Fibre Blanket Moulds

Fibre blanket moulds are good for free form moulds. The blanket can be cut into shapes or crumpled. It does not have binders as the papers do, so kiln wash is not necessary. Still, I have always sprinkled alumina hydrate powder over the mould. You can then support the high spots with kiln furniture – existing or custom made.

Pre-wetted fibre blanket is available - Moist Pack is one brand name.

Or you can make the mould yourself from fibre blanket and hardener. You need:

• ceramic fibre blanket. It should be 3 mm or thicker, but 25 mm needs to be compressed when wet. It is possible to use two layers of 3 mm fibre blanket, but they do not stick together well unless thoroughly wetted.
• colloidal silica - often is called mould hardener or rigidiser. Paint this onto the fibre blanket liberally, both sides if possible.


The rigidiser can be brushed on or sprayed on. Some people soak the blanket in the rigidiser and then squeeze out the excess.

You must protect the master with cling film, Vaseline, or other waterproof separator. Be sure about whether you want a draping or slumping mould, as the inside needs to be smoothest for a slumping mould and the outside smoothest for a draping mould.

Press the wet fibre blanket to the master. Then let it dry for a couple of days to become stiff enough to remove from the master. Let the negative dry for another period when out of the mould.

The drying method for rigidised fibre mould depends a bit on the structure from which you are taking the shape. If the shape is a piece of glass you can heat slowly to about 300C, but you have to be careful not to go much above that temperature to avoid the mould sticking to the glass. When cool you can carefully remove the mould from the glass and fire it to about 720C to cure it.

Other materials should be able to withstand at least 400C if you are drying in the kiln.

Materials that cannot be subjected to heat should be air dried. This will take a long time, possibly a week or more. The master should be coated with petroleum jelly or cling film to ensure the drying of the mould does not also cause it to stick to the master.

When the mould is dry, put into the kiln and fire to around 760C to cure the mould. You can fire fast, and after 10 minutes at 760C, you can just turn the kiln off, as there is no possibility of thermal shocking the mould. The point is to get the glass which has been in suspension to soften and stick together. Upon cooling the mould will be hard, as it is held together by the glass structure within the fibre blanket.

Once rigidised, you can sand the mould to refine the shapes. But you must use dust mask as the dust and fibres are dangerous to your health.  Do it out doors if possible. Otherwise a well ventilated room is necessary. You can sand down the high spots and generally smooth the mould to obtain a finer texture. Usually 100 grit sandpaper does the job quickly and leaves a relatively fine surface texture. If unhardened blanket is exposed during the sanding process, You can add a mixture of the rigidiser and the "dust" from the sanding to any holes, dimples or exposed unhardened fiber in the mould Then re-apply rigidiser to the sanded areas, and cure the mould at 760C again.

If you are rigidising, you need a separator – kiln wash – either powder or in a solution brushed on. A rigidiser does not burn off; it fuses to itself within the mould material and makes it harder. The resulting mould material will also be more brittle and should be handled with some care. I.e., never pick up the mould by the edges or with a piece of glass on top.

When you are satisfied with the shape and texture, you apply the kiln wash and fire.

The rate of heating the kiln and the soak will depend on the complexity of the shape of the mould and the thickness of the glass but there are no concerns about the mould as it is not subject to thermal shock.

With delicate treatment, the mould can be reused many times.

Two examples are shown here:

Lamp shade panel form

This is a "free form" mould made to give the glass sheet the appearance of crumpled paper

Cutting Small Diameter Circles

It is possible to cut regular, small diameter circles without buying a lens cutter. It can be done with the assistance of a Lazy Susan or cake decorating turntable.

Draw the circle of appropriate diameter on the turntable with a compass. Place the glass on top of the turntable, and position your cutter above the drawn circle. Press on the cutter with one hand and rotate the turntable with the glass on it, with the other.

