Showing posts with label Zinc came. Show all posts
Showing posts with label Zinc came. Show all posts

Wednesday 13 May 2020

Strong Frames for Stained Glass Panels


Metals
Zinc is a popular material for framing copper foiled or leaded glass panels.  It is stronger than lead – up to eight times.  It gives a feeling solidity to the edges of the panel. 

However, it does have some disadvantages.  It is difficult to patina evenly and obtain the same colour as patinaed solder.  It resistance to progressive corrosion is weaker than lead. It requires special tools to fit around curves, making it best for rectangular panels.  It does need a saw to cut evenly, but so do a lot of the stronger metals.  A look at other options is worthwhile.

The strongest option is stainless steel.  This is difficult to cut and has special welding requirements, so is only useful in large and high corrosion installations.

Mild steel is widely available and cheap.  In certain circumstances – mainly small, thin profiles – it can be soldered.  The most secure joining is done with welding.  This requires equipment that stained-glass workers do not usually have.  However, there are a large number of metal workers that can to the work for you.

Brass is more expensive than mild steel.  It is an alloy of copper and tin and so can be soldered with the tools we normally use.  It is about half the strength of stainless steel, but three times the strength of zinc.  The tin content leads to a better patina result than zinc.

Copper is up to twice the strength of zinc, but the price fluctuates more than zinc.  It can be soldered. It requires different patina solutions than used for solder.

Aluminium is the same strength as zinc, but requires different joining methods as aluminium welding is a specialist activity.  Still, it will work on rectangular items with screws at overlapping joints.

More information on the relative strengths of various metals is given in a post on metal strengths.


Strengthening lead came
Lead is weaker than lead but can be bent to conform to curves and indentations for irregular perimeters.  If copper wire is incorporated and attached to the foiled glass, the soldering of the lead came to the joints at the intersections of the solder lines and the coper/came combination will provide greater strength than the zinc alone. 

When wanting to strengthen the perimeter of rectangular or shaped perimeter leaded panels, you can use 10mm “H” lead came soldered as usual to the whole piece as an alternative to soldering the wire to the panel.  Run the copper wire in the open edge of the “H”.  Pull the wire tight at the bottom and sweat solder at each corner.  Run the wire to the top on each side, where you can make a loop for attaching hanging wires and sweat solder the wires there too.  Then close the two leaves of the lead with a fid until they come together forming a single straight line.  If you want, a “U” or “C” edging came can be soldred to the outer edge of the "H" came to cover the line created by folding the leaves.

This post gives more detail about the process of incorporating copper into the perimeter of a leaded panel.



Friday 27 March 2020

Structural Reinforcement


Leaded light panels often require additional support against wind pressure or vibration. Whether this is needed depends on the size and location, e.g. if in a door or a ventilating window that is constantly being opened and shut.  Large leaded glass windows need some bracing against the force of wind and rain. This can be achieved by using one of the following supports:
  • Saddle Bar
  • Reinforcing Bar (Rebar)
  • Steel Core or Steels
  • Zinc Section

Saddle Bars are the strongest method of support and are used in large external windows for preventing panels from bowing inwards. They resist wind pressure in exposed situations. Saddle bars form part of the latteral support structure of the window. These bars are attached to the panel with copper or lead ties.  These ties are soldered to solder joints across the narrow width of the panels.  The bars are fixed to the perimeter of the opening either by the mouldings or by being inserted into holes in the frame. The sides of the opening provide the ancor points for the bar.  The panel is fixed to the bar by twisting the ties around it.



A saddle bar fixed in position at the side and the ties being twisted around the bar.


Sometimes the opening is divided by sideways "T" bars.  Generally the leg of the "T" faces outwards and the panel is set onto the ledge formed by the leg of the "T".  This leg often has a series of holes drilled in the leg, for pins to be inserted to hold the panel in place until the sealant has cured.


An example of "T" bars being used on a small side opening window


Rebar is another external support.  It generally is a zinc coated steel strap about 2mm by 10mm and asl long as needed to cross the panel.  This tends to be soldered directly to the panel at the solder joints either on the inside or outside. One advantage of this material is that it can be bent to conform to the lead lines of the panel.  In consequence it is not as stiff as saddle bars are.




Steel core
Steel cores take two forms - either steel-cored lead or steel strips fitted into the lead cames when leading.  The steel cored lead came is less available nowadays.  They are mainly used in domestic glazing where support is required particularly in leaded lights with diamond panes when they are inserted in continuous diagonal leads. The steel cores are not adaptable to significant curves.


Steel cored lead came cut away to show the steel core


Zinc

Zinc section came is often used to frame a panel that is not glazed into a window or frame. It has been used in the past for both straight and curved lines.  Using it for curves requires a came bending machine to give good, regular curves.  It gives a panel strength for ease of handling, but does not resist sagging or bowing at the centre.  The other disadvantage of zinc is that it corrodes much faster than lead.


