Diagnosis of Cutting

If your scoring and breaking of your glass is not going well, you need to diagnose the reasons.  There are always a lot of suggestions that warming the glass will solve the problem. Yes, warming glass may help. A discussion of the effect is here. But it will not overcome any faults in the basic skills of scoring.

A lot of images, shown on the internet, of straight line scores failing to break along the score, indicate some possible elements in scoring that lead to these unwanted break-outs. 

One possibility is you are using too much pressure. A discussion of the amount of pressure required is here.  You should be scoring to the pressure required, rather than any sound that may come from scoring.  This is emphasised when cutting opalescent glass.  The correct scoring pressure makes almost no sound or only a gentle rumble as it cutter moves over the undulations of the glass.  The most frequent reason for more difficulty in breaking opalescent glass is excessive pressure while attempting to get the same sound as from transparent glass.  There are even a few transparent glasses that make little or no sound when being scored with the correct pressure.

Another common problem in scoring is keeping an even pressure throughout the score.  It can be difficult to keep the pressure even on complicated cuts.  When the cartoon has multiple curves or deep concave lines, it can be difficult to keep the pressure even as you move your body around to follow the line.  One piece of advice I received early on in my learning was to rehearse the score allowing the cutter wheel to move along the score line with virtually no pressure.  This shows how the piece of glass needs to be oriented to ease your movement around the glass to make the score.

Slowing the cutting speed can help to keep the pressure evenly distributed along the score.  Straight lines are often scored quickly.  But, even on straight lines, slowing the speed can make the pressure more even throughout the score.  It can also avoid variable speed during the scoring, which leads to different forces being placed on the glass.  The pressure may be consistent, but the effective pressure is greater when slow than when fast scoring is used.  If the speed is variable, the effective pressure differs along the score line.

A fourth thing that may be happening on straight lines is that the cutter wheel is at an oblique angle to the direction of the score.  This will often be heard as a scratching sound as you move along the score line.  This can be overcome by a gentle pressure against the straight edge you are using to align your score.  Of course, the straight edge needs to be held firmly to avoid having it move.  Allowing the head of the cutter to have a little freedom of movement also helps keep it parallel to the straight edge.

All this is merely speculation about your scoring practice.

You need to get someone to observe you scoring.  They do not need to be experts, nor other glass artists.  They just need to be observant. Tell them what you are looking for in each of the four elements of scoring and have them observe only one thing at a time.

First get scales that you can zero when you have a small piece of glass on it. Score without touching the glass. Have the observer tell you if the pressure was consistent throughout the score, and if you are in USA, whether the pressure was above 7 pounds or below 4 pounds. (For the rest of the world 3kg to 1.8kg). Practice until you can score consistently at about 2.2kg (ca. 5 pounds).

Second, have the observer stand a little distance from you. Score toward the observer. They need to observe whether your cutter is perpendicular to the glass while scoring and if there is any variation.

Next, they need to tell you if your head was directly above the cutter all the way through the score. They will be able to see whether your eye is directly above the cutter

Is your body behind the cutter, or do you use your arm to direct the cutter?  The observer will be able to tell that when you are scoring curves. The most consistent speed and pressure is delivered when the cutter is steered from your torso, rather than your arm and wrist.  It slows the scoring action, gives smoother curves, and more even pressure.

The last element, you can do yourself.  Once you are doing all the things above, you will be able to hear any scratching noise, rather than the gentle creaking noise of an even score with adequate pressure.  If the scratching noise is intermittent or only at one point, the likelihood is that you are twisting the cutter head, so the wheel is not in line with the score line.

Adjusting Cut Runners

There are a number of types of cut running pliers.  These photos show some of them. 

The apparently most popular is this:

Cushions

It is frequently difficult to find replacements for the plastic cushions that come with a new pair of cut runners.  People resort to a number of means to provide a substitute.  Some wrap electrical tape around the jaws, others use fabric bandages (Elastoplast/band aids).  I have even used the liquid plastic that is designed for coating tool handles.

However, if you adjust the cut runners appropriately, you can use them to run your scores even without cushions.  The purpose of these cushions is only to compensate for too much pressure in running the score.

Use without covers

You can run the score without cushions by using the adjustment screw on the top jaw of the tool. Yes, it does tell you which is the top jaw without having to check the end of the runners, but it has a more important use.  It is not just a pretty cool way to tell which is up. 

