Patina Application for Copperfoil

My observations:

• Wash the whole item, concentrating on the solder lines.

• Use small brush such as a toothbrush.

• Avoid ammonia as it creates the possibility of residue.

• Whiting/calcium carbonate rubbed over whole project will effectively clean as it is a very mild abrasive. It is not good at cleaning acids from under solder though.

• Baking soda – there is some fear of scratching, but in solution there should be no granules. It bubbles in the presence of acids, so there is a visual indication of the presence of acid. But make sure you get it all off the project before applying patina. as it is alkaline, and tends to neutralise the acidic patina.

• Use of an abrasive like fine steel wool, or to prevent transfer or metal, a kitchen scouring pad on the solder to help with a smooth application of the patina.

• Waxing is usually done after the patina application.

• Application of the patina is best done with gentle, light pressure from brush, sponge, cotton buds or rag.  Allow time to react with the solder it is a gradual chemical reaction.

• Buffing or polishing the patina is to be done after it is dry, using light pressure to avoid rubbing the patina off.

• Waxing will polish the patina as well as protect it from oxidisation.

• Note that patinas are acids specific to various metals, so black for zinc is different from that for solder and lead, and both are different from each other.

• Patinas will get darker with time.

More Details

The application of patina to solder and other metals consists of three stages:

• cleaning,

• application,

• protection.

Cleaning

 Flux residues and other contaminants are left after soldering.  Cleaning can be a combination of cleaning with abrasives and alkaline materials.   After soldering, cleaning and drying your piece, use fine (000) or extra fine (0000) steel wool and a brass wire brush to go over all the beads. Use a brush first if you want, and follow with the steel wool, since it will provide fewer scratches. This helps remove any leftover flux that on solder lines.  Some advise metal abrasives as residues can be left. However the plastic abrasive pads used in scrubbing pots can be used to finish the cleaning without leaving metallic residues.

Omitting this step increases the chances of developing whitish blotches later on the solder lines.  Including this step also makes a better base for applying the patina.  After using the steel wool, use a soft brush to remove any residues from the steel wool, brush, flux or solder.  Baking soda – sodium carbonate – can be used to neutralise any of the acidic flux left. It bubbles in the presence of acid,  giving a visual check for any acid left.  It is important to rinse the baking soda off with plenty of clean water.

After cleaning the solder beads, wash the panel off with warm water and a little dish washing liquid to remove oils and other residues. When washing use a very soft scrubbing brush to get in all the little crannies.

Dry the piece with a soft towel. If the piece is framed in zinc, make sure that any trapped water is eliminated and the piece is entirely dry. Often letting it stand overnight will be sufficient. A panel with no moisture will help the polish be more even.

Apply the Patina

As patinas work by chemical reaction, they are specific to various metals. Those designed for solder react with the tin mainly, those for lead react with lead, and those for zinc react with zinc. Although 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. It is a chemical reaction, not a buffing process.

Pour a small amount of the patina into a small container so as not to contaminate the rest of your patina. Do not pour the remainder back into the bottle, as it will begin to neutralise the main supply.  Apply your patina with a small flux brush reserved for the purpose, or a piece of a rag. If you use a rag, renew it frequently. Do not be afraid of putting too much on. If you are not happy with the colour when dry, you can rub the solder over with a 400 (also known as 000) wire wool or an abrasive scrubbing pad to abrade the surface. Then give it a further coat.

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

Sometimes a white residue appears alongside the solder bead after a piece is finished, covered in patina, and waxed. This seems to have two causes.

Residual acid

As there is a possibility of some acid remaining on the piece, rinse with a bit of bicarbonate of soda added to the water. This will neutralise the acids from the flux and patina that may still be lurking under the foil and solder beads. If you get a frothing while cleaning with the soda, you will know there is still acid present. Wash - rather than scrub - those areas again with the water and soda solution until there is no foaming.

