Still metal question

Forum for the discussion of any material/synthetics.Only posts with info /or links to research info allowed . Any posts recommend the use of any material without copy's or links to show proven research will be deleted

Moderator: Site Moderator

Post Reply
Olin Haad
Novice
Posts: 2
Joined: Sat Jul 08, 2006 12:56 pm
Location: Willamette Valley

Still metal question

Post by Olin Haad »

I have tried to read, read and then read some more to find the answer to this question, but have failed to find the information I seek. The question is this, why do we not use aluminum to distill with?

I fully accept that aluminum is not good for distilling (as with fermenting and beer making), but I am just curious why it is not a good metal...
Enlikil
Swill Maker
Posts: 248
Joined: Wed May 11, 2005 12:21 pm

Post by Enlikil »

aluminium is not used for many reasons. but i can think of 2 off the top of my head.
1) its porus so it retains bactieria..
2) anything acidy will leech aluminum into your food or drink.
and both of those are at normal temps. not ethenol either.
hornedrhodent
Rumrunner
Posts: 732
Joined: Sat Mar 04, 2006 1:42 am
Location: Nth coast NSW

Post by hornedrhodent »

Enlikil wrote:aluminium is not used for many reasons. but i can think of 2 off the top of my head.
1) its porus so it retains bactieria..
2) anything acidy will leech aluminum into your food or drink.
and both of those are at normal temps. not ethenol either.


Any thing acid or alkaline will react with aluminium to give off hydrogen - this causes pitting which may harbour bacteria etc which should not survive the boiling process.

AFAIK it does not react with ethanol.

I wouldn't use it for fermenter or boiler because of corrosion.
I wouldn't use it for a pot still because of the water and other stuff carried over with the ethanol and possible corrosion.
I wouldn't use it for a reflux still column because of the same in the lower parts of the column
I wouldn't use it for a condenser because copper is so much better and easier to join than Al.


In short I wouldn't use it - except for testing concepts for a fuel still.
Olin Haad
Novice
Posts: 2
Joined: Sat Jul 08, 2006 12:56 pm
Location: Willamette Valley

Post by Olin Haad »

Thanks for the responses! It all makes sense now...
muckanic
Swill Maker
Posts: 433
Joined: Tue May 23, 2006 1:19 am
Location: Canberra

Post by muckanic »

If a metal is used in cooking then it can probably be safely used in distilling, and aluminium cookware isn't exactly uncommon. The main caution that is usually issued is not to expose it to strong alkalis like dishwasher detergent.

Here's a conundrum for the reader. Al forms explosive H2 gas in the presence of acid. How come more kitchens haven't blown up? Less spectacularly, how come peoples' saucepans don't corrode away?
Harry
Swill Maker
Posts: 198
Joined: Sun Jan 30, 2005 7:46 pm
Location: Paradise (aka Cairns Qld Australia)

Post by Harry »

I wonder how many more time I have to point people to this info, before the penny drops?

http://groups.yahoo.com/group/Distillers/message/35812" onclick="window.open(this.href);return false;" rel="nofollow

.
Slainte!
regards Harry
Grayson_Stewart
retired
Posts: 1030
Joined: Sun Oct 24, 2004 10:56 am

Post by Grayson_Stewart »

Nice job Harry! First time I've seen that, I need to get back on that site more often.
Light travels faster than sound. That is why some people appear bright until you hear them speak.
fahdoul
Bootlegger
Posts: 125
Joined: Tue May 02, 2006 5:02 pm

Post by fahdoul »

1 - Same reason we don't blow up, even though we are methane generators. Inadequate concentration and lack of an ignition source.

2- They do. Have you ever looked at old aluminum saucepans at a flea market or in your grandmother's kitchen? The older they are, the more pitted they will usually be.
muckanic wrote:Here's a conundrum for the reader. Al forms explosive H2 gas in the presence of acid. How come more kitchens haven't blown up? Less spectacularly, how come peoples' saucepans don't corrode away?
User avatar
Tater
Admin
Posts: 9678
Joined: Mon Oct 25, 2004 9:19 am
Location: occupied south

Post by Tater »

Harry Ill put a sticky on it and maybe it will get read metals in Distilling Topic List <Prev>
Reply | Forward <Prev>
As promised, the first draft of the metals paper. It is incomplete, and remains a 'work in progress', subject to alteration without notice. However there should be enough info in it to give some food for thought, which is what the 'spirit' of this group is about (hopefully). It is a long dissertation, so feel free to read, save or discard as you see fit. Slainte! regards Harry


Chapter 03 - Metals



From time to time, the subject comes up of `what metals can or can't be used in distilling equipment'. A very simple and safe rule of thumb is this: for contact with alcohol or its feedstock, never use any metal that is not used in commercial distilleries for that stage of processing. While this may be the easiest approach, it tells you very little about why this or that metal is acceptable or not. Any distiller worth his salt should know exactly why a particular material or procedure is employed. Therefore a more complete analysis is in order.



