Kiln Furniture

You do not have to buy all your kiln furniture. Any refractory material – any heat resistant material that will stand up to the forming temperatures – that you have from broken shelves or used material will do.

The advantage to home made kiln furniture is that you can have exactly the shape you want. There are a number of possibilities.

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

Fibre board is not as strong or rigid as kiln shelves and vermiculite are, but is much more adaptable to curves and undulations. They can be cut with a knife and used with or without hardener – colloidal silica. If the hardener is used some kind of separator will be required to keep the glass from sticking. Dust masks are required for working with ceramic fibres.

Soft fire brick

Soft fire brick can be cut with a hand saw into many shapes and and sizes. They are suitable as supports and braces for dams.  There are also higher density bricks that are much heavier to resist the movement of dams.

3mm fibre paper

Fibre paper can be cut and stacked to provide shims to level shelves and moulds. Shapes can be cut into stacked layers of the material to provide dams for irregular shaped projects.

Uneven Slumps

Uneven slumps are an occasional feature of kiln forming. There are a number of possibilities that can cause this.

A mould that is not level will lead to an asymmetrical slump. You need to make sure on each firing that the mould is level, as well as your kiln and the shelf or supports. A three-way level can check this quickly.

Glass that is placed unevenly on the mould can cause uneven slumps. The glass should be placed on the mould so that it is equidistant from the edges of the mould all the way around. The glass needs to be level too. Again the three way level can help.

A slight bevel on the bottom edge can help avoid any catching of the glass as it moves within the mould.

Baffling or shielding parts of the glass can keep the heat off areas that tend to heat up faster than the rest and so begin moving before other parts of the blank.

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.

Most importantly, slow temperature rises solve most of the problems of uneven slumps. Fast temperature rises allow the component parts of the piece to absorb heat differently for different colours and glass of different viscosities. Slow rises in temperature help avoid any unevenness in the way the kiln heats the piece. Slow rises give more control and achieve the result at a lower temperature.

Note that a number of the solutions require observation while firing. The best results come from observing what is happening in the kiln. It allows you to make corrections either while firing, or – more often – in the next firing of a similar project.

Leaking Cutters

People sometimes comment that their cutters are leaking. Most cutters of the pencil type are not prone to leaking. Some of the pistol shaped cutters seem to have more difficulty.

One possibility is that the oil being used is too thin for the system that dispenses the oil. In that case a little thicker oil may cure the problem.

It may be that the oil is leaking from some where else than the valve or wick that is intended to dispense the oil. This sometimes happens when excessive pressure has been put on plastic handled cutters whether pencil or pistol. In this case, the alternative is to replace the cutter or use another method.

The other method could be called the dip and cut method. In this case you leave the reservoir empty and have a shallow container filled with oil soaked cotton wool. Dip the cutter wheel into the cotton wool before each cut and this will give you enough lubrication for the score. A variation on this is to dip a brush in a container of oil or turpentine substitute and paint along the line of the cut before scoring. Both are effective.

Although it is not a repair, you can push a cotton wool lump down to the valve or wick, saturate it with oil and then there is enough oil to lubricate the cutter wheel, without an excess to leak out. You do need to renew the oil for the lump of cotton wool from time to time.

Reworking Designs

Principles of design practice for stained glass, 5

Having created the design, you should consider re-working the designs for a variety of reasons. Some of these are:

- to save time in the later stages of the work. It all too easy in the excitement of creating a new piece to want to get directly on with making, however this often gives construction or design difficulties that have to be solved in the making, leading to compromises. In general far too little time is spent in the design stage. Time spent on the design will be more than saved in the construction and will produce a more satisfactory piece.

- to ensure the structural stability of the piece. Although reinforcement should be considered from the beginning of the design, this is the time to ensure that the piece will stand up to the use it will receive during its – expected – long life.

- Make sure you have investigated every possibility to answer the challenges of your design.

There are a number of activities that can help with these elements.

Reworking will enable you to maintain the essence of the design while simplifying lines and easing the labour of the construction of the panel. Often the design contains a number of lines that are not essential to the whole design.

As you re-work the design, you can make sure every curve, dip and angle are to your liking and so improve the whole. Redrawing also helps understanding of the design and the placing of lines. It will also help in considering the placement of lead came and the widths to be used.

Make sure the design is still structurally sound. The design should avoid long nearly straight lines with few interruptions, especially those that go from edge to edge in any direction. The lines should interlock rather than have many joins onto long lines.

It gives an opportunity to ensure that you can cut all the pieces. This is the time to look at the negative or background pieces to make sure you can cut them as well as the foreground pieces. Usually people are so concentrated on designing the main image that the background becomes too complicated to cut easily.

Make successive tracings with each change, so there is a record, allowing you to step back wards to an earlier version if necessary.

If this re-working stage leads to the realisation of design problems, there are some things that can be tried:

• 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.

Elements of Design:

Designing for strength 

Colour selection

Design lines 

Design sources 

Reworking designs 

Design Sources

Principles of design practice for stained glass, 4

Use the everyday visual experience and make interpretations and adaptations. E.g.,

• 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

These may never become useable designs or cartoons, but will increase you abilities to design from the real world toward the abstract.

Make and keep sketches as personal references. These do not need to be finished drawings, just a reminder of the thing(s) that caught your eye. Many artists always carry around a notebook to record these observations. Even if you only make drawings on paper napkins, make a folder to keep these separate sketches together.

Take photos of shapes and interesting images. These can then be used later to develop images.

Make up composite images by using overlays or collage. This helps develop your compositional abilities.

