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.

Pricing Classes

There are lots of things related to preparing to give instruction whether for a few hours or days.  This is only about the easier element – calculating the costs.

Costs – these are both variable and fixed costs.  These are important in calculating costs per student.

Variable costs. These are the expenses you have no matter how many may attend. E.g.:

Tools – how many people do you intend to cater for?  What kind of tools do you need? Does everyone each need the tool? Can some doubling up occur?

Advertising, promotion – The costs in printing and time to distribute leaflets and other promotional efforts.  Costs of advertising online or in print.

Course Preparation and delivery time – Every course requires time to plan the course and organise the materials, take bookings, set up at venue.  The amount of time you spend delivering the course/class needs to be claimed.

Travel expenses and time to get to the venue.  Mileage expenses only cover the transport costs, it does not include your time.

Venue costs – If you have been invited, check the venue is free to you.  In some cases, you will have to pay for the venue and this needs to be added to your variable costs.  In this case, I am assuming the host is providing the venue free.  If it is your own venue, you should add a sum to cover the overheads of your premises at the very least.

Fixed costs. These are the costs for each person on the class/course.

Materials and consumables. The materials the students will use varies directly with the number of people.  Any provision of food, refreshments will depend on the number.  Any handouts or demonstration materials are also related to the number of people.

Price.  The price of the course/class will depend on the costs and the profit you wish to have as well as what the market will stand.

Working out the Costs

I will go through the main areas of costs and give examples to demonstrate.  Not all these areas will apply.  When they don’t the cost is zero.

Equipment

You can estimate the number of classes over which the tools and any other equipment will last. 

Example

Say, you plan on 6 students and the cost of the tools for that many will cost 440.00 and you expect the tools to last for 10 courses. (you will have to top up on tools due to loss during that period, so you may want to add an additional sum to your calculations.)  Ten classes of 6 gives you 60 people to spread the cost across.  This gives you an individual cost of 7.34 on this basis.

Cost sub total:  7.34/student

Promotion and administration

The promotional effort includes time to prepare, costs to produce and time to distribute.  You can prepare the advertising before the pricing begins, so that amount of time can be known before you start.  The costs of printing or publishing can be determined by getting estimates.  The amount of time you spend in distributing leaflets, and in using the internet to advertise needs to be included in the promotional time. 

I am going to assume your administration of the applications and payments for the course are taken by the venue.  If you do them, you need to add a notional amount of time to cover that aspect of delivering a course.

Example

Say, you have determined the printing and advertising is going to be limited to 50.00.  In addition, you are going to spend 5 hours distributing the printed leaflets and 10 hours of social media time promoting the classes.

As you can see, your time is going to be a large part of this promotional work, so this is the occasion you must decide how much you are going to pay yourself.  There are ways to do this.  Here is one.

Say you have decided that you need to pay yourself 20.00 per hour.  This is the figure that needs to be applied to all the time-based costs you incur in preparing and delivering the class.

The promotional costs for the course are going to be 50.00 plus the 15 hours (distributing leaflets and 10 hours social media) at 20.00 (=300.00) totalling 350.00.  Will this promotion be useful for subsequent classes? Probably not.  This means that you can’t spread the cost over more than one course unless you redesign the materials in some way.  It may be that subsequent classes will require less effort to promote them, but don’t count on it.

Assume your promotion cannot be spread over more than one course, which is the most likely.  This means the cost for each of the six people is 58.34

Cumulative cost sub total:  65.68/student

Preparation

You need to prepare a course syllabus or outline at least.  This will guide you in the presentation of the class and will help you determine the equipment and materials your students will need.  Any additional materials and equipment needed for the course will need to be added to your initial equipment calculations.  You need to keep track of the amount of time you spend on designing the course.

Example

You may have spent 10 hours researching and writing your course.  You can decide that little alteration of the course will be required over the life of the equipment.  This then becomes 200.00 divided by 60 students or 3.34 per student.  You may also have course handouts.  These will be fixed costs as they relate to each student.

Cumulative cost sub total:  69.02/student

Some of these promotional and preparation costs will have to be guesses until experience is gained. How long will the advertising last? One class or more? Will you need additional preparation time each time the class is held?  The answers you give will affect the calculations by the number of students or classes the cost is distributed.