Steady your hand with the cutter by keeping your elbow tight against your side. This enables you to make a very good, if not perfect, circle without buying an expensive small circle cutter.

If the glass is too dark or opalescent to see the line, make a template and put it onto the glass. Cut beside the template or use the template to mark the glass. Then place the marked glass on to the turntable and cut as with transparent glass.

You will not be able to run the score by turning the glass upside down and pressing as you can with larger circles. You will need to make a number of relieving cuts to the tangent of the circle and break them away one by one. Yes, this does leave a rough edge at various places around the circle, so grozing or grinding will be necessary.

Removing Cement

Sometimes life gets in the way and a partially cemented panel is left for days. When you come back to it the lead light cement is hard. Removal requires a material hard enough to shift the cement but not cut into or damage the lead or glass.

The best tool is a rectangular stick of hard wood. It should be at least 6 mm thick to stand up to the pressures of cleaning, but not much more than 12 mm - 15 mm wide to enable you to get into corners. It should be 200 mm – 250 mm long for ease of handling. Shape one end in a chisel or wedge shape. I prefer the wedge shape, but the chisel shape can be re-formed more quickly than the wedge because there is only one edge.

Use the stick by running it along the lead with some downward force, but remember you can break the glass with too much pressure. This should break the adhesion between the cement and the glass. To get all the cement off the glass, you will need to use the stick in localised areas almost as a kind of pick. This is the kind of tool that I use in conjunction with a stiff brush for the final clean up of each panel before polishing.

Stress Testing

You should be testing for stress in any new set up. This includes new processes, different layering, different colour combinations, and any other variation that you make in your basic processes.

You can buy kits called stressometers. The devices called stressometer are not actually meters. They are battery powered light sources with two pieces of polarized film in frames. This is very good for small kiln formed pieces. For larger pieces you can use your light table with larger pieces of polarized film. A description of how to use these is given here.

Stress appears as a “halo” of light around the stressed areas. The more light that appears in, or at the edges of the piece, the greater stress is being indicated. The amount of acceptable stress is given in a Bullseye Technical Note.

However, if you test only the combination of glass you propose to use, you will not know if the stress is from incompatibility or from annealing – the appearance is the same for both. This means that you need to place an additional test into the kiln, to determine the adequacy of annealing. This is especially important when tack fusing and doing thick work. The process for doing this is given here.

Bending Wide Cames

The way to bend larger leads such as flat outside leads around pieces of tracery or other curved shapes in window panels is to lay the lead upon the bench, and use a curved, preferably wooden, lathekin.

Progressively manipulate the lead into the curve. Hold the lead steady by keeping your fingers spread on the top and back of lead and manipulate the curve between your extended fingers. Gently push the curved lathekin along the heart of the lead with small, smooth, circular strokes. Smooth the lead flanges by pressing down on the flanges on the inside of the curve as you go. If you try to do it too quickly the lead will probably buckle.

Frequently turn the lead over, applying the process to both sides.

If the flange crimps or buckles, put smooth jawed pliers inside the lead and squash the flange flat. The pliers can be used to flatten any kinks that develop in the lead.

The key is to handle the lead gently and in stages, gently flattening the complete lead and not flattening completely one spot before moving on to the next.

The advantage of round over flat in this circumstance is that round came of the same size can be bent into smaller curves that the flat came of the same width.

The technique for finishing a curve around a single piece of glass can be seen in the tip “Leading Small Circles”

Glass Stains

A lot of people want to use old window glass – for recycling reasons, for the character of the older glass or because it is cheap or free. This glass often has stains or the appearance of corrosion or etching from age or storage conditions. To remove these blemishes you should start from the least aggressive method and work your way through the more aggressive methods until you find one that achieves the cleanliness you desire.


When using these methods appropriate breathing and hand protection are a requirement. 

Surface deposits

The first method is to wash the glass in water with a bit of crème cleaner. Place the glass flat on a work bench and scrub it with a brush containing the water and cleaner. Rinse and dry. This may be all that is needed.

