by Stephen Richard
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 ... 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. Never use abrasive or
corrosive materials to clean solder lines holding glass. The
most aggressive cleaner I use is that intended for fibreglass
baths.
2. Do not use metal or scouring pads when cleaning.
3. I never use abrasive methods in conjunction with painted glass.
4. Never use patina on a panel that has
painting. The acid will remove or damage the
painting.
5. I never use patina on leaded panels at all.
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
hydrogen tartarate/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
Source:
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.
Note that a
grayish black patina can be achieved on both tin and zinc by the use
of the iron chloride III solution. That may be the best
starting point for a multi use patina.
Safety
Is any of
this safe? No. Protective clothing, thick gloves, and
breathing protection are required. Also see the comment below.
Revised
1 comment:
Micke6
March 2019 at 21:06
It
deserves to be mentioned that many of the formulations mentioned
include one or more hazardous chemicals both to the individual and
to the environment and anyone trying them out should read up on the
material safety data sheets from their suppliers and handle any
waste responsibly. That said the post makes for good reading on an
interesting subject