Colour “theory”

You will need to decide which colours combine well, whether they are toning, harmonious or complimentary.  By getting to grips with the rules of colour, you can give your work a unity of concept.

Primary colours

Primary colours are three key colours - red, blue and yellow. They cannot be made from any other colour.

Secondary colours

If you mix equal amounts of the primary colours, you get the secondary colours - purple, green and orange.

red + yellow = orange
red + blue = purple
blue + yellow = green

Tertiary colours

If you mix a primary with a secondary colour, in a ratio of 2:1, you get a tertiary colour. red-orange, blue-green etc.

Colour wheel example

Cool versus hot

Look at the colour wheel and you will see the left hand side of the colours are 'warm' or 'hot' and the ones on the right are 'cool' or 'cold'. This is useful when you want to create a mood in a particular room or need to make your space cosier or lighter.

Neutrals

Neutrals are one of the easiest groups of colours, or non-colours to work with. They don't appear on the colour wheel and include Black, Grey, White and sometimes Brown and Beige. They all go together and can be layered and mixed and matched. No neutral colour will try to dominate over another.

Accent colours

An accent colour is a colour used in quite small quantities to lift or to add punch to a colour scheme. An accent colour should be in a complementary colour. It works best if it's a bright, vibrant colour. Accent colours are perfect if you're concerned about using strong colour - simply add a splash of an accent colour. Keep most of your piece in shades and variations of one single harmonious colour. Then pick out just a few objects in an accent colour.

Clashing colours

Using clashing colours is thought to be inappropriate in formal settings. But in other settings they can provide drama, if they are used carefully. If they are of equal tonal strength, you can mix them together. You don't have to stop at two, you can try three or four. But if one is paler or weaker than the rest it will get lost in the overall scheme.

Sticky Labels

There are a number of products to help get the label adhesive off the glass. However you need to make sure you get the product residues off the glass before firing.

A simple and usually effective method is pull label off, use white spirit or turpentine substitutes with a plastic kitchen scrubber or fine brass wire brush to remove the adhesive. Then clean up with alcohol or methylated spirits, followed by good cleaning with your normal cleaning method, as here.

Why do kiln shelves break?

Kiln shelves are made of clay – a very hard clay, sometimes called mullite. So when firing you need to remember that like other ceramic materials it can be heat shocked.

examples of broken shelves

The recommendation is that you put the shelf on supports to keep it above the base of the kiln and allow air to circulate around both the top and bottom of the shelf.

The question remains, why do the shelves break. There are at least two reasons: physical impact and thermal shock. It is possible to knock the shelf while moving it around the studio. This impact does not always cause a break, but sometimes creates a stress point that later can develop into a crack and break. You can sometimes see the start of the crack from the edge of the shelf. In this case, you can either continue to use the shelf with support under the crack or dispose of it immediately, because at some point during a firing it will separate.

The thermal shock that causes the break occurs because (usually) uneven cooling. It seems the shelves are pretty resistant to rapid heating, but less tolerant of rapid or uneven cooling. In general un-dammed fusing and using moulds elevated a little from the shelve do not create that uneven cooling.

However placing a large refractory mould directly on the shelf can promote cracking either immediately or on subsequent firings.

Broken shelf with casting moulds laded to one side 

The main culprit in any breakage seems to be large or heavy and damp refractory moulds directly on the shelf. The mould is giving off water vapour which cools the immediate area around the mould. So as the temperature rises, the covered part of the shelf stays cool, in addition to being shielded from the general heat of the kiln while the uncovered parts of the shelf rise in heat. At some point the temperature differences in the shelf are too great for its strength to resist. The solution is to remove the shelf from the kiln and place the mould, slightly raised, on the floor of the kiln. The bricks, being softer, do not react in the same way as shelves to uneven heating.

For thick fusing with dams all around, it seems best to do this on a shelf that almost fully covered with glass and dams. This promotes more even heating and cooling of the shelf than having a small part of the shelf covered. It does mean having different sized shelves, but then you may already have some of them due to the breaking of other shelves. Just cut the broken shelf to the size you want on a tile cutter.

Small Glass Balls

You can create tiny balls of glass in several ways. You can cut small squares of glass as small as 5mm, place them in the kiln and fire to at least a rounded tack fuse temperature.

