Build a Rotovap

1st order of business is the rotary seal.

If you’ve got a rotary seal design you want to try or share, please don’t stop on my account.

If you don’t, you’ll get further down the road starting with a salvaged seal. It doesn’t need to come from a Rotovap, but that IS the easy place to look.

Stainless has enough advantages over glass that such a build would likely be a win.

You may or may not be better served by an FFE…

Depends on what you actually need.

Edit: @Rowan was playing with ferrofluid seals at one point, and might have a place you could go looking.

You’re looking at a 3year old thread.

Most of the folks around here that I would label as “up for this” have instead built FFEs.

Take from that what you’d like.

And check out Optimizing your RotoVap

Eg: Optimizing your RotoVap - #250 by SidViscous


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The cost to put together a little dinky rotovap
(An antiquated design in terms of thin film evaporation)
Is rediculous, when compared to the cost to build a benchtop falling film.

With that said….
I will be presenting my own fusion of timeless tradition and modern innovation before the clock strikes 12 tonight.


So it was detmined that this midnight thing was not correct.

I didn’t like the way it was oriented so i added some more bends

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Here’s a couple threads to chew on

:point_up:t2:Has small ffe ideas

:point_up:t2: Add your 2¢ I’m always looking for ideas.

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Yes, that’s the underlying idea; The solvent evaporates faster due to being spread over a larger surface area inside the rotating flask.

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I suppose the better question is what is the purpose of this is to ask what OP need this for (if they even care anymore). Is it for bulk solvent recovery? Is it general use? Or is it residual solvent recovery? Bulk is obviously an FFE, and you can make a small one with off the shelf parts for $1,000-$2,000. General use would be rotovap. Residual, you can actually get away if your temp is high enough (depending on solvent). Steel is always easier to handle than glass because glass sucks other than seeing what’s happening.

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5L rotavap - R&D, smaller batch production
20L rotavap - Scale up work, medium batch
FFE - Large batch production

A rotary evaporator is indispensable in a chemistry lab setting.


I think it’s just nice to have something where you can harvest the oils easier than a rotovap. A rotovap is a BITCH!!! At harvesting oils. I’m still gonna build a FFE at some point. It’s just that even at a small batch with just doing a 1lb eho extraction. Using 3.3 L/1 gal of ethanol it’s more worth it to make a mini ffe. I think that mini ffe are the future and should be used at all costs.

You can literally get your solvent out quicker and left with an easier to remove oil in a ffe than a rotovap. Once I build a functional ffe that completely decimates the time my 5l roto takes to evaporate 3.3L then I’m going to store my rotovap away.

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You can make many tweaks for cheap that will make a roto piss solvent, especially at your scale. They definitely aren’t the most efficient but until you need serious recovery i dont see the point, i can do more than enough in my 20L’s and decarb and volatile strip before i ever open it.


You could salvage a worm drive out of a skill saw or a pinion gear out of an angle grinder if you wanted to build your own rotovap

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the vacuum rotary union seems to be the difficult part to source

it’s also possible I just don’t know the right combination of words to make google happy


That was the answer I got in the stainless rotovap thread.

The more you work with a rotovap, the easier it becomes. It is not uncommon for a rotovap to be fired up first thing in the morning, to run in the “background” all day long, and be the last tool to be turned off at the end of the day.

To some degree of approximation, the rotovap’s usage becomes an indicator of the chemist’s overall productivity.


Yup, you can set it and forget it!

Once you find a rotary seal, or make a halfway decent one, the receiving flask (if it isn’t a ground joint) becomes the leaky seal. Little trick of the trade for larger rotovaps (5-50L), is to use the rotovap clamps and cut the lip off one side of a triclamp gasket with a razor blade, you can make a very solid metal to glass transition that holds vacuum overnight.

32/50 flat glass joints fit a 1.5" triclamp
40/60 flat glass joints fit a 2" triclamp

For my 50L rotovap, the 2" triclamp flange goes to a hose barb, to hose, to a sanitary keg. This relieves strain from the joint, so your vacuum stays at pressure without an active vacuum


And set a timer and empty collection flask, refill rotavap flask, top off water bath.

Seldom did I go on lunch break without the rotavap in action.

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A really good trick is to use glycerin as a heat bath fluid. Its flashpoint is 160C so you can crank to 140 under vac to prep for distillation, it doesn’t evaporate very quickly, it’s easy to clean since its water soluble, and ok to inhale in small amounts. It’s 10x cheaper than silicone, safer than mineral oil to inhale, and lasts forever!

Edit: Don’t crank past 150C so you don’t dehydrate the glycerin and make acrolein and add a bit of water as a preventative measure; since you’re hydrating the glycerin (similar to sugar), the water won’t evaporate readily because it would need to dehydrate and boil the water.


I think I found our solution Swivel Joints - Rotating Pipe Joints | Arm-Tex