Our Patinas

David M Bowman Studio


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Patinas

Blue-green & White Blue-green

Brown & White Brown

Dark Green & Black

Ochre, White Ochre, & Black Ochre

Grey, Silver, Silver Brown, & Stone Grey

Mottle, Burnt Mottle, & Brown Mottle

Spray Blue-black

Apple Green

Pigmented Blue & Antique Blue

Flame colored copper


Patina care


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David M Bowman Studio
Box 738
Berkeley, CA 94701
510 845-1072
david@davidmbowman.com
reed@davidmbowman.com

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Formulas for patinas we use

NOTE: read all safety information and take appropriate precautions before mixing or using these formulas. They are to be used at your own risk.

Apple Green
(cold application)

3 oz. (85 grams) Cupric chloride
½ oz. (15 grams) Ammonium chloride
1 pint (approx. ½ liter) Water

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Add the chemicals to the water and stir with a nonreactive implement. Brush or sponge the patina all over the metal's surface, leaving it puddled all over the piece. Allow to dry several hours or overnight. Reapply gently, so as not to disturb the first layer, which will be powdery. Reapply at least one more time. Rinse surface gently.

Ronald D. Young gives this patina in his book, Contemporary Patination (pp 69-70), where he recommends different application techniques than ours, and suggests ways of getting many different color variations.

Discussion:
Apple Green

Liver-of-sulphur black
(Torch technique)

approx. 50 grams Sulphurated potash (Liver of sulphur)
1 liter water

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The amount of potash can be varied in a very wide range to produce different densities of black. Grind the potash in a mortar, add it to the water, and stir with a nonreactive rod until the chemical is totally dissolved. This patina is much-used on bronze sculpture, but we currently use this patina only over a layer of blue-green. In good ventilation, and wearing a face-mask, heat the metal with a torch until the solution—brushed on with a soft brush—steams off instantly. Take care not to burn the surface of the blue-green while applying the second layer.

Our Dark Green patina, from which this formula comes, is Hughes and Rowe's number 5.117 (p 296). It is a traditional patina, and is found many other places as well.

Used in:
· Dark Green & Black
· Black Ochre

Blue-green
(Torch technique)

200 grams Cupric nitrate
1 liter water

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Grind the cupric nitrate in a mortar, add it to the water, and stir with a nonreactive rod until the chemical is totally dissolved. In good ventilation, and wearing a face-mask, heat the metal with a torch until the solution—brushed on with a soft brush—steams off instantly, and leaves the color solid and dry on the surface. If the metal is overheated, the brush will stick and burn. If the color on the surface is accidentally burnt black with the torch, the patina may be simply reapplied to that area with good results.

This is patina 5.116 in Hughes and Rowe (p 296). It is the least toxic, and one of the easiest to use, of the many patinas which produce similar colors.

Description:
· Blue-green
also used in:
· White Blue-green
· Ochre & White Ochre
· Dark Green & Black
· Pigmented patinas

Brown
(Torch technique)

30 grams Ferric nitrate
1 liter water

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Add the ferric nitrate to the water and stir with a nonreactive rod until the chemical is totally dissolved. In good ventilation, and wearing a face-mask, heat the metal with a torch until the solution—brushed on with a soft brush—steams off instantly. The patina is very transparent, and must be built up slowly.

This is based on patina 5.51 in Hughes and Rowe (p 280), but our formula (above) is three times the strength given there, for quicker application.

Description:
· Brown
Used in:
· Ochre, White Ochre, & Black Ochre
· Brown Mottle
·
Silver Brown

Mottle
(Sawdust burial patina)

50g Ammonium Chloride
50g Sodium Chloride (salt)
150ml Ammonia
3 liters water

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Add the ammonia and other ingredients to the water and stir until dissolved. Out of doors and out of reach of children, soak sawdust or wood chips with the liquid and bury the piece to be patinaed in the wood chips, and wet it down with more of the patina. Cover to slow evaporation. Check once or twice a day to see how the patina is developing; keep putting on more wood chips and/or patina liquid to fill gaps. We find that the patina only develops well on the upper surface where the chips and liquid are resting, so you will need to rotate the piece once its top is done to get each side in turn. Usually it takes two to three days to develop a good patina on brass, if you are assiduous in tending it and filling gaps.

Once the color has achieved good coverage, let the piece dry out in the sun for a few hours, then wearing a mask and gloves brush off the wood chips, back into the pile for reuse. You may then go over the surface lightly with a scouring pad to take away some of the powdery residue, if you wish. Either before or after brushing it, you can burn the patina with a torch. This should be done under a fume hood and with eye and breathing protection.

This is based on patina 5.164 in Hughes and Rowe (p 280), but our formula is a stronger variant we adopted based on a mistaken formulation of the patina by our friend, the sculptor Martin Metal.

Description:
· Mottle
Used in:
· Burnt Mottle & Brown Mottle

Silver patina
(Torch technique)

approx. ½ tsp. silver nitrate
approx. 1 cup water (250ml)

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This is a very easy patina to use - it sticks and reacts well on brass. You should wear long sleeves and gloves in addition to ordinary eye and face protection when applying it, since splatters from the the hot patina actively and semi-permanently discolor skin and fingernails. Stir flakes or powder of silver nitrate into water. It should dissolve easily. Apply while heating the metal till the water steams off as the patina is brushed on. Patterns can be made with brushstrokes and puddling, but note that much of the effect of these patterns comes from a powdery surface layer, which can be smeared or rinsed away. If you wish to keep the grey and white effects as they stand when the surface is first cooled, use a spray fixative. Otherwise, rinse the surface, wearing rubber gloves to keep the residue off your hands. Once it is rinsed and completely dry, it can be waxed. Once the wax is dry, the surface can be buffed to produce a shiny silver or silver-grey color, sometimes dramatically different from the unbuffed look.

Our silver patina was suggested by a fellow craftsperson, but similar formulas can be found many places, including Ron Young's book on page 54.

Description:
· Silver patina
Used in:
· Grey, Silver, Silver Brown, Stone Grey & Silver Blue-green

White
(Torch technique)

1 heaping tbsp bismuth nitrate
1 heaping tbsp titanium dioxide
1 heaping tbsp stannic oxide
approx. 1 liter water
(optional: several drops of sodium silicate)

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In the concentration we mix this patina, it is mostly useful only for a transparent layer on top of other patinas. In any case, it does not stick and react strongly with bare brass. If you add the sodium silicate, the patina will stick much better, and very little if any will rinse off, at least when applied over other patinas. If you do not include the sodium silicate, rinse the patinaed object well under running water and rub it with a cloth or a rubber-gloved hand to remove the excess, or it will smear badly when you seal the patina with wax. Experiment with different concentrations, keeping the main three ingredients in equal proportions.

This formula was given to us by a fellow sculptor, Cheryl Barnett, but it closely follows a recipe given by Ron Young on page 55.

Used in:
· White Ochre
· White Blue-green
· White Brown