Thursday 5 January 2012
Paper
Friday 30 December 2011
Soldering Radiating Lines
Monday 26 December 2011
Kiln Furniture
Example of broken shelves |
Broken kiln shelves can provide supports and dams. They can be cut with a tile saw to give long strips that can be used as dams. Smaller squares and rectangles can be stacked to give height to other supports for the glass.
Cutting a shelf with a hand saw |
25mm vermiculite board |
Vermiculite in the form of a pressed board provides a medium strength kiln furniture. It can be cut with a wood saw, although it dulls cutting tools quickly. The board can also be carved with wood working tools although it is very abrasive, requiring tools to be sharpened before use on wood again.
25mm ceramic fibre board |
Soft fire brick |
3mm fibre paper |
Thursday 15 December 2011
Uneven Slumps
A slight bevel on the bottom edge can help avoid any catching of the glass as it moves within the mould.
Deep moulds most often present difficulties with uneven slumping. The best approach here is to use multiple, progressively deep slumps.
It also is possible to reach in with a wet stick and move the glass back to an even slump during the firing. Please observe all the safety requirements.
Saturday 10 December 2011
Leaking Cutters
Monday 5 December 2011
Reworking Designs
- Cropping the design can transform it. The focus of the design can be enhanced by removing some of the surrounding “information”. The change of proportions say from landscape to portrait can make significant differences.
- Enlarging and using only a portion of the original design can be a solution. This is similar to the cropping operation, but has the added advantage of making the pieces larger and easier to cut.
- Further simplification of background design lines can be considered. This will bring the focus back onto the main part of the image.
- Changing relative proportions can transform the design, e.g., by enlarging a busy background, it can be made simpler and easier to read the whole panel.
Wednesday 30 November 2011
Design Sources
- draw lead lines on an illustration to make it suitable for stained glass, using the fewest lines possible
- Use your photographs of interesting subjects and scenes
- Study abstract representations. Dissect – decomposition is a popular word - and analyse how the work is put together.
- Use geometric design as an introduction to abstract design. This forces your attention to structure, balance and colour.
- Once the distribution of the physical and visual weights is understood, this enables the jump to more free forms of abstraction.
Friday 25 November 2011
Beautiful Design Lines
- Put the work aside for a day or two before taking it out and looking at it again.
- Alternatively, pin up the design on a wall where you can look at as you pass by. When you see a change to be made, do it immediately and pin it back up.
- Get a new perspective, e.g.:
- Turn it upside down. This will enable you to observe differences and spot inconsistencies
- Look at it in a mirror. You might see people studying still life or live subjects together with their drawing in a hand mirror to get a new perspective that will help spot difficulties.
- Put the design on the floor and climb a ladder to look at it. This provides distance and changes the angle at which you look at your design.
Sunday 20 November 2011
Responsive Colour Selection
Tuesday 15 November 2011
Designing for Strength
- Hour glass shapes – those where the ends are wider/larger than the middle - will crack at the narrowest part. If the shape – usually a negative or background one – is necessary, break it up into smaller pieces that make sense in the whole design. It is also possible to add details that will break up these shapes, but be careful that the details do not detract from the whole.
- Exaggerated, deep inner curves will crack at apex of curve. If unavoidable, you should consider adding design lines where the glass would break anyway, or moving elements closer together so they almost touch to avoid the single deep inner curve.
- Thin long and tapering glass pieces will crack at the point or be covered by the lead or copper foil. Where you need to have such shapes, try drawing the lead or copper foil lines on the design. You can do this on a piece of tracing paper to avoid messing up your original design. This will show you how the finished panel may look. Alternatively, you can divide the long tapering piece of glass into several pieces so that any flexibility of the whole panel does not break the long thin piece. Short thin pieces are not so likely to be broken by any movement of the panel.
Thursday 10 November 2011
Re-Firing Holes
Occasionally you need to re-fire a piece that already has holes drilled into it. The smaller holes tend to close up or reduce in diameter when they are larger. There is a method to resist this and still have a neat smooth hole.
To keep the holes open during a re-firing, cut a strip of Thinfire a little thinner than the thickness of the glass to be fired, roll it up tightly and put it into the hole to be kept open. Starting the wrapping around a pencil or pen makes the start easy and the roll can be tightened by holding the centre and pulling the end.