Its purpose is to adjust the width of the opening so that it provides the appropriate amount of bending force no matter how much pressure you exert at the handles.  If you are running scores in three-millimetre glass, set the jaws to that width by turning the screw until the jaws are that width apart.

Place the jaws in line with the score, aligning the mark on the top jaw with the score line and squeeze the pliers.  As you squeeze, the curved jaws provide enough bending force to run the score without over stressing the glass.  It is the adjustment screw that limits the over-stressing of the glass during the running of the score. Yes, you may not be able to run the whole length of the score this way, but you can repeat from the other end and that is usually enough to complete the running of the score.

You can continue to use cushions of various sorts with this adjustment for thickness, but I found that these were not necessary when the runners were properly adjusted.  In fact, I found that soft cushioning made more difficulties than using them with the bare metal.  I discovered this during the period of using the liquid plastic coating as used for tool handles.  I dipped the jaws multiple times to give a cushioning effect and it worked fine.  The cut runners continued to work even after the coating had worn off.  It was then that I realised I could control the running pressure more directly than by having a cushion between the glass and the jaws.

Setting the spacing

An easy way to set the correct opening of the jaws is to test against the glass you are about to score and break.  Place one side of the jaws against the edge of the glass. Slide that corner just a few millimetres over the glass.  Turn the set screw on the top of the jaws anticlockwise until they are fitting the glass snugly.  Back off a half turn (clockwise) so the jaws move easily along the edge.  This is now set to run the score on this glass. 

Open the jaws and place the centre mark in line with the score.  Close them gently and you can observe the arc of the jaws above the score line. Squeeze the handles and the score will run along the line away from the cut runners.  As you have adjusted the opening, no matter how hard you squeeze the cut runners, you cannot add more pressure.  This means you avoid crushing the glass.

The principles

The curve of the jaws is designed to provide the bending force required to run the score.  The radius of the curve has been designed to provide the correct bending pressure for differing sizes of glass.  The most common ones are useful for glass up to, but not including, 6mm glass.  The screw adjustment provides compensation for differing thicknesses of glass.  Setting the width of the gap to match the thickness of the glass prevents the application of too much pressure.

Thicker glass

For thicker glass you need cut runners with wider jaws.  These usually are fitted with three points to apply the breaking pressure - one under the score and one each side of the score on the top.  Again, these are adjusted to be just less than snug to the glass before applying the pressure.

One example of  cut runners for thick glass.  There are a variety of others.

Polishing Edges by Hand

 This post is about hand polishing edges, although the most common method seems to be a fire polish.  But the other, less considered, method is to polish by hand. 

Advantages of cold working

• Hand polishing edges does not need to take long, as the area to be polished is very small in relation to the whole piece.
• The effort of manual polishing is rewarded by kiln time saved for additional pieces that can be produced while refining the edges of the current piece.
• There is much less risk of anything going wrong in hand work than in re-firing the piece.

Equipment

Handheld smoothing pads and water are all that is required. 

The pads are normally diamond ones and should start with 60 grit, if a lot of glass needs to be removed, but 100 grit will be good to start with for smoothing a ground edge.  Then double the grit number (which is a halving of the particle size) to remove the coarser scratches and finally a 400 grit.

Then move to a 220 grit resin smoothing hand block.   These hand pads with diamonds encased in resin, are similar to this from HIS Glassworks.  

Credit: HIS Glassworks

They give the edge a satin finish, and that may be enough to be so pleased with the appearance that you do not need to do any further work.

In all these stages you need to have the surface damp.  When a white paste appears around the grinding area, it indicates that more water is needed.

If you want to go further toward an optical finish, you can use a cerium impregnated hand pad such as this. 

Credit: HIS Glassworks

For cerium impregnated pads you need less water than previously, to be able to generate the heat required to cause the chemical reaction between the cerium and glass.

You, of course, can use machines such as a handheld rotary tool.  You can get small diamond and cerium pads for these from many suppliers such as HIS Glassworks or Eternal Tools.  You will need to turn the speed down to almost the minimum to do the work needed without generating too much heat, or spraying water all over the workspace.  Most importantly you need eye and breathing protection against glass particles and dust when using rotary tools with no guards on them.