Travel and accommodation

Of course, The travel expenses and time, and the class delivery time will remain relatively constant; varied only by the distance and the facilities at the venue.

Example

The venue is 25 miles away. The travel time is 45 minutes each way. The set-up time is 30 minutes.  The course is for 4 hours and clean-up is 30 minutes.  This means that at 0.50 per mile the expense is 25.00; the travel time is 1.5 hours (1.5*20.00) gives an expense of 30.00 to get to and from the venue.  Set-up and clean-up is 20.00. Class delivery time of 4 hours equals 80.00.  All these on the day costs are 155.00.  For six students, this will be a cost of 25.83 each.

Cumulative variable cost sub total:  94.85/student

Of course, your accommodation expenses for a multiple day course will need to be added, although not the time between class sessions.

Fixed costs are the ones directly related to each student.  These will vary according to venue, style, length etc.

Materials/consumables. The materials the students will use varies directly with the number of people.  The costs of this relate to the materials the students will consume during the class/course.

Example

The glass used by each student will cost 20.00

Additional consumables will be 10.00

Firings for each student will be 5.00

fixed cost sub total:  35.00/student

Hospitality - provision of food, refreshments - will depend on the number. 

Example

Refreshments at the beginning and middle of the course 5.00 each

fixed cost sub total:  40.00/student

Any handouts or demonstration materials are also related to the number of people.

Example

Handouts and examples for students – 10.00

fixed cost sub total:  50.00/student

Student accommodation – this is relevant for those who need to stay overnight either because of their travel or the length of the course.  Normally, this is the responsibility of the student.  It may be that you wish to include the cost of this in the course fee, although that usually makes the course appear to be very expensive.  In this case, I will assume accommodation is the responsibility of the student.

Cumulative variable cost sub total:  94.85/student

Cumulative fixed cost sub total:  50.00/student

Total cost for a one-day, six-person class:  144.85/per student

Profit

You do need to make a profit on this class, or you can’t continue.  You can’t continue with an “at cost” basis, because this is time away from making where you can generate an income.  A small profit margin of 20% is the minimum. It does give you some recompense for your knowledge and provides a small margin for contingencies.

Example.

A margin of 20% on the above example would add 28.97 per student.

Cumulative cost total:  173.82/student

If you feel this does not represent good value for your experience and knowledge, increase the price.  This exercise only provides the base cost level for setting the price.  Also remember that it is easier to reduce prices than it is to increase them.

On the other hand, you may decide that your hourly charges are sufficient profit for the course.  This is not advisable, but is a choice you can make.  You should always be aiming for doing your work on a cost, plus profit basis.  Not simply covering material costs and expenses. Remember your time is also a cost factor.

If you were to feel this is too expensive, there are some ways to reduce expenditure.  The only ones that you cannot reduce are your hourly rate and the profit margin.

Possible reductions include:

Tools and equipment – get the venue to share costs or underwrite costs.

Promotion – reduce your expenditure, or get the venue to take all or most of the promotion costs.

Venue – get them to set-up and clean-up, or better, get the students to do these things.  Get travel expenses from the venue.  Move the venue closer.

Accommodation – get the venue to provide at their cost.

Student numbers – get more students which will reduce the variable cost per student.

But – to repeat – do not reduce your hourly rate, ever.

This is a general introduction to costing, profit, and pricing.  There are a lot of more sophisticated ways of calculating these things, but until a lot of experience is gained, most of the work will be from estimates and guesses.  So, investing in highly detailed methods will not make the pricing more accurate, as all the calculations are based on estimates.

Cutting Lead Came

Cutting came is a gentle process rather than an abrupt chopping effort.
There are at least three kinds of implements in common use to cut lead came.

Lead nippers or lead dykes
Lead nippers/dykes are a kind of adapted side cutters, used for cutting wire and by electricians. But these have the bevel only on one side of the jaws, making them almost useless for anything other than cutting lead. This arrangement only crushes the lead on the cut-off side and also leaves a minimum of lead next to the back of the jaws.