Image showing a variety of zinc came

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.

Wednesday 22 February 2017

Solder for Zinc



A number of people seem to have difficulty soldering zinc around their projects.  This is because zinc transmits the heat quickly – more quickly than the tin/lead solder – requiring more heat to be put into the process.  There is a solder that can make this process easier as it is designed for soldering zinc.

“Galvanite is a lead-free galvanizing solder formulation designed specifically for high quality repairs to galvanized steel surfaces. Simple, effective and easy to use, in both manufacturing and field applications. It metallurgically bonds to the steel, for a seamless protective barrier.”
https://en.wikipedia.org/wiki/Solder#Lead-free_solder

It composition is 50% tin, 49% zinc and 1% copper.  It becomes solid at 200C and liquid at 300C.  This makes it a high temperature solder for stained glass purposes, but will give a firm attachment between the zinc and the solder or lead came it surrounds.  The high temperature aspect means you need to keep the iron on the zinc rather than the more easily soldered metals or the glass.



Wednesday 19 February 2014

Panel Framing Options


Some framing options for free hanging stained glass panels are given here.  They are not exhaustive, of course, but do give some principles to be considered when making frames.  Wood and metal are the two traditional materials for framing panels to be hung.

Wood
A wood frame requires joints of some kind. These joints are important to the durability of the frame. The two main kinds of joints are glued and screwed.

Glued joints


Lap joints seem to be strongest. An odd element relating to the strength of this joint is that placing a wooden pin in the joint weakens, rather strengthens the lap joint.

Mortice and tenon is also a strong joint. It requires considerable skill to make a good joint.



A mitred is among the weakest, but can be strengthened with a biscuit or fillet in the joint.

A mitred joint with biscuit ready for glueing.


Screwed joints
These have a lot of movement before failure, but do give a lot of resilience to the joint as they can stretch rather than immediately give way. They also can be used with any of the glued joints if appearance is not of prime importance.

Frame style
The width and thickness of the frame are interrelated – thicker frames (front to back) can be narrower, thinner frames need to be wider. So the desired appearance of the frame width has a significant effect on the dimensions of the frame.

Metal cames or angle

Lead can be an adequate framing material, but if strengthening is required, you can use copper wire within the came and fold the leaves closed over it. You can also use steel rod within the came, as shown in the posting.

Zinc is a stronger metal than lead – about 8 times, but still has a weak tensile strength. I corrodes easily, but accepts solder as a joining method. It is more expensive than lead.

Some of the variety of zinc came available

Aluminium is a little stronger than zinc, but does not take solder. It has similar costs to zinc.

Some of the aluminium profiles available

Copper is about 1/3 stronger than zinc and also takes solder. It corrodes to a verdigris, but can be protected by clear varnish or paint. It is more expensive than zinc, but can be used as wire which is less expensive than other forms of copper.

Brass is over two times stronger than zinc and also takes solder. It resists corrosion well, and is a little cheaper than copper.

Some of the brass came options.


Mild steel is over 3 times stronger than zinc, but does not take solder at all well. It is relatively cheap and welds easily, making it a good framing material, although a method of fixing the panel into the frame is required.

Stainless steel is about 4.5 times stronger than zinc, but does not take solder and needs special welding. It resists corrosion very well, but is expensive in relation to zinc.


Hanging and fixing options
Two point hangings are the most common as they prevent twisting and distribute the weight to the sides of the panel.

The hanging material is straight up from the zinc framed sides to the fixing points

The hanging material whether line, wires or chains should be straight up from the sides to two separate fixing points. A triangle shaped hanging puts a bowing stress on the panel or frame.

A variation where the chain is taken to the corner of the window, is less secure, as it stresses the joint away from the sides

Loops or holes for screws should be placed in the frame rather than the panel.

The hanging is from reinforced corners directly to fixing points on the overhead beam

Ensure the fixing points for the hanging wires are sound and secure.

If the panel is fitted tight to the opening, consider ventilation requirements to reduce condensation between the primary glazing and the hung panel.

Saturday 5 May 2012

Soldering Zinc

Brass, copper and zinc are heat sinks. That is, the metal conducts the heat rapidly so more heat has to be applied than for lead and tin to keep the soldering site hot enough to accept the solder.

The important elements are:

Use a hot iron. If you use a rheostat, turn it up to full. If you can, change the tip/bit to one rated at 800F – it will have an “8” stamped on the end that goes into the barrel of the iron.

Apply the flux liberally at the soldering point to ensure the area is “wetted”.

Keep the iron in contact with the came for a few seconds to heat the metal. If you are using zinc as your border around a leaded panel, make sure you do not heat up the lead came so that it begins to melt.  Keep the iron on the zinc.  It will transmit heat to the lead came without getting it hot enough to melt.

When the came is hot, apply the solder to the bit. 

Keep the bit on the metal until you see the solder begin to flow on both the zinc and the lead or onto the solder bead (on copper foil), then gently lift directly up.