 

 

Soldering Iron Maintenance

“How do I maintain my soldering iron?  I see so many different methods online that I find it confusing.”

Regular cleaning

There at least two reasons for regular cleaning of the solder bit.

The first is to avoid the build-up of carbon and other contaminants which impedes the transfer of heat from the soldering bit to the solder and surfaces to be joined.

Many soldering stations come with a sponge which, when wet, is used to quickly swipe the iron's tip clean. A small amount of fresh solder is usually then applied to the clean tip in a process called tinning.

The second is to maintain the soldering bit in good condition.

The copper that forms the heat-conducting bulk of the soldering iron's tip will dissolve into the molten solder, slowly eroding the tip if it is not properly cleaned. As a result of this, most soldering iron tips are plated to resist wearing down under use. To avoid damaging the plating, abrasives such as sand paper or wire brushes should not be used to clean them. Tips without this plating or where the plating has been broken-through may need to be periodically sanded or filed to keep them smooth.

To avoid using abrasives, cleaning with sal ammoniac is recommended. This comes in a block. You rub the hot soldering iron bit on the surface. As the surface becomes hot, it begins the cleaning process, noted by the smoke rising from the block. When the block under the bit becomes clear, the bit will be clean and can be tinned as above. If this is done at the end of each session of soldering, the bit will last longer and will be ready for soldering immediately when you next need to use it.

Turn off the Iron

The most important element in the deterioration of soldering iron bits is long idle times. This is where you leave the iron on, and not in use, for a long time.

Have everything ready when you start soldering, so the iron will be used continuously, and will not sit there building up heat, while you get ready to use it again. An idle iron without internal temperature control will keep heating to its maximum capacity and, without anything to transfer the heat to, it will start burning off the tinning after a short while. If you will not be using the iron for a while turn it off until you are ready again.

Tinning

If a bit has not been properly tinned, solder will not wet to it. Without solder on the bit heat transfer from the bit to the work surface may become extremely difficult and time consuming, or even impossible.

You will understand that proper wiping and continuous wetting is important and a lot easier than continually having to clean and re-tin the bit, especially at the risk of damage to the plated surface because of accidentally scratching, or over abrading it.

When you notice that an iron is not performing as well as it did when it was new you will find that poor thermal transfer from the soldering bit to the work is usually the cause. Improper care and maintenance and the lack of a periodic cleaning of the bit can cause a layer of oxides to form, which will inhibit the transfer of heat through the bit.

These factors are reasons why keeping a film of solder on the bit (tinning) is important in maintaining the long life of the soldering bit.

Courtesy of American Beauty Tools

Cleaning the whole Bit.

Each soldering bit has a shank which fits into a heating collar of one kind or another.  The bit should be removed at periodic intervals and the build-up of oxides should be cleaned from the shank.  The oxides inhibit the transfer of heat from the elements to the soldering bit.  This cleaning work, of course should be done when the iron is cool.  You can use fine abrasives on the shank to remove the oxides.  You can also make a tube of fine sand paper to clean the inside of the heating collar.  This should not be done on ceramic heated soldering irons such as the Hakko.

Wattage

Another element in the maintenance of soldering irons is to have an iron of high enough wattage to readily melt the solder and be able to reheat fast enough to maintain the necessary melting temperature. An iron with enough power will reduce the strain on the heating element of the iron and the strain on the user while waiting for the iron to catch up.

For example, an 80-watt iron is sufficient to solder with, but it will continue to get hotter, as it has no temperature control, becoming too hot for stained glass soldering, and often causing breaks in the glass. An iron of this type is often used with a rheostat in order to prevent overheating while it is idling. However, this  reduces the power to the iron and so increases the time needed to recover sufficient heat to continue soldering.  Also, a rheostat only slows the heat up, it does not limit it, so eventually the iron will still become too hot if left to idle.

Most temperature-controlled irons seem to be produced in 100 watts or higher. These irons attempt to maintain a constant temperature. Their ability to do so depends on the wattage and the amount of heat drained from the bit during soldering. The temperature-controlled irons are normally supplied with a 700°F bit (identified by the number 7 stamped on the internal end of the bit) and is sufficient to melt solder without long recovery times. You can obtain bits of different temperature ratings, commonly 800°F and 600°F. The 800°F bit is particularly useful when doing a lot of copper foil soldering, because it recovers to a higher temperature, allowing much more continuous soldering action.