As a starting point, let's take a look at the metals in commercial distilling plants. Black iron, cast iron, galvanized iron, steel, stainless steel, copper, chromium, aluminium, lead, zinc, nickel, brass, various alloys, and several other metals in smaller proportions are all found somewhere in a distillery. That does not mean they should all be used in the distillation process. On the contrary, most of the aforementioned metals are found in the construction of buildings, peripheral and non-critical machinery. For the distilling process proper, where alcohol and vapours are being manipulated, there are only four acceptable metals to use, namely silver, copper, treated brass, and stainless steel. The reasons why will become clear as you read further.



Beverage alcohol and the feedstock it is derived from are classed as foods meant for human consumption. Grains, fruits, sugars, ethanol liquid and vapours, and yeasts; all are categorized as foodstuffs. There are very strict rules and regulations governing what materials are allowed to come in contact with foods during processing, storage and packaging. These regulations have been formulated after many years of rigorous testing of materials and their influence on the foods in question and/or the affects they have on human metabolism. Many countries adopt the policies of International monitoring bodies such as the World Health Organization (WHO). This body has published information and recommendations for the materials likely to come into contact with foods.



Like many substances in common usage, the pH of foodstuffs plays an important role in determining which metals are suitable for food contact. Whether a food is acidic, such as tomatoes and soft fruits, or neutral or (less common) basic, has a marked influence on the types of metals and other materials such as plastics that can be allowed for processing and storage. The temperature of the foodstuff also plays a part in determining suitability or otherwise as many foods when hot have accelerated reactions in contact with metals. It should be noted here that commercial processing and domestic or household usage of materials for food contact are two separate situations. In a commercial distillery, everything is subject to regulations regarding suitability, safety, and consumer protection and well-being. There are no such safeguards for household usage, save for commonsense and `current practice' methodology. However, as I intimated earlier, a hobby distiller should at least try to follow the practices of commercial processing. Therein lies safety and relative peace of mind.



The reaction of a metal in contact with foodstuffs is a selection criteria used predominately to avoid metal corrosion and mechanical failure, necessitating costly replacement of equipment. Mashes or `worts' will almost always be acidic, as it is a requirement of yeast to have an acidic environment to perform its functions of producing ethanol and other desirable substances. Mashes fermented by yeasts tend to become more acidic as the fermentation progresses. Thus the completed wash or `beer' will have a pH of nominally 4.0 or even lower. When fermentation is finished, this acidic beer is now charged to the still and heated. Elementary school chemistry teaches that hot acids are extremely corrosive to certain metals, notably aluminium, black iron, certain steels and tin. For this reason alone, the aforementioned metals are not really suitable for stillpots, boilers or re-boilers, unless of course you like the idea of frequently replacing components of your still. You will note this corrosion resistivity is a separate issue and has nothing to do with possible metal migration into the foodstuff or chemical reactions that may form undesirable substances in the wash. That is a selection criterion we'll look at later.



Regardless of regulations, commonsense tells you that all still parts likely to come into contact with hot acidic liquids and vapours should be made from a material relatively impervious to corrosion, heat, and toxic leaching of chemicals. Copper, food-grade or Austenitic stainless steel (304 & 316), and correctly treated brass fill this role admirably. I will deal with each in turn, but while we're on the subject of `treated' metals I should make mention of two other metals sometimes considered by the unwary, namely Tin or Tinplate, and Galvanized Iron.



Easily corroded metals such as Black Iron are often coated with a surface layer of chemicals or other metals to protect the base metal from corrosion. What is not understood by many people is that the composite material is meant to be used in normal everyday use, not in harsh chemical processing environments. The galvanizing on the surface of the Iron contains Zinc, which is a toxic metal that leaches badly under hot acidic conditions. The Zinc is rapidly eaten away and finishes up in the distillate. The base Iron is then exposed to the acidic wash, resulting in corrosion (rust), which also gets into the processing chain. The stillpot wears out very quickly and needs to be replaced frequently. Galvanized Iron has no place in process distilling of foodstuffs such as beverage alcohol.



Similarly, Tin is attacked by both acids and bases (alkali) but has the curious property of being relatively stable under neutral pH conditions. For this reason, it was commonly used in centuries past as an alternative to copper. However to use Tin, the stillman had to be sure the wash was brought to a neutral pH condition, not always an easy thing to do given the crude and inaccurate measuring instruments and methods (or lack thereof) employed in bygone eras. It is a source of much confusion when the distillers of old tell the young folk "You gotta neutralise the beer". So `young pistol' follows this sage advice and adds Sodium Bicarbonate (a neutralising buffer, pH 8.5) to the beer in his brand new copper potstill (tinplate has been largely superseded). Then he gets the fright of his life when the distillate runs with a pretty bright blue colour. The blue is, of course, the well-known Cuprous Hydroxide or Schweitzer's Reagent, formed by a complex chemical reaction triggered by the neutral-to-alkaline conditions set up in the Copper still by the S. Bicarbonate. If Tin were the construction material used, there would be no such reaction.