Trapped moisture

Moisture can also produce this white residue, as it allows minerals to migrate from under the solder seams. The advice centres on cleaning. Do not use much soap in the initial cleaning solution. After rinsing ensure the piece is completely dry by setting it aside in a warm dry place for a day or two before waxing or sealing.

Preservation

To preserve the desired finish, a coat of beeswax, carnuba, or other car wax helps, but remember that copper will oxidise over time no matter what you do. It is this what gives it a rich deep antique lustre.

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 or copper. 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 bright copper the first day.

Those that use paste waxes seem to have less difficulty than those who use thin or spray on waxes. The heavier waxes seem to seal any moisture within the structure. The moisture seems to be able to migrate through the thinner waxes. Still, it is not optimum to have moisture sealed within the panel, as it will eventually come through the wax as it ages. It seems the best long term result will be achieved by ensuring everything is absolutely acid free and completely dry before waxing.

Use a good quality furniture polish or wax. Shake the bottle well if it is a liquid, then apply liberally to a soft cloth, or good quality paper towel, rubbing all over solder. If you have a glass with a deep texture, try to avoid this all over process, as it can be hard sometimes to remove all of the polish from th edepth of the undulations afterwards, and it is noticeable when it dries. Alternatively, mask off the glass from the solder.

Immediately after applying the polish, take a clean, dry soft cloth or new paper towel, and begin to gently rub the solder seams. If you are using paper towels, you will need a lot of them, as they tear up quickly. When both top and bottom sides have been polished, check for any missed spots, especially along the edges of your solder seams. Also check for polish residue in tight corners and along the edge of the solder. An old toothbrush often works to remove it. If you need stiffer bristles, make sure you keep this new toothbrush separate from all the others in the house.

Observing these methods should provide long lasting patinaed pieces.

Revised 4.8.2025

Drilling Holes in Glass

There are many aspects to drilling into glass.  This post attempts to address many of them.

Keeping Things Wet

When drilling glass it is important to keep the drill bit and glass wet always, otherwise the glass gets too hot and will break and deteriorate the bonding of the diamonds. There are a variety of things you can do to achieve this.

 Drill with the glass surface under water in a container.

    

Drill in a ring of clay, plasticine, etc., holding water. To do this, you need to make a ring about 50mm/2"  in diameter and press it around the drill site. Fill the ring with water to cool the drill site and glass. Diamond coolant is not necessary, but can extend the life of the bits.

    

Use a re-circulating water pump such as those made for indoor water features. Direct the small flow of water (rapid drips) to the drilling site and catch the overflow in a separate bucket to the one in which the pump is submerged.  This extends the life of the pump and helps prevent clog ups in the water pipe.

    

Use a glass drill with hollow core bits and an internal water feed. This is the most expensive but it is the best equipment with which to drill holes of more than 4mm/0.158".

Drill Press

Drill presses vary from purpose-made through adaptations of industrial drill presses to hobbyist versions.

For light duty drilling that most glass workers do, a small press as set up for a dremel are suitable.

Example of a rotary tool press setup

This is an inexpensive solution to holding the dril steady while drilling.  It avoids the various contortions to stop the bit skittering across the glass when starting the hole.

Keeping the glass wet and cooling the drill bit for small pieces can be achieved by using a small temporary reservoir around the drill site to hold the water.  Alternatively, a small receptacle to submerge the glass can be used.

A plastic take-away container to hold a quantity of water

The water needs to be deep enough to cover the glass, but not so deep that it rises to the drill chuck, as that is likely to draw water into the rotary tool and short it out.  Notice also that the speed for the tool is at the minimum, because it is far too fast otherwise, and will overheat both the drill bit and the glass.

It is best to have an industrial drill press if you are doing a lot of drilling. It provides a stable drilling action and the pressure on the bit can be controlled. It is important to ensure the bit is running true without wobble. The drill press should have instructions to help correct any untrue running of the chuck. Make sure the drill bit is secured firmly. Core drill bits are easier to keep true, as they normally have a threaded fitting.

