If you have an irregular opening, it may be best to take a tracing of the opening. Usually this will be in a larger opening and so a helper may be necessary to hold things.
The material used to take the template must have a few characteristics:
- It must be stiff enough to have the minimum possible bend over the width or height of the opening
- It must be easy to mark with a pencil or other implement
- It must be easy to cut or shape
- It should be light to make it easy to lift it to the opening for the many adjustments that will be required.
A number of materials can be used: stiff card, mounting board, corrugated cardboard, thin plywood, and many other sheet materials. I have found stiff corrugated cardboard easy to use.
More information in this series is at:
Irregular rectangles
Circles
Round headed windows
Irregular shapes
Stone
Friday, 26 June 2009
Monday, 22 June 2009
Measuring a Rectangular Opening.
1 - Measure at both the top and bottom for width.
2 - Measure at the left and right sides for height.
If it is a tall or wide opening measure at intervals and at least in the middle of each side.
So far so good. But how do you know that it is a rectangle rather than a parallelogram? Measure the diagonals – bottom left to top right and top left to bottom right. If these measurements are equal or +/- 5mm you can consider the opening to be a rectangle.
With bigger variations you may set out the cartoon using the measurements for the opening. Still, you need to know where the right angles are, if there are any, to be able to set out the cartoon to properly fit the opening.
So you may wish to take a template of the opening.
2 - Measure at the left and right sides for height.
If it is a tall or wide opening measure at intervals and at least in the middle of each side.
So far so good. But how do you know that it is a rectangle rather than a parallelogram? Measure the diagonals – bottom left to top right and top left to bottom right. If these measurements are equal or +/- 5mm you can consider the opening to be a rectangle.
With bigger variations you may set out the cartoon using the measurements for the opening. Still, you need to know where the right angles are, if there are any, to be able to set out the cartoon to properly fit the opening.
So you may wish to take a template of the opening.
Saturday, 13 June 2009
Bulging lead panels
There is probably no means by which leaded glass, because of the innate character of lead as its skeleton, can resist its propensity to bend, bulge and sag. Evidence of these occurrences does not necessarily foretell disaster or immediate collapse. Bulging does not necessarily indicate the need for action or re-leading.
There are three basic stages through which stained glass passes on the way to requiring repair;
1. Bulging, bending and sagging
2. Loss of putty and breaking of solder joints
3. Unhousing of the glass from the lead
The points at which solder joints break depends on the materials used.
Since lead, compared with solder, is a resilient material abutting the more resistant solder, breaks will occur most frequently at the junction of the solder with the lead.
With zinc, the situation is reversed. The zinc is of greater resistance than the solder. As a result the break most often occurs on the solder at the point of the zinc junctions.
It is the very existence of resilience in lead which responds to the expansion and contraction of glass that permits the more healthy survival of the glass over the less sympathetic accommodations of either zinc or copper foil. Leaded glass, unlike any other medium, has the unique capability of having its skeleton (lead) replaced, when the need arises, without damaging its body (glass).
There are three basic stages through which stained glass passes on the way to requiring repair;
1. Bulging, bending and sagging
2. Loss of putty and breaking of solder joints
3. Unhousing of the glass from the lead
The points at which solder joints break depends on the materials used.
Since lead, compared with solder, is a resilient material abutting the more resistant solder, breaks will occur most frequently at the junction of the solder with the lead.
With zinc, the situation is reversed. The zinc is of greater resistance than the solder. As a result the break most often occurs on the solder at the point of the zinc junctions.
It is the very existence of resilience in lead which responds to the expansion and contraction of glass that permits the more healthy survival of the glass over the less sympathetic accommodations of either zinc or copper foil. Leaded glass, unlike any other medium, has the unique capability of having its skeleton (lead) replaced, when the need arises, without damaging its body (glass).
Wednesday, 10 June 2009
Combing Glass
This process is done at relatively high temperatures for fusers – around 925C. It consists of pulling or dragging the surface of the hot glass to produce a marbling effect.
Preparation:
A batt washed ceramic shelf is the best surface. You can use fibre paper on your shelf, but you must be careful to avoid raking deeply enough so that you pick up the fibre and drag it into the glass.
Make a boundary with 10-12mm fibre board on your shelf. You can use strips - for the most efficient use of the board – or cut a shape from a sheet. If you are using strips, fasten them together with wire staples. This will resist the glass flowing at the edges.