One must always use caution when evaluating procedures from the past. Manufacturers from every era strive to refine their processes based on the materials and knowledge at hand. However time marches on, and advances in Science & Technology march right along with it.





Corrosion of Metals



The biggest problem with most metals in distilling, or indeed most processing-type applications, is corrosion. Often it is the deciding factor when weighing up the suitability of a metal for a particular duty. It is the driving force behind mankind's quest for newer and more durable metal alloys.





Corrosion occurs when the exposed metal surface reacts electrochemically with the surrounding medium in the presence of moisture and oxygen. This reaction results in the formation of surface compounds of the metal (e.g. hydroxides). The rate at which corrosion proceeds will depend in part on the composition of the aqueous medium. Corrosion of iron in very pure water will be considerably slower than in water containing acids or salts.



The rate of corrosion depends also on the solubility of the formed compounds in the medium, and their rate of removal. Thus the formed compounds may be removed rapidly in a flowing aqueous medium, and the corrosion rate will be high (thinning of the walls of water pipes). In a static medium, the rate of corrosion will be moderated as the ionic concentration of the surrounding medium increases.



Corrosion products formed in the atmosphere are more or less adherent e.g. rust on iron, verdigris on copper. Rust is essentially hydrated ferric oxide which usually also contains some ferrous oxide and may contain iron carbonates and/or sulfates. The equivalent in copper is verdigris, consisting mainly of basic copper carbonate, but may also contain copper sulfates and chlorides. However, rust forms loose scale and is easily removed, while verdigris forms a stable patina on the Copper surface.





Corrosion resistance



Some metals (e.g. aluminium, chromium) are rendered "passive" (very resistant to corrosion) by the spontaneous formation, in the presence of oxygen, of an invisible and impermeable oxide film a few Angstrom units (0.1 nanometers) thick. This passive layer is very strong, very adherent and self-repairing if it is damaged. One of the main reasons for the production and use of metallic alloys is that alloys are virtually always more resistant to corrosion than are their basic metal components.



This is partly due to the fact that migration of the constituent elements is much lower than migration from non-alloyed metals, because of the micro-structural binding of the elements within the alloys. Stainless steels, which are alloys of iron with a minimum of 10.5% chromium, are orders of magnitude more resistant to corrosion than iron itself. This is partly because they possess the general properties of alloys, referred to above, but mainly because they have a surface "passive film" which is naturally and rapidly formed on contact with the oxygen in air or water. Stainless steels used in food contact applications are invariably used in the passive state.



So, back to the in-depth analysis of the metals in contact with foodstuffs and how these facts relate to alcohol distillation. For this section I draw heavily on the "Guidelines on Metals and Alloys Used as Food Contact Materials", as published by the World Health Organization 09.03.2001. The following metallic materials (and others) are covered by these Guidelines: Aluminium, Chromium, Copper, Iron, Lead, Tin, Zinc, Stainless Steel, and other alloys. While not a construction material per se, the following metals are also covered because these elements are present as impurities or contaminants in some metallic materials and therefore they can migrate in foodstuffs: Cadmium, Cobalt, and Mercury. At this juncture it must be stressed that the release of a substance through migration should be reduced as low as is reasonably achievable, not only for health reasons but also to maintain the integrity of the foodstuffs in contact.





Aluminium



Aluminium Hydroxide, Al(OH)3, is the most stable form of aluminium under normally benign conditions. As found in nature it is known as `Gibbsite'. Closely related are `Aluminium Oxide Hydroxide', AlO(OH), and `Aluminium Oxide', Al2O3. They differ only by loss of water from the molecule. These compounds together are the major components of the aluminium ore, `Bauxite'.



Pure aluminium has good machining properties and high ductility. However its mechanical strength is low. Therefore, aluminium is often used combined with other metals as alloys (Beliles, 1994). In general usage, aluminium and its alloys are highly resistant to corrosion (Beliles, 1994). When exposed to air, the metal develops a thin film of aluminium oxide (AL2O3) almost immediately. The reaction then slows because the film seals off oxygen, preventing further oxidation or chemical reaction. The film is colourless, tough and nonflaking.



However, aluminium reacts with acids. Most dilute acids attack pure aluminium. At neutral pH, aluminium hydroxide has limited solubility, although the solubility increases markedly at pH below 4.5 and above 8.5 (Elinder and Sjögren, 1986). Alkaline solutions attack both pure and impure aluminium rapidly and dissolve the metal (Hughes, 1992).





Aluminium is widely used in food contact materials such as saucepans, aluminium -lined cooking utensils, coffee pots, and in packaging products such as food-trays, cans, can ends and closures (Elinder and Sjögren, 1986; Codex, 1995). Aluminium food contact materials are often coated with a resin based coating.



