Patination for copper roofing?

[Andy Dingley]

Bright green copper roofing is a traditional sight in much of Europe. What's used to patinate it? If I put copper outside I get the usual dark brown, not this bright green.

[S Viemeister]

An architect I once dated, claimed that the copper was treated with male urine.

[Stephen Howard]

That's one way of doing it....you can also use a weak acid, such as vinegar ( acetic ).

Tradition has it that the roofers would place a bucket on the roof into which they'd all urinate in the course of the day. This was then spread liberally over the roof.

Regards,

[Thomas Prufer]

Nothing -- it patinates itself.

I looked it up in the site German copper institute[1], and they say, "wait a few decades -- takes up to fifty years". There are patinations to turn copper green, but they are suited to small craft items only, as it can't be applied evenly enough on roofing and the effect would be blotchy and streaky.

Thomas Prufer

[1]

[nightjar]

Age and pollution.

The brown is actually a thin layer of black copper oxide and, possibly, black copper sulphide over the copper , which shows through to give the brown colour. In the presence of moisture, these slowly react with atmospheric carbon dioxide and sulphur dioxide to create a mix of green hydrated copper sulphate, green hydrated copper carbonate and blue hydrated copper carbonate. The rate of formation varies, but lots of sulphurous coal smoke helps speed the process, hence green copper roofs tend to be old and in towns.

If you want to do it artificially, there are various chemical treatments, but they generally are only suited to small articles that can be completely cleaned of all oxides prior to application and subsequently protected by wax or a similar treatment.

Colin Bignell.

[A.Clews]

Thus spake Andy Dingley ( [e-mail]) unto the assembled multitudes:

The dark brown you are seeing is the supporting roof timbers, because the copper roofing will have been nicked by enterprising scrap metal dealers.

[The Natural Philosopher]

Wait longer..

[Peter]

Pee on it.

My father used to do copper roofing and that's what he always said was the best way.

[Andy Dingley]

I keep hearing this - except that it doesn't work worth a damn.

I have a copper acetate production rig going in the workshop (it's a useful chemical for small-scale patination work). Vinegar is pumped (one of those electric cat waterdishes) over copper sheet and recirculated. It takes _ages_ to make copper acetate this way. It's even slower than lead acetate.

[dennis]

I like it shinny, varnish is useful to stop the copper rot.

[Adrian]

[e-mail] gurgled happily, sounding much like they were saying:

[The Natural Philosopher]

That'st true. My flux goes really green really quickly. Maybe bakers fluid sprayed on with a pressure washer?

[Stephen Howard]

So it works, but very slowly. I think that was understood.

I find LaCo flux does a pretty swift job, but I doubt anyone would want to spread it all over a roof.

Regards,

[Dave Plowman (News)]

Active flux soon turns it green.

[Stephen Howard]

It's just a stronger acid really, I'd imagine that its use would cause complications some way down the years.

Regards,

[Rod]

And to greenify sculptural pieces (typically bronze) in a moderate length of time they often use veridian artists' oil paint. :-) However I seem to remember something else - some iron compound - could be ferrous sulphate. I shall try to remember properly and post again if I do.

[Dave]

How did you extract that out of him? ;-)

Dave

[Bruce]

The architect was probably taking the piss.

;-)

[Rod]

The following applies to bronze - but probably well worth a bit of experimentation on copper. Quite fancy the peacock blue...

Found at:

but pasted in entirety as I don't trust that URL to remain usable. (Perhaps its complexity actually means it will be available. But I don't know. :-) )

U.S. General Services Administration Historic Preservation Technical Procedures

05030-02

PATINATION FORMULAS FOR BRONZE

This standard includes formulas for patinizing bronze to achieve a specific color. It is intended as a reference only, for validating project and/or vendor recommendations and specifications. Formulas are listed below and designated by color.

FOR RAW 85-5-5-5 (Semi-transparent finish; Nitric acid pickle process):

- Nitric Acid (diluted)

FOR BASIC GREEN (Semi-transparent finish; Hot process):

- Copper Nitrate (1 tsp.)

- Clean, potable water (1 pint) Note: A fresh mixture is needed for each coloring.

FOR ANTIQUE GREEN (Opaque finish; Cold process):

- Cupric Nitrate (40 grams)

- Ammonium Chloride (40 grams)

- Calcium Chloride (40 grams)

- Clean, potable water (enough to make 1 liter) Note: Frog green results after several applications, 1/2 hour intervals, color is not satisfactory alone.