More persistent stains require chemicals. Use rubber gloves for this kind of process. Soak the glass in a dilute (5-10%) solution of lye. This is also known as caustic soda. Chemically it is sodium hydroxide (NaOH). After the soak wipe with a disposable towel and dip it into a dilute solution of hydrochloric acid (5-10% again) or vinegar to neutralise the caustic soda. Wipe the glass with a towel and rinse with plain water and polish dry.

Metallic stains or iridescence and etched surfaces

If the blemishes are more than surface deposits, more aggressive methods are required. The metallic-like stains and iridescence are usually evidence of the corrosion of the surface of the glass. These and any etching require grinding and polishing.

You should start with a polishing process to determine if that will be sufficient to bring clarity back to the glass. The use of an optical polishing material such as cerium oxide paste and a felt polishing head is often enough. Ensure that you do not let the cerium oxide get any drier than a paste to avoid localised heating and therefore breakage of the glass. Rinse the glass in clean water and polish dry.

If this does not remove enough of the surface to provide the desired clarity of the glass you can try either using pumice or jeweller's rouge, or dilute hydrofluoric acid.

Hydrofluoric acid used in a 10% or less solution will remove the surface of the glass, so eliminating the evidence of corrosion. It will even out, but not eliminate, the evidence of any etching. The disadvantage to this method is the risks associated with such a dangerous chemical. There is within this note on acid etching a door panel some advice on safety.

If you decide to avoid the hydrofluoric acid method, you can use mild abrasives such as jeweller's rouge or pumice with water and a felt polishing head. Once you have ground the whole of the surface, you need to wash it very thoroughly in clean water. Then change the felt head and go to cerium oxide to provide the optical finish.

Note:

All the dilutions and solutions suggested here are with water.

This note assumes the glass has had any paint already removed. For a method of removing house paint see this tip.

Negative assembly

To get a crisp design finish to a fused piece especially with thin elements like stringers it is often recommended to fire upside-down. This means that the bubbles move toward the final bottom of the piece rather than rising and disturbing the design on the top.

Assemble the piece on your workbench as usual on top, but use a toothpick or small brush to dab some GlasTac or other glue near the two ends of each piece. Let it dry overnight and then carefully flip the whole arrangement upside down onto the kiln shelf.

If you don't like the glue and flip over technique you can try another. Draw your design onto Thinfire shelf paper in negative with a graphite pencil. If you have a strong light source you can draw on the reverse (printed) side and trace the negative onto the upper face of the Thinfire. Then assemble your pieces upside-down on the shelf. You can assemble the whole in the kiln and there is no need for glue.

When fired, clean the piece thoroughly and decide whether you want that texture or a smoother surface. If you want the smoother surface, put in the kiln for a fire polish. This is often known as “flip and fire.”

Soldering Zinc

Brass, copper and zinc are heat sinks. That is, the metal conducts the heat rapidly so more heat has to be applied than for lead and tin to keep the soldering site hot enough to accept the solder.

The important elements are:

Use a hot iron. If you use a rheostat, turn it up to full. If you can, change the tip/bit to one rated at 800F – it will have an “8” stamped on the end that goes into the barrel of the iron.

Apply the flux liberally at the soldering point to ensure the area is “wetted”.

Keep the iron in contact with the came for a few seconds to heat the metal. If you are using zinc as your border around a leaded panel, make sure you do not heat up the lead came so that it begins to melt.  Keep the iron on the zinc.  It will transmit heat to the lead came without getting it hot enough to melt.

When the came is hot, apply the solder to the bit. 

Keep the bit on the metal until you see the solder begin to flow on both the zinc and the lead or onto the solder bead (on copper foil), then gently lift directly up. 

Starting

“Where should I start cutting the glass from the inside or outside of the cartoon?”