Aluminium alloys for food contact materials may contain alloying elements such as magnesium, silicone, iron, manganese, copper and zinc (European Standard EN 601; European Standard EN 602). In aluminium cans the production of hydrogen gas from aluminium migration produces an over pressure in the can.



The temperature and storage time is known to influence the migration of aluminium into foodstuff. In a migration study with 3% acetic acid (Gramiccioni et al., 1989), the migration was approximately 10 fold higher at 40°C compared to 5°C after 24 hours.



In human metabolism, the kidneys excrete aluminium, and only a small amount of aluminium is absorbed (JECFA, 1989). However, soluble aluminium salts are more easily absorbed. Patients with impaired renal function treated by dialysis could show a higher aluminium blood level. In the past, some of these dialyzed patients have shown neurological symptoms of aluminium intoxication due to an inappropriate treatment, which is no longer used. These symptoms have sometimes been mistaken for those of Alzheimer's disease. WHO (IPCS 1997) has concluded that aluminium is not the origin of Alzheimer's disease.



Conclusions

Aluminium and its alloys are a poor choice as metals for fabricating distillation equipment. The metal and its normally protective oxide coating formed by atmospheric exposure are subject to severe attack and migration in all pH conditions save for neutral pH. As most liquids distilled are normally quite acidic, rapid degradation in the form of corrosion and large-scale pitting can be expected. To minimize this situation would require careful neutralization of the wash, which has its own inherent problems, particularly if there is any copper further along in the distilling path. Alcohol distilled under these conditions very often contains undesirable compounds such as the previously-mentioned Schweitzer's Reagent, which will require further processing to eliminate, thus substantially increasing the time and cost of distilling.



If the wash is other than neutral i.e. acidic or alkaline, then metal migration will occur into the wash. While the metal and its salts may largely remain in the stillpot, undesirable compounds are formed which will appear in the distillate and alter the flavour to something very different to what was expected. Generally these compounds leave a nasty metallic taste on the palate. In wood, this taste gets more pronounced as maturation progresses, ruining this batch of spirit. Any subsequent batches barreled in that cask will also suffer the same fate, as the undesirable compounds permeate the wood and by virtue of alcohol's known ability as a strong solvent, will leach into any new spirit placed therein.



Rigorous cleaning, perfectly neutral balanced pH wash, meticulous attention to distilling detail, accurate analytical tools e.g. a gas chromatograph, and production of nothing else but flavourless neutral ethanol such as vodka, would be the only practical way to employ aluminium successfully in distilling equipment, i.e. a still. Given that there are very few amateur distillers with these skills and instruments, or willingness to be limited to a single product, distillation fabricators would be well advised to discard ideas of using aluminium. Utensils and boilers made from aluminium and its alloys for grain mashing may fare better, however a minimal maintenance, passive metal such as stainless steel would be easily a better option. There are eminently more suitable metals than aluminium to employ in spirits distilling.









References

1. ATSDR (1997). Toxicological profile for aluminium. Draft for public comment. U.S.

Department of Health and Human Services. Public Health Service. Agency for Toxic

Substances and Disease Registry.

2. Beliles, R.P. (1994). The metals. In: Patty's Industrial Hygiene and Toxicology, Fourth

edition, Volume 2, Part C. Edited by Clayton, G.D., and Clayton, F.E. John Wiley & Sons, Inc.

3. Codex Alimentarius Commission (1995). Doc. no. CX/FAC 96/17. Joint FAO/WHO food standards programme. Codex general standard for contaminants and toxins in foods.

4. Directive 95/2/EC: European Community. European Parliament and Council Directive on food additives other than colours and sweeteners.

5. Directive 98/83/EC: Council Directive 98/83/EC of 3 November 1998 on the quality of

water intended for human consumption.

6. Elinder and Sjögren (1986). Aluminium. In: Friberg, L., Nordberg, G.F., Vouk, V.B.:

Handbook on the toxicology of metals. Second edition. Elsevier, Amsterdam, New York,

Oxford.

7. European Standard CEN EN 601. Aluminium and aluminium alloys - Castings – Chemical composition of castings for use in contact with food.

8. European Standard CEN EN 602. Aluminium and aluminium alloys - Wrought products - Chemical composition of semi products used for the fabrication of articles for use in contact with food.

9. Gramiccioni, L. et al. (1989). An experimental study about aluminium packaged food. In: "Nutritional and Toxicological aspects of food processing". Proceedings of an international symposium, Rome, April 14-16, 1987. Walker, R. and Quattrucci Eds. Taylor & Francis London, p. 331-336.

10.Gramiccioni, L., Ingrao, G., Milana, M.R., Santaroni, P., Tomassi, G. (1996). Aluminium levels in Italian diets and in selected foods from aluminium utensils. Food Additives and Contaminants. Vol. 13(7) p. 767-774.

11.Hughes, J.T. (1992). Aluminium and your health. British Library Cataloguing in Publication Data, Rimes House.

12.IPCS (1997). IPCS report no. 194: Environmental Health Criteria - aluminium. World Health Organization.

