Short Path Head designs

I wanted to start a short path head thread to discuss the designs made by different sellers.
What I want to focus on here is the design elements that we think are most useful and effective and the ones that are either superfluous or even detrimental. Again we are to focus on the specific elements and not to hype or bash any sellers, manufactures, etc.
Most of the current designs today are variants on the Chemglass design

Seller design elements (only whats different)

Across International

  • packable

Best Value Vacs
*Straight Column

Goldleaf Scientific



*cup collector (not yet released)
*Silvered option
*Modular (not yet released)

Lab Society

*Cup collector


*cup collector
*Double Wall Insulation

Xtractor depot
*Silvered option


Generally the flow rate is sacrificed for better separation so there is always a trade off between speed and purity. Speed is highly dependent on vacuum levels and temperature which fluctuate between runs and an apples to apples comparison between heads is nearly impossible. So those that tend to boast that their heads are faster are only telling half the story. The question is does it offer better separation and speed rate. I see this mistake happen perpetually with the BR’s. Lets be very clear spinning band is for better separation. That’s the whole function of the machine, not to go fast. It bugs me that people are buying these expecting them to be wiped film machines. The two are at opposite ends of the spectrum and the short path kits fall right in the middle.
Cup designs offer up to 2x flow rate
Silvered Columns lower the temperature gradient and are thus either faster, or allow you to use a longer column
Double insulated heads offer seemingly no benefit over a single insulated jacket, but if anyone has experience that says otherwise I’d be open to hear.
Modular heads offer extreme flexibility in uses. Basically its a short path head that’s been split into 3 separate pieces (the column, the distributor, and the condenser). Obviously the down side is the potential for more leaks. Lot’s of different configurations to run them for different uses. For example if you want better purity you would use a silvered column below the distributor, if you want to go faster just remove the column. You can stack heads with a column (or hot condenser) in between and pull your volatiles out of the top and your main body out of the bottom. Sort of like the hot condenser tech but vertical. You can even run a continuous fractional column like the big frac columns for petroleum.


Good idea for a thread. Let me point out that there is another style easily used for this as well.

A simple bent tube adapter feeding into the collection vessel constitutes a short path head all its own and is likely much shorter than even that Chemglass unit you show and one of which I own.

Take the Chemglass unit as an example. It incorporates a condenser. However, in our application the cannabinoids do not need to be condensed so the “condenser” gets pressed into service instead as a heater to overcome the shortcomings of an unneeded condenser not the least of which is the distillate path must be made very narrow to fit inside the condenser. This is not the intended function.

The instrinsic problem all these short path heads have in common is that they are being used to seperate by fractional distillation compounds containing substances with wildly different boiling points some of which require molecular distillation. “Fractional distillation” and “molecular distillation” are incompatible terms. Molecular distillation is characterized by vacuum conditions generally ten microns and below. Any type of fractioning device used during true molecular distillation will virtually shut down the distillation. Those heads above are fractionating heads and if a system was designed for true molecular distillation they could not be used with much success.

Any given crude is a mixture of terpenes and lower boiling point stuff and cannabinoid which is very high boiling stuff. A head designed to fraction terpenes alone and do a great job might be any one of those shown. A head designed to fraction only the cannabinoids and which never had to fraction terpenes would look pretty much like a bent tube fitted into the collection vessel and there would be no condenser, packing, indents, or anything else needed. The temperature alone is used to fraction these compounds under mean free path conditions when they are free of lower boiling compounds.

This idea is what has tripped up folks who have consulted me about which system to use. The secret is there is no secret. The “short path” devices I see above don’t look all that short frankly and are being pressed into service in a way generally shown posted that is not the intended use really. Furthermore ALL of the SPD heads shown above rely on a vertical orientation which in turn relies on a thermal stack being continuously fed from the distillate to keep the uptake tube heated.

With a simple bent distillation tube the boiling flask can be oriented into a more horizontal aspect in which the distillate no longer needs to provide the energy for the uptake path. This means dramatically lower temps can be run.

