Have I been doing SPD all wrong?

Recently the time it takes me to complete a distillation has gotten out of hand. Regularly takes 14+ hours to distill 1-300g of crude. I was getting good color and decent potency so I didn’t look to much into. Well now, while color is still good, potency is going down the tubes. See my posts here on this topic:

My theory for SPD has been to collect mains at the lowest possible mantle temperature. What this looks like for me is getting up to about 155C vapor temp and slowly increasing mantle temp, degree by degree until I get the nice stringy stuff collecting. Once I swap flasks to collect mains, I leave my mantle temperature alone until the vapor temp starts to decrease, then I increase mantle bit by bit.

Typically my parameters for collecting mains are something like this:

1st pass:

vac depth - 210 micron
vapor temp - 164-169C
mantle temp ~200C

2nd pass:

vac depth - 90 micron
vapor temp - 159 - 167C
mantle temp ~200C

More details:

Pump - Welch CRV 4 pro 2.8cfm
Mantle size - 1 & 2L
Temp controller - JKEM
Glassware - Labsociety

Always decarbed -80C ethanol extracted crude.

So some fine members of this forum helped me come to see that the reason my runs might be taking so long is because I’m being too much of a pussy with mantle temp. Does that seem likely? I never take mantle temp during mains above 210C. Is that abnormal for the vac depths posted above?

So now, what would a properly run distillation look like? What range on mantle temperature should I collect mains at? What about vapor temperature? @Roguelab kindly suggested that at 200 micron, vapor temp range should be 210-230C and at 80 micron 185-205C. Does that seem reasonable?

Thank you!

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I never go above 210 ever, i just finished 2nd pass at 195. Your parameters seem decent but that is ridiculously long, i would normally say raise temps but you already are. I would probably get a bigger pump or larger bore size.


Is 2.8 cfm really not sufficient for 1-2L? My boss ordered the 2L SPD kit from LS and they paired it with a 2.8 cfm welch crv4 pro. Since we haven’t yet had sufficient material to fill the 2L, I’ve been using the same glassware with a 1L along with a 1L heating mantle (no top mantle on that one).

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They in my opinion always undersize there setups with small pumps. My rule of thumb is at least 4cfm per 1ml. But the main factor is open size, if your running gl18 your cfm is gonna be limited either way. I would get and alcatel 2021, and since your running a cow use a 2neck flask for one of them and pull your vac from the 24/40 on the 2neck easy and fast way to go semi full bore


So would pulling from 2 neck require a 24/40 to kf25 adapter? I have a cold trap with gl fittings. I see that there are gl to kf25 adapters. Would that work or does the small gl hole size make those traps useless for full bore?

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Your mantle prob isn’t Calibrated. You could be ten degrees in either direction for all you know. Dont be set on mantle temps. Work off reactions etc…


That’s the wrong pump, you’ll limp home on it but you really want a 2120i or a edwards28.

You could also be loading solvent into pump during heads and preventing it from working right. FYI the Welch crv is a woosung pump. It’s trully not a performance pump at all. It’s a korean/China pump Welch got a expired contract for when another company dropped th n from distribution.


Ya the gl will basicly make trying to go full bore in one spot pointless, you could use a male/male adapter for the 24/40 joint and then just would need a wider bore cold trap. Also a roughing pump helps tremendously since it wont be soaked with volitales when you get to mains

This is actually a really good idea! semi full bore!

Get a bigger flask and keep it in dry ice and use it also as your first cold trap, what i did before going to 1”

its hard to say much for certain without being there… one thing is for certain though, you need to push that material through much faster.

dont do this. if you let the head temp dip youve lost. push that shyte out!


Will start being more aggressive with mantle temp, thanks for the info! What is generally an acceptable vapor temp range for collecting mains assuming my vac depth is 100-200 micron? Knowing the upper limit would make me more comfortable raising mantle temperature.

its dependent on a number of factors… just looked at your setup pic in the other thread, you have a tall head, is it packed?

honestly, the high end of that range is going to be somewhat at the producers discretion. id describe it as 155-whenever your stuff gets too dark for your liking. but if you push your target molecule out hard/fast enough, you should be able to get a ~complete~ cannabinoid fraction without it getting too dark. yes there will probably be a point where you wanna pull a tail fraction, maybe 180ish? but you might have stuff dumping out at 180 thats still an okay color. this is definitely a part of the distillation that is more nuanced. your tail should be small.

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This is helpful, thank you. On my last run I only went up to 170 for mains. So it seems I have some room.

As for the head, I have a structured glass packing from lab society and a bunch of glass ratchings. I’ve only ever used the structured one. Which is considered better?

i dunno! surface area plays a role but thats not the only factor i think…

whats the color look like coming over at 170?

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I’m still quite new to this so I don’t know how good the color actually was, but I thought it was decent. What do you think? Pics in first post of this thread.

looks fine to me. you can always collect two fractions if you arent sure in the moment and recombine based on color/potency results after the fact.

At 100 mic. 205 C upper limit
At 200 mic 230C upper limit
These are your tail temps

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those are head temps or mantle?

on the mantle?