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Step 3The Column
Alcohol and water have surprisingly similar properties - each will dissolve in the other. This means that you will get water vapours in with the alcohol vapours, but they can be reduced. A tall column above the vat gives the water vapour a chance to condense and fall back.
If you can increase the surface area within the column, so much the better. Looking in my shed, I see a three-foot length of two-inch diameter tube that would be ideal - it's an old bed-leg. To increase the area inside, I could hammer lots and lots of nails into the pipe, or fill it with steel wool. If I was bothered about rust, I could use a similar copper tube and fill it with broken glass.
The column can be connected to the vat by drilling a suitable-diameter hole in the lid of the pressure-cooker, removing the weight-system. The gap between the column and the lid can be sealed with solder, epoxy, welded, or sealed with a compression-fitting, depending on the size of the column and the materials involved. Do not worry about removing the weights or blocking the safety-valve, as the still is never under pressure unless you do something stupidly wrong. The top of the column needs capping, with a hole in the cap to allow insertion of the thermometer. As with the joint at the bottom, this depends on the exact materials you used - it could be as basic as dropping a tin can over the top and epoxying it in place.
If you can increase the surface area within the column, so much the better. Looking in my shed, I see a three-foot length of two-inch diameter tube that would be ideal - it's an old bed-leg. To increase the area inside, I could hammer lots and lots of nails into the pipe, or fill it with steel wool. If I was bothered about rust, I could use a similar copper tube and fill it with broken glass.
The column can be connected to the vat by drilling a suitable-diameter hole in the lid of the pressure-cooker, removing the weight-system. The gap between the column and the lid can be sealed with solder, epoxy, welded, or sealed with a compression-fitting, depending on the size of the column and the materials involved. Do not worry about removing the weights or blocking the safety-valve, as the still is never under pressure unless you do something stupidly wrong. The top of the column needs capping, with a hole in the cap to allow insertion of the thermometer. As with the joint at the bottom, this depends on the exact materials you used - it could be as basic as dropping a tin can over the top and epoxying it in place.
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Also, I see a lot of comments about solder & flux, etc... What about welding? I work with a bunch of PED welders that would give me a hand...
Actually the same effect can be had with a pot-still + thumper.. That would also allow you to reduce the stupid materials that could make it into your product without much for additional supplies.. If you build the thumper safely, then I'd only be concerned with solvents coming through.. You're right that heavy metals tend to fall back, but I know from experience that crap ends up in the down side.. Perhaps because of tilting/moving the still etc, but the end result is contamination of the downward slope.. The thumper would be easy to keep clean, and would trap any heavy impurities..
I'd seriously consider having your product tested, that is begging for trouble!!
Copper, stainless steel, or lab-glass column (doubtfully available if you used your bed-frame), with PROPER sealant, and SS, Cu, clay, or glass packing.. SS or copper dish scrubbies are ideal.. Their HETP is much smaller than marbles or raschig rings..
Personally I think the person you wrote this instructable has no business teaching others.. Its like the blind leading the soon to be blind..
For $50-100 you can build a still to write home about, that won't have the potential to poison ppl..
Copper, SS, silver solder and foodsafe flux, and flour based pastes.. Those are pretty much your allowed materials.. PERIOD!
Yet again, try reading the Instructable. I specifically stated that I have not constructed this still, due to the extreme illegality in the UK.
I also point out that people can use other materials if they wish - this is a guide to form and function, not a detailed instruction booklet.
... teaching others ...
I find this remark both personally and professionally offensive. I have been an educator of some form for over twenty years, either training others in industry, or teaching, including helping formulate teaching programmes and schemes of work.
I write for an international education journal, and have participated in the formulation of aspects of British governmental science policy.
As any reasonably-educated eleven-year-old is aware, dissolved solids do not evaporate with a low-bpt solvent such as alcohol or water. Any electrochemical residue generated by reactions between disparate materials within the column will not carry over in the vapour because they do not vapourise at the temperatures generated by the still.
If you are as expert as you claim, put your money where your mouth is. Write your own Instructable, with images of your own still(s). Don't just point people at homedistiller, show us your own, unplagiarised, distilling prowess (and if homedistiller is such a good site, why haven't you posted in the forums there since last July?).