With a drill press, you can drill continually until the hole is completed, or until a white paste or dust begins to appear. This indicates the drilling is being done dry and will in a few moments heat up the glass too much. When the white paste appears, back out of the bottom of the hole a little to allow water to flush the glass out. Then continue.

Keep a firm grip on the glass being drilled.  If there is any chance of the glass spinning,  wear cut proof gloves.  Maintain the glass position, especially if you are intending to back out of the hole intermittently to allow water to the bottom of the hole. This enables you to get back into the hole without scratches.

If possible, submerge the piece if you are drilling without a core drill bit. But if that isn’t possible, just squeeze a little puddle of water on the surface and watch it swirl around. You can see if it is pulling ground glass out of the hole by watching the circulation. Placing a plasticine or clay dam around the drill area will keep the water confined.

Don't push down any harder than you comfortably can on the lever with the tips of your fingers. Keep it steady. Listen for the sound of diamond grinding glass

White core stuck in the drill bit

If the core gets stuck in the bit, knock it out with some stiff wire or a nail. Always remove each core right after drilling. They are very difficult to remove if there is more than one in there.

Core pushed out with 16 gauge copper wire

 When using a Dremel for drilling glass, slow it down to the minimum with the speed control. Drill presses do tend to be on the slow side for glass drilling so it takes a bit longer, but there are big advantages in other respects.

Drilling with a Flushing Head

A Typical Drill Press Set Up

A flushing head with a re-circulating pump will deliver water to the drill site through the core of the drill. These are supplied complete or as a fitting for an existing drill press. This is suitable for holes of 4 mm and larger. Smaller core drills are impractical both because the glass is easily trapped in the drill and the wall thickness of the drill makes them almost solid anyway.  An additional requirement is to have a means to direct the water to the waste bucket.

            Pump (black) at the bottom and flushing head where the water enters (chrome) at the top

Avoiding Chipping

There are a number of methods to avoid chipping out the back of the glass when drilling:

Place a piece of scrap glass under your good glass to avoid break-outs on the backside. By pressing firmly but gently on the glass (not the bit) the bit will go through the upper piece of glass without chipping the back. This can be a difficult process to keep stable when both the pieces of glass are wet.

Another method is to put duct tape under the glass to help minimise chip out.
 Although I find a smooth firm base is best - it could be wood, hard plastic, or any other thin firm material that will not dull the bit when it goes through at the end of drilling.

A further process, used in industry, is to drill from both sides to avoid chip out. Go slowly toward the bottom of the hole. When the hole is almost through, turn the glass over and drill back to front.  It is critical to centre the drilling on the back exactly with the hole on the other side. 

Sometimes the glass is curved and drilling from the back is not easy. This is when a drill press mechanism to stop the bit comes into its own. Before switching the drill on, lower it to the surface supporting the glass. You can adjust the mechanism to stop the press just as it reaches the support surface. Then place the glass under the press and the turn the drill on to begin the drilling.

Don't push hard as you come to the end. Don't push down any harder on the drill press levers than you comfortably can with the tips of your fingers throughout the process. Keep it steady. Listen for the sound of diamond grinding glass.

All these things will help to avoid chipping out the glass at the bottom of the hole.

Drilling holes with copper tube and grit

You can drill holes by using loose grit and a copper tube of the correct diameter. It can take quite a while. You will need to have a chuck big enough to take the tube, or have a means to reduce the tube diameter to the chuck size. Alternatively, use core drills that have had the diamonds worn away.  This is not a common process, now that diamond drill bits are more affordable.

Prepare the glass as for a drill press without a flushing head, so the water and grit are confined. The dam can be putty, plasticine, clay, or other mouldable material put around the area to be drilled.  The grit can be sandblast grit or other abrasive of about 100 to 200 grit.

Drill as normal.