13.JECFA (1989). Evaluation of certain food additives and contaminants. Thirty-third report of the Joint FAO/WHO Expert Committee on Food Additives. World Health Organization, Technical Report Series 776.

14.Lione, A. (1985). Aluminium toxicology and the aluminium-containing medication.

Pharmacol. Ther. Vol. 29 p. 225-285.

15.Liukkonen-Lilja, H. and Piepponen (1992). Leaching of aluminium from aluminium dishes and packages. Food Additives and Contaminants, vol 9(3) p. 213-223.

16.MAFF (1998). Lead arsenic and other metals in food. Food surveillance paper no. 52. The Stationery Office, London. ISBN 0 11 243041 4.

17.Mei, L., Yao, T. (1993). Aluminium contamination of food from using aluminium ware. Intern. J. Environ. Anal. Chem. Vol. 50 p. 1-8.

18.Müller, J.P., Steinegger, A., Schlatter, C. (1993). Contribution of aluminium from packaging materials and cooking utensils to the daily aluminium intake. Z. Lebensm. Unters. Forsch. Vol. 197 p. 332-341.

19.Nagy, E., Jobst, K. (1994). Aluminium dissolved from kitchen utensils. Bull. Environ. Contam. Toxicol. Vol. 52 9. 396-399.

20.Pennington, J.A.T., Jones, J.W. (1989). Dietary intake of aluminium. Aluminium and Health – A critical review. Gitelman, p. 67-70.

21.Pennington, J.A.T., Schoen, S.A. (1995). Estimates of dietary exposure to aluminium. Food additives and contaminants, vol. 12 no. 1, p. 119-128.

22.WHO (1993). Guidelines for drinking-water quality. volume 1, Recommendations.

Chromium



Chromium is an essential element to humans. Chroms, knives, spoons and forks. Chromium is also used to coat other metals, which are then protected from corrosion because of the passive film which forms on the surface of chromiumium is found at low levels in most materials used as foods. The main sources of dietary chromium are cereals, meat, vegetables and unrefined sugar, while fish, vegetable oils and fruits contain smaller amounts (Codex, 1995).



Chromium is found in some types of cans and utensils. In cans it serves to passivate the tinplate surface. Chromium is used in the production of stainless steel of various kinds and in alloys with iron, nickel and cobalt. Ferro chromium and chromium metal are the most important classes of chromium used in the alloy industry (Langaard and Norseth, 1986).



Chromium-containing stainless steels (see guideline on stainless steel) are important food contact materials used for transportation, e.g. in milk trucks, for processing equipment, e.g. in the dairy and chocolate industry, in processing of fruit such as apples, grapes, oranges and tomatoes, for containers such as wine tanks, for brew kettles and beer kegs, for processing of dry food such as cereals, flour and sugar, for utensils such as blenders and bread dough mixers, in slaughter-houses, in processing of fish, for nearly all of the equipment in big kitchens, such as restaurants, hospitals, electric kettles, cookware and kitchen appliances of any kind such as sinks and drains, for bowl.



Canned foodstuffs in non-lacquered cans and other processed foodstuffs, particularly acidic foodstuffs such as fruit juices, may be significantly higher in chromium than fresh foodstuffs. A small contribution to chromium intake can be made by uptake from cans. However, the significance of this is probably negligible. Chromium from materials and articles is expected to migrate as Cr(III) and not as Cr(VI) (Guglhofer and Bianchi, 1991). Cr(III) can not migrate at neutral pH in foodstuffs. Therefore, the migration of Cr(III) to foods of pH 5 or above is low. Formation of Cr(VI) as a result of a conversion in water of Cr(III) is not possible. Therefore, formation of Cr(VI) does not occur in foodstuffs. This implies, that Cr(VI) is generally not considered to be an issue of food contact materials. Also, chromium does not migrate significantly from articles made of stainless steel, and any released chromium is Cr(III) (Cunat, 1997).



Due to alloying with chromium, the stainless steels resist corrosion by foods and are readily cleaned, thereby providing hygiene in food preparation and handling. Chromium is one of the metals which naturally forms a corrosion-resistant passive film when in contact with water and air (see section on corrosion).



The specification of chromium is of great importance in determining any possible toxicity issues. Cr(III), the most stable oxidation state in biological materials, is an essential element for normal glucose metabolism, while Cr(VI) is highly toxic (Beliles, 1994; Costa, 1997; Nordic Council of Ministers, 1995). Cr(III) has a low toxicity due to low absorption (about 0.5%) (Nordic Council of Ministers,1995). Toxic aspects of chromium are related to Cr(VI) (Nordic Council of Ministers, 1995), due to its high absorption, easy penetration of the cell membranes and its genotoxicity and oxidising properties (Codex, 1995).

