Metal supports

It is often desirable to have supports that terminate inside the glass rather than clasping or otherwise holding the glass.  However, metal that would survive the firing and be strong enough to support a substantial piece would be of such a size that it would break the glass due to the differing expansion and contraction of the two materials.

The wire or rod to support the fused or cast piece does not have to be incorporated at the point of kiln forming.  Instead you need to plan for these supports and keep the glass open at the support points during the kiln forming.  It is relatively easy to wrap short pieces of appropriately sized stainless steel rod with fibre paper, or coat with kin wash and build the glass around these, keeping the ends free of the glass.  You can of course, use other metals, although most – except brass – are likely to spall quite a bit, so wrapping them with fibre paper is best.

When the kiln work is finished, the short rods are pulled out.  Clean the cavity formed for the rods. If the glass is transparent or translucent, I like to have the cavity as clear as possible, so I prefer wrapping the rod with fibre paper what ever metal is being used. This provides a clearer surface when clean. Kiln wash leaves a white deposit that is difficult or impossible to clean away completely, although citric acid is good at getting rid of most of the deposit. Of course if the glass is opalescent, it does not matter whether there is a white deposit.

The cavity does need to be as clean as possible to enable the glue to stick to the glass. The support rods need to be secured with a silicone or other flexible glue to avoid any expansion problems in the future.

Information on inclusions of metals:
copper
Wire
Silver foil

Revised 5.1.25

Fusing with Rocks

Rocks contain a lot of water and so require a long gentle drying process of days or weeks to avoid steam building up within the rock and breaking the rock and so also breaking the glass in any attempt to fuse the rock into the glass.

Rocks and glass have radically different expansion rates and viscosities from glass. Also rocks are not consistent in their characteristics as they are made up of different proportions of materials even within one site. So fusing rocks to glass is likely to be unsuccessful.

However, you can use the rock as a master for a mould. Make a mould of the rock, then pour investment material into the mould and use that to drape the glass around. Then glue the rock into the shaped glass.

Using Scraps

There are a number of ways to use fusing compatible cullet, also known as scraps. There are probably many more ways to use cullet in kiln forming processes, but these are the ones I use.

Arrange the cullet in a pot or over a mesh for a pot melt or a mesh melt and use the result on the shelf or container for elements in other fusing. 

Boil the glass. This involves arranging the cullet on the shelf – normally dammed – and taking it to around 925C with a significant soak. The resulting bubbles that rise and break leave patterns in the glass.

Pattern bars can be made through arrangement of the pieces in a dammed area to make long rectangular bars.

Cut or arrange the cullet into strips, curves and other shapes. Shingle them into appealing patterns without being concerned about gaps. The result can be presented as panels or, when slumped, as vessels.

Crush the cullet into frit and sort into various sizes for subsequent use. Use a dust mask while doing this.

Use as cullet for casting. Then you don't need to crush the pieces.

Sell it.

Sands for Texture

Firing on sand can give an even stippled texture. It can also provide immediate, free form textures and shallow shapes. You can use different sized grains for variations in texture size. So it can be a quick, responsive medium to give textures and shallow shape to the glass.

Although you can fire on sand, you must use a separator. When I fire directly onto the sand for texture, I dust alumina hydrate over the sand. People who watch me dust it through a sock have a laugh, but it does work to provide a fine layer of separator, so that any sand picked up by the finished glass can be removed as it is not fused to the glass. Sometimes it takes a bit of cleaning effort.

There are a number of sands that you can use, although all require a surface separator.

Silica sand is the kind of sand found on a beach and is the most commonly used sand. It is the most commonly used sand because of its great abundance and low cost. Its disadvantages are high thermal expansion and low thermal conductivity which requires caution in annealing the glass.

Olivine sand is a mixture of orthosilicates of iron and magnesium from the mineral dunite. Its main advantage is that it is free from silica, although a separator is still required. Other advantages include a low thermal expansion, high thermal conductivity, and high fusion point. Finally, it is safer to use than silica.

