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Glass lab still operation


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I just received a small glass still to use for proofing. i ran a flavored product, with sugar in it, through it . By the time the "pot" was almost empty it was a mess with burnt looking stuff all around the flask. it was hard to clean off. first off, is that normal? The bigger concern is the fact that the condenser was surging during the whole run. At one point the the entire contents of the condenser was "sucked" back into the boiling flask. It did not look right at all. I was using a butane burner for heat, and wonder if i was putting to much, to quick. how long should a 200 ml run take on a set up like this?

Thanks for any input,


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You are dehydrating the sugar by cooking all of the water out, you'll need to add water to the pot first then distill to ~100oC to collect all of the alcohol. Add enough water to get back to exactly the amount of liqueur you put in your still (i.e. add 750.0ml of product, then dilute your distillate to 750.0ml), and then determine the proof. You can dilute to another volume, but you will need to back calculate how much alcohol came from your original sample. Hope that helps.


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Cleaning the flask is fun, huh? I've had varying degrees of success with dish detergent, gojo, and even a local product called Durashine...I add ball bearing or similar (actually, I use all the little Oetiker clamps in sizes I never had a use for) with a bit of liquid and swirl it around. Like one of those wrist exercisers... :-)

And then a colleague who partakes in a type of recreation that I do not partake in told me to use isopropyl alcohol and rock salt. Worked a treat! Now I use some heads and rock salt.

When people see me cleaning my FLASK, they often think I'm cleaning my thing that starts with a "B."

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A proper Lab still setup should have a thermometer that measures the still head temp. Once your still head hits 100oC you have distilled all of the alcohol out of the pot. You surging problem can also be fixed by adding boiling stones to the pot. A glass still has no surfaces to nucleate vapor bubbles, so your pot super heats and then flashes into vapor that you see as a surge, the flash cools the pot down which you observe as suck-back, you just need to add something with a rough surface so vapor bubbles can easily form. You can buy proper boiling stones online, or just use some pebbles or small bits of ceramic.

PS. An electric heating setup is much easier and safer to operate.

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+1 on using electric rather than flame on a small setup. Even a cheap (cycling) electric hotplate is fine, as long as your boiling flask is in a sandbath (a larger flask with sand in it) which will even out the heating of the internal boiler a lot. You can also, in the short term, get around the lack of an integral thermometer in the still by using an infrared thermometer and aiming it at the top of the stillhead. If you do that use some black tape to aim at on the outside of the glass, and calibrate it with water first to make sure the boiling point is correct. (I'll note that Much of my experience is labwork unrelated to ethanol, but similar principles apply.)

I would also recommend not running all the way to dry. If you run to 100C (which you should run directly into a graduated cylinder), then add water to the initial volume (or half of the initial volume, etc) you can very easily calculate the %EtOH. This also lets you pick the most accurate range of your hydrometer, if you'd like.

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  • 1 month later...

Hi Brad,

We sell a 1000ml distillers test kit on Amazon. It comes with a heating mantle and we have never had a compaint about burning. You can also buy the mantle separately.

Distiller Kit :


Heating Mantle:




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