Place the glass into the space created by the fibre board. You can place 10mm strips on edge to form very tight lines, you can shingle glass to give broader lines, or you can place the glass in a more random way to give quite different effects.
When shingling or placing glass randomly, it is often best to cut a sheet of iridised clear to lie on the bottom to ensure you have enough depth of glass. Placing the iridised side of glass down toward the shelf provides an additional release, and can give added interest to the back. Anything less than 8-10mm thick leaves the glass pulled away from the edges in the direction of the combing.
Firing:
The initial temperature rise can be fast because the glass is made up of narrow strips. No bubble squeeze is required for the vertical or shingled strips, as there are easy ways for the air to escape. Randomly placed glass should have a bubble squeeze at around 650°-675°C for 30 minutes at least. Otherwise you can fire at about 300°C/hr to 925°C.
You need to programme a soak at that temperature for approximately 120 minutes. This soak allows you to do the combing and have the kiln recover temperature without needing to re-programme. When the combing is finished you cancel the soak after the kiln recovers to 925°C (which allows any peaks generated during the combing to settle down).
Allow or programme the kiln to cool as fast as it can to the annealing temperature and soak for 120 to 180 minutes. Set the annealing cool at 30°C/hour down to 450°C, then 60°C/hour to 370°C and finally at 200°C/hr to 21°C.
Combing:
Safety first. You must do you combing in a kiln that has a safety switch to turn the power off once the lid is opened a short way. If your kiln does not have such a safety device you should reconsider your desire to comb in your kiln. Many say you can overcome this by switching your kiln on and off at the wall socket. However, in doing so you also turn off the controller, making it necessary to re-programme your kiln each of the several times you have to reach into the kiln with your raking tool. This is essentially impractical.
The combing tool is a pointed steel rod, bent at right angles to the shaft - often called a rake. The shaft should be of wood to avoid holding a hot metal rod in your hand. Stainless steel rods are best as mild steel can spall and leave flakes of metal in or on the glass. The rod and wooden handle should be soaked in water while the kiln is heating up. The wet wood will not char so quickly as the dry. This bucket of water should remain beside the kiln so you can cool the metal point, when it begins to stick.
The second bit of safety. You will need to wear gear to protect yourself against the heat. A full face visor is important as the heat will singe you hair. You need to have heat resistant gloves. You need to have heat resistant sleeves to go over your arms. You should wear only natural fibres - cotton and wool are best, as they smoke before bursting into flame, giving you some warning that things are just too hot. An assistant to hold the kiln door/lid open while combing is advisable. And the assistant should have the same heat resistant gear that you have.
You begin to do the combing at 900°C. The glass will be soft enough to be pulled by a gentle stroke across the surface of the glass. Avoid digging into the glass. That will pull or push a gather of glass ahead of point. This leaves a characteristic droplet shaped mark in the glass at the end of the stroke. It may also go deeply enough that the kiln wash or fibre paper that is underneath the glass will be pulled up into the glass. Only light pressure is required to do the combing.
You will only be able to do a few strokes with the rake before the temperature of the glass falls and the glass resists movement. When the glass becomes difficult to move, it is time to close the lid and let the temperature recover. You will have to do this numerous times, until you have the look you want.
Another limitation is the speed that the rake metal heats up. When the metal becomes hot, it sticks to the glass. Whenever the rake is not in use, it should be in the bucket of water cooling off, and re-wetting the wooden handle.
You can comb the glass in any manner you wish. To get the traditional feathered look, you need to alternately pull and push the rake to give chevrons in opposite directions. Experienced people sometimes use two rakes – one to pull and one to push - at the same time. You can also rake diagonally across the sheet and even across the previous rakings. Some experimentation will show which effects you like best.
Preparation:
A batt washed ceramic shelf is the best surface. You can use fibre paper on your shelf, but you must be careful to avoid raking deeply enough so that you pick up the fibre and drag it into the glass.
Make a boundary with 10-12mm fibre board on your shelf. You can use strips - for the most efficient use of the board – or cut a shape from a sheet. If you are using strips, fasten them together with wire staples. This will resist the glass flowing at the edges.
Place the glass into the space created by the fibre board. You can place 10mm strips on edge to form very tight lines, you can shingle glass to give broader lines, or you can place the glass in a more random way to give quite different effects.
