Showing posts with label Patina. Show all posts
Showing posts with label Patina. Show all posts

Wednesday 6 March 2019

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).


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.

Friday 30 March 2012

Patina Application

The application of patina to solder and other metals consists of three stages, cleaning, application, protection.

Clean the solder bead
Both flux residues and contaminants are left after soldering. Cleaning can be a combination of cleaning with abrasives and also with alkaline materials. Baking soda – sodium carbonate – can be used to neutralise any of the acidic flux left. It bubbles in the presence of acid, so gives a visual check on the amount of acid left. Since it is an alkaline substance, it will react with the acid of the patina to weaken the reaction. It is important to rinse the baking soda off with plenty of clean water.

Abrasive cleaning with materials such as steel or copper wool can be used. Some advise against this as metal residues can be left. However the abrasive scrubber used in scrubbing pots can be used to finish the cleaning without leaving metallic residues.

Apply the Patina
As patinas work by chemical reactions, they are specific to various metals. Those designed for solder work by reaction with the tin mainly, those for lead obviously react with lead, and those for zinc react with zinc - while each of these may work with other metals, they work best with the metal they are designed for. Too much rubbing while the patina is wet simply interferes with the action of the acid. Application of enough patina to allow it to "soak" - actually time to react with the metal - is much better than rubbing. To repeat, it is a chemical reaction, not a buffing process.

Once the patina is dry, you can use the baking soda solution again to neutralise the remaining acid on the metal. Rinse well. rub gently with a dry cloth to assist the drying, do not scrub. When dry again you can wax the metal.

Protect the Patina
Some allow the waxed piece to sit for 24 hours and then re-wax it. The applicator should be a soft object such as a cotton bud or soft cloth. Do not polish it until it no longer is showing black. Rather allow it to sit undisturbed for several days. The patina will get darker and smoother over time. Don't worry too much about getting it pitch black, or birght copper the first day.

Friday 7 November 2008

Copper Foil Repairs

Repair or not

First consider whether any repairs should be carried out at all. Repairing can sometimes cause more damage, and if it is an older piece, finding an exact match may be impossible. So gluing may be the better approach.

If small shards of glass are missing, daylight is visible through the broken part, or sharp bits are exposed, then it should be repaired, assuming the client is willing to pay.

Starting the repair

Having decided to repair, the first action is to use fine steel wool to remove any patina from the solder around the broken pieces, on both sides.


Removing the broken glass

Next, work out the shards using a fine blade to get between the broken pieces. You should be wearing safety glasses during all the processes of getting the glass out of the piece.


In some cases in may be necessary to score the remaining part of the broken piece with your cutter in a criss-cross pattern, from edge to edge. Also try to go toward the centre of the piece from each corner while making the score lines.

Now start tapping the centre of the broken, scored piece of glass with the ball on the end of your cutter and then work out to the edges. Keep tapping the glass and it should start to fall out. When most of the glass in the middle has fallen out, take out small pliers and gently wiggle the broken shards out, one at a time. Remove all the glass possible, but you might not be able to get the glass in a tight corner.

Removing the solder and foil

Now take your soldering iron and melt off the bulk of the solder seam, slowly going all the way around the hole. Wipe excess solder off on your iron stand sponge. Do the same on the other side. During this process you will be able to remove any remaining small pieces of glass.


Apply the hot iron to the corner joint to expose the piece of copper foil that was wrapped around the broken piece of glass. With a pair of tweezers, grasp and very gently tug out that inner piece of foil while keeping the iron on the solder line to keep the solder molten. Try not to pull the foil off adjoining pieces. If some other foil does come off, then remove that entire length, scrape clean, wash off, dry, and re-apply a piece of the same type of copper foil, cut to size.

Re-flux the exposed foil lines, remove any solder blobs - particularly in any corners - with your iron, wiping excess off on your sponge again.

Replacing the glass

Taking the shape
Take your piece of glass that best matches the broken piece, and position it underneath the hole. Trace the shape of the hole onto the glass. This works best for flat panels. Curved forms usually need to have a paper template made by tracing from the back onto the paper. Cut the shape out of the paper and put it on the piece of new glass. Make sure that the grain of the new glass is in line with the original. Cut the piece out, grind to shape, doing lots of test-fitting in the hole, until it fits.

Foil
Clean any flux off the new piece from your test fittings, and apply the same size and colour backing of copper foil that was used on the piece that you removed.

Soldering
Fit your replacement piece into its place, making sure that it is level with its surrounding pieces. You might want to tape it into place. Check its position, and if you are happy with it, then tack it twice per side.
Proceed to solder it into place. If your fit wasn't perfect, or the piece is a little rough, fill in any gaps with some 50/50 solder. Let it cool, and then finish off with 60/40 solder. Blend your new solder lines with the quality of the solder lines on the rest of the piece.

Cleaning
Wash off the flux, scrub clean, and patina if required. If copper patina was used on the piece, don't worry when you apply the copper patina. It will not match if the panel is not brand new as copper patina ages much more than black patina. Wash the patina and polish it to blend the piece in.