Toughened or tempered glass is a type of safety glass that has increased strength and will usually shatter in small, irregular pieces when broken. It is used when strength, thermal resistance and safety are important considerations.
Toughened glass is made from annealed glass by a thermal tempering process. The glass is placed onto a roller table, taking it through a furnace which heats it to above its annealing point. The glass is then rapidly cooled with forced draughts of air to below its annealing point, causing it to harden and contract, while the inner portion of the glass remains free to flow for a short time. The final contraction of the inner layer induces compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass.
It is this compressive stress that gives the toughened glass an increased strength - typically four to six times the strength of annealed glass. The pattern of cooling during the process can be revealed by observing the glass with polarised light, which shows the strain pattern in the glass.
See also Prince Rupert's Drops
Monday, 9 March 2009
Friday, 6 March 2009
Soldering 3-D Pieces
When soldering 3-D pieces together, first tack the panels together with a single tack at each end. If it later turns out that there is an alignment problem, it is much easier to dis-assemble a few tacks, with a piece of paper inserted into the space between the pieces of glass and moved up into the molten solder while your iron is at the tack joint. The paper will strong enough to move through the solder, separating the two piece of glass.
Once your 3-D piece is tacked together and looks OK, turn the piece over on its side, and, using 50/50 or 60/40 solder, fill in the inner seams, moving the piece around. Be careful to support the piece with boxes or blocks and by holding it at the top part above where you are soldering, to prevent the piece collapsing.
Once the inside of the piece, say a panel lamp, has been soldered smoothly with 50/50, turn the lamp over. Get a few boxes or similar supports to prop the lamp up against, and make it so that there will be a level solder seam. Using the 50/50 solder again, fill in the seam. It doesn't have to be perfect, at first. Do all of the seam filling first, to ensure the stability of the piece. Then go back with 60/40 solder and, again making sure the lamp seams are level, finish by smoothly soldering each seam.
Once your 3-D piece is tacked together and looks OK, turn the piece over on its side, and, using 50/50 or 60/40 solder, fill in the inner seams, moving the piece around. Be careful to support the piece with boxes or blocks and by holding it at the top part above where you are soldering, to prevent the piece collapsing.
Once the inside of the piece, say a panel lamp, has been soldered smoothly with 50/50, turn the lamp over. Get a few boxes or similar supports to prop the lamp up against, and make it so that there will be a level solder seam. Using the 50/50 solder again, fill in the seam. It doesn't have to be perfect, at first. Do all of the seam filling first, to ensure the stability of the piece. Then go back with 60/40 solder and, again making sure the lamp seams are level, finish by smoothly soldering each seam.
Thursday, 5 March 2009
Perimeter Foils
Foil pulling away from the glass on perimeter
If this is happening to you, there are several things to remember.
Clean all the edges and surfaces just before foiling. This ensures there are no oils to interfere with the contact adhesive of the foil. Avoid hand creams just before foiling as this increases the amount of oils getting onto the glass.
Remember that lots of heat breaks down the adhesive. So do not remain in one place too long. However the adhesive is not the element that keeps the foil attached to the glass in the long term. Instead, think about whether the bead on the edge is thick enough to provide the rigidity required without relying on the adhesive of the foil.
Finally, think about whether an edging came would provide better support and finish to the piece.
If this is happening to you, there are several things to remember.
Clean all the edges and surfaces just before foiling. This ensures there are no oils to interfere with the contact adhesive of the foil. Avoid hand creams just before foiling as this increases the amount of oils getting onto the glass.
Remember that lots of heat breaks down the adhesive. So do not remain in one place too long. However the adhesive is not the element that keeps the foil attached to the glass in the long term. Instead, think about whether the bead on the edge is thick enough to provide the rigidity required without relying on the adhesive of the foil.
Finally, think about whether an edging came would provide better support and finish to the piece.
Wednesday, 4 March 2009
Media for Glass Enamels and Paints
Mixing agents
These are the carriers that give "tooth" to the paints and are water-based or oil-based.
Common water-based media are:
· water & gum arabic,
· wine,
· sugar water,
· vinegar
Common oil-based media are:
· clove oil,
· lavender oil,
· damar varnish
Gum arabic
This natural gum (also called gum acacia) is a substance that is taken from two sub-Saharan species of the acacia tree, Acacia senegal and Acacia seyal. It is used primarily in the food industry as a stabliser, but has had more varied uses in the past, including viscosity control in inks. For artists it is the traditional binder used in watercolour paint. It is sold in powder and liquid forms.
Dammar gum
This is obtained from the Dipterocarpaceae family of trees in India and East Asia, principally those of the genera Shorea, Balanocarpus, or Hopea. Most dammar gum is produced by tapping trees, however some is collected in fossilised form from the ground. The gum varies in colour from clear to pale yellow, while the fossilised form is grey-brown. It is used in foods, as a glazing agent, and in the making of incense, varnishing and in other processes. Dammar was first introduced as a picture varnish in 1826 and is commonly referred to as Damar varnish.
