Pot still Copper contamination???

[CuWhistle]

I have now been distilling for just over 12 months and using my copper pot still for more than 10. In that time I have probably done close to or over 50 boiler charges and distilled well over 1000 litres of wash and spirit runs of mainly UJSSM. The boiler is a 50 litre stainless beer keg and have been using a Teflon tape gasket fashioned around some cardboard from the instruction provided on this site. The pot still was soldered using aquasafe solder which is lead free. I have some SS scrubber stuffed up in the condenser and collect into a copper parrot and glass jars. The only non-preferred material in the vapour path is a brass union that connects the still head to the liebig condenser and this was pickled according to instructions and the surface area of contact is minimal.

Yesterday I did a stripping run and after the boiler had reached temperature and production had commenced I noticed that my Teflon gasket was not providing a perfect seal and there was a small amount of liquid pooling and trickling on top of the boiler. This is probably due to the fact that the weather has cooled down and the vapour was condensing on the outside surface of the boiler. As it was only a very small amount and everything was hot plus it had already been going for a while, I decided to let it go.

Towards the end of the run I noticed that as this liquid pooling was evaporating it was leaving the blue / green crystal salts typically associated with copper. This raises a concern for me and is somewhat puzzling. Firstly, the leak is at the top of the boiler before the vapour has hit copper. I know the vapours will mix around the still head chamber so I can't discount contact with copper before the vapours escape.

The most concern for me is the fact that there is any blue / green copper in the vapour at all. If it is accumulating out of this evaporated liquid from the leak, is it also going to be present in the distillate coming from the end of the condenser? Logical thought tells me that it is.

Does anybody have experience of this occurring? What are the implications?

I intend to take a sample of the stripped spirit and deliberately evaporate it off slowly to see if there is any presence of solid crystal salts, especially blue / green.

The other thing is that it may explain a suspicion I have had about my product for some time now. While nobody who has tried it has mentioned anything and when you drink it, it certainly tastes pretty good, I have occasionally experienced a metallic aftertaste. I have always disregarded it since I am prone to having this metallic taste in my mouth anyway. It is a known medical condition called dysgeusia or parageusia and is caused by some medications and foods as well as dental problems. I was having these tastes in my mouth long before I started distilling, but I am now quite worried after seeing these salts develop out of the condensed vapours.

There is no way that it can be attributed to not cleaning the still after fabrication because of the volume of spirit that it has produced.

Any thoughts or ideas?

[BentJar]

Im not sure what you got there but before running again, I would try cleaning the still head with citric acid. Also give your boiler/keg a good wash too.
Then you at least know its clean. Procede from there.
I noticed the gasket between my keg and still is dirty looking but dont think I seen any crystals or green/blue color. Copper has a way of turning blue green with time and exposure to weather. Not sure of recomendations on the number of runs vs. cleaning. I wash mine out with the hose but it is turning dark inside.
Perhaps the cleaning will get you back in the game, best of luck.

Bent

[Stainless]

Hi, dont know if I can help you here but I'll tell you my thoughts on this,
1st You have 4 different metals in your still, copper,brass,stainless steel [the keg] and stainless steel[the scrubbers]its possible that you may have galvanic corrosion occuring,
the stainless steel scrubbers may be of very poor quality[do they stick to a magnet] I could not find any SS scrubbers that were not magnetic, I ended up using copper welding cables and made my own scrubbers.
2nd Could it be that you have very high humidity and water is condensing on your copper work? then running down and pooling on your keg?
personally i would strip it all and do more cleaning runs.
I thought your idea to boil off the alcohol and see what was left was good.
hope this helps in some way
cheers
Stainless

[CuWhistle]

Yeah, thanks for the replies.