Chromite sand is a form of magnesium aluminium. Its advantages are a low percentage of silica, a very high fusion point, and a very high thermal conductivity. Its disadvantage is its cost.

Zircon sand is a compound of approximately two-thirds zircon oxide and one-third silica. It has the highest fusion point of all the refactory sands, a very low thermal expansion, and a high thermal conductivity. However, it is expensive and not easily available

Chamotte sand is made from previously fired clay. It has a relatively high fusion point and has low thermal expansion. It is the second cheapest sand, however it is still twice as expensive as silica sand. Its disadvantages are coarse grains.

Cut Running Pliers

Cut running pliers are intended to assist with the running of long straight or gently curving scores.  Sometimes they are referred to simply as running pliers.

There are a wide variety of these made for different purposes.  The following are illustrations of some of the styles.

This plastic cut runner is an economy version of the metal one below

 To use these cut runners, you align the raised line on pliers with the line of the score and squeeze gently.  The single line on the bottom jaw acts a fulcrum, allowing the two raised parts on the upper jaw to provide pressure to the score and run the break along the score line.

Metal cut running pliers

The metal cut runners are pliers with curved jaws. When looking at the pliers from the nose toward the handles you will see the curve like a down turned mouth. These assist the breaking of the score by putting tension on the glass.

Cut running pliers almost always are supplied with covered jaws. This are normally two pockets of flexible plastic that fit snugly onto the slightly flared, curved jaws. Keep these on. When worn they can be replaced by buying more, or by wrapping the jaws with tape using "liquid plastic" or sometimes even using them bare.

There is a spacing screw on top which allows adjustment for different thickness of glass. It is intended that the jaws should not close completely – which can place excessive pressure on the glass – but be adjusted so that there is about 1mm less opening than the thickness of the glass. So when cutting 3mm glass there would be a 2 mm gap. On 4 mm glass the gap would be 3 mm, and so on. experience will show what relationship is best for you. The principle is that the pliers perform a gentle tensioning of the glass. Using your hands exerts more tension on the glass and cannot be so delicate.

Use

Align the centre of the top of the jaws - often the pliers have a centre line on the top to assist – along the direction of the score. Squeeze gently and the score will begin to run.

I have found my best success when using cut running pliers is to avoid trying to run the whole score from one end. With a bit of practice you get the feel for how much pressure you should be applying and so when to stop. Then turn the glass around and start the run from the other end. Usually the open ends of the score will meet and the break is completed. Occasionally the two runs will not meet. Then it depends on how complicated the curve is as to whether you use your hands to complete the break or start tapping the score line to finish the break.


More that one tool

There is a second variety of cut running pliers designed to run long scores near the edge of the glass.  These can be used in the same way as the cut runners pictured above.

The Ring Star cut runners

These cut runners made from plastic have a pad with a central raised point on the bottom jaw and a circular pad on the top jaw.  Placing the point directly under the score line will begin running the score.

 A more durable, but also more expensive version is the Silberschnitt cut runner.

Moveable pad oriented to run scores in line with the pliers orientation

The advantage of these is that the upper pad can be rotated to accommodate any angle, allowing shallow curves to be broken out.  If progressively deeper curves are scored, this too can assist in breaking out deep inside curves.

Pad oriented at about 60 degrees for running score at an angle to the plier's orientation

This allows a score to be run gently over a long distance. This is especially advantageous when the score is a curving one.  

Use
The upper pad is rotated so that it is at a right angle to the score.  The lower pad has a point to act as the  pressure point when the pliers are squeezed.  As you move along the score, you continue to adjust the upper pad to maintain a right angle to the score.  This is a much more gentle breaking action than the standard cut runners and runs the score in shorter distances.  However these short runs make it more certain to run the score successfully. 

Tools for Thick Glass

There are a variety of tools for breaking thick glass - usually 6mm and thicker.  Some examples are illustrated.

