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).
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.