You can do the same with frit. Make your own by smashing the glass within some container, which can be as simple as newspaper. Sieve out the finer and larger glass and put the chosen size into the kiln at the same temperature. This will give more irregular pieces than squares, so you may want to include these pieces of frit in a regular fuse firing in the spare spaces.

You can also make balls individually by putting the piece of glass on a graphite block and heating it up with a blow torch. This will round up even a rectangular piece of glass. You can put these into a fibre blanket, but it really is not necessary as the round form will contain a lot of stress that will later be removed by subsequent firing. It is possible to over heat some glass, especially opalescent, so be careful about the amount of heat you apply.

Slumping Etched Glass

In general slumping will not remove the evidence of etching. There will be very little effect on etching on the bottom even at fire polishing temperatures.

When the etching is on the top side exposed to the radiant heat of the elements, you need to be careful to use the lowest practical temperature for slumping. It is possible to achieve a satin finish to a sandblasted surface at 677ºC with a soak of two hours. It depends on the delicacy of the etching texture as to whether the slumping will affect it much.

The more the glass will need to move during slumping the more distortion will be apparent in the finished piece. This can be minimised by using a low heat for considerable time.

If the mould is very detailed, it would indicate that etching should be done before the slumping due to difficulty in attaching the resist to the shaped glass, unless you paint it on. But again, a significantly long soak will be required to achieve the detail of the mould.

If it is a simple and relatively shallow slump it may be easy to etch after shaping. It is a question of how easy it is to get the resist to conform to the curve.

Keeping Copper Inclusions from Oxidising

The colour change in the copper foil is due to oxidisation - if the copper foil is completely deprived of oxygen it stays shiny and copper coloured. If you leave copper exposed at all it will go metallic blue or even bottle green, mostly it turns a lovely burgundy red colour- an intermediate oxidisation stage.

Klyr fire or borax solutions may help the copper stay bright.

Through doing some experiments with art school students, I have found the speed of firing is critical in an electric kiln. In a gas kiln the speed is normally fast anyway and produces better results than an electric kiln. It also is a kiln with a reducing atmosphere rather than oxidising one of an electric kiln.

Summary:

The main elements in keeping copper inclusions (and by extension, other metals) bright is to keep the metal from oxidising. Two elements are important in this:

• Keep oxygen from the metal
• Reduce the time the metal is exposed to high temperatures

Various methods are used to keep the metal from exposure to oxygen. Some of these involve: 

• coating the metal with fluxes to reduce the amount of oxygen in contact with the metal. 
• using a reducing atmosphere, such as a gas kiln. 
• placing an oxygen hungry material in the kiln with the glass and metal. 
• coating the metal with glass powder before encasing it within the glass.

Reducing the heat exposure of the metal also indicates that firing fast would provide better results. This requires very even heating within the kiln to avoid heat shocking the glass.  This is where a gas kiln is most advantageous - it can be fired fast without breaking the glass and it has a reducing atmosphere within it.

In general, it is easier to make use of the effects of the oxidised metal rather than striving for bright metal inclusions.

Fixing Paint for Transport

The very cheapest hair spray works well with glass paint, if you need to transfer your painted glass to another place for firing. Complete the painting and then spray with cheap hair spray as you would to fix a charcoal drawing. This will hold the paint firmly during transport and does not affect the paint during firing.

Tracing on Opalescent Glass

Opalescent and dense glass presents problems as the usual method of tracing the image through the glass is not possible. If you first spray the glass with a cheap hair spray, this gives a “toothed” surface to the glass. Then using carbon paper an image can be transferred. However, the carbon paper leaves a greasy residue, so water based paint will not take, but an oil medium will.

Matting

Oil, and Water and Gum as Media for Matting by Dick Millard [edited from a discussion]

Oil has been used, I believe, since the 16th Century, and certainly up through the 1970's to today. It is used wherever it is determined it should be used, and one is sufficiently informed and facile to use it in a manner of delivering its full and lovely potential.

First of all, oil is not characteristically employed as a matt, out of which, by the negative process, one "takes out lights". In overwhelming instances, with which I am acquainted, it is used as a shading material applied over a pre applied and "worked" under matt of water and gum base.