If the core gets stuck in the bit, knock it out with some stiff wire or a nail. Always remove each core right after drilling. They are very difficult to remove if there is more than one in the core of the bit.

Tools

There are a variety of tools that can be used to power glass drills.

Dremmel and similar rotary motors

These are light duty high-speed drills. Those with variable speed controls are especially useful. They work best for small diameter holes. They must have the speed turned down for drilling, especially for larger holes.  These can be combined with a flexible drive shaft for lighter weight.

Drill press

However, the most important thing to have when drilling glass is a drill press. Doing it by hand is very difficult and wears out diamond bits very fast. Dremel and others make drill presses for their tools, as illustrated earlier.

Drilling machines

A portable glass drilling machine 

Purpose-made glass drilling machines are important for larger holes and production work. The important thing about these is that they use hollow core drill bits, allowing the water to be fed through the drill bit directly to the glass-drilling site.

Drill bits

The other tool needed is drill bits. The recommended type depends on the size of hole to be drilled.

• Small diameter holes, up to and including 3 mm require solid bits. These can be  solid diamond-tipped bits.  A number of manufacturers make solid drill bits from 2-6 mm and some (especially lapidary suppliers) make the very small diameter bits from less than 1 mm to 2 mm.
• Larger diameter holes are best drilled with hollow core bits, as less glass needs to be removed to achieve the hole. These can be used with a flushing head or simply by directing water to the drill bit, with a dam to hold the water around the site.
• The bits will last longer if you use a drill press. The press keeps the bit wobble to a minimum and maintains the vertical, both helping to reduce the wear on the bit.

A selection of hollow core drill bits, wire and punches to clear the drill bit of stuck cores, and dressing stones

Hollow core bits

Hollow core diamond bits are of two types:

• One -where a heating process attaches the diamond - is called sintered in Europe and a number of other countries. These are long lasting and more expensive than the alternative. These can be dressed with an aluminium oxide dressing stick to maintain their effectiveness.
• The second – where the diamond is bound to the metal with resins and other chemical attractants – is called bonded in Europe.  These are less expensive and are a good alternative for those drilling smaller quantities of holes.  Bits of this type of bonding wear more quickly and should not be "sharpened" with dressing stones.

A diamond core drill breaks out much less glass at the bottom of the hole than a solid drill bit.  So they are quicker and have a lower risk of creating failures.  Buying better (more expensive) bits is worthwhile as they work much better and last much longer than the cheaper ones.

Water pump and reservoirs

A further tool that is useful to have is a re-circulating pump. This can be a small fountain pump with a flexible spout to aim the water on the drilling site.  A bucket is required to act as the catch basin for the water that comes off the drill and and anoters as the reservoir for the pump.

Drilling glass without a drill press

It is best to have a drill press for drilling holes in glass, but there are ways of doing it with a hand drill.  Make a ring of modelling clay, plasticine, putty or other mouldable material about 5cm/2" in diameter and press it around the drill site. Fill the ring with water and a little diamond coolant if you like. The liquid will cool the drill site and surrounding glass as well lubricate the drill bit.  Adding diamond coolant to your water can extend the life of the bits. 

Use a paint pen to mark the spot where the hole is to be. Without a drill press, starting at an angle with a slow drill speed will stop the bit from sliding around as you establish the drilling point. As the glass surface is roughened, bring the drill to vertical. Move the drill up and down a little as you drill to allow the water into the hole. If you are using a solid or spade drill, a little oscillation keeps the bit from jamming in the hole. Do not do this with a core drill.

A Dremel running at top speed is way too fast. Slow it down with the speed control.

Every diameter drill bit has an optimum drill speed. The smaller the bit is, the faster the speed required.

Hole Placement

The general rule on drilling holes in glass is that the edge of the hole should be further away from the edge than the thickness of the glass. This means that the edge of the hole on a 6 mm thick piece of glass must be more than 6 mm from the edge of the glass.