These are the carriers that give "tooth" to the paints and are water-based or oil-based.
Common water-based media are:
· water & gum arabic,
· wine,
· sugar water,
· vinegar
Common oil-based media are:
· clove oil,
· lavender oil,
· damar varnish
Gum arabic
This natural gum (also called gum acacia) is a substance that is taken from two sub-Saharan species of the acacia tree, Acacia senegal and Acacia seyal. It is used primarily in the food industry as a stabliser, but has had more varied uses in the past, including viscosity control in inks. For artists it is the traditional binder used in watercolour paint. It is sold in powder and liquid forms.
Dammar gum
This is obtained from the Dipterocarpaceae family of trees in India and East Asia, principally those of the genera Shorea, Balanocarpus, or Hopea. Most dammar gum is produced by tapping trees, however some is collected in fossilised form from the ground. The gum varies in colour from clear to pale yellow, while the fossilised form is grey-brown. It is used in foods, as a glazing agent, and in the making of incense, varnishing and in other processes. Dammar was first introduced as a picture varnish in 1826 and is commonly referred to as Damar varnish.
Tuesday, 3 March 2009
Lead Came
Lead came is often just called came. There are two basic types of lead: hard lead and soft lead.
Soft lead is 100% pure lead with nothing added. Soft lead strips need to be straightened in order to remove the propensity to stretch and sag. The advantage of soft lead is being easier to bend and shape to curves and that straightening removes any kinks in the length. Within 50 years it will need to be replaced.
Hard lead has antimony added which stiffens the lead. This results in a stronger finished panel. However this kind of lead deteriorates relatively rapidly. The advantage of hard lead is the added strength and not having to stretch it. It will need to be straightened just before use though. It is still malleable enough to conform to most curves.
Came is available in many shapes, although H, U and C are the most common. The lengths are usually about 2 meters (6 feet). C and U shaped lead is used on the outside of a panel. H shaped lead can be used on both the interior and edge of a panel.
The came’s top and bottom are the flanges and the width of the flange is the nominal size of the lead. These flanges can be flat (parallel surfaces) or rounded (a slight dome on each of the flanges). The central part of the came is called the heart, normally 1.2mm (1/16”) thick.
Soft lead is 100% pure lead with nothing added. Soft lead strips need to be straightened in order to remove the propensity to stretch and sag. The advantage of soft lead is being easier to bend and shape to curves and that straightening removes any kinks in the length. Within 50 years it will need to be replaced.
Hard lead has antimony added which stiffens the lead. This results in a stronger finished panel. However this kind of lead deteriorates relatively rapidly. The advantage of hard lead is the added strength and not having to stretch it. It will need to be straightened just before use though. It is still malleable enough to conform to most curves.
Came is available in many shapes, although H, U and C are the most common. The lengths are usually about 2 meters (6 feet). C and U shaped lead is used on the outside of a panel. H shaped lead can be used on both the interior and edge of a panel.
The came’s top and bottom are the flanges and the width of the flange is the nominal size of the lead. These flanges can be flat (parallel surfaces) or rounded (a slight dome on each of the flanges). The central part of the came is called the heart, normally 1.2mm (1/16”) thick.
Monday, 2 March 2009
Lead Knife
Description
The lead knife is used to cut the lead cames. There are many kinds of lead knives on the market. They fall into two basic types – the curved blade and the straight blade.
This is a necessary tool because lead dikes can't achieve acutely angled cuts readily.
Use
The important things to remember are to lubricate the blade, to maintain the proper angle, and to keep the blade sharp.
The blade is lubricated by wiping it through beeswax. Beeswax is slightly sticky so it will adhere to the metal better than ordinary wax. This greatly increases the ease with which the knife will slip through the lead.
The proper angle is maintained by keeping the blade in a line between your eye, the handle, and the blade where it contacts the lead. To push the blade through the came, you need to wiggle the blade from side to side (for a straight edge) or to rock it (for a curved blade) as you apply downward pressure. Too much pressure in relation to the wiggling or rocking movement will cause the lead to be crushed. Too little movement, will make the cutting slow.
Additional use
The lead knife can also be useful in positioning the lead around the pieces of glass, usually by gently pushing on the heart of the lead.
The lead knife is used to cut the lead cames. There are many kinds of lead knives on the market. They fall into two basic types – the curved blade and the straight blade.
This is a necessary tool because lead dikes can't achieve acutely angled cuts readily.
Use
The important things to remember are to lubricate the blade, to maintain the proper angle, and to keep the blade sharp.
The blade is lubricated by wiping it through beeswax. Beeswax is slightly sticky so it will adhere to the metal better than ordinary wax. This greatly increases the ease with which the knife will slip through the lead.
The proper angle is maintained by keeping the blade in a line between your eye, the handle, and the blade where it contacts the lead. To push the blade through the came, you need to wiggle the blade from side to side (for a straight edge) or to rock it (for a curved blade) as you apply downward pressure. Too much pressure in relation to the wiggling or rocking movement will cause the lead to be crushed. Too little movement, will make the cutting slow.