When shingling or placing glass randomly, it is often best to cut a sheet of iridised clear to lie on the bottom to ensure you have enough depth of glass. Placing the iridised side of glass down toward the shelf provides an additional release, and can give added interest to the back. Anything less than 8-10mm thick leaves the glass pulled away from the edges in the direction of the combing.
Firing:
The initial temperature rise can be fast because the glass is made up of narrow strips. No bubble squeeze is required for the vertical or shingled strips, as there are easy ways for the air to escape. Randomly placed glass should have a bubble squeeze at around 650°-675°C for 30 minutes at least. Otherwise you can fire at about 300°C/hr to 925°C.
You need to programme a soak at that temperature for approximately 120 minutes. This soak allows you to do the combing and have the kiln recover temperature without needing to re-programme. When the combing is finished you cancel the soak after the kiln recovers to 925°C (which allows any peaks generated during the combing to settle down).
Allow or programme the kiln to cool as fast as it can to the annealing temperature and soak for 120 to 180 minutes. Set the annealing cool at 30°C/hour down to 450°C, then 60°C/hour to 370°C and finally at 200°C/hr to 21°C.
Combing:
Safety first. You must do you combing in a kiln that has a safety switch to turn the power off once the lid is opened a short way. If your kiln does not have such a safety device you should reconsider your desire to comb in your kiln. Many say you can overcome this by switching your kiln on and off at the wall socket. However, in doing so you also turn off the controller, making it necessary to re-programme your kiln each of the several times you have to reach into the kiln with your raking tool. This is essentially impractical.
The second bit of safety. You will need to wear gear to protect yourself against the heat. A full face visor is important as the heat will singe you hair. You need to have heat resistant gloves. You need to have heat resistant sleeves to go over your arms. You should wear only natural fibres - cotton and wool are best, as they smoke before bursting into flame, giving you some warning that things are just too hot. An assistant to hold the kiln door/lid open while combing is advisable. And the assistant should have the same heat resistant gear that you have.
You begin to do the combing at 900°C. The glass will be soft enough to be pulled by a gentle stroke across the surface of the glass. Avoid digging into the glass. That will pull or push a gather of glass ahead of point. This leaves a characteristic droplet shaped mark in the glass at the end of the stroke. It may also go deeply enough that the kiln wash or fibre paper that is underneath the glass will be pulled up into the glass. Only light pressure is required to do the combing.
You will only be able to do a few strokes with the rake before the temperature of the glass falls and the glass resists movement. When the glass becomes difficult to move, it is time to close the lid and let the temperature recover. You will have to do this numerous times, until you have the look you want.
Another limitation is the speed that the rake metal heats up. When the metal becomes hot, it sticks to the glass. Whenever the rake is not in use, it should be in the bucket of water cooling off, and re-wetting the wooden handle.
You can comb the glass in any manner you wish. To get the traditional feathered look, you need to alternately pull and push the rake to give chevrons in opposite directions. Experienced people sometimes use two rakes – one to pull and one to push - at the same time. You can also rake diagonally across the sheet and even across the previous rakings. Some experimentation will show which effects you like best.
Friday, 5 June 2009
Annealing Open Face Castings
You need to double the annealing time for an open-faced casting over the schedules for the same thickness, because the glass is cooling from one side only. The usual schedules are premised on cooling from both sides equally. The schedules given for 50mm thick open face castings should be used for a 25mm thick open face casting.
If you could cover your open-faced casting with something of equivalent insulation as the investment around the glass you could go back to a 1" schedule.
So an open-faced casting 25mm thick needs to be annealed using the schedule for 50mm thick castings as follows (for Bullseye glass - make adjustments for different glasses):
482°C for 8 hrs
4°C/hr to 427°C
7°C/hr to 370°C
23°C/hr to 21°C
See the Bullseye chart for annealing thick pieces.
Based on Don Burt’s work
If you could cover your open-faced casting with something of equivalent insulation as the investment around the glass you could go back to a 1" schedule.
So an open-faced casting 25mm thick needs to be annealed using the schedule for 50mm thick castings as follows (for Bullseye glass - make adjustments for different glasses):
482°C for 8 hrs
4°C/hr to 427°C
7°C/hr to 370°C
23°C/hr to 21°C
See the Bullseye chart for annealing thick pieces.
Based on Don Burt’s work
Monday, 1 June 2009
Cutting Oil
Why use a cutting fluid?