The calculations are simple arithmetic. You calculate the centre point of the hole by adding the radius of the hole to the thickness of the glass plus at least 1 mm. For example, to drill a 10 mm hole in 6 mm glass, you add 5 mm (radius of hole) to 6 mm (thickness of the glass) plus 1 mm = 12 mm as the minimum distance from the edge of the glass to the centre of the hole.

Remember this is the minimum distance. For safety and durability in architectural or heavy circumstances, an additional margin must be added.

For methods of centring the drill see here

Drilling speeds for diamond bits in glass

Every diameter drill bit has an optimum drill speed. The smaller they are the faster the speed. Drill presses do tend to be on the slow side for glass drilling, but often have ways of altering the speed. So they take a bit longer, but there are big advantages in other respects.

Diameter -- Speed

3-4 mm -- 6000 rpm

5-8 mm -- 4500 rpm

9-12 mm -- 3000 rpm

13-16 mm -- 2500 rpm

17-25 mm -- 2000 rpm

26-28 mm -- 1800 rpm

29-44 mm 1500 rpm

45-64 mm -- 1200 rpm

65-89 mm -- 900 rpm

90-120 mm -- 800 rpm

[Based on CR Lawrence and Amazing Glazing recommendations]

As you can see the larger the diameter, the slower the speed. This is because you are attempting to keep the speed of the diamonds moving against the glass at approximately the same speed, regardless of the diameter. If you did not slow the speed as the diameter went up, the speed of the diamonds would increase, leading to overheating of the bit and reduction in its life.

Playing in the Sandbox

This process provides flowing, abstract images that can be used as autonomous pieces or formed into other objects, such as free drops, bowls, cut for jewellery or into pattern bars.  The appearance provided is unique to this combination of using frit and pressing.

In principle, this process is the same as creating sand pictures.  The process is in three stages: making the box, adding frit, and pressing.

The Sandbox

Determine the size of the box.  It should not be more than two-thirds the size of your kiln shelf depending on thickness.  Thicker glass pressed to 6mm will spread more than thinner.  As a guide, 12mm should have an allowance to spread to about 1.3 times the original size; 19mm should have an allowance to spread about 1.5 times the original dimensions.

Cut two sheets of the same size from clear fusing glass. One will be the front. The other will be the back.

Determine whether the image you are creating will be portrait, landscape, or square.  Orient the sheets in the appropriate way to have the top away from you.  Choose the top piece of the pair and cut two 6mm strips from the designated top.  This gives you a lip to be able to pour the frit into the box easily.

Box formed with bottom and sides glued to back and front.  The filling lip shows on the right.

From another piece of clear glass cut two 6mm strips for the sides.  If you cut them the same length as the side of the glass, they will stick above the back about 3mm. You can cut this off, but it really is not a worry for the construction of the box.  These strips form the spacers to allow the frit to be poured into the box.  Their thickness will determine the amount of frit needed to fill the box.

Get out the back sheet and clean and prepare it for attaching the strips. My preferred method is to glue the bottom 6mm strip on its edge with super glue.  It is advisable to wear plastic gloves when gluing the strips, to avoid sticking your fingers to the glass.  Super glue cures quickly and does not delay the construction of the box.  It burns out cleanly without any health and safety concerns.  Place a thin film of super glue on one edge of the strip.  Attach it to the bottom by placing it carefully at the edge of the sheet.  Do the same for the sides.

  

When the strips are stuck down to the back, place  a thin line of super glue on the top edge of the strips in preparation for attaching the top sheet.  Using a strip of wood placed at the bottom of the backing glass will help in placing the sheet accurately. Lower the sheet from contact with the bottom to the strips forming the sides of the box.

When the glue is cured, inspect the sides of the box for gaps. If there are gaps, use clear Sellotape to seal the gaps in the sides. It will burn off cleanly in the kiln.

Adding the Frit.