Note: these running pliers are pictured upside down.  The two plastic pads should be on the top of the glass.

These are used in the following fashion:

Adjusting cut running pliers for different thicknesses of glass.

Pounce Wheel

The pounce wheel is used in reproducing images and comes from a time before photocopying or carbon papers. It gets its name from its use together with a pounce bag. In the past the pounce wheel would make holes through the paper or card along the design lines. The paper or card is put over the material which is to have the imaged copied onto it. A small bag of black powder would be dabbed (pounced) on the cover paper leaving black dots on the surface below. These could then be used to trace the same image many times in what ever medium was being used.

Two Pounce Wheels of Different Sizes

As the photo shows, the pounce wheel consists of a pencil-like holder with the spiked wheel at the end. The wheel is on an angled axle similar to a bicycle to make it easier to follow straight lines by pushing away from your body. This allows a clear view of the line being copied. The smaller wheel is useful for tight curves.

The pounce wheel still retains a use in transferring images through opaque materials, although the full pounce process does not need to be used.

To copy part of one stage of a design onto a new one without using tracing or carbon papers you only need to layer a new sheet of paper under the current design and run the pounce wheel over the parts you want to copy. As you move the wheel along, it punctures through the top layer into the lower layer. Normally, the puncture marks are all that are needed to be able to reproduce the original lines.

A crude pounced design

You can also get symmetrical images by folding the paper along the centre line and running the pounce wheel over the line. Unfold the paper and use the puncture marks to make lines symmetrical to the other side.

You can use the wheel to create mirror images by running the pounce wheel over the card, turn the card over and draw using the puncture marks.

Lead knives

The advantage of lead knives over lead dykes are that a wider variety of angles can be made with the knife. There are a number of varieties of lead knives - ranging from adapted paint scrapers to specially made sophisticated tools.

The technique in using a knife is to wiggle or rock the blade with some moderate pressure down through the lead came. Excessive pressure will twist the came rather than cut it cleanly and squarely. When you find the effort or time required to cut through the came has increased, it is time to sharpen the blade. The sharpening angle should be very acute. You can use a fine oil stone or wet and dry sand paper to hone the cutting edge. You can also use a little bit of wax or soap on the blade to ease its passage through the came.

The most simple knife is a stiff paint scraper. The blade should be of good steel so that it takes and retains the sharpening that is needed from time to time. This blade works best by wiggling through the came.

A range of cutting tools:  left - lead snips/dykes; middle - curved knife; right - paint scraper type.

Another style of lead knife has a curved blade. This has a number of variations. This knife works both by wiggling and by rocking.

Experience and personal preference will determine which style you settle on. The important elements are to make sure it is made from good steel and that it fits your hand comfortably.

You can add a metal end to the handle to provide a tool with more uses, especially as a hammer to put the nails into the board, or to snug up wooden borders, sometimes even gently tap the glass into place.

Also look at the use of lead dykes.

Large Edge Cames

The purposes for large perimeter cames are several.

Easy adjustment on site. It is often the case that windows are not totally regular in their dimensions, even though you have taken the measurements carefully. Variations in width and height can be accommodated by shaving the lead in appropriate places. This avoids having to take the panel back to the studio to reduce the size of the glass and put new perimeter came on the panel.

The width of the rebate has an effect on the width of the came to be used. The wider the rebate, the wider came you will want to use. The minimum width of came you want to use with a 10mm wide rebate is 10mm came. This will give a maximum of 2.5 mm of came showing if you have a glazing allowance of 5mm. Often 12 mm came is better. In general the came should be wider than the rebate is, but not so wide that the heart of the lead is outside the rebate. In church windows, where the panels are installed into the stone, the cames are frequently 16mm or 25mm wide to accommodate the variations in width and the flexibility needed to get the panels into the slots.