In use, the jaws of the dykes are aligned in the same angle as the heart of the lead, cutting across the leaves of the lead. They do not cut from the top and bottom of the came. These are very quick for right angle or very oblique angles on the came. However they are of little use for acute angles.

Lead knives
For more acute angles, blades are more commonly used. These can be either straight edges or curved blades. The straight edge lead knives are essentially putty knives or stiff scrapers sharpened to an acute angle. This kind of knife is normally wiggled from side to side while applying pressure to work through the came.

Other knives are curved to make rocking back and forth easier. There are a variety of knives such as the Pro or Don Carlos. Some look more like a scimitar than a lead knife! These are used to rock along the line where you are cutting the came.

Whatever kind of knife you are using, be sure to be directly above the knife, looking along the blade to ensure vertical cuts.

Saws
Of course, saws are sometimes used. The blade needs to be coarse toothed to enable the soft lead to drop out of the teeth. These saws can be hand held or table saws. Normally, it is quicker to use lead dykes or knives. However, if you are in production mode, a powered table saw may be worthwhile.

Sal Ammoniac

There are sometimes concerns expressed about the use of sal ammoniac to clean the tips of soldering irons.  My conclusion is that there are no elements of the block that will affect the copper plating of the soldering iron bolt.  It is safe to use this as an occasional cleaning method of soldering iron bolts. This is based on the following information.

What it is

The common term, sal ammoniac, refers to the chemical ammonium chloride.  Sal ammoniac is the archaic name for it. The Romans named it from the ammonium chloride deposits that they collected from near the Temple of Jupiter Amun in ancient Libya.  It is found as encrustations around volcanic fumaroles, guano deposits and in burning coal seams. Notable occurrences include Tajikistan; Mount Vesuvius, Italy; and Parícutin, Michoacan, Mexico.

Wikipedia

Ammonium chloride is the product from the reaction of hydrochloric acid and ammonia.  Ammonium chloride is obtained as a by-product in different chemical processes.  It consists of white crystals that are also available in rods or lumps.  The substance changes directly from being solid to gas with no intermediate liquid state. The gas does not consist of ammonium chloride molecules but ammonia and hydrogen chloride. This shows that the salt decomposes easily. When stored, ammonia is continuously emitted and the substance gradually becomes more acidic.

https://www.fishersci.co.uk/shop/products/ammonium-chloride-99-6-analysis-acs-acros-organics-3/p-3586389

Safety

It is widely used in human medicines as an expectorant, diuretic, etc. and in veterinary medicines to reduce gallstones, so it is a relatively benign material in relation to human health. 

There are some hazards though.  It can cause serious eye irritation on prolonged exposure, and is harmful if swallowed.  The precautions are to avoid eating, smoking, and drinking when using it.  Use gloves and eye protection if you are using it for extended periods. If it gets into your eyes, rinse with water for several minutes. https://www.fishersci.co.uk/shop/products/ammonium-chloride-99-6-analysis-acs-acros-organics-3/p-3586389

It is highly soluble in water, and forms a slightly acidic solution. Its main characteristic that you need to protect yourself against is that it vaporizes without melting at 340 °C to form equal volumes of ammonia and hydrogen chloride gas. https://www.britannica.com/science/ammonium-chloride

The amounts of the gas are small when used to clean soldering irons, but as the gas forms hydrochloric acid in contact with moisture, you should use dust masks rated for inorganic acids.  The amounts are small and generally only cause sneezing and coughing upon contact.

The primary hazard is the threat posed to the environment. Immediate steps should be taken to limit its spread to the environment.

https://pubchem.ncbi.nlm.nih.gov/compound/ammonium_chloride#section=Top

Uses

In addition to medicine, it is used to clean soldering irons. It has uses in jewellery-making and the refining of precious metals.  Sal ammoniac has also been used in the past in bakery products to give cookies a very crisp texture.  In some areas, particularly Nordic countries and the Netherlands, it is still widely used in the production of a salty licorice candy known as Salmiak, or Salmiakki.  Formerly it was used as the electrolyte in dry batteries.  It has uses in fertiliser as a source of nitrogen mostly for rice and wheat crops in Asia. It is also an ingredient in fireworks, safety matches, contact explosives, cosmetics and many other applications.

https://thechemco.com/chemical/ammonium-chloride/

Conclusion

Although there are some mild safety precautions that need to be followed, there is nothing in the sal ammoniac block that can harm the copper coating of the soldering iron tip.