Additional use
The lead knife can also be useful in positioning the lead around the pieces of glass, usually by gently pushing on the heart of the lead.
Friday, 27 February 2009
Common Solder Compositions for Stained Glass
Common solders for stained glass are mixtures of tin and lead, respectively:
- 63/37: melts at 183°C (362°F)
- 60/40: melts between 183°C (362°F) and 188°C (376°F)
- 50/50: melts between 183°C (362°F) and 212°C (421°F)
- 40/60: melts between 183°C (362°F) and 234°C (454°F)
- lead-free solder (useful in jewellery, eating containers, and other environmental uses): melts between 118°C (245°F) and 220°C (428°F), depending on composition.
50/50 and 40/60 solders are more often used in leaded panel work. Their wider range of melting temperatures allows the solder to spread and become flat.
Wednesday, 25 February 2009
Lead Dykes
Description
Lead dykes are used to cut the lead came when the angle to be cut is oblique. The cutting edge of the tool is flattened on one side and is very sharp. This is a tool where you get what you pay for. It should be spring loaded to return to the opened position readily. The jaws should move freely and easily and should be large enough to span 3/8" lead.
Use
The tool is held with the jaws pointing down with the flat side of the tool facing the side of the lead you want flat. The lead is held oriented as it will be used. The tool will be cutting into the sides of the lead strip, not from the top and bottom of the came. When cut and observed directly from the top, the upper came flange should be directly over the bottom flange. If one flange extends beyond the other, there will be a gap where the cames meet.
Observation
This is a tool that cuts square or nearly square angles on came quickly and neatly. It is not very good for angles. A lead knife is better there.
Lead dykes are used to cut the lead came when the angle to be cut is oblique. The cutting edge of the tool is flattened on one side and is very sharp. This is a tool where you get what you pay for. It should be spring loaded to return to the opened position readily. The jaws should move freely and easily and should be large enough to span 3/8" lead.
Use
The tool is held with the jaws pointing down with the flat side of the tool facing the side of the lead you want flat. The lead is held oriented as it will be used. The tool will be cutting into the sides of the lead strip, not from the top and bottom of the came. When cut and observed directly from the top, the upper came flange should be directly over the bottom flange. If one flange extends beyond the other, there will be a gap where the cames meet.
Observation
This is a tool that cuts square or nearly square angles on came quickly and neatly. It is not very good for angles. A lead knife is better there.
Monday, 23 February 2009
Loops for Hanging Panels
Loops
These can be made from copper or brass wire. The single strand wire is better than twisted strands.
Take a length just over twice the length to be covered. The larger or heavier the panel, the longer the loop should be. Bend the middle over a nail to maintain an “eye” space at the middle.
Hold the tails so they do not overlap or twist when closing the legs to form the eye.
Grasp wire with the pliers just below the bend and close the loop.
Inserting chain into the loops can be done at the time of forming the loops, thus avoiding the need to split chain links and re-solder them.
Alternatively, you can open a chain link, insert it into the loop’s eye and solder it closed afterwards.
If you are using fishing line or other lines or wires that can be joined or tied, you can insert them into the loop eyes later.
These can be made from copper or brass wire. The single strand wire is better than twisted strands.
Take a length just over twice the length to be covered. The larger or heavier the panel, the longer the loop should be. Bend the middle over a nail to maintain an “eye” space at the middle.
Hold the tails so they do not overlap or twist when closing the legs to form the eye.
Grasp wire with the pliers just below the bend and close the loop.
Inserting chain into the loops can be done at the time of forming the loops, thus avoiding the need to split chain links and re-solder them.
Alternatively, you can open a chain link, insert it into the loop’s eye and solder it closed afterwards.
If you are using fishing line or other lines or wires that can be joined or tied, you can insert them into the loop eyes later.
Friday, 20 February 2009
Pattern Cutters
These are really only needed when the glass is so dark that a light table does not transmit sufficient light through the glass to see the cartoon lines. An alternative is to cut at the side of the cartoon lines, leaving the appropriate sized pattern piece.
Pattern shears
Pattern shears are specially designed three-bladed scissors that are used to cut out patterns. The middle blade cuts out the allowance for the heart of the lead came or copper foil. Different shears are available for lead or foil work. The allowance for lead came is usually 1.5mm; foil allowance is 0.75mm.
Pattern Knife
Knives with two parallel blades properly spaced for the lead came or foil allowance are also available for pattern cutting. These are ideal for tight curves, as they are easier to manipulate than shears.
Pattern shears
Pattern shears are specially designed three-bladed scissors that are used to cut out patterns. The middle blade cuts out the allowance for the heart of the lead came or copper foil. Different shears are available for lead or foil work. The allowance for lead came is usually 1.5mm; foil allowance is 0.75mm.
Pattern Knife
Knives with two parallel blades properly spaced for the lead came or foil allowance are also available for pattern cutting. These are ideal for tight curves, as they are easier to manipulate than shears.
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