Put the roll into the hole and allow it to expand to fill the hole. It does not have to be solid. If the roll is as high or higher than the surrounding glass there is a tendency to get spikes.
This works fine on 6mm and thicker glass, but I have never tried it on 3mm glass. No reason why it shouldn't work though in my estimation if you can cut and manipulate 2mm strips of fibre paper.
Saturday 5 November 2011
Slumping cracks
This bowl split as it was much thicker than I thought. The firing was too fast and the top began to slump before the bottom was warm enough to move. This is an extreme version of the split described above.
Sunday 30 October 2011
Annealing Thickness
A rule of thumb is to consider these variables and add to the soak times and reduce the speeds of anneal cooling in accordance with the number of variables exhibited in your piece. With the first of these variables - cooling from one side - use the schedule for twice the actual thickness of the piece. Then add another step up in thickness for each additional variable.
Tuesday 25 October 2011
Copper Backings
and then coat it with borax or other devitrification spray that can act as a glass flux.
Thursday 20 October 2011
Ramp Speeds for Slumps and Drapes
Saturday 15 October 2011
Candle Bridge Moulds
With a candle bridge you are trying to do a combination of slumping and draping at the same time. You are slumping into the middle and draping over the curved sides.
Additionally the candle mould requires the glass to fall into a small opening and this requires long soak times. Long soak times mean the glass that is draping stretches while the central portion is trying to fall into the opening. Of course, if you don't want the depression to be flat, you don't have to soak so long and the stretching effects on the draping part of the of the glass won't be so great.
It would seem logical to measure the mould around the drapery curve (or arc of the mould) and to the shape of the ends, but experience has shown me that this leads to glass that is too long along the sides and bent at the ends. So I cut my blanks for candle moulds as a rectangle without curved ends and then round the corners of the rectangle just a little by nipping them with my grozing pliers before fusing.
If you measure along the top and along the length of the mould you have a piece of glass that will be increasing in length at the draping part of the mould, meaning that it will fall off the curve and onto the draft (or side) of the mould. The draft is an angle from the vertical. Good moulds are made with a draft so that if glass were to fall over the edge it still will be possible to get the glass off the mould.
The draft on a mould means the diameter of a circular one is greater at the base than it is at the rim. And it is common to measure only the diameter at the rim. In the same way the dimensions at the outside base of a rectangular mould are larger than the rim of the mould.
Back to the rectangular candle mould. The draft on this means that measuring the base of the mould is slightly wider than the curved part of the mould, but less than if measured around its curved portion.
Experience has shown that in the case of the candle moulds measuring the width of the mould is sufficient. There is enough height in the moulds I have used that it does not make any functional difference if the glass does not reach the bottom of the curve on the mould. It is better than hanging off the edge.
The length of the glass should be no longer than the shortest part of the mould's length. Cutting a curve into the glass to allow a small overhang produces a depressed lip because of the length of the soak required for the slump into the small aperture of the candle depressions.
My soak for candle moulds is 90 minutes at my process temperature. This gives me a flat depressed area for the candle to sit, but it also means that the draping glass has been stretching. And it also means that the glass will drape unevenly as the various colours absorb heat differently allowing some parts of the glass to stretch more than others.
The placing of the glass on the mould is absolutely critical. It must be exactly parallel to the sides of the mould. Any slight movement from that will induce a twist in the resulting piece allowing it to rock. Arranging it exactly right and placing some kiln washed furniture at each side to keep it in place until it begins to slump is an important aid.
The glass will begin to bend before it sticks to the kiln furniture.
I have never been able to get a stable candle mould whether from 3mm or 6mm thick glass. I always have to grind the base a little to make a stable piece. I take it as part of the process, but careful placing reduces the work.
Monday 10 October 2011
Cutting Box Hinges
Wednesday 5 October 2011
Vase Cap Fitting
Make up your shade in a cardboard mock-up. Use 3mm thick card or foam board to represent the glass, as the thickness of the glass is important in determining which vase cap is the correct size. Try your vase cap against the cardboard model, then if you need, alter the pattern so the glass pieces meet at just the right place to make the lip of the vase cap fit just over the top of the glass. You can do this by either shortening or lengthening the pattern a little at the top edge.