Marker Pens

A lot of us use marker pens on our glass to determine cut lines, indicate areas that need grozing, etc.  These pens have a variety of names – felt tips, Sharpies, paint pens, fibre tips, permanent markers, laundry markers, and many other generic and trade names.

Most, except the paint markers, contain water or spirit based colours. Many of these pigments are reputed to burn away during the firing of the glass. 

Paint markers and the ones that contain metallic colours rarely fire off.  They are more likely to fire into the glass.  Some people take advantage of this fact to quickly add marks that will survive the firing.

I no longer trust anything to burn off. Even if the marks do apparently burn away, the residues are sites for devitrification to begin.

I clean all my marks off before firing.  It only takes the marks to be fired into a favourite piece to convert you to cleaning. If you use paint markers on black glass or coloured felt tip marks on clear, clean it all off before firing.  This removes the chance that the pigment will remain throughout the firing and ensures the glass is spotless when it goes into the kiln.

Glass Cutting Surfaces

There are several considerations about your surface for cutting glass.

Make sure you are putting the glass on a flat surface. If the surface is uneven, it will give difficulties in scoring and breaking.  This means that large sheet timber is an excellent surface.  These boards need to be securely screwed down to the bench structure to avoid any warping.

There is some advantage to having a slightly cushioned cutting surface. This will help accommodate glass with a lot of texture and those sheets that have slight curves in them. 

In this example the user has placed corrugated cardboard under the glass for cushioning, but with a hard surface underneath

Consider ease of cleaning.  As you score and break glass, small shards will be left on the cutting surface.  The tell-tale squeaks as you move the glass indicate there is other glass under the sheet. These shards and any other small almost invisible things under your glass can promote unwanted breaks. Also, if there is glass or other grit on the surface, it may scratch the glass. So make sure you brush the cutting surface clean frequently.

An example of a ready made cutting bench.  It has the advantage of being easy to clean and compact when not in use. 

Think about the size of sheets you will be cutting.  Large sheets often have minor imperfections in texture, or some bowing.  These benefit from a slightly cushioned surface. It also allows the sheets to be put down onto the surface with more confidence that it will not break in contact with the bench top.  But if you are cutting mostly smaller sheets, they benefit from a smooth hard surface to support the whole of the sheet especially when cutting long thin or curved pieces.

An example of a large cutting bench with composition board top surface

Some of the materials used are sheet boards (such as marine plywood, MDF, and other composition boards), short pile carpets,  thin rubber or foam sheets, dining table protectors and pin boards. 

All these are useful for cutting each with advantages and disadvantages.

• Carpets and foam can trap shards of glass, so have to be cleaned very carefully to avoid retaining sharp glass within the pile or foam.
• Smooth, wipe-able surfaces avoid trapping glass, but can be slippery. Choose one with a non-slip surface.
• A slightly cushioned surface is good for large sheets
• Smaller sheets of glass are best cut on smooth hard surfaces, providing support for all of the glass sheet.

You can also consider, as in the example above, the use of different cutting surfaces on top of the larger smooth and hard surface.  This allows adaptation to the needs of your glass without duplicating surfaces.

Before scoring, clean the glass on both sides, to ensure any sounds you hear when moving the glass relates to glass shrds on the bench rather than grit on the glass.  At the very least, clean along the cut line, as this makes the action of the cutter smoother. The grit on the glass actually interrupts the action of the wheel, so you get a staccato effect in the score line.

Stencils vs. Saw

Saw

Frequently when people want to make a complicated shape they resort to a saw to create the shape.  This is used in both stained glass and fused glass work.  Although it may be necessary in stained glass applications, it is not as necessary in fusing.

One of a variety of saws

Stencils

There is an alternative to an expensive saw – stencils and frits.  You can make a stencil from stiff card. Place the stencil in the appropriate place. Then sift powder or sprinkle frit over the stencil.  Lift carefully and the shape is there ready for fusing.

