Dealing with copper and brass:

A haven dedicated to manual espresso machine aficionados.
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rpavlis

Postby rpavlis » Jan 05, 2014, 10:10 am

Copper and brass are widely used in lever espresso machines. To me properly cared for copper and brass machines have a truly outstanding appearance. There are several things to consider here:

1. Pure copper tends to become dark with a surface layer of CuO. Unless the material is kept clean the layer may become uneven and blotched. Cleanliness is especially important immediately after a thorough polishing. Pure copper always seems to benefit from a thorough polishing with various copper polishes every few months. To me it looks its very best about two weeks after the polishing. Others may like other colour shades it goes through as the oxide coatings deepen.

2. Brass (really zinc bronze) has a tendency to become very dull (and ugly) from formation of Zn compounds on its surface. Simply washing most brasses at least daily and wiping them with a clean towel will keep them looking beautiful. Only a few days without washing and wiping will result in the beautiful shiny appearance giving way to dull and ugly. A few months without such a treatment requires polishing with materials like Bar Keeper's Friend, Brasso, or Semichrome to get them sparkling again.

3. Bronzes with metals other than zinc often have quite different properties. Many remain beautiful for long periods with no polishing at all, and with no protective coatings. Others tarnish rapidly.

4. Copper and its alloys can be coated with materials to cause them to remain bright for long periods of time--often many years--without any polishing at all. These coatings often are not very thermally stable, and most are prone to scratching. Polyurethane works very very well for this.

On espresso machines some brass parts just sit there! Other parts are subject to use every time the machine gets used. Portafilters are subjected to steam all the time, which often causes protective coatings to deteriorate. Drip trays have cups sliding over them all the time so that the coatings scratch and become worn. I like to have a brass and copper machine's base and other fixed parts coated, and portafilters and drip trays bare metal. (Bare metal looks somewhat better than metal coated with protective polymers.) I always wash both in clear water after each use and rub them with an ordinary towel. About once every month or two I may rub them with a flannel cloth that I use for polishing things that retains the polishing agent. That generally removes any tarnish that may have developed. If I go away from home for a month or more I usually have to get out the polish to make them look decent again.

Another hint: When coating brass and copper with various protective finishes like clear polyurethane, one must allow the polymer plenty of time to cure very well or it is apt to get damaged by using it too soon.

There is more maintance with copper and brass. However, plated things peel. Dealing with peeling is a VERY difficult thing. Also copper and brass are far more stable to corrosion than steel unless they are allowed to contact too much chloride.

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drgary
Team HB

Postby drgary » Jan 05, 2014, 11:32 am

Another helpful post, Robert. Someone in a restoration thread asked about verdigris when exposing copper to vinegar and warned of exposure to verdigris. Can you please say something about this? Here's that link:

1950's-1960's Era Conti Empress-New Project

Thanks!
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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grog

Postby grog » Jan 05, 2014, 12:39 pm

Thanks so much for posting this, Robert. I have some recently acquired hand grinders with copper domes and/or brass parts that are in desperate need of cleaning. I was just going to do a search for this very topic as I prepare to clean them up.
LMWDP #514

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rpavlis

Postby rpavlis » Jan 05, 2014, 3:03 pm

I should have mentioned that under certain conditions serious corrosion of copper and copper alloys can occur to produce green deposits of variable chemistry.

Such green to cyan coloured deposits are often called verdigris regardless of their chemical structure. When copper acetate forms it is water soluble, but there are other materials that are not, they are probably best dissolved away with distilled white vinegar, which is acetic acid. (One should avoid chloride salts! Cuprous chloride is chemically stable. Solid CuCl or chloride complexes of CuCl can become a catalyst for destruction of more copper or its alloys.) After cleaning something that has been partly converted into copper salts, the surface will need some careful cleaning, possibly sanding. It is also a good idea to wash the thing very carefully, treat with sodium bicarbonate solution, and then wash again. Keep a close watch on copper things for green or cyan deposits. If copper and its alloys be kept clean deposits should not form, because they are generally formed from auto catalytic processes.

When descaling a copper boiler results in blue solution, one should realise that it is blue because the boiler is being dissolved!!!! This is a signal that something is seriously wrong with the water being used.

Copper is required for life, but copper salts in large amounts, of course are toxic.

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drgary
Team HB

Postby drgary » Jan 05, 2014, 3:34 pm

Thank you!
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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FotonDrv

Postby FotonDrv » Jan 07, 2014, 11:55 am

Great information! Thank you.

I have a large copper hood that I would like to clean but am not sure where to start. Ideas?

I realize it is not an espresso machine, but I do sit there and watch the ships go by while drinking espresso :D

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That Light at the End of the Tunnel is actually a train

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TomC
Team HB

Postby TomC » Jan 07, 2014, 1:58 pm

I'd just go with Wright's Copper Cream and a big foam pad and a rag to polish it up. But I imagine it would re-oxidize rather rapidly and you'd be back to square one.

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rpavlis

Postby rpavlis » Jan 07, 2014, 2:23 pm

I have had fairly good results with larger copper objects by polishing them up with polishes like Wrights or Bar Keeper's Friend, then washing them with soapy water, then rinsing them well, preferably with distilled water, and when thoroughly dry, applying a coat of clear polyurethane coat. It is actually better to make two coats. The polyurethane must be given plenty of time to cure. I do not know how this would stand up long term in constant bright sunlight? There may be "clear coats" with special ultra violet resistance.

There are quite a few espresso machines out there with rather massive brass or copper surfaces!

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FotonDrv

Postby FotonDrv » Jan 07, 2014, 2:34 pm

Thanks guys!

I had this up for a year and there was very little color change, even being next to salt water! So, in an attempt to mask what was clearly obvious to the renters next door(bad situation) that I wanted it to go green. I tried several methods to get the copper to turn a nice verdigris but when I combined 2 of them it was instant. Vinegar, by itself did very little, saltwater from the bay did very little, BUT COMBINED it was instant :shock:

I took a pressure washer to it last summer since the house next door went from rental to new owner/occupied (nice folks). It barely phased the several years of green.

It looks like Wrights and a large random orbit buffer, like for my car, might work! Next summer it will happen, if not sooner because it might be good shoulder rehab exercise :)
That Light at the End of the Tunnel is actually a train

jmc

Postby jmc » Jan 08, 2014, 2:58 am

rpavlis wrote: There may be "clear coats" with special ultra violet resistance.


Marine spar varnish such as Epifanes and others.
Not cheap if doing a yacht, but for something as small as a coffee machine could be ideal.
I'm not sure of the temperature ratings, but Spar Varnishes are designed to spend their time in full sunlight.

John
John