The second also involves making a cardboard mock up. After making this maquette, choose a vase cap that overlaps the top opening, covering all the edges. The third option is to use two vase caps, one above and one below the opening to clamp them together trapping the edges of glass between them. Use a furling and lock nuts with no solder at all to hold the lampshade together.
A general discussion of panel lamp dimensions
Friday 30 September 2011
Squaring Panels
Sunday 25 September 2011
Vase Caps
Tuesday 20 September 2011
Sieves, Gauges and Grits
The commonly used designation for grits has become the gauge This is a confusing measure as it increases in number as the size of the material decreases in size. This is because the number of wires per unit increases with decreasing size and the gauge refers to the number of wires used to sieve the material.
In an attempt to indicate the actual sizes of material refered to by the gauge sizes, I have used part of a standard table of equivalents.
12 gauge is 1.7mm or .0661inch
14 gauge is 1.4mm or .0555inch
16 gauge is 1.18mm or .0469inch
18 gauge is 1mm or .0394inch
20 gauge is .85mm or .0331inch
25 gauge is .71mm or .0278inch
30 gauge is .6mm or .0234inch
35 gauge is .5mm or .0197inch
40 gauge is .425mm or .0165inch
45 gauge is .355mm or .0139inch
50 gauge is .3mm or .0117inch
60 gauge is .25mm or .0098inch
70 gauge is .212mm or .0083inch
80 gauge is .18mm or .007inch
100 gauge is .15mm or .0059inch
120 gauge is .125mm or .0049inch
140 gauge is .106mm or .0041inch
170 gauge is .09mm or .0035inch
200 gauge is .075mm or .00295inch
230 gauge is .063mm or .0025inch
270 gauge is .053mm or .0021inch
325 gauge is .045mm or .0017inch
400 gauge is .038mm or .0015inch
450 gauge is .032mm or .0012inch
500 gauge is .025mm or .001inch
635 gauge is .02mm or .0008inch
Thursday 15 September 2011
Soldering techniques
Saturday 10 September 2011
Residues
Friday 9 September 2011
Scoring Glass
Holding the Cutter
Generally, you use the cutter by moving it away from you, so you can see the cartoon lines as you score. When using a straight edge such as a cork-backed ruler to guide your cutter, you can pull the cutter toward you, or push it away as suits you. The cutter should always be held at a 90 degree angle (left to right). You can determine this by looking down the cutter to the wheel and to the cartoon line below.
It is important that the work be done from the forearm rather than the fingers or the wrist. The forearm should be held closely to the body. This reduces the freedom of movement, giving clean flowing score lines. It also reduces the actions that can lead to repetitive stress injuries. Any turning required by tight curves can be done by turning the body from the hips or shuffling around the bench with the glass at a corner. Of course, for long cuts your arm will have to extend from you body in a parallel direction with the score line.
Scoring Pressure
The second and very important element in scoring glass is the amount of pressure used. Very little pressure is required. You should hear no more than a quiet hiss on transparent glass and almost no sound on opalescent glass. However some manufacturer's transparent glass has almost no sound either. So the important element is the pressure, not the sound. Most people start with applying far too much pressure. Tests have shown that only about 2 kg of pressure is required for a clean score.
You can test the effect of this amount of pressure on a bathroom scale. Place a piece of clear glass on the scale and without touching the glass with your other hand, score it noticing how much weight is being recorded. Keep trying until you are at the 2 kg area of pressure. Try breaking the glass. Score a curve with the original amount of pressure and break the glass. Then using the same curve score the glass with the 2 kg pressure and break the glass. You will see and feel the lesser pressure provides a clean break.
Excessive pressure leads to breaks showing significant stress marks on the edge of the glass. Too little pressure has no effect on the glass, making it impossible to break along the score line. The correct pressure (ca. 2 kg.) leads to almost vertical stresses being put into the glass which assists the breaking along the score line. Too heavy pressure creates stress marks which are at increasingly large angles with the increasing pressure. This will still break cleanly on straight lines, but when working around curves the glass can follow one of the lateral stress marks away from the score line. Excessive pressure is often the cause of glass breaking away from the score line on a curve, especially a tight one.