It has me confused because stainless and copper are meant to be inert and that is why we use it.
I don't think galvanic reaction is a possibility. I've studied and taught corrosion in my career as an Engineering Science teacher. Both stainless steel and copper are used in the production of boats that sit in salt water, along with other metals as well. The reason for this is because they are close together on the galvanic series.
I doubt it is the brass union because it's contact surface area is minimal, it's been pickled, and it is usually only warm to touch since it is immediately adjacent to the condenser so the vapours are on the downhill already. It isn't condensation from the outside of the still. Definitely had a small leak for this run and this is confirmed by the fact that I did another run immediately afterwards, having retaped the gasket and sealed it all up. No leak and no evaporation or crystal formation. It was definitely coming from inside so it was dissolved in the distillate vapour, which is the worrying part.

The inside of my still head has turned a dark, dull brownish black colour. I regularly rinse it out after a few runs and the boiler is emptied and flushed as well.
This one has me stumped.

I'll do the evaporation testing of the product today and keep you informed.

[Jaybird]

http://Www.distillique.co.za/documents/ ... llate.html" onclick="window.open(this.href);return false;" rel="nofollow

Good luck!

Jaybird

[CuWhistle]

@ jaybird:- The distillate is not blue. Perfectly clear and I don't add nutrient to UJSSM. Corn, sugar, water and yeast.

Just boiled off 250mls of collected spirit and it disappeared into the air leaving a clean saucepan. This is reassuring but does not help me explain where the green / blue came from the other day.

There is one possibility though. The flange I put on the bottom of my still head to facilitate clamping to the keg is a brass bull nose ring. It is soldered externally onto the copper pipe and ground to a flat mating surface. With the Teflon gasket properly in place it does not come into contact with the vapour path, but with the gasket not sealing properly it is possible that the escaping vapours could come into contact.

I might do a deliberate leaking run to see if I can duplicate the problem and take some pics.

I have had wash spillages on the boiler top evaporate off before. These usually then burn off and leave a typical burnt brown / black stain that you would expect from burning a sugar / corn liquid, but the stains that appeared the other day were as coppery in appearance as you could get.

Anyway I feel a little better now that the boil off produced nothing.

[CuWhistle]

Here are 2 pics I just took this morning.

top of boiler keg

Teflon Tape Gasket.

[heartcut]

That could be salts forming from suphides in your wash, those typically form after reacting with copper in the ascending vapor path and fall back into the boiler. Heat some of the salt in air to 1100degF and it'll release some H2S if that is what it is.

[CuWhistle]

OK. Thanks for that heartcut. These stains are occurring only where I have had a small leak at the mating surface between the keg boiler and the still. I'll have to make or probably buy a new Teflon gasket.
So are there any implications from the presence of these compounds in relation to the product?
If it wasn't for the leak I wouldn't have known they were present.
Do they go through the condenser and stay in solution in the distillate?

[kaiyara]

I've always cleaned stainless pots with sand paper after cooking accidents. I would use the finest one that does the job, like "emery cloth" and then maybe try to find some info about polishing steel to restore the abraded surface to like new condition.

[CuWhistle]

Update. I haven't done much cooking for a while but I had 180 litres of UJSSM beer in cubes. Gave 3 to the old boy and did the others myself last week. Just stripping and storing to spirit run when I get the chance and some bottles to put it in.

Anyway, I turned the boiler off the other day after the run and left the glass jug under the output tube. Some spirits (not much) must have kept coming as it all cooled down and when I went back to it the liquid had evaporated and the bottom of the jug was covered in the blue salt. This didn't show out when I deliberately did an evaporate test after first noticing it.

This has me scratching my head. Just UJ. Corn, sugar, yeast, water, backset. No nutrients.

But I have now realised I used a small amount of sodium carbonate instead of calcium carbonate to adjust pH 1 time, back a few generations. Is this the culprit???

What's the damage? Can it be salvaged?

[S-Cackalacky]

This could be way off in left field somewhere, but if you're running electric, have you checked your ground connection. I've heard of others having some kind of electrolysis going on in the boiler because of a bad ground.

Just sayin',
S-C

[CuWhistle]

Nope. Gas, but thanks anyhows.