Once the colour selections are made, you can start the cutting in what ever order suits you. Some cut colour by colour. Others cut the glass in the order that fits together. This usually means the main image is cut first and the pieces laid up on a glass easel to determine their interactions. When satisfied, the background or in-fill pieces are cut and fitted.

“Where should I start building a panel?”

When starting the assembly, begin at a lower corner. Whether left or right will depend on whether you are right or left handed and the way the panel fits together. Although sometimes it can be easiest to build from the top toward the bottom. Starting in a corner, together with battens or supports for the outer edge  will keep everything in place as you work.

When working on an oval or circle, you can use a multiplicity of nails around the outside edge to hold the glass pieces. An alternative is to cut the curve into a piece or pieces of float glass and fix this to the work board to hold the glass. If you do this use the outside of the cutline so that there is space for the heart of the perimeter lead.

Separators for Steel

Steel moulds, whether stainless or other steel, require separators as glass will stick to hot metal.

The preparation of steel is a little different from ceramic or fibre moulds. First the steel has to have the oil coating removed. This can be done by sanding, sandblasting or by heating to about 550C.

The separators can be just normal kiln wash, boron nitride, or fibre. When using kiln wash or boron nitride, the steel needs to be heated – about 200C should be enough. Too hot and the water will boil leaving gaps in the coating. If the metal is too cool, the kiln wash will drip. A little experimentation will be needed to find the right temperature for your purposes. Remove the mould from the kiln and brush or spray on the separator. Return to the kiln to heat up again and apply the separator again. Continue this until an even complete covering of the metal has been achieved. It does not have to be thick.

Fibre paper works best on cylinder or wave moulds with curves in one plane only.  Bowl shapes lead to wrinkling of the fibre papers and marking of the glass with wrinkles.  This applies to the Bullseye Thinfire too.

Just as on shelves and ceramic moulds and as long as you fire below 700C, you can use the coated mould over and over with no problems. Once you fire hotter than 700C, it is best to remove the old kiln wash and put a fresh coating on before firing again.

Single Layer Slumping

Contrary to expectations, single layers are more difficult to slump than multiple layers, as you do not have so much mass for the gravity to act upon. Especially if the pieces are small, the slump will be slower than for large pieces.

It is possible to take the glass up in temperature very quickly without breaking it, but that will not give you much control over the slump. You may not get the curve you want, and you may over fire it so that it distorts.

If you feel the need to go quickly, slow down from 630C to a rate of advance of 40 or 50C/hr. For the first firings and new moulds, observe how the glass settles into the mould. This will give you the top temperature.  In future you can back off 10C or more and soak for about 30 minutes to get less marked pieces.

You can drape or slump a single layer over a mold or drape two overlaid layers on or over a mold – assuming the layers are 2 mm to 3 mm thick.  Draping double layers together is a popular way to make two colour double layered handkerchief vases with art glass. But when you fire one piece of glass on top of another, the air between the two pieces acts as an insulator, slowing the heat transfer between the two pieces of glass. So you should advance at about half the rate you use for a single layer. Anneal soak and cool for 6 mm glass.

Note that there are different behaviours between single and double layered pieces.

Draping and slumping processes work by taking advantage of the action of gravity on the just pliable glass. This means that thicker, heavier glass slumps and drapes more quickly than thin light glass does. You will need longer soak times for thin glass than for thick glass. You can go higher, but the effects become less controllable.

The size of the opening of the mould has a strong effect when slumping single 3 mm layer glass. You need much more time – often as much as three times as long as for a 6 mm piece over a small diameter.

The effect of the shape of the mould has little effect on simple shapes. But when angular or complex curves are part of the mould the single layer will have much more difficulty in conforming to the mould than the thicker pieces.

Annealing the 3mm piece can be a bit quicker than for 6 mm, but a reduction of more than a third in the soak time and more than doubling the cooling rate may cause problems.

Short Cuts in Fusing

There really aren't any. Trying to do two things such as fusing and slumping in a single firing requires compromises that can make the result unsatisfactory. Normally, trying this uses more time and glass in having to re-do things.