No matter how good a fissure is when scored dry, it is better if scored with a liquid between the wheel and the glass. Several good things happen with an "oil" cut and only one undesirable thing.
The bad thing is you have to wash the glass afterwards, but in many cases washing is required anyway.
A good thing is the fluid reduces the effect of healing - the compressive strength overcoming the fracture caused by scoring. It is probable that the liquid seeps into the fissure contaminating it enough to prevent atomic reattachment of the molecules.
Cutting oil reduces chipping and prevents a flaky score line. The oil tends to provide a hydraulic cushion between the glass and the wheel. This allows more uniform transmission of the shearing forces into the glass at an angle dictated by the wheel, not by particles of crushed glass.
It is important to check the cutter wheel is moving freely, since a wheel not rolling freely may skid. Skidding causes abnormal wear to the wheel and subsequently it becomes a skipper.
You should not use kerosene by itself because it removes whatever oil is on the axle.
Prepared from information provided by Fletcher-Terry company
No matter how good a fissure is when scored dry, it is better if scored with a liquid between the wheel and the glass. Several good things happen with an "oil" cut and only one undesirable thing.
The bad thing is you have to wash the glass afterwards, but in many cases washing is required anyway.
A good thing is the fluid reduces the effect of healing - the compressive strength overcoming the fracture caused by scoring. It is probable that the liquid seeps into the fissure contaminating it enough to prevent atomic reattachment of the molecules.
Cutting oil reduces chipping and prevents a flaky score line. The oil tends to provide a hydraulic cushion between the glass and the wheel. This allows more uniform transmission of the shearing forces into the glass at an angle dictated by the wheel, not by particles of crushed glass.
It is important to check the cutter wheel is moving freely, since a wheel not rolling freely may skid. Skidding causes abnormal wear to the wheel and subsequently it becomes a skipper.
You should not use kerosene by itself because it removes whatever oil is on the axle.
Prepared from information provided by Fletcher-Terry company
Thursday, 28 May 2009
Tilted Cutter Effects
A tilted glass cutter has the effect of changing the angle of the cutter wheel.
It narrows the angle on one side and increases it on the other side. So on the side tilted away from vertical (which is what happens when you look down the side of the cutter) has an sharper angle with the glass. This is likely to produce chips along the cutting line.
The side which is tilted toward the glass has a more blunt or shallow angle with the glass. This produces high stress along the line.
The combination of these two effects make for a rough edge when broken and for break failures because of the stresses being at angles to the desired vertical fissure line.
Prepared with information from the Fletcher-Terry company
It narrows the angle on one side and increases it on the other side. So on the side tilted away from vertical (which is what happens when you look down the side of the cutter) has an sharper angle with the glass. This is likely to produce chips along the cutting line.
The side which is tilted toward the glass has a more blunt or shallow angle with the glass. This produces high stress along the line.
The combination of these two effects make for a rough edge when broken and for break failures because of the stresses being at angles to the desired vertical fissure line.
Prepared with information from the Fletcher-Terry company
Tuesday, 26 May 2009
Cutting Wheel Angles
These are the wheel angles recommended by The Fletcher-Terry Company for various glasses:
114 to 134 degrees – 2mm float glass
130 to 140 degrees – 4mm float glass
134 to 140 degrees – 3mm to 6mm float glass
148 to 154 degrees – 12mm to 25mm float glass
134 to 140 degrees – stained glass
88 to 114degrees – borosilicate glass
http://www.fletcherviscom.com/home.shtml
114 to 134 degrees – 2mm float glass
130 to 140 degrees – 4mm float glass
134 to 140 degrees – 3mm to 6mm float glass
148 to 154 degrees – 12mm to 25mm float glass
134 to 140 degrees – stained glass
88 to 114degrees – borosilicate glass
http://www.fletcherviscom.com/home.shtml
Monday, 25 May 2009
Water Proofing of Pattern Pieces
Many people put their pattern pieces onto the glass they are going to grind, or saw to attempt to get a good fit to the cartoon. The water from the grinder makes paper templates soggy and liable to tear or disintegrate so failing to for a good guide to grinding.
One solution is to stick self adhesive plastic on top of the pattern before you cut it all apart. Then you have some protection when you grind. The plastic sticks to the surface of the paper and resists the water. However, the water can seep between the glass and the unprotected bottom of the paper or, even if protected with plastic on both sided, through the exposed edge.