Conclusions



Chromium as a constituent of Stainless Steel manufacture is perfectly acceptable as a fabrication material in distilling equipment. Likewise, chromium products where the chromium is in direct contact with the distilling fluid path are very safe. As to chromium in foodstuffs through migration, even in harsh acidic conditions below pH 5.0 as commonly found in distilling, it is not considered to be a toxicological problem because the recommended human dietary intake is higher than actual values. However chromium tubing and other products as made by the electroplating industry for decorative purposes e.g. bath towel rods and hand railings is an entirely different matter when applied to still fabrication.



Decorative chrome-plating is a process whereby a thin layer (sometimes 50 millionths of an inch) of chromium is applied via chromium salts, acids and electricity, to aesthetically enhance (beautify) the appearance, and/or to prevent tarnishing (staining). It is usually deposited over a thin base layer of nickel or copper previously deposited over the black iron or steel that the tubing is made from. To keep costs down the interior of these tubes, not usually seen by the human eye, are prevented from being coated by either the chromium or the copper or nickel. Consequently the base tubing metal of black iron or steel is exposed to the surrounding environment. Using these tubing products as still components, while they might look pretty, would place the exposed iron or steel in direct contact with hot fluids. Thus rapid interior oxidation (rusting) of the tubing and/or contamination of the ethanol product would result.







References



1. Beliles, R.P. (1994). The metals. In: Patty's Industrial Hygiene and Toxicology, Fourth

edition, Volume 2, Part C. Edited by Clayton, G.D., and Clayton, F.E. John Wiley & Sons,

Inc.

2. Codex Alimentarius Commission (1995). Doc. no. CX/FAC 96/17. Joint FAO/WHO food

standards programme. Codex general standard for contaminants and toxins in foods.

3. Costa, M. (1997). Toxicity and carcinogenity of Cr(VI) in animal models and humans. Critical Reviews in Toxicology. 27(5) p. 431-442.

4. Cunat, P.-J. (1997). Healthy eating and drinking with stainless steel. 1st SS congress,

Thailand, Dec. 1997.

5. Guglhofer, J., Bianchi, V. (1991). Metals and their compounds in the environment. VCH

Verlag, Weinheim, Germany.

6. Florence, T.M., Batley, G.E. (1980). Chemical speciation in natural waters. CRC Critical

Reviews in Analytical chemistry. p. 219-296.

7. Langaard, S., Norseth, T. (1986). Chromium. In: Friberg, L., Nordberg, G.F., Vouk, V.B.

Handbook on the toxicology of metals. Second edition. Elsevier, Amsterdam, New York,

Oxford.

8. Nordic Council of Ministers (1995). Risk evaluation of essential trace elements - essential

versus toxic levels of intake. Report of a Nordic project group. Ed.: Oskarsson, A. Nordic

Council of Ministers, Copenhagen, Denmark.

9. SCF (1993). Report of the Scientific Committee for food (thirty-first series). Nutrient and

energy intakes for the European Community.

10. Veien, N.K., Hattel, T., Laurberg, G. (1994). Chromate-allergic patients challenged orally

with potassium dichromate. Contact dermatitis. 31 p. 137-139.

11.WHO (1993). Guidelines for drinking-water quality. Volume 1. Recommendations.

Copper



Copper exists in two oxidation states: Cu(I) (cuprous) and Cu(II) (cupric). Copper can also occur in a trivalent state due to certain chemical reactions. Copper is among the most effective of metal biochemical oxidising agents. Copper is an essential element to man (Aaseth and Norseth, 1986). Copper also has the ability to restrict bacterial growth, e.g. Legionella, in drinking water systems (Rogers et al., 1994).



Copper is naturally present in most foodstuffs in the form of copper ions or copper salts (Codex, 1995). The main sources are meat, offal, fish, pecans, milk chocolate and green vegetables (Aaseth and Norseth, 1986).



Copper vessels are traditionally used in many specialised food processing activities, such as breweries and distilleries, for cheese-making, chocolate, dry vegetables, jam and sweets production. In food utensils, copper is in general used unalloyed, for exam ple in saucepans, which are usually lined inside with tin or stainless steel. Copper is used in alloys, particularly brass, bronze, and nickel silver (British Non-Ferrous Metals Federation, 1997).



Copper is slowly attacked by dilute hydrochloric acid or dilute sulfuric acid and is soluble in ammonia water (Beliles, 1994). Acidic foodstuffs can attack copper in utensils. Therefore, copper may be present in foodstuffs due to migration from food contact materials, e.g. copper utensils, copper pipes, etc. (Codex, 1995) or from using drinking water from copper pipes for food preparation. In some cases, high copper migration might induce some discoloration. Migration from copper into sugar confectionery cooked at 125-140 °C and at pH 5.1-6.0 on average increases the copper concentration in the confectionery from 0.13 mg/kg to 0.25 mg/kg (Written comments from BCCCA, 1999).



Copper is one of the best conductors of heat available. Only silver has a higher thermal conductivity, while stainless steel is a relatively mediocre conductor. (Hypertextbook Physics, 2006).





