnification (trust me YOU WILL the first time lolz) then you know for certain that at one point in time at least a gas was present to make the bubble. If it is carbon dioxide from decarboxylation then the gas will still be present. If the bubble forms from expanding gas of solvent, the solvent will quickly condense back to liquid and disolve again into the extract, but the bubble will leave evidence of solvent presence.

I learned it takes MUCH longer for extract to decarb than is generally recognized in public forums. The bubbles tell the tale.

As an aside you will see things in the near optical purity of the melted extract that are at the very least informative and very cool to look at too. Labs generally do not show an indication of turbidity or any indication of the ability to absorb or transmit light - also an indication of how much "gunk" there is leaving the user guessing just exactly what the non cannabinoid stuff is. When it tests at 60% thc, just exactly what the rest of the compound components are is left up to the imagination really. A microscrope will clue you in on what it is.

Nice, I see when butane solvent is used and not purged completely that the bubbles with the gas solvent dont seem to dissolve but rather they ignite with flame or evaporate when the bubble pops as butane does when warmed/flamed. Are you saying that they go from gas to liquid once again and return to the concentrate as a liquid solvent or speaking of other solvents ?

chemphlegm said:

Nice, I see when butane solvent is used and not purged completely that the bubbles with the gas solvent dont seem to dissolve but rather they ignite with flame or evaporate when the bubble pops as butane does when warmed/flamed. Are you saying that they go from gas to liquid once again and return to the concentrate as a liquid solvent or speaking of other solvents ?

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I am just quoting basic chemistry really. Butane only remains liquid at room temperature because it is under pressure. At standard atmosphere it is gas at room temperature. Ethanol commonly used in extractions for example must be held above its boiling point to remain a gas. This is true of all matter including solvents. The instant the gas cools to below the boiling point a phase change from gas to liquid occurs. If the gas has not had time to migrate out of the hot extract, as in stirring or with time, then it turns to liquid again (a phase change) and remains disolve in the extract. Popping the bubble at this point would not therefor release the solvent. The gas must be carried away while in gas form to purge solvent from extract.

This of course is why a vac chamber is so useful - it lowers the boiling points making it possible to hold solvents in gas form longer and at lower temperatures which facilitate purging immensely. Flame to purge extract is something I always do but it is a combustion process which only augments purging.

so when a non purged concentrate shows a rising (butane)bubble when heated and that bubble pops it is gas that escapes into the air and not a liquid remaining in the solvent?

chemphlegm said:

so when a non purged concentrate shows a rising (butane)bubble when heated and that bubble pops it is gas that escapes into the air and not a liquid remaining in the solvent?

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If a butane bubble rises and pops it is purged from the extract.

I am pretty long winded but am retired early and do not have much contact with people so I enjoy explanations. With luck my information will someday reach 75% accuracy...

Any bubble in the extract that is visible is composed of gas. If the gas is butane and breaks free of the surface then since butane gas is miscible in all proportions with atmosphere then once exposed to atmosphere it will dissipate instantly into the air. The ONLY way to make butane liquid is to make it cryogenically cold and keep it that cold, or place it under high pressure and keep it under high pressure. The instant it is no longer cold enough or the pressure is not high enough then the butane will undergo a phase change from liquid to gas. At normal atmosphere at room temp butane is always gas whether it is inside extract or not, so the heating process I described has nothing to do with making butane a gas and has to do with making the gas expand AND reducing the viscosity of the extract by heating it. Extract must be liquid enough for the gas to migrate out as a bubble and the hotter extract is made the less resistance it has for bubbles to exit because it acts "thinner" as a liquid when hot. Other solvents being purged that are normally liquid at room temp (like say ethanol) must be heated and kept at their own boiling temp or higher until the gas breaks free of the extract. Then, like steam rising from a pot it is absorbed into the air because like butane gas it too is miscible with atmosphere, but not in all proportions. Amounts being purged typically are miscible in air so when you see the bubble rise and pop it too as a practical matter has been purged.

There is honestly no practical way for us to know really what any given set of bubbles represent. What we can say for sure is that bubbles represent contaminants of some sort. Carbon dioxide is not necessarily a contaminate of course but it is a breakdown byproduct and if the goal is to purge through decarboxylation the THCA (thus convering it to THC) then the bubbles represent an incomplete conversion.

In any case you can accellerate purging by stirring so as to help the bubbles to the surface where they can pop. Tiny bubbles of solvent gas often cannot travel at all in the thick extract so mechanical motion will bring them to the surface where simply heating the extract without stirring often cannot.

You ask good questions.

I also use stirring during decarbing. If I'm going to cook with some wax, I'll mix it with equal mounts of coconut oil and heat to 245°F. Once the major out-gassing is done at 15-20 minutes, stirring will show more bubbles until the decarb is done. I don't use magnification, but a headlamp helps. Over the years, I can say that water vaporizing causes much larger bubbles than the CO2, orders of magnitude different. When I use coconut oil to extract with water, the water comes off long before it gets to 245°.