The Cotton Candy Extraction Technique

We bumped into the Cotton Candy extraction technique by accident, while shaking out the original Mk III Terpenator.  We were so taken by its properties, that we standardized the process.

Our first serendipitous Cotton Candy extraction

What is Cotton Candy extract?

Cotton Candy extract is a concentrate that has been expanded into foam and purged of solvent in that state, so as to form a solid foam extremely low in residual solvents. 

It is lower in residual solvents than conventional extraction techniques, because there is no thinner film from which to purge than the wall of a bubble.

Solidified gossamer thin bubble walls

How do you make Cotton Candy?


A recovery vessel with a sight glass in the lid, because it is both an art and science to determine the timing of “now.”

A vacuum gauge capable of reading inches Hg to determine when to start visually observing pool.

A vacuum pump capable of safely pumping LPG vapor mixes and discharging to the ventilation system so as to not set off the HC detector alarm.

The way we reliably make Cotton Candy is to monitor recovery vacuum pressure using a simple Bourdon vacuum gauge.  When the recovery pressure in the recovery pot reaches -22” Hg, we start observing the puddle and when it reaches the thick viscous “blurpy” stage, we valve off and shut down the recovery pump.

We then turn on the high vacuum pump, which inflates the remaining concentrate into foam and holds it in that position until the LPG evaporates away and the bubble walls solidify.

The exact “blurpy” point is a learned thang and if you go to early you are wasting recoverable LPG as well as adding to atmospheric VOC.

Conversely, if you go a little late it won’t inflate all the way and if you go too late, the mixture won’t inflate at all.

When to stop pumping vacuum?

An artisan sense of “now” is also required to tell when the cotton candy has solidified as well.  The sight glass allows you to observe its surface and as the LPG exits, the bubbles lose their sheen.  When they are completely dry, there are reflections from flakes like the one shown above, but balance of the foam appears dry like an expanded Polyurethane foam insulation block.

The way I tell, is that when the foam appears dry observing it through the view port, I valve off the vacuum pump and start backfilling with N2 while closely observing the foam.  If it starts to sag, I immediately stop backfilling and open the vacuum valve again for further purging.

Once you collapse the foam, it won’t reinflate, so do this step carefully! 

How do you process Cotton Candy?

We had some fun experimenting with it and settled on sticking the collection pot of Cotton Candy in the freezer to make it more uniformly dry an brittle, and then simply stirring it with a spatula and pouring it out and spreading it in a thin layer on parchment.

We place the parchment in a preheated vacuum oven at 115F and observe the material through the window to see when it reaches fully molten state.  Once it reaches fully molten, we start the vacuum pump and open the isolation valve.

The molten concentrate will start to bubble as the absolute pressure falls and at some point the flurry of bubbles becomes excessive, so when the puddle begins to boil violently, we hold the vacuum at that level until it calms down and then resume lowering the absolute pressure with the vacuum pump.

When we reach ~-29.5”/10,000 microns (10,688) and the bubbling subsides, we backfill the oven with N2 and cool the slab down enough to remove and flip onto another parchment sheet.

Returning that to the oven we again bring the slab to molten state, and resume vacuum purging.  Repeating the above steps with regard to bubble rate.    When the slab reaches -29.5/10,000 microns this time and there are no longer solvent bubbles, only sporadic small fizzy CO2 bubbles, keep pumping until your reach the residual solvent standards you seek.

At the time we ran initial our experiments, we used 10% of the FDA 5000 ppm maximum residual solvent standard for Class 3 solvents as our standard, which we were consistently below after about four hours in our vacuum ovens. 

At that point, we again backfill with N2, shut off the heat, and let cool to solid state in the inert atmosphere with the pump still running.

ASSuming prime material, once cooled the concentrate typically becomes a pull and snap to a brittle shatter at room temperature, depending on starting material.

Other forms:

For ya’ll crumble fans, as our first experiment, we questioned how much residual LPG remained in the Cotton Candy, so we folded a wad and stuck it in the vacuum oven that we had preheated to 115F and began to pull vacuum immediately.

This would be a good point to mention that you can easily handle Cotton Candy with your hands and ambient, if you do it rapidly, but once it starts to warm up to body temperature it becomes one of the planets stickiest substances.  Because of their gossamer thin walls, flakes warm up relatively fast, so don’t let any sit on your skin long.

Folded Cotton Candy patty

Outgassing folded patty  in a 115F vacuum oven

Oops, clearly more purging required, soooo we broke the patty into samples and continued to purge one at a reduced 85F until it turned into Crumble.

Patty purging under vacuum at 85F


We process the second one by processing at 100F and rolled it into a Temple Balls while still warm.

Temple Ball

We then flattened the Temple balls into a thin film between folded parchment while warm, and melted at 115F under a vacuum of -29.5” Hg.  Observing no solvent bubbles, we shut off the heat, backfilled with N2 and when solid removed from the oven.  It produced a hard brittle shatter at ambient temperatures.

Brittle Shatter

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