Patina

The successful application of patina to solder or zinc depends on an understanding of what patina is, how it works and the methods of applying it.

What is it?

Definition:

Patina is a thin layer that variously forms on the surface of copper, bronze and similar metals (tarnish produced by oxidation or other chemical processes), or certain wooden furniture (a sheen produced by age, wear, and polishing), or any similar acquired change of a surface through age and exposure.

The chemical process by which a patina forms or is deliberately induced is called patination, and a work of art coated by a patina is said to be patinated.

The word "patina" comes from the Latin for "shallow dish". Figuratively, patina can refer to any fading, darkening or other signs of age, which are felt to be natural or unavoidable (or both).

https://en.wikipedia.org/wiki/Patina

A description of patination and the industrial process:

“In their natural state, most metals combine with chemicals in the earth or air to create metallic compounds that change their surface colour, which appear as rust or tarnish. These thin layers of corrosion are nature's patinas.”

“Among the most common procedures [to patinate] are immersion and spraying. During immersion, a piece is cleaned with sandblasting or chemicals, then dipped into a prepared liquid compound, creating an immediate change in colour. Alternatively, a piece is sprayed or brushed with a patina solution, allowed to air dry, and spritzed again. This oxidation process creates corrosion on the metal's surface that forms a layer of patina. Other methods include heat, dabbing and wiping, anodizing, and random contact patina.”

Source: Triple-S Chemical Products

A product – Black on Solder – is described and the industrial process illustrated:

“DESCRIPTION: Black on Solder is a chemical formula developed to achieve a black antique finish on Tin/Lead or Solder areas (60-40 or 50-50). This solution is a non-chromate, non-cyanide liquid solution widely used on lighting fixtures, tin wares, sculptures, gift items and other decorations. The surface will not chip, flake or peel.

“PREPARATION: Parts must be free of grease, alkalinity or acid when Black on Solder is applied. Parts must be thoroughly cleaned and deoxidized prior to blackening. … Do not use petroleum degreasing solvents that leave a residue on the surface. Rinse thoroughly with over flowing cold water to remove residual cleaners and dust. It is important that alkaline cleaners are completely rinsed off prior to blackening.

“IMPORTANT: Triple- S does NOT recommend using any sort of alcohol, solvent, acid or degreaser to clean parts prior to solution application. … Powdered cleaners such as Ajax or Comet can also be used. Use the cleaner in conjunction with a scotch brite pad and apply medium strength scrubbing to prepare the part then thoroughly rinse with fresh water. ….

“APPLICATION: Clean the part with [your chosen material]. Rinse thoroughly with water and dry. Apply [the patina] solution with a brush or spray evenly and let it react. Rinse with water and air dry or wipe with a cloth to dry the surface. [Repeat this as necessary.] It is recommended to protect the finish with a clear [varnish]”

Source: Triple-S Chemical Products

Take note:

The above quote is from a company that works with metals exclusively and is an illustration of how important cleaning is for good results in patina application.  When cleaning in proximity or on glass different processes must be used to protect the glass.

1. I never would use abrasive or corrosive materials to clean solder lines holding glass.  The most aggressive cleaner I use is that intended for fibreglass baths.
2. I never use abrasive methods in conjunction with painted glass.
3. Do not use metal or scouring pads when cleaning
4. I never use patina on any part of a panel that has painting on any of the glass. The acid will remove or damage the painting.
5. I never use patina on leaded panels at all.

I suggest these precautions should always be followed.

Cleaning

These sources indicate that a patina solution is used to form a thin layer of corrosion to the material.  To do this, the metal must be cleaned of oils, and be acidically neutral.  Cleaning is to be done with household cleaners such as powdered or cream cleaners applied with moderate pressure by synthetic scrubbing materials such as a dish scrubbing pad (sometimes called a green scrubby). The metal then needs application of running water (not a bath of water) to rinse off any residues. 

Application

The clean metal needs to be dried before application of the patination solution.  Apply with a brush or sponge, or spray and allow time for the patina to react with the metal.  Rinse with water and allow to air dry.  If wanted, the drying can be aided by wiping with a soft cloth or absorbent paper.  Often a second or third application is required to achieve the depth of colour desired.

Protect

You can then apply a varnish or wax to shine and protect the colour of the patination.  This protective process must not involve scrubbing, as that will remove the patination layer from the metal.

Do it Yourself Colourations

Goran Budija has listed a wide variety of patination formulas and methods in his publication.  What follows is a reworking of his data.

Patination of Tin

Black 1

Method:

Immerse objects in heated solution(70C). When colour is developed rinse well, dry and wax.

Formula:

5 gms Bismuth nitrate

50cc Nitric Acid

80gms Tartaric acid

1 litre water

Black 2

Method:

Immerse objects in the hot (70C) solution.

Formula:

30gms Ammonium chloride

7.5gms Molybdenum acid

1 litre water

Greyish black

Method:

Immerse objects in the room temperature solution.

Formula:

200gms Iron III chloride

1 litre water

Bronze brown

Method:

Dissolve ingredients in water acidified with nitric or hydrochloric acid. Apply to the surface(s).

Formula:

3 gms Ammonium chloride

12gms copper acetate

20ml vinegar

500ml water

Bronze colour.

Method:

Mix diluted solution of copper sulphate and cream of tartar, Rub it on an object.

Formula: equal parts of:

Copper sulphate

Potassium hydrogentartarate/cream of tartar

Patination of Zinc

Black. 1

Method:

Ingredients must be dissolved in hot water, then filtered and used.  Immerse objects and take them out immediately. Colour develops after contact with air.  Repeat if needed, rinse well and dry.

Formula:

125gms copper sulphate

60gms potassium chlorate

1 litre water

Black. 2

Method:

Immerse objects in heated solution (90 C).

Formula:

12gms copper sulphate

15gms potassium permanganate

1 litre water

Black. 3

Method:

Immerse objects in the solution. (room temperature)

Formula:

20gms ammonium molybdate

5gms sodium acetate or sodium thiosulphate

1 litre water

Greyish black.

Method:

Immerse objects in the solution (approximately 20 minutes).

Formula:

200gms Iron III chloride

1 Litre water

 

From:

Collection of formulas for the chemical, electrochemical and heat colouring of metals, the cyanide free immersion plating and electroplating, by Goran Budija.  March 2011.  Zagreb, Croatia

Summary of applicable DIY formulas and methods

Tin

Goran Budija recommends hot application to get a black patination, but this is not usually suitable for stained glass work.  Cold application will also work but needs more time and repeated applications to have the same effect as hot immersion.  Whether you choose Black 1 or 2 will depend largely on the availability of the chemicals.

A cold method of patination is the Greyish Black using iron III chloride, which is easily available. More applications and drying will intensify the colour.

To get a bronze patination of solder equal parts of copper sulphate and cream of tartar made into a paste and rubbed onto the solder will be effective, although not a copper colour.

Zinc

Black 1 seems the most useful method and formula for zinc framing of stained glass panels.  It is a cold application and immersion can be substituted by painting or brushing on the chemical solution.  Note the multiple applications required to get the depth of colour required, and the thorough cleaning and rinsing noted in the industrial process.