FOR YELLOW GREEN (Heavy opaque finish; Cold process):

- Ammonium Chloride (7 parts/weight)

- Copper Acetate (4 parts/weight)

- Clean, potable water (8 parts/weight) Note: Takes effect after several applications.

FOR LIGHT GREEN (Opaque finish; Cold process):

- Ammonium Chloride (16 parts)

- Sodium Chloride (16 parts)

- Ammonium Hydroxide (16 parts) Note: Twelve hour Intervals for several days, for deeper green, add 16 parts of copper sulfate.

FOR BLUE GREEN (Heavy opaque finish; Cold process):

- Vinegar Note: Bury object in sawdust saturated with vinegar for several days, sprinkle more if needed.

FOR WINE VINEGAR GREEN (Opaque finish; Cold process):

- Red or White Wine Vinegar (1/2 liter)

- Ammonium Hydroxide (1 tbsp.)

- Muriatic Acid (1 tbsp.)

- Sodium Chloride - salt (1 tsp.)

- Ammonium Chloride (100 grams)

- Clean, potable water Note: Apply solution for several days at 12 hour intervals.

FOR APPLE GREEN (Heavy opaque finish; Cold process):

- Sodium Chloride (5 parts/weight)

- Ammonia (4 parts/weight)

- Ammonium Chloride (5 parts/weight)

- Glacial Acid (4 parts/weight)

- Clean, potable water (32 parts/weight)

FOR GREEN RUSSET BRONZE (Cold process):

- Sodium Thiosulfate (8 ounces)

- Nitric Acid (0.25 fluid ounces)

- Clean, potable water (1 gallon) Note: Normally applied to brass objects

FOR GREEN FROM BROWN PATINA: (Cold process)

- Liver of Sulfur (1 large lump crushed)

- Clean, potable water (1 pint) Note: Silica bronze only!

-OR-

- Cupric Nitrate (1 tbsp.)

- Clean potable water (1 pint)

FOR BROWN: (Cold process)

- Sodium Thiosulfate (1 part/weight)

- Ferric Nitrate (8 parts/weight)

- Clean, potable water (128 parts/weight)

-OR- (Vat dipping process)

- Cubric Sulfate (4 ounces)

- Potassium Chlorate (2 ounces)

- Clean, potable water (1 gallon) Note: Immerse for a minute or so, then immerse in a solution made of 1 ounce liquid sulfur to 1 gallon water. Rinse in how water. Scratch-brush dry with sawdust.

-OR- (Cold process)

- Ammonium Carbonate (3 parts)

- Cupric Acetate (1 part)

- Tartaric Acid in Vinegar (1 part)

- Sodium Chloride Salt (1 part) Note: Make a paste of these ingredients, smooth it over the bronze for 1 hour and rinse with hot water.

-OR- (Vat solution process)

- Ammonium Chloride (4 parts)

- Potassium Oxalate (1 part)

- Acetic Acid (200 parts) Note: Heat solution, then dip for 4 to 5 minutes. Dry and repeat until desired color is achieved.

FOR LIGHT TO DARK BROWN: (Transparent finish; Hot process)

- Ferric Nitrate (1/2 tsp.)

- Clean, potable water (1 pint) Note: A fresh mixture is needed for each coloring.

-OR- (Semi-opaque to opaque finish; Hot or cold process)

- Liver of Sulfur (1 large lump crushed)

- Clean, potable water (1 pint)

FOR MATTE BROWN (Opaque finish; Cold process):

- Barium Sulfide (1 ounce)

- Potassium Sulfide (1/4 ounce)

- Ammonia (2 ounces)

- Clean, potable water (3-5 quarts) Note: Darkens immediately after applications, matte color is best without a preservative.

FOR JAPANESE BROWN (Transparent finish; Cold dip process - dip or brush):

- Copper Sulfate (5 ounces)

- Cupric Acetate (5 ounces)

- Copper Carbonate (5 ounces)

- Clean, potable water (1 gallon) Note: Works well on 85/3/5 bronze, but will turn black on silica bronze.

FOR GOLDEN BROWN TO RED BROWN (Transparent and opaque finish; Cold process):

- Ferric Nitrate (1 tsp.)

- Clean, potable water (1 pint) Note: For transparent finish, use and air gun; For opaque finish, use a stippling brush.

FOR ORANGE-BROWN (Hot process):

- Liver of Sulfur (1 large lump crushed)

- Clean, potable water (1 pint) Note: Heat bronze.

-OR-

- Cupric Nitrate (1 tbsp.)