An increasingly popular soldering iron has a ceramic heating element, requiring less time to recover heat, and with a lower wattage.  Most of these have a temperature dial for setting the soldering temperature, and most find 410C suitable for copper foil work, although 380C may be enough for leaded glass soldering.

You can also get several sizes of tips for different detail of work.  Upon first sight a fine tip would be useful for fine copper foil work.

But fine tips loose heat quickly, requiring the user to wait while the tip regains the required heat.  A 6mm to 8mm wide bit is useful to maintain the heat during the running of a long bead.  Of course, the bit is wider than the bead being run, but the solder has enough surface tension, while molten, to draw up into a bead on the copper foil without spreading – unless too much solder is being applied. Really big bits of 12mm or larger are not practical – long initial heat up times, and too much area is covered, even though there is enough heat stored for really long solder beads.

Revised3.1.25

Cutter Wheel Angles, 1

The Effects of Wheel Angles on Glass Cutting

The wheel of a glass cutter does not “cut” the glass. The objective is to create a crack or "fissure" along which we expect the glass to break when we bend it. The idea is to produce a fissure which is continuous, and of uniform depth, without creating a flaky score line full of loose glass chips. While the wheel angle is only one of several variables which influence the quality of the fissure, it is the best place to start. The other main variables are wheel diameter and cutting pressure.

The angle of a wheel is identified as the included angle to which the apex is honed. This means it is measured from one beveled face of the wheel around through the wheel to the other face. Thus the angle between the wheel and the glass on a 150° wheel will be 15° on each side.
When downward pressure is exerted on the wheel rolling along the glass, forces are created which radiate down and to the side trying to shear or separate the glass along the surface. These forces are in a downward direction with little angle to the side when an appropriate angled wheel is used. If these forces are great enough to overcome the inherent compressive conditions near the surface, a crack or fissure will be generated along the path of the wheel. The direction of these shearing forces is determined by the wheel angle.

A wheel with a large or blunt angle produces shearing forces that tend to be directed downward more than to the side. It would require a great deal more cutter pressure to create enough lateral force to overcome the compression in glass. This explains why a cutter requires more pressure as it gets older. The apex tends to flatten so its effective angle becomes greater.

With a very sharp wheel angle, the shear forces are directed more parallel to the surface of the glass. This might suggest it is easier to produce a fissure with a sharp wheel than a dull one. The shear forces are directly opposing the compressive condition near the surface of the glass therefore, requiring less downward pressure to make a crack. But a sharp wheel tends to cause chips and a flaky score. Also, when the shear forces run close to the surface of the glass they are more likely to cause a lateral crack which then breaks out to the surface, creating a chip. You can see these chips leap out of the glass a short time after scoring. Again, the compressive condition of glass near the surface literally squeezes the fissure closed, spitting out loose chips. They can be seen lying on top of the glass.

Part 2

Based on information from the Fletcher Terry Company.

See also wheel angles

Revised 23.12.24

Cutter Wheel Angles, 3

The effect of glass thickness on cutting

Most of the thicker glass being used today is produced by the "float" method. In this process the glass travels horizontally from the furnace, through a molten tin bath, through annealing lehrs, then continues on rollers where it is inspected, scored and broken into the sizes required. The thickness generally dictates how fast the ribbon of glass moves. The thicker the glass, the slower it is processed and the more effective the annealing. This applies to thicker art glass too.

The key to subsequent cutting float glass is the annealing cycle. Thicker glass tends to have less compression at the surface and tension in the interior. As a result, the glass cutting wheel encounters less resistance to producing a fissure with the shearing forces. However, this means the glass surface will chip more readily. Therefore, a larger wheel angle is required to prevent chipping. It is also common practice to use a larger diameter wheel and larger angle so the fissure can be driven deeper without chipping.

Part 1

Part 2

Prepared from information provided by the Fletcher-Terry company.

Cutter Wheel Angles, 2

Effect of wheel angles on the cut edges of glass

Another factor to consider in selecting the proper wheel angle is the "edge". The objective of good glass cutting is to produce an edge which is flat and relatively free of irregularities such as "shark teeth".