Conclusions



The level of contamination of copper observed in drinking water and foodstuffs does not constitute a safety problem. There is a greater risk of adverse health effects from copper deficiency, than from excessive copper intake.



Copper has been employed for centuries as the metal of choice in distilling equipment, particularly in still fabrication. This was originally due to its abundance, its malleability using simple hand tools, and its superior heat transfer capabilities over other metals. Later, when more modern metals such as stainless steels became widely available, it was discovered by accident that these metals produced a different and clearly inferior spirit to that produced from the same mash employed in copper stills.



The cause of this anomaly was proven to be stainless steel's inert nature, which allowed the spirit vapour to pass unaltered, whereas copper reacts with any sulphides (rotten egg gases) which are always present in grain mashes and removes them from the distillate as sulphates and sulphites. Consequently traditional distillers like the Scottish and Irish Whisk(e)y producers rapidly went back to using copper. Today you will see stainless steel used in mash tuns and transfer piping, but in the stills themselves where the ethanolic vapours destined to become potable spirits are separated from the water, copper is the fabrication metal.





References

1. Aaseth, J., Norseth, T. (1986). Copper. In: Friberg, L., Nordberg, G.F., Vouk, V.B. Handbook on the toxicology of metals. Second edition. Elsevier, Amsterdam, New York, Oxford.

2. Beliles, R.P. (1994). The metals. In: Patty's Industrial Hygiene and Toxicology, Fourth

edition, Volume 2, Part C. Edited by Clayton, G.D., and Clayton, F.E. John Wiley & Sons, Inc.

3. British Non-Ferrous Metals Federation (1997). Written comments on the draft guideline.

4. Codex Alimentarius Commission (1995). Doc. no. CX/FAC 96/17. Joint FAO/WHO food standards programme. Codex general standard for contaminants and toxins in foods.

5. Environmental Health Criteria for Copper (1996). PCS/EHC 96.28 unedited, page 9.

6. IPCS EHC 200 Copper (1998). Environmental Health Criteria 200. World Health

Organization, Geneva.

7. JECFA (1982). Evaluation of certain food additives and contaminants. Twenty-sixth report of the Joint FAO/WHO Expert Committee on Food Additives. World Health Organization,

Technical Report Series 683.

8. Rogers, J., Dowsett, A.B., Dennis, P.J., Lee, J.V., Keevil, C.W. (1994). Influence of plumbing materials on bio film formation and growth of Lagionella pneumophila in notable water systems. Appl. Environ. Microbiol. p. 1842-1851.

9. SCF (1993). Reports of the Scientific Committee for Food. Thirty-first series. Nutrient and energy intakes for the European Community.

10. WHO (1998). Guidelines for drinking-water quality. Addendum to Volume 1,

Recommendations.

11. Online http://hypertextbook.com/physics/thermal/conduction/" onclick="window.open(this.href);return false;" rel="nofollow as retrieved on 8 Mar 2006 1:36:26 GMT





Sat May 27, 2006 4:29 am

Show Message Info
#35812 of 36475
Msg List <Prev>
View Source
Use Fixed Width Font
Unwrap Lines
"Harry" <gnikomson2000>
gnikomson2000
Offline Offline
Send Email Send Email
Invite to Yahoo! 360° Invite to Yahoo! 360°
I use a pot still.Sometimes with a thumper
muckanic
Swill Maker
Posts: 433
Joined: Tue May 23, 2006 1:19 am
Location: Canberra

Post by muckanic »

Harry wrote:I wonder how many more time I have to point people to this info, before the penny drops?
That point about Al and metallic-tasting distillates is an interesting one. Do the references actually go so far as to suggest that a volatile organo-metallic compound is being produced?

As for corrosion, there wouldn't be too many washes that had more attack than, say, boiling pasta sauce. Possible exemptions for sour mashes, citrus wine, and (if someone is silly enough to contemplate it) Coca-Cola. :shock:
hornedrhodent
Rumrunner
Posts: 732
Joined: Sat Mar 04, 2006 1:42 am
Location: Nth coast NSW

Post by hornedrhodent »

I want a still with a platinum boiler, gold column with copper packing, silver cooling coils and platinum needle valves. :lol:
stoker
Distiller
Posts: 1093
Joined: Fri Dec 02, 2005 9:16 am
Location: not there

Post by stoker »

OK, I'll order 2 of them. :D
-I have too much blood in my alcohol system-
Harry
Swill Maker
Posts: 198
Joined: Sun Jan 30, 2005 7:46 pm
Location: Paradise (aka Cairns Qld Australia)

Post by Harry »

Harry Ill put a sticky on it and maybe it will get read metals in Distilling Topic List

Yeah thanks Tater. It may help a lot of people to avoid costly bad choices in metals when they're starting out. Knowing why certain materials are promoted over others also improves our overall distilling knowledge and ultimately proves to legislators that we and our hobby should be taken seriously, not just as mickey mouse pissheads.