- Clean, potable water (1 pint)

-OR-

- Cupric Chloride (3 ounces)

- Ammonium Chloride (1/2 ounce)

- Clean, potable water (1 pint)

FOR ORANGE BROWN TO RUST BROWN: (Semi-opaque to opaque finish; Hot or cold process)

- Ferric Nitrate (1 tbsp.)

- Ferric Perchloride (1 tbsp.)

- Clean, potable water (1 pint) Note: Combined cold w/cupric nitrate (allow 2 to 3 hours for results).

-OR- (Opaque finish; Hot process)

- Ferric Nitrate (1 tbsp.)

- Cupric Nitrate (1 tbsp.)

- Clean, potable water (1 pint) Note: Stipple with a brush. Many coats may be required. Will appear slightly dark, yet more transparent.

-OR- (Semi-opaque finish; Hot process)

- Ferric Nitrate (1 tsp.)

- Ferric Oxide (1 tsp.)

- Clean, potable water (1 pint) Note: Deeper rust brown in low areas.

-OR-

- Golden Antimony Sulfide (1 tbsp.)

- Caustic Soda - lye (2 ounces) Note: At boiling temperature, repeat brush process if not dark enough.

FOR RUST BROWN:

- Ferric Nitrate (3 ounces)

- Perchloride of Iron (2 ounces)

- Clean, potable water (1-3 quarts) Note: Takes immediate effect.

FOR RED/BROWN (Hot process):

- Cupric Sulfide (40 grams)

- Liver of Sulfur (40 grams)

- Ferric Oxide (10 grams)

- Clean, potable water (4 liters) Note: If just cupric sulfide and liver of sulfur are used, a blue-black will occur.

FOR DARK RED, BROWN: (Hot process)

- Cupric Sulfide (1 tsp.)

- Liver of Sulfure (1 tsp.)

- Clean, potable water (1 pint)

-OR- (Hot process - 140 F)

- Nickel Sulfate (1/2 ounce)

- Cupric Sulfate (1/2 ounce)

- Potassium Chlorate (1/2 ounce)

- Clean, potable water (1 gallon) Note: Apply with a moderate wet scratch brush to even out color. Works better on 85/3/5 bronze than everdur. Wax improves the color greatly.

-OR- (Cold process)

- Sodium Thiosulfate (1 part/weight)

- Ferric Nitrate (1 part)

- Clean, potable water (128 parts) Note: Works well on everdur.

FOR PURPLE-BROWN (Hot process):

- Cupric nitrate (1 tbsp.)

- Saturated potassium Ferrocyanide (coat)

FOR BASIC BROWN TO BLACK (Transparent finish; Hot or cold process):

- Potassium Sulfide (1 grape size lump)

- Clean, potable water (1 pint) Note: Solution becomes neutral after the first application.

FOR BROWN TO BLACK (Semi-opaque finish; Hot or cold process):

- Antimony Sulfide (2 parts/weight)

- Sodium Hydroxide or Caustic Soda - lye (4 parts/weight)

- Clean, potable water (256 parts/weight) Note: Works well on 85/3/5 bronze but turns black on silica bronze.

FOR CHESTNUT TO DARK BROWN TO BLACK (Hot process):

- Ferric Nitrate (1 cup)

- Motor Oil

- Clean, potable water (1 pint) Note: Apply nitrate solution to hot bronze, then 1 coat of motor oil. Heat until chestnut brown. 3 coats will be darker. Cool in water or air and apply wax to alleviate stickiness.

FOR BROWN TO BLACK ON SILICA/GOLDEN YELLOW TO ORANGE ON 85/3/5 (Hot process or VAT solution):

- Sodium Thiosulfate (1/2 ounce)

- Ferric Nitrate (2 ounces)

- Clean, potable water (1 quart) Note: Toxic mixture, use in a sell ventilated place. Either heat the bronze or dip in the mixture heated to the boiling point.

FOR BLUE (Transparent finish; Cold dip process):

- Sodium Thiosulfate (60 grams)

- Nitric Acid (4 grams)

- Clean, potable water (1 quart)

FOR PEACOCK BLUE (Transparent finish; Cold dip process):

- Sodium Thiosulfate (150 grams/liter)

- Lead Acetate (25 grams)

- Cream of Tartar (30 grams)

- Clean, potable water (1 liter) Note: Immerse object for 20-30 minutes, preservative should be applied immediately after solution has dried.

FOR BASIC BLUE-BLACK (Transparent finish; Hot or cold process):

- Ammonium Sulfide (1 tsp.)