Shark teeth are the occasional deep spikes in the edge and are accompanied with flakes or tiny chips on the surface. A three mm thick glass scored with a sharp wheel (114°) will produce this effect. This edge irregularity may lead to failure during the life of a window.

A three mm thick glass scored with a proper angle (134°) of wheel, will produce a fissure that is made up of individual "hackles" which overlap one another. They have a unique semi-circular shape and indicate the direction of the cutting wheel. With proper pressure the edge will be relatively free of irregularities and without shark teeth.

Part 3
Part 1

Prepared from information supplied by the Fletcher-Terry company

revised 23.12.24

Deep inside cuts with turntable

Deep inside cuts can be assisted by using a lazy susan – a turntable affair, similar to a cake decorating turntable.

image credit: Amazon

The first question you have to ask yourself is whether you should make such deep inside cuts or redesign the piece to avoid creating such fragile shapes.

OK. You have decided to go ahead with your plan in spite of good advice. Put your cartoon onto the turntable and the glass over it. If the glass is too dark or opalescent, make a template and mark the glass. Adjust the starting point, put one hand on the glass and cartoon, and turn the glass instead of yourself to get round the score with ease.

You still have the task of breaking out the glass from the score line. This is the subject of another tip on concave curves.

revised 23.23.24

Cementing Brushes

image credit: stainedglasscraft.co.uk

Use stiff, but not hard bristle brushes for cementing. Nylon scrubbing brushes have a good stiffness without being too hard. Some natural bristle brushes are very hard and scratch the came excessively. In general, moderately stiff brushes with about 1 1/2" bristles are fine for cementing. There should be space between the bristle bunches to aid cleaning.  As they do not last very long, they should be cheap, but with firmly attached bristle bunches.

Cleaning the brushes is very simple. The action of rubbing the cement under the leads with whiting causes a natural cleaning action to take place. As the bristles flex back and forward over the came, the cement is forced upward toward the handle, and then outward between the bristle bunches. Only a little effort is required to finish the cleaning: push a rounded stick between the bunches to move out the remaining cement. You now have a clean brush for the next job.

The alternative is keeping the brush in water, but this presents the problem of getting rid of the water (oil and water do not mix) before beginning to cement. As the water will emulsify with the linseed oil, it will be carried into the putty, leaving gaps in the cement when the water eventually evaporates. The cement will eventually harden, even though in water, as linseed oil cures by creating an organic polymer through oxidisation. It can also rot the wood handles.

Keeping the brush in mineral spirits does keep the brush flexible but requires drying/evaporating the spirit before beginning the cementing to avoid the residue of the spirit creating cement that is too thin at the start. This can be a really messy problem!

If you choose the “dry” method, it is important to keep the brushes free of hardened cement as it will scratch the leads badly, if not the glass too. Most brushes will only last 5-10 uses, and as they are not expensive, should be easy to throw away.

Grinder Bit Chipping Glass

Credit: Techniglass.com

A new grinder bit chips the glass excessively, especially with a coarse grit. It can also be the result of a bare spot on the bit.  You need distinguish between these states.   Check the surface of the bit.  If there are any small bare spots, the bit needs to be replaced.

 

Credit: WWGrainger

The best thing to do with a new coarse bit is to treat it with a dressing stone.  This is a block of aluminium oxide which can remove high points on the bit, and clean up the spaces between the diamonds on the bit.  It is relatively inexpensive to buy and lasts a long time.  The dressing stone can be a brick, although it is not as efficient because it is much softer.  

If the grinding bit still chips off too much glass from the edge, you need  a finer grit.  It will not take glass off as quickly as the coarse one, but it eliminates or reduces the chipping.  The three common grades are: coarse, standard, and fine.  It is a good idea to maintain a stock of the medium and fine grit grinder bits as replacements for worn ones.

Core drill bits

Credit: JMbestglass.cn

Using core drill bits needs a drill press. It keeps the drill bit steady and avoids breaking the core which plugs the hollow part of the bit.

Oscillating a core diamond drill bit is not the correct procedure. Oscillating the bit creates two undesirable things.