.
Slainte!
regards Harry
Ardent Spirit

Post by Ardent Spirit »

This is one of the most informative threads I have seen so far.
Thanks guys
azeo
Site Donor
Site Donor
Posts: 212
Joined: Tue Sep 05, 2006 12:56 am
Location: nr Wgtn, EnZed

Post by azeo »

brilliant, absolutely brilliant, one never stops learning with this hobby, and thanks to this site and it's members the information is out there, cheers to all :-)
azeo
Site Donor
Site Donor
Posts: 212
Joined: Tue Sep 05, 2006 12:56 am
Location: nr Wgtn, EnZed

Post by azeo »

I've tried to find information I've found previously on the treatment for brass - plumbing fittings and the like, but can't remember or locate this info again. Can anyone point me in the right direction? Thanks :)
User avatar
Tater
Admin
Posts: 9678
Joined: Mon Oct 25, 2004 9:19 am
Location: occupied south

Post by Tater »

Sure can go to search and type in brass
I use a pot still.Sometimes with a thumper
azeo
Site Donor
Site Donor
Posts: 212
Joined: Tue Sep 05, 2006 12:56 am
Location: nr Wgtn, EnZed

Post by azeo »

ahh lovely thanks! found it! the seachbar on this site for some reason is always nearly hidden for me on this computer, I can juust click what looks like the go key, so don't make use of it.. until now cheers
Pikluk
Swill Maker
Posts: 332
Joined: Sun Nov 04, 2007 8:22 pm

Post by Pikluk »

I want a still with a platinum boiler, gold column with copper packing, silver cooling coils and platinum needle valves. Laughing
he forgot the hand full of diamonds for boiling chip :P
The more you read the more you learn.
The more you learn the more you realize you don't know shit :)
schnell
Angel's Share
Angel's Share
Posts: 224
Joined: Tue Jan 30, 2007 2:47 pm
Location: desert mountains of the west

Sn

Post by schnell »

I have a historian distiller friend who's been asking me about tinning the interior surface of copper.

Is this a traditional method of passivating the reactive copper?

Or could this be for a somewhat different reactive and/or catalytic influence on the process than we experience when using clean copper?

His interest stems from the stills used in France for absinthe production in the height of it's popularity. He has used historical equipment in europe and has been able to compare the tinned and untinned copper stills. He has told me this produced noticable flavor variations, with plain copper on the losing end.

Can anyone point me to more info on the topic?
grizzly1
Novice
Posts: 53
Joined: Sun May 18, 2008 9:16 pm

Re: Still metal question

Post by grizzly1 »

want to see how bad AL pits and leaves a metalic taste in a food. put ordinary cabbage in an allum pot or bowl and let it sit for 10 min. the metalic taste will be in the food :oops: . let it sit over night and you will feel the pits in the metal with your hands even on a new bowl. I did this in culinary class. Harry's info is right on, thats why you will only see restaurants use AL for short cooking methoids and low acid foods, everything else is stainless.
Pervak
Novice
Posts: 11
Joined: Fri May 30, 2008 10:46 am
Location: BC, Canada

Re: Still metal question

Post by Pervak »

From my own experience, a word of cation on aluminum.
Back in a day I used to use aluminum baking trays with vinegar to mask some smell (vinegar does wonders BTW). After a few days the trays would corrode so much that vinegar would all leak out thou the HOLES in those trays :shock:
I realize that pH of vinegar is roughly 2.4 and my washes and up with pH of about 3.5*, but that just means it will take slower to dissolve it or might need a higher temp to do so (like in a boiler :wink: ).
Think about this experience as an exaggeration to prove a point.
Lots of REALLY bad stuff have a metallic taste to it, so I try to avoid it as much as poison.

*Edit: pH of my last wash, variation of UJSSM.
User avatar
bmaj
Novice
Posts: 8
Joined: Mon Dec 21, 2015 12:08 pm

Re: Still metal question

Post by bmaj »

Junk Yard Copper? I have at my disposal some 1-1/2 inch copper that was once used as a drain line it has some nasty bits on the inside of the pipe. I hope to build a mini BOK out of 1-1/2 inch or 2 inch. Would cleaning up the inside of this old pipe be worthwhile?
Prairiepiss
retired
Posts: 16571
Joined: Sat Dec 18, 2010 7:42 am
Location: Somewhere in the Ozarks

Re: Still metal question

Post by Prairiepiss »

Could you have found an older thread to post in. Damn it's 10 years old. Lol

Drain pipe usually ends up being very thin. I have put my finger through some it was so thin.

Could you clean it up and use it? Maybe. But I'm not sure I would even try.

There is more then a few threads around here asking this same question. You may find the answers you seek in them. But it's kinda off topic with this thread. Since it's really about aluminum.
It'snotsocoldnow.

Advice For newbies by a newbie.
CM Still Mods
My Stuffs
Fu Man

Mr. Piss
That's Princess Piss to the haters.
Post Reply