Referring to what heat does to glass and when is important in thinking about what you are trying to achieve. Bullseye in their tech notes give the information in both concise and visual ways.

Fixing a Bubble

It is often recommended that large bubbles can be fixed by drilling out the hole if the raised part is thick, or by breaking the thin skin of the bubble and filling with a piece of glass or frit.

My experience leads me to say that "drilling and filling" is hardly ever successful. There always is a mark where the fill has been made, often there is a colour variation too.

There is another possible solution for small bubbles which are at the surface but not yet burst.

Turn the whole piece over and take to just below full fuse. This will allow the bubble to begin moving to the "bottom" of the final piece. Then flip over, clean really well and  fire polish - quickly up from bubble squeeze temperature and with no soak - to give a smooth surface, but not allowing it to get so hot the bubble comes back to the top. This will require observation to stop the temperature rise as soon as the surface is shiny.

Small burst bubbles

Small burst bubbles can be fixed by placing small “beads” of glass made from frit in the kiln. The appropriate sized bead can be placed in the hole and others arranged in a pleasant arrangement and all taken to a tack fuse. The beads are made by cutting small squares of glass 5-6 mm and taking them to full fuse. The glass will round up at the fusing temperature and give a number of completely rounded spheres with a flat bottom.

Prevention

Of course, the prevention of bubbles by inserting a bubble squeeze is the best solution.

revised 24.12.24

Resists

Avoiding bubbles between the resist and the glass on large sheets when preparing etching or other resist based processes is often difficult.

A trick learned from the firms that apply advertising vinyl to vehicles is to use a spray filled with slightly soapy water.

Their process uses pre-cut vinyl with an adhesive backing. So the first thing to do is to pick out the unwanted pieces. That is the pieces covering the areas that will be etched. Then you need to put a backing onto the front surface of the picked out vinyl – usually really wide masking tape.

Lay out the vinyl on the glass. Tape one end of the vinyl securely to the glass. This ensures that you get the vinyl correctly aligned over the whole area. Fold the whole piece of combined vinyl and backing back to the taped edge.

Carefully peal back the covering for the adhesive side making sure you do not pull off any of the isolated vinyl pieces. Spray the glass with a mist of soapy water to ensure all the glass is covered, do not have the glass running with liquid, but be generous. Too much liquid means that there will have to be a long wait for the vinyl to be firmly attached to the glass.

Start the application process by folding the vinyl onto the glass. Use a credit card or better, a large squeegee such as used for grouting mosaics. The tool you use must be smooth to avoid scratching the vinyl. Push the soapy water forward and to the sides as you move along the piece of glass. Keep pulling the protective layer evenly off the adhesive side as you work forward.

When completely attached, remove the backing from the vinyl. This will enable you to see any bubbles you may have left. Work out any bubbles by further pressing the soapy water out from under the vinyl to the edges. Where any remaining bubbles are in the way of the design, puncture them and work out the bubble of moisture through the hole. Cover the puncture with a small piece of vinyl.

Leave for a day for the vinyl to become firmly attached to the glass and then you are ready to do the etching.

Where you are going to cut the vinyl by hand, you do not need the backing. All the rest of the process is the same.

How Annealing Affects Slumping

It is often claimed that inadequate annealing of the fused blank can cause breaks during a slump firing.

If annealing is the cause, it is likely to break on the rise in temperature.  Once the piece has reached the annealing temperature, any breaks will be due to thermal shock on the way down.  An annealing break usually has a hook at both ends of the break, although this is more difficult to determine in a shaped piece.

Thermal shock tends to be along straight(ish) lines, often between thick and thin, or strongly contracting colours.  It tends to happen on the cool down. 

Breaks on the rise or fall in temperature are difficult to distinguish on slumps.  The temperature is low enough that there is little to distinguish the sharpness of the edges.  The real method of determining, is to try to fit the pieces together.  If they fit exactly, the break was during the cooling.  If they have even a little variation in fit, the break occurred on the rise in temperature.