This provides the required "tooth" to provide both a degree of adherence and ease of application.

So, I would suggest an oil matting, or a shading application over a smooth glass surface, would be generally problematical!

A group of blending brushes

Add a bit more gum to your water under matt which will reduce the necessity to fire that matt, which changes the character of the desired "tooth". The purpose of the "tooth" to receive the oil matt is also to provide "porosity" as an "absorbant", which additionally holds the oil mixed paint to the matt. Otherwise, the oil remains too liquid and does not float in a controlled fashion. It will require a much dryer application of kerosene, or increased absorption by additional blending.

I had a large landscape piece, hills in the back ground, that I matted and applied an alcohol mat too, but I was lifting the water mat trying to cover it with alcohol, so I added more gum to my mat and that did the trick. I also used a very soft Chinese brush. I have found that firing the mat first and looses tooth.

A group of stippling brushes

I have noticed over time that some people seem to have the impression that the less gum used, the better. I advise not to use an excessive amount of gum arabic, as a soft matt, with a soft touch produces a soft look. This is interpreted to mean 'less is better'. That is true, but only up to a point. If too little gum is used, or none, it will come off as if it were flour or mud diluted with water and applied. Too little gum severely jeopardizes any opportunity to produce soft gradation from the highlight to the untouched matt.

Tracing with a Pen

Example of a pen nib

Using paint mixed with essential oil or turpentine and with a fine mapping pen for small lettering works well, as the oil flows better than water. Although with practice, a water based paint can be used with a pen, but it is a little tedious as the pen has to be loaded frequently with a tracing brush and constantly cleaned as the water dries quickly.

Examples of nibs and holders

Radiating Lines

In designs for leaded and copper foiled glass it is important to avoid lines radiating from a single point. Some of these reasons are:

It is important to reduce the number of lines that meet in any design to avoid a big bright solder place in a panel.

Example of pattern with radiating lines

It makes for large solder blobs, especially on leaded glass panels, and therefore provides a focus where one may not be wanted or required.

The difference between the harder solder and softer lead came leads - over time - to cracks in the lead at the edge of the thick solder blob.

In leaded and copper foiled glass it is a point of weakness, as there are likely to be multiple thin or tapering pieces of glass that are liable to fracture early in the life of the panel.

Methods of Avoiding

This umbrella image avoids long narrow pieces by having the ribs and supports crossing to make short narrow pieces

Narrow tapering pieces can be compensated for by making the narrow parts shorter than the wider parts of the taper – although this does add to the density of lead and solder around the termination point. There is a difficulty in adapting single radiating points in a drawing to the practicalities of the medium of glass. Examination of older panels (in either technique) will show some of the problems of thin tapering pieces. It is obvious in older windows, especially in the Victorian Era, when tapered pieces where in their glory. Almost always, the tips are broken. It is the nature of glass, and goes back to knowing how the medium will react to the conditions you create.

The central circle avoids joining all the radiating lines at one point

Good design will avoid multiple radiating pieces from a single point of origin.

It is not possible to make a neat termination by joining half a dozen tapers at one point. The finished piece will not look like it did when it was drawn out with a pencil. You can pencil in a termination with six points, ending at one point and it may look good, but when you draw the design with the width of the led or foil will show the clumsy nature of the design with a large termination point.

As you can see, the answer starts with the design, before you cut and foil, or fit the came to the glass. Art is not about the physical placement of what you see in your mind, as much as it is about the "illusion" you are creating that you want others to see. That starts with the design, and avoiding something that you know is going to give you a problem.

It is not possible to make a neat termination by joining half a dozen tapers at one point. The finished piece will not look like it did when it was drawn out with a pencil. 

Example of a design that will present difficulties at the centre

You can pencil in a termination with six points, ending at one point and it may look good, but when you draw the design with the width of the led or foil will show the clumsy nature of the design with a large termination point. As you can see, the answer starts with the design, before you cut and foil, or fit the came to the glass. Art is not about the physical placement of what you see in your mind, as much as it is about the "illusion" you are creating that you want others to see. That starts with the design, and avoiding something that you know is going to give you a problem.