Example of sifting powder over a complicated stencil

To get the depth of colour obtained from sheet glass, you need to apply the powder or frit to at least the thickness of sheet glass. This also means that you need to go to a full fuse with the powder or frit on the top surface.  You can, of course, later cap and fire again.

Example of the cutting of a stencil

More guidance on stencils is available here: 

Make Your Own Stopping Knife

“Stopping knife” is a traditional term for an oyster knife with a weighted end.  This makes it a multi-purpose tool that manipulate glass, dress lead came, act as a fid, act as a putty knife, and become a hammer.  It also stands up on its own.  I find it the single most useful too in leaded glass panel construction.

This note is how to get from here:

To here:

The process relies on the low melting temperature of lead.  This means that you can use stiff paper wrapped around the handle of the knife to contain the molten lead until it cools.

First you set the oyster knife into a vice and cut two dovetail joints at right angles to each other into the end of the wood handle.  This will insure the lead is firmly grasped by the wood and will not come loose during use.

I do this with a fine bladed saw such as a hacksaw, coping saw or even a dovetail saw.  There are Japanese saws that work very well too, but are not so widely available.

The top of the dovetail joint should be just a millimetre or two off centre. 

The angle should be about 30 degrees from vertical.  Saw down far enough to get a 6mm chisel into the space between the two angled cuts.

Chisel out the wood between the cuts.

Repeat for the second dovetail at right angles to the first.

Now you are ready to prepare the oyster knife to become the stopping knife.

Use paper of more than 90 grams per square metre, such as cartridge paper to form the narrow cone.  Set the knife at a slight angle on the paper. 

Secure the beginning edge to the knife handle with a bit of masking tape.  Mark the paper 5 mm – 10 mm above the top of the handle.  This will be the fill indicator when pouring the lead.  If you over-fill the cone, the stopping knife will be heavy and uncomfortable to use.

Roll the paper around the handle to form the cone.  This cone should be as close to vertical as possible.  A wide based cone will, of course, provide stability, but it will add so much weight as to be uncomfortable to use.  It will also be so wide as be uncomfortable for the palm of your hand.

You can unwrap the paper and start over if the cone becomes too wide.  The key is to start the wrapping just before the handle begins to taper toward the end of the handle.  The other way of looking at it is to attach the paper just as the expanding taper stops.

Try to keep the paper cone as smooth as possible.  This will form the shape of the lead end of the handle.  You want it to be as circular as possible without dents or angles.

Now you are ready for the casting.

I use a small old cast iron pot to melt the lead.  I place this over a camping gas burner to provide the heat.  I promise that I did straighten the stabilising legs before lighting the camping burner.

Put some old lead came into the pot to be melted.  While this is coming up to heat, place your wrapped oyster knife in a vice with heat resisting materials around the site to catch any spills.

Put sufficient lead into the pot, as there will be impurities floating on top and the lead will cool quickly when taken off the heat.  The photo below shows the amount of lead used.  This 100mm diameter pot has lead barely covering the bottom.  You do need enough lead to complete the pour at one go, as a second pouring will not stick to the first adequately.

The photo shows the last piece of came just about to be melted.  This is the time to begin the pour.  If the lead is too hot, it burns the wood creating gases and multiple bubbles splashing hot lead and leaving an unpleasant surface for the tool.  As the last piece of the came melts and leaves its impression as the piece on the left, it is time to pour.

Pour at a steady rate into the paper cone until you reach the height indicator you previously marked in the paper.  When you stop pouring, set the pot on a heat proof surface.  You will notice some smoke and browning of the paper.  That is normal.  This picture shows the effect of the hot lead on the paper once the smoking has finished.

This photo shows the inside of the cone while cooling.  The cooling process will take about an hour.  You will be able to check, by touching the paper, how hot the whole is. 

When the whole is cool, you can unwrap the paper from the handle.

This shows the roughness of the handle end.  This is due to the bubbling from the scorching of the wood and paper.

When the paper is removed and the lead is fully at room temperature you can use a rough file to remove the bubbling and to round the edge of the lead.

The oyster knife has been transformed into a stopping knife and is ready to use.