Work on abstraction in your design practice:

• 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.

Elements of Design:

Designing for strength 

Colour selection

Design lines 

Design sources 

Reworking designs 

Beautiful Design Lines

Principles of design practice for stained glass, 3

Stained glass is a graphic medium where line and colour are very important. Achieving pleasing lines and forms requires practice and use of various approaches and techniques.

The two dimensional world is one of abstract thought. Work and development are the way to creativity – there is no mystical talent. Practice drawing every day – set aside time to do it, if you normally shy away from drawing as an exercise.

Study and learn from what has gone before. Look at the images and objects you admire and analyse what you like about them and why. Also consider what things could have been done differently. Consider how those changes would affect the character of the piece.

Of course, maintaining your creative attention is difficult, so when blocks occur try some or all of these things:

• 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.

Remember that design tends toward realism or abstraction. You need to work on both forms, remembering that glass is a graphic medium that tends toward abstraction. Working on both forms develops your flexibility and knowledge. Having a working knowledge of both enables you to have a responsive approach to the client.

Elements of Design:

Designing for strength 

Colour selection

Design lines 

Design sources 

Reworking designs 

Responsive Colour Selection

Principles of design practice for stained glass, 2

The graphic form of much stained glass means that the medium is about line and colour. This requires that you think about both your and the viewer's response to the colour combinations. Respond to your instincts. Use you feelings about colour and their relationships. Try different colour ways. Formal training does help, but experience develops your skills. The individuality of the piece depends on the use of your instincts about the colour. There are some checks you can make while selecting colours.

Think of colour and impact. Hot colours tend to have more impact, as they give bright points or areas. Impact can also be created by using non-complementary colours together. If a more subtle impression is desired, use tonal variations without great contrasts.

Vary areas of colour and their proportions. This provides interest to a panel. It avoids a mechanical symmetrical appearance, even if the design is symmetrical

Think about colour balance. Although the colours may vary it is important that the weights of the colours are balanced so that the focus of the panel is not taken to another part because of the imbalance of the colour with the design.

When you are in difficulty selecting or arranging the colour, step back and view from a distance. This is one of several techniques to enable you to get a larger or different view. Others include viewing the design through a mirror, viewing through half closed eyes, look at the design from the other end, and viewing the design from acute angles.

When something feels wrong, trust your intuition and use other colours. Colour theory is just that -theory. It is through using your reactions that the piece becomes individual.

Seek out the nuances of the glass in tones and textures. These alter the perceived colour and weight considerably.

Keep the design lines simple when your emphasis is on colour, light and texture. This allows those qualities to dominate the panel, rather than the lines.

Always make a coloured drawing, before choosing the glass, as a reference. This is a rendering of your original idea. It provides a reference as you select the colours. It is something that can be altered, of course, but does provide an essential reference point.

Choose glass colours in the kind of light for which the panel is intended. This is essential, as the glass colour is subtly different in daylight, incandescent, and fluorescent lights.

Elements of Design:

Designing for strength 

Colour selection

Design lines 

Design sources 

Reworking designs 

Designing for Strength

Principles of Design Practice for Stained Glass, 1

There comes a stage when each of us moves from using patterns developed by others to trying to realise our own vision. This is the time where in attempting to reproduce an image from our mind or from natural and man-made forms that we begin to encounter difficulties with the medium of glass and lead or copper foil.

There are a number of principles that should be kept in mind while designing, or at least referred to when the design is reaching its final stages. This series of notes is an attempt to outline a number of the most important points in designing glass panels, especially larger ones.

Structural strength

The panel needs to be strong to last for a long time. Glass is a very resilient material; so is lead and solder. It would be a shame to design a panel in long-lasting materials that will not last because of the design and construction. There are some things to remember about creating a strong panel.

The strength of a panel is in its glass.

Glass in compression is stronger than steel. It is only when it is in tension that its weakness - or fragility – becomes apparent. So the structural arrangement of the glass needs to be such that each piece of glass supports its neighbours. It also needs to use shapes that are strong.

Avoid the following shapes:

• 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.

Lines radiating from a single point provide weak areas. This is due to long thin pieces of glass being liable to breakage. Break up long thin pieces of glass with lines. This ensures that the length of the glass is in a strong relationship with its narrowness.

Avoid “hinges” - lines that run from edge to edge – as that provides an area where the panel can bend. This is why windows made up of rectangular quarries need so much support and even then over time begin to concertina.

Don’t over complicate the cut lines. This makes for difficulty in cutting the pieces. Also the more difficult it is to cut the pieces of glass, the more likely it is to fail by breaking after being installed.

Elements of Design:

Designing for strength 

Colour selection

Design lines 

Design sources 

Reworking designs 

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.

Slumping cracks

Cracks on the bottom of slumped bowls initially appear mysterious if not impossible.

It seems that what is happening is that the crack results from too fast a heat up.

The top gets plastic during a - relatively speaking - too quick a rise in temperature, while the bottom is still too cold to move. The piece splits on the bottom to relieve the stress of the weight of the upper portion of the glass. It does not break completely through, because the top is hot enough to move rather than break.

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.

You need to put much more heat into the piece in the 50C above the annealing temperature if you experience this splitting effect. This can be done by a soak in the region of 540C-600C for Bullseye, or by a very slow rise in this region. The heating above this also needs to be slow to ensure the glass at the bottom of the piece is nearly the same as the top.

You will find that as a result of these slow rises or long low temperature soaks that the slump will occur at a lower temperature than with a rapid rise. This will also have the additional benefit of leaving fewer mould marks on the bottom of the piece.