I run a lot of med on the micro scale and have SPD heads and all sorts of other things to work with. I produce high purity. I have not used a SPD other than a bent tube from boiling flask to collection vessel when running a distillation, even terpenes, for a long time. I do think all those units are very cool and serve well for what they are but I also believe in most ways just a bent tube adapter works just fine too


Can you use the bent tube adapter at any kind of scale?

That brings up another point, there’s also alembic and bump trap style heads


There is no limit on the size of the bent tube. A bump trap would be a fractioning device that would allow passage of lower boiling stuff until vacuum pulled down to MFP conditions. Honestly though it is a simple set up if you use a two neck flask as a catch vessel. This couples the boiling flask to it and adds a port for vacuum. Then just a short path bent tube set so both flasks are tilted equally towards each other with the vacuum adapter pointed up and voila! I have done this or variants many times and it works without a problem.


I think you are grossly over simplifying the components in a crude extract. Sure the terpenes and cannabinoids have a fairly large difference in boiling points but what about flavonoids? There’s lots of junk with similar enough boiling points to the cannabinoids to carry over. Surely the inclusion of these components shortens the shelf life of end product and should be removed. Thus fractional distillation is not only warranted it can be much more efficient process overall.

which would be an argument for packing the distillation head?

but what about all the extra heat I then have to add to get my target compound up and out of the head and into the condenser?


The packing gives more intimate contact between the uprising vapor and the falling liquid. This in turn gives better separation.
It will slow down your flow rate some but shouldn’t require much more heat. I don’t think the extra time and heat would do much

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If you are trying to separate low BP volitiles, then a tall packed head might the move… That’s what I use my @goldleaf_scientific head for.

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man its been a while since we had that one. That head we sent you is definitely too tall for the cannabinoids but I bet if we get it silvered it would be awesome! Good for the terps though like you mentioned. We got shorter packable ones with cup collector too now.
I’ll have to send you one of the newest designs soon.


It’s so perfect for distilling HT pour off… Smallest amount of @Shadownaught s new clay and they are water clear every time

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Was trying to spur discussion on wtf each head is best for & why. Figured packing was a place to start :slight_smile:

Eg: how would silvering a head that was too tall help?

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silvering retains more heat and this creates less of a temperature difference between the top of the column and the bottom.
A taller head might be better for situations where you want better separation or more purity (up to a point I’d say 12" or so, after which the extra energy needed is detrimental due to degradation)
Shorter head with less packing would be better for faster flow rates.
The short path head has 3 different sections and the column length, width, condenser size, etc all change the optimal capabilities of the piece. That’s why the modular heads are coming out now. The idea is that you can frankenstein the parts together for any need instead of having a separate head design for each need.


I notice that some of the heads have indentations, others don’t. Yet “vigreux” are not mentioned under distinguishing features.

Presumably these also add theoretical plates?

As does packing??

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Vigreux is just a fixed “packing” if you will. Both vigreux and packing material like raschig rings offer more surface area but are balanced with openness that allows everything to flow through.


A few small vig indents at the bottom of the column help hold packing too.

I am currently using a chemglass head and the overall length of the head i feel is too short because with the cow attached; my receiving flask is hugged super tight next to the heating mantle and the flask gets hot; and even if i keep my head temps low (close to clogging) i get vapors that go past, but if i take an ice cube or something and put it on top of the cow, it will start condensing some of the vapors/ the vac port on the cow catches oils.

like the length of the condenser on the goldleaf head

if heads are ‘silverized’ for heat retention why arent heads wrapped with fire rope or hit with a heat gun and wrapped during use?

I’ve had a few customers tell me that they heat their column section of the head with a heat gun. It cuts off a bunch of time because the column coming up to temp takes forever. Literally like an hour of refluxing. Although the silvering would prevent that.

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ya id hit mine with a heat gun when i was using a separate vig - what about condenser length? seems the Lab society and chemglass heads are shorter then goldleaf and summit - any fancy science words behind the different styles?