If the annealing of the slump is marginally inadequate, it may break hours, days, weeks after cool.  The less stress the longer it will survive.  This will not be the result of any inadequate annealing of the fused blank. Only the last annealing is relevant to the soundness of the piece.

How can you ensure the annealing on a slumped piece is adequate?

You need to check the fused blank for stress before slumping to ensure it has no or very little stress.  The anneal for unstressed items needs to be at least equivalent to, or longer, as for the fused blank.  Testing has shown that annealing for one layer greater than the calculated thickness results is less stress than annealing for the thickest part.

Fire more slowly than usual for blanks with moderate stress to avoid thermal shock during the first ramp.  Anneal the slumped piece for one layer more than was done for the blank.  There is no other requirement for slower annealing.

Pieces with significant stress need to be returned to the kiln to be annealed.  Fire them up significantly more slowly than you normally would for a piece that thick.  This may be one half or less the speed used on the un-fused pieces. Anneal as for a thicker piece.

Patina Application

The application of patina to solder and other metals consists of three stages, cleaning, application, protection.

Clean the solder bead

Both flux residues and contaminants are left after soldering. Cleaning can be a combination of cleaning with abrasives and also with alkaline materials. Baking soda – sodium carbonate – can be used to neutralise any of the acidic flux left. It bubbles in the presence of acid, so gives a visual check on the amount of acid left. Since it is an alkaline substance, it will react with the acid of the patina to weaken the reaction. It is important to rinse the baking soda off with plenty of clean water.

Abrasive cleaning with materials such as steel or copper wool can be used. Some advise against this as metal residues can be left. However the abrasive scrubber used in scrubbing pots can be used to finish the cleaning without leaving metallic residues.

Apply the Patina

As patinas work by chemical reactions, they are specific to various metals. Those designed for solder work by reaction with the tin mainly, those for lead obviously react with lead, and those for zinc react with zinc - while each of these may work with other metals, they work best with the metal they are designed for. Too much rubbing while the patina is wet simply interferes with the action of the acid. Application of enough patina to allow it to "soak" - actually time to react with the metal - is much better than rubbing. To repeat, it is a chemical reaction, not a buffing process.

Once the patina is dry, you can use the baking soda solution again to neutralise the remaining acid on the metal. Rinse well. rub gently with a dry cloth to assist the drying, do not scrub. When dry again you can wax the metal.

Protect the Patina

Some allow the waxed piece to sit for 24 hours and then re-wax it. The applicator should be a soft object such as a cotton bud or soft cloth. Do not polish it until it no longer is showing black. Rather allow it to sit undisturbed for several days. The patina will get darker and smoother over time. Don't worry too much about getting it pitch black, or birght copper the first day.

Home Made Billets

You do not always have to buy cullet for casting or billets - you can make your own. Billets lead to less veiling and bubbles than just putting in your old cullet into the mould.

Create a mould by using dams or pouring investment materials around something like a plastic salad tub to make a billet – the shape is not usually critical. Place a reservoir such as a terracotta flower post above. Take the temperature to the 650C – 670C region for a 1- 2 hour soak followed by a long soak at 830C.

Normally, the higher you allow the glass fall, the fewer bubbles, but you're usually limited as to how high you can go in the average glass fusing kiln. You'll get some bubbles, but if you then put your new billet as a single piece in a reservoir for your casting you'll get the second flow that removes more of the bubbles.

All the glass must be thoroughly clean before being put into the pot for making the billet. Do not use iridised glass as it reduces the clarity of the billet. Do not use glass that has been ground as that will cause hazing in the billet. Instead, cut off the ground sides before washing the remainder and including in the melting process. Do not include the ground off-cuts.

Based on information from Cynthia Morgan (Morganica)

More information here

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.

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.