You can spray or apply clear lacquer on the paper pattern pieces before attaching them to the glass and grinding. This has slightly better results as the edge is most often sealed better than with two layers of plastic.
You can use clear acetate film (ca. 0.2mm thick) as a completely water resistant pattern. Cut your pattern pieces from the acetate film and stick them on to the glass with blutack or any other gum based adhesive. This works well and does not suffer from the water deteriorating the pattern piece.
One solution is to stick self adhesive plastic on top of the pattern before you cut it all apart. Then you have some protection when you grind. The plastic sticks to the surface of the paper and resists the water. However, the water can seep between the glass and the unprotected bottom of the paper or, even if protected with plastic on both sided, through the exposed edge.
You can spray or apply clear lacquer on the paper pattern pieces before attaching them to the glass and grinding. This has slightly better results as the edge is most often sealed better than with two layers of plastic.
You can use clear acetate film (ca. 0.2mm thick) as a completely water resistant pattern. Cut your pattern pieces from the acetate film and stick them on to the glass with blutack or any other gum based adhesive. This works well and does not suffer from the water deteriorating the pattern piece.
Friday, 22 May 2009
Window Measurements
There are a number of measurements that are critical for a good design and a sound installation of window panels.
1. Tight Size: This is the full size of the glass opening with no allowances for expansion and contraction. In a wood or metal rebate frame one would measure from steel to opposing steel or wood to wood; in a stone groove installation, from the bottom of one groove to the bottom of the opposing groove. Depending on the size of the opening, this measurement should be checked in multiple areas; at a minimum at the top, bottom and middle horizontally and at the left and right jamb.
2. Sight Size is the daylight opening or the largest opening that allows light to pass through.
3. Rebate or groove details. With a rebate frame, the depth and the width of the rebate must be measured, as well as the interior return if round bars will be used (this dictates what size bar will fit and how long the bar should be). These dimensions are also necessary to determine the dimensions of the retaining molding if one is to be used. If it is a groove, the depth of the groove and the width of the groove (measured from interior to exterior) are important.
4. Panel Size. This is the ideal size of a panel that will be installed into the opening in question. Typically, this will be a function of the tight size less 3mm in both width and height for a leaded glass panel, to allow for expansion and contraction. One must also recognize if the size varies throughout the frame and make allowance for this as well. With dalle de verre, you need a deep rebate or groove and allow at least 5mm in both directions for expansion.
5. The depth of the rebate or the width of the groove are critical measurements. To allow for a proper installation, allow a minimum of 13mm to be added to the thickness of the panel to provide room for a proper putty fillet.
Based on comments from Art Femenella
6. When measuring older openings and especially doors, measure the diagonals in addition to all the other measurements. This provides a check of all your other measurements and also tells you whether the opening is a true rectangle or parallelogram.
1. Tight Size: This is the full size of the glass opening with no allowances for expansion and contraction. In a wood or metal rebate frame one would measure from steel to opposing steel or wood to wood; in a stone groove installation, from the bottom of one groove to the bottom of the opposing groove. Depending on the size of the opening, this measurement should be checked in multiple areas; at a minimum at the top, bottom and middle horizontally and at the left and right jamb.
2. Sight Size is the daylight opening or the largest opening that allows light to pass through.
3. Rebate or groove details. With a rebate frame, the depth and the width of the rebate must be measured, as well as the interior return if round bars will be used (this dictates what size bar will fit and how long the bar should be). These dimensions are also necessary to determine the dimensions of the retaining molding if one is to be used. If it is a groove, the depth of the groove and the width of the groove (measured from interior to exterior) are important.
4. Panel Size. This is the ideal size of a panel that will be installed into the opening in question. Typically, this will be a function of the tight size less 3mm in both width and height for a leaded glass panel, to allow for expansion and contraction. One must also recognize if the size varies throughout the frame and make allowance for this as well. With dalle de verre, you need a deep rebate or groove and allow at least 5mm in both directions for expansion.
5. The depth of the rebate or the width of the groove are critical measurements. To allow for a proper installation, allow a minimum of 13mm to be added to the thickness of the panel to provide room for a proper putty fillet.
Based on comments from Art Femenella
6. When measuring older openings and especially doors, measure the diagonals in addition to all the other measurements. This provides a check of all your other measurements and also tells you whether the opening is a true rectangle or parallelogram.
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