Aesthetics have an effect on the width of the perimeter came too. Various people want more or less came showing. The important limitation is that the heart of the lead should be within the rebate.

In autonomous panels the need for large edge cames is to act as a framing device. Zinc might be used but there are other possibilities than using a different metal that will provide as good or better solutions.

Light Box Lighting

Light is a central consideration in building the light box. 

The best way toward even light distribution even with good dispersion sheets, is to have multiple light sources. I recommend placing them at the same distance apart as the depth of the box. It would be possible to pack the box with light fixtures, but this is expensive and generates a lot of heat. It also may make the light too intense to be comfortable to work with. If you can control the general lighting of your studio and you can turn it off or down, you will not need such intense lighting in your box.

An alternative, but more complicated method is to build the light box with baffles so the light is never directly under your work. Commonly, this would require the box to be built wider than the glass upon which you will be working. The light reflects from the sides and bottom of the box to give an even light. In this case, the single sandblasted surface would be sufficient to disperse the light and keep your eye focused near the surface of the glass or cartoon on which you are working.

You need to have daylight corrected light sources for you light box, especially if you are doing any glass selection on it. Fluorescent tubes are easily available, but other light sources can be used if they can be found in daylight colours. Fluorescent tubes do not generate much heat and are available in daylight corrected colours. So these are the common choice.

You still need to have ventilation to allow the heat to disperse, though. Ventilation can be provided in a number of ways ranging from drilling holes in the sides, to providing a slot in the side or bottom.

You need to have access to the light fittings to replace bulbs. It is easiest if this is by removing the glass top. You can provide tabs on or under the glass to lift it with, but these often interfere with other uses. You can use the ventilation holes if they are high on the box to stick a lifter under the glass to be able to grasp the edge. You can have a removable section to the beading that holds the glass top in place. You can provide a couple of finger holes at the top edge of the box to enable more direct lifting of the glass without disturbing any of the box fittings.

Another important element in getting the maximum amount of light out of your box is to paint the inside white. This should be a matt or at most silk finish. Any glossier finish will produce bright reflective areas. Shiny surfaces such as aluminium foil also produce these unwanted bright areas. In fact, a matt white surface gives more apparent light than aluminium foil in the light box.

The lights should be wired in series so they all come on at the same time. It is of course possible to have a switch for each fitting, to vary the intensity of the light for the work you are doing. This does add a bit to the expense, but may be valuable for your way of working.


Additional information:
Uses
Requirements
Flexibility
Top surfaces

Light Box Tops

I recommend your top should be 6.4 laminated or 4mm toughened glass for anything up to 610 by 1000mm. If it is larger, you should go to 6mm toughened, as 8.6mm laminated glass is pretty expensive. I suggest glass because it is strong, rigid, scratch resistant and easy to clean.

You can use a router to form a ledge for the glass to sit on. You can use a less machine intensive method, by nailing thin battens or quarter rounds around the glass. But the structure which confines the glass should be no higher than the glass surface. If it is higher than the glass, you can simply plane or sand it down. Insure there is no part of the fixings of the glass higher than the glass surface This is especially important when cutting glass on the light box. If the surround is higher, you run the risk of breaking glass that is for one reason or another overhanging the edge. It also makes it easier to get the glass on and off the light box.

To get the appropriate diffusion you need to do more than sandblast the under side of the glass. While this will provide some diffusion, it is not enough. You can put another sheet of glass, sandblasted on both sides, underneath the top sandblasted sheet to provide good dispersion of the light. However, I have found a 3 or 4 mm sheet of white acrylic that is 70% -80% opaque provides the best diffusion of the light elements, even tough it is more expensive than glass.

You also need to have a method to be able to get at the lights. This can be by having a removable section of the boundary. You can also make use of the ventilation holes, if appropriately placed, to lift the glass. A portion of the box sides can hinge to allow access to the lights through the side, although this is more awkward than fitting from above.

Additional information:
Uses
Requirements
Flexibility

Lighting