Place the box on an easel or other support so it is slightly tipped backwards.  This helps ensure the box does not fall toward you while working on it.  It also allows the frit to slide toward the bottom rather than bouncing off the other frit.

The early stages of filling with the box on a stand

The size of frit you choose to use will affect the final appearance.

·        Generally, powder will appear greyer and more opaque than frit. This is due to the multiplicity of tiny bubbles between the grains of powder.

·        Fine and medium frit provide more clarity than powder.

·        Coarse frit provides the most clarity, but with fizzy bubbles between pieces of frit.

When preparing to place the frit in the box, it is a good idea to take small amounts out of jars and place it into small cups to avoid contamination of the main source of the frit.

Pouring the frit into the sandbox

You can use a jeweller’s scoop or a teaspoon to move the frit from the cup to the box.  Tip the frit into the box above where you want the colour to be placed.  

Using a wire to poke frit through to lower layers.  This also shows  a difference between front and back.

If the frit does not land just where you want it, you can move it with stiff wire that is long enough to reach the bottom of the box.  Gently sweep the frit with the end of the wire toward the place you want the coloured frit to be.

Using a jewellers scoop to add the frit.

Continue adding colours to create the profile and shapes you wish.

You can make additional alterations to the way the frit is placed.  You can poke the frit from one layer into lower layers with a stiff wire by pushing the wire directly downward.  You cannot do this more than 2 or 3 centimetres deep, as the frits and powders become compacted.

A thick copper wire being used to poke down from an upper layer to the lower ones.

When filled to the top or to your desired level, use the fourth strip to close the box.  If full, glue the strip to the top.  If not full, cut strip to the length needed to drop into the opening of the box.  Place a couple of drops of super glue on the top of the already placed strip to keep it in place while moving to the kiln.

The Pressing

Prepare the shelves

You will need two shelves for each pressing. One is the base to hold the glass and the spacers.  The other is to provide the weight to press the glass thinner.

Clean off old kiln wash from the shelves. Experience shows that adding new kiln wash over old for this process promotes the sticking of the kiln wash to the glass.  Add new kiln wash that performs well at extended times at upper temperatures.  I find Bullseye shelf primer works very well.

Once partially dried, with the pink beginning to pale, you can smooth the surface brush marks.  Some use balled up material such as tights to rub over the surface.  I find very good results from rubbing lightly over the kiln washed surface with a sheet of paper between the palm of my hand and the shelf.  The advantage of doing this smoothing while slightly damp is that no dust is created that needs to be cleaned away.  The disadvantage is that too much pressure will pull bits of kiln wash from the shelf.

Do not use fibre papers as the separator.  The glass will be moving within the space between the shelves.  It will pick up and incorporate parts of the fibre paper, if used.

If you have shelves of different thicknesses, reserve the thickest shelf for the upper, pressing one.  If all your shelves are the same size, put a second on top for adequate weight, or add heavy bricks or a steel weight to the top shelf.  (Note: if you use bricks for weights, they need to be dried first.  A two-hour to three-hour soak at 95C should be sufficient.)

Placing

Place the sandbox centrally on the shelf.  If you are doing more than one, ensure there is plenty of space between the pieces and from the edge, so they don’t contact each other, or drip over the edge of the shelf.  The allowances given for the size of the sandbox are a guide.

Two sandboxes placed on separate shelves

Place spacers of the desired thickness around the four corners of the shelf to restrict the extent of thinning.  This also regulates the evenness of the glass across the whole surface.  Usually, 6mm is a desirable height for the pressing.  Other thicknesses can be chosen for different purposes.  The spacers can be steel washers, although they will spall in the cooling stages of the firing.  If you have pieces of ceramic of the desired height, they can be used.  Fibre paper stacked up to the appropriate height are surprisingly robust spacers.  They also provide a cleaner set of spacers than steel.