- Clean, potable water (1 pint)

FOR METALLIC BLUE-BLACK (Cold Dip process):

- Yellow Barium Sulfide (1 part/weight)

- Clean, potable water (128 parts/weight) Note: Immerse overnight.

FOR PURPLE (Transparent finish; Hot process):

- Copper Nitrate (1 tsp.)

- Clean, potable water (1 pint)

- Potassium Ferrocyanide

FOR DESPIAU BLACK (Hot process): Solution 1:

- Copper Nitrate (1 tsp.)

- Clean, potable water (1 pint) Solution 2:

- Ferric Nitrate (1/2 tsp.)

- Clean, potable water (1 pint) Solution 3:

- Ammonium Sulfide (1/2 tsp.)

- Ferric Nitrate (1/2 tsp.)

- Clean, potable water (1/2 pint) Solution 4:

- Potassium Sulfate (1/2 tsp.)

- Ferric Nitrate (1/2 tsp.)

- Clean, potable water (1/2 pint) Note: Form a base patina with Solution #1, then add a light coat of Solution #2, then apply Solution #3, then water, then Solution #4, then water, then Solution #3...until desired intensity is achieved.

FOR TRANSPARENT BLACK (Transparent finish; Cold process):

- Chlormoauric Acid Crystal or Cold Chloride (1/2 gram)

- Clean, potable water (100 milliliters) Note: Paint or spray (with a glass atomizer) one coat; can also be used as a dip.

FOR WHITE (Opaque finish; Cold process):

- Gesso (diluted liquid)

- Powdered colors Note: Paint gesso to the surface, a light spray of acrylic can be used on patches of exposed bronze.

FOR ANTIQUE WHITE (Semi-opaque finish; Hot process):

- Bismuth Nitrate (2 tsp.)

- Potassium Sulfide (1 pinch)

- Clean, potable water (1 pint) Note: Slightly oxidize object with torch, ferric or copper nitrate may be substituted.

FOR STRAW YELLOW (Transparent finish; Hot process):

- Ferric Nitrate - homemade grounds (1/2 tsp.)

- Clean, potable water (1/2 pint) Note: Pour nitric acid over a pint jar of rusty nails until 1/4 full, perform outdoors, mixture betters with age but can only be used once.

FOR NICKEL PATE (Opaque finish; Hot process - 110-140 F):

- Nickel Sulfate (24 ounces)

- Ammonium Chloride (3.3 ounces)

- Boric Acid (4 ounces)

- Clean, potable water (1 gallon) Note: 25-50 amps/sq. ft. varied effects by blocking out areas with lacquer.

FOR CHROMIUM PLATE (Opaque finish; Hot process - 120 F):

- Chromium Acid (53 ounces)

- Sulfate (.053 ounces)

- Clean, potable water (1 gallon) Note: 200 amps/sq. ft., same characteristic as the nickel plate formula.

FOR VERDE (Cold dip process):

- Copper Sulfate (8 parts/weight)

- Ammonium Chloride (4 parts/weight)

- Sodium Chloride (4 parts/weight)

- Zinc Chloride (1 part/weight)

- Glacial Acetic Acid (3 parts/weight)

- Clean, potable water (128 parts/weight) Note: Immerse for a few minutes, then remove and repeat until color appears.

FOR LIGHT OLIVE (Cold process):

- Copper Chloride (8 ounces)

- Ferric Chloride (8 ounces)

- Clean, potable water (1 gallon) Note: Normally applied to brass objects.

FOR OLIVE ANTIQUE (Cold process):

- Potassium Polysulfide (0.33 ounces)

- Methyl Orange Indic Soln (5 milliliters)

- Clean, potable water (1 gallon)

-OR-

- Ferric Nitrate (8 ounces)

- Sodium Thiosulfate (2 ounces)

- Clean, potable water (1 gallon) Note: Normally applied to brass objects.

FOR VERDE ANTIQUE (Cold process):

- Sodium Dichromate (12 ounces)

- Copper Sulfate (4 ounces) Note: Normally applied to brass objects.

FOR COLOR THAT VARIES (Hot or cold process):

- Cupric Chloride (3 ounces)

- Ammonium Chloride (1/2 ounce)

- Clean, potable water (1 pint) Note: Works well on everdur. If put on cold, patina will turn green. If put under hot tap water, will turn orange-brown. If put on hot over an ammonium sulfide or liver of sulfur patina first and cupric nitrate second, the bronze will turn orange to brown.

END OF SECTION

Have fun.

[Anne Welsh Jackson]

It's not pure copper?

The copper we use for our ridging is 99% pure, and it goes the colour of an old penny.