• It breaks off the core that  is being drilled out, plugging the drill bit, and blocking the cooling water being pumped to the drill bit.  This means the bit heats up and loses some of the diamonds. Additionally, it can heat up the glass so much that it breaks. If you are not using a flushing head with your drill, you will need to raise the bit a little from time to time, allowing water to the grinding surface. 
• Starting at an angle or oscillating with a core bit wears out the sides of the drill bit more quickly than necessary. Core drill bits need to be applied directly and vertically. This is why core bits do best in a drill press. It holds the bit in a vertical position without breaking the core being drilled out, or prematurely using the diamonds higher up the bit.

Credit:  Lawson-HIS

There are generic drill presses available for holding Dremel-type craft motors and hand-held drills. They are inexpensive and make the drilling process so much more certain to regulate the pressure. It also makes an easier start without skipping over the glass. They are so inexpensive that a few holes without skipping will pay it.

Credit: Bhole ST1542 Pico Dril

Drill speeds should be varied according to the size of the hole being drilled. This is important with the high speed Dremel-type motors.  Larger holes need a slower speed than smaller ones. The rim speed of a small bit is nearer the rpm of the drill than a larger one, because the larger one travels a greater distance per revolution than a small one. A listing of recommended speeds is given in this blog.

Hollow core diamond bits are of two types:

•     One, where a heating process attaches the diamond, is called sintered in Europe and other countries.
•     The second, where the diamond is bound with resins, is called bonded in Europe.

They seem to have different designations in North America.

Bits of the first type are longer lasting, and more expensive. These can be “sharpened” with an aluminium oxide dressing stick to expose new diamonds and maintain their effectiveness.

Credit: W W Grainger.com

Bits of the second type wear quickly and should not be “sharpened” with a dressing stone. The normal wearing away of the bonding material exposes the new diamonds.  Dressing them wears away the diamonds that could be used in drilling.

Another advantage to core bits, is that a core drill grinds out much less glass from the hole than a solid drill bit, so it takes less time to drill a hole.

One disadvantage, especially on core drills of 5mm and less, is that the core needs frequent cleaning out of the cores that get stuck inside the drill bit. To maintain efficient and effective drilling, the core needs to be poked out from the bit from the base toward the drilling surface.  This applies whether water is being pumped through the core or not.  Without clearing the core, more pressure must be used to continue drilling, resulting in larger break outs as the hole is completed, and more breaks of the complete piece.

Home Made Frit Maker

Recently, when looking for a small frit maker, no shop had one in stock.  Having heard of making one from plumbing pipes, I went in search of material.  I came across stainless steel pipe and caps.

 

The practical size seemed to be 50mm.  Short sections of threaded pipe were available with matching caps.  That forms the containment cylinder.

 

A threaded 25mm pipe and cap can be fitted loosely into the larger one, and so forms the plunger or piston.

 

There needs to be a handle.  It could be a turned piece of wood to fit the inside of the pipe.  In this case, I obtained a reducing connector to fit a 12mm pipe to the plunger and topped it with another cap. 

The whole was put together in less than a minute, once all the parts were assembled.

The completed frit maker

Galvanised pipe would be cheaper but carries the possibility of introducing zinc into the frit.  Stainless steel risks introducing non-magnetic particles into the frit.  As I sieve out powder from my own frit making before washing, I am not too concerned about steel contamination.  If you want powder, use uncoated mild steel so the contamination can be drawn out with a strong magnet.

Silberschnitt Runners

 
The use of the highly acclaimed Silberschnitt cut runners requires a bit of experience to get the best from them.  They are at their best on inside curves and thin strips.  This is a few notes on how to make best use of the runners.

 

 
Always use the runners with the name visible to you.  This is the right way up.
 

Make use of the adjustable bar at the top of the runners.  Rotate the adjustable bar to be at right angles to score line.  This means the pliers do not have to be at a particular angle to the score line, which has advantages in tight areas.
 

Each press of the handles opens only a small run of the score.  Excessive pressure risks breaking glass and reducing the life of the pads

 

Move the runners along to the front edge of the opened score and press again.  Work your way all along the curve adjusting the angle of the bar as you go.  This progressive opening of the score line gives a break with almost no flares.
 

These runners are much better than the plastic ring star breakers, because there is much more control over angle of pressure.
 
Note: make sure you get replacement pads when you buy, they are robust but do wear out over time.).
 
 
Silberschnitt running pliers are excellent but require some experience to get the best from them.