A corner of the shelf with the 6mm fibre spacer

Place the upper shelf gently down onto the glass piece. The glass at this stage is taking the whole of the weight of the pressing shelf.  The shelf must be placed both gently and evenly down onto the glass to avoid breakage.

Check that everything is in place. This may require additional, directional light such as from your mobile phone or a torch.  It is now ready to fire.

The Firing

This assembly of materials has a lot of mass.  It is 2 to 3 times the normal mass for a standard firing.  

Pressing shelf placed on top of the glass sandbox

This promotes variations in practice:

·        Even with this additional mass, you can fire quickly.  This is because the glass is in small pieces and that the mass of the shelves gains heat slowly. 

·        The greater mass does require longer soaks than a normal fuse firing. 

·        The upper temperature for a full fuse is required to get the glass to a sufficiently low viscosity to allow the glass to move.

·        The long soak at the top temperature does not promote devitrification as in normal fusing.  My speculation is that the glass is not exposed to the air, so the devitrification cannot form. 

·        A further difference in a pressing firing is that the annealing can be at the rate for the final thickness of the glass.  The mass of the shelf and weights above the glass means the glass is cooling evenly from both sides, unlike normal fusing.  The glass may be cooling more slowly than programmed, but the programmed rates limit any possibility of too rapid a cooling.

A schedule for a 12mm thick Bullseye piece with a 19mm upper shelf might look like this:

300°C/hr to    670C       for   180 minutes

300°C/hr to    816C       for   180 minutes

AFAP       to    482C       for   180 minutes

55°C/hr   to    427C       for   0 minutes

110°C/hr to    370C       for   0 minutes

200°C/hr to    50c         for   0 minutes

Off

A piece of 19mm should be slower:

150°C/hr to    670  for   240 minutes

150°C/hr to    816  for   240 minutes

AFAP       482  for   240 minutes

45°C/hr   to    427  for   0 minutes

90°C/hr   to    370 for   0 minutes

180°C/hr to    50    for   0 minutes

Off  

The schedule for glasses other than Bullseye only needs to have the top and annealing temperatures altered to the ones appropriate to the glass.

Results

The pressed glass will have the texture of the shelves on both sides.  Normally, no kiln wash will be stuck to the glass.  If there is kiln wash to be removed, you can do this by abrasive means – sandblasting, diamond pads, wet and dry sandpapers or Dremel style tools.  It is important to keep the glass damp during this process.

If the surface of the glass is without sticking kiln wash or other marks, you can use it with the matte surface.  You can also fire polish the piece, once you have thoroughly cleaned it.

Alternatives

Tape box together

After super gluing the bottom and side strips, you can bind the box together with clear Sellotape.  Pull off at least three strips of tape and set them where you can reach them easily.  Place the upper sheet on the prepared base. Move the box to the edge of the work surface so a little of the box hangs over.  The first stage is to place a strip of tape at right angles to the side to bind the top to the bottom.  Do this for each of the three sides.  When the top is securely attached to the base and sides tape along the length of each of the three sides. 

This shows on the lower left a loosened piece of sellotape on the edge of the sandbox.

This process avoids any difficulty in attaching the top.   Attempting to use only Sellotape to bind the box together is very difficult and requires at least three hands.

Spacers for the frit

Spacers do not always need to be strips on edge.  The spacers can be one or two wider strips placed on their sides to provide the needed height.  They can be coloured, forming a border; but remember the border will become curved. The strips will need to be glued to the back.  The top can be attached with super glue, or taped to the sides and back.

Pressing without a box

It is possible to use the pressing technique without a box or frit.  You can arrange clear and coloured cullet on the shelf.  The arrangement needs to be such that there are no gaps between the pieces.  This means that the glass will probably be 3 to 4 layers thick.  Be careful to avoid creating thick layers of dark colour by interfiling clear. Place the spacers at the corners of the shelf in the thickness desired and fire.  The slower rate of firing (as for 19mm) should be used.

This sandbox process is a combination of arranging frits and pressing.