Breaking glass with your fists

No, this is not about punching the glass – a dangerous approach. But it is a two-fisted approach to holding glass to break it.

For scores with significant, but not necessarily equal, amounts of glass on each side of the score this is a quick simple approach to breaking glass. After scoring, raise one edge of the glass and put your fingers under the glass on each side of the score. Curl you fingers into your palm, and put your thumbs on top of the glass. Turn your wrists outward and the glass will break cleanly.

With practice, the initial part of a curved score can be run by applying light pressure. Then you can turn the glass around and run the score from the other end to the opened score. This avoids lots of tapping and gives clean edges to the cut glass. It is just as simple as using cut running pliers and avoids the flare often associated with using cut running pliers.

This technique works best with glass that has at least 50mm each side of the score and on gently curved lines. For tight curves and narrow strips other methods need to be used.

Care of Your Soldering Iron Tip

Wipe your hot iron tip on a wet sponge on a regular basis while soldering.  It must be done on a natural sponge, not a plastic based one. This should be a quick pass, rather than a lingering one to avoid cooling the tip of the soldering bolt.  This keeps the tip clean of carbon and other contaminants that can reduce the effective heat from the tip.  

There are also brass wool tip cleaners.  These are a bit more agressive than the sponge, but do not cool the tip. 

If you have any dark gunk build up that won't come off on the sponge, rub the hot iron tip against a block of sal ammoniac until the block clears. If the dirt is difficult to remove with the sal ammoniac, use a brass wire brush to scrape the dirt off and then go back to the sal ammoniac block. When it is clean, add a touch of solder to re-tin the tip, and then wipe against your wet sponge.
  

Remember, all this is done while the iron is hot, so be careful.

Other links to Soldering Iron Maintenance:
https://glasstips.blogspot.com/2019/11/soldering-iron-maintenance.html

https://glasstips.blogspot.com/2010/01/maintenance-of-soldering-bits-periodic.html

https://glasstips.blogspot.com/2009/12/soldering-bit-maintenance-wiping-bit.html

https://glasstips.blogspot.com/2009/12/soldering-bit-maintenance-tinning.html

Polishing Panels with Paint and Enamels on the Glass

Do not use black patina on the lead/solder lines on your finished work if there is any painted glass into the panel whether leaded or foiled. This relates to traditional painting on glass, using vitreous paints, fired at ca. 670C and to cold paints often cured in a domestic oven.

When using enamels within the painting, do not let any patina come in contact with the finished production. The patina will etch out all the enamel colour. The patina will etch off the outer layer, either removing the shiny top layer of paint, or the delicate lines of detail work altogether. Copper patina takes a little of the paint off, but not nearly as badly as the black.

Instead, brush the panel with a natural bristle brush, as used for putty clean up, and polish.

Silver stains that have been properly held at the maturing temp, should withstand any patina application, as they have become incorporated at the molecular level with the glass.

Turning Panels

Panels should be turned by supporting as much of the panel as possible. In general this means that the panel should be moved until about half of it is off the bench and supported by one hand. Then pivot the panel on the edge of the bench until it is vertical. During this process, the other hand should be supporting the other edge.  Pivot until vertical.  Lift and set it on the bench. Turn it around, keeping it vertical. Lift it off the bench and set the middle against the edge of the bench with one hand on each otherwise unsupported edge. Pivot the panel on the edge and slide it back on the bench.


If the panel is going to be a large one, make it on a board placed on top of your bench. Then when it is time to turn the panel, you can tip the board, set the panel together with the board on the floor. Move the board to the other side of the panel, turn the board around, placing it against the edge of the bench and raise it while pivoting it on the bench. Additional help is to have two short pieces of wood on the floor to set the panel and board on, so you can get your fingers under easily and without getting them trapped.


If you have the space and spare boards, you can place a second board on top of the panel. Make sure the panel is at the edge of the boards next to you. You can then, with the help of another person, turn the whole panel in one movement (although your arms will be in a bit of a twist). This removes the danger of the panel wobbling too much while shifting the supporting board.


A panel of any size with one or more long lines going through the panel should be made on a board, so that it can be turned without the danger of breaking any of the glass or of the panel folding along the lead lines.

Straightening the came

Before using the came it is important to straighten it. This increases the stability of the came during the leading process. Most often nowadays, you use a lead vice. This operates similarly to a cleat on a sailing boat. The more strain that is applied, the tighter the vice grips the came.

You place the end of the came into the vice so that the came appears at the back of the vice. Give the top of the vice a firm tap with your pliers to set the teeth into the came. Grasp the other end of the came with the pliers, and put one foot behind you to brace yourself if the came does slip out of the vice. Draw the came toward yourself until you can see the lead is straight and any kinks have straightened.

Take the came out of the vice and keep it straight. You transport it by grasping each end and keep the came under tension until you get it to the destination. It is often easiest to cut the full length in half before moving it, as it will not then be longer than your arms can stretch.

Remember, this process is to straighten the came to give pleasing lines in the leaded panel. It is not stretching the lead. Stretching the came can weaken the lead.

Dressing the Cames - part 2

Of course, it is not enough just to dress the came at the start. There is an analogous procedure after the whole panel has been leaded, soldered and cemented.

In this instance the term ‘dressing the cames’ means to close or bend the leaves/flanges of the came toward the glass. It provides a neat rounded appearance to the lines, traps the cement you have already added, presents less area for the rainwater to collect, and makes polishing easier. It is also the time when you may break the glass by putting too much pressure on the glass, so be careful!

Dressing the cames is done with an oyster knife or fid. It is best to avoid metal and better to use wood sticks or plastic tools. The pressure is placed on the came rather than the glass. Run the fid lightly at a shallow angle along each flange of the came. It is helpful to use a finger of your other hand to guide the fid along the cames. You may want to do this several times, as repeated light pressure will cause the flanges of the came to move gently toward the glass with less risk of breaking the glass. This can only be done while the cement is pliable. If it is done after polishing, you will need to re-do the polishing, as it will make the edges of the came silvery rather than shiny black.

Amount of Fill for a Frit Mould

There are several ways to determine the volume of a mould. 

Calculation of the weight of glass needed

Calculate the amount in the metric system of measures, as that gives much easier calculations. Cubic centimetres of volume times the specific gravity of glass (2.5) will give you the number of grams of glass required.

This works best on regular geometric forms.  Rectangles and parallelograms are easy to measure the length, width and depth in centimetres.  Multiply together and you obtain cubic centimetres.  That times the specific gravity – 2.5 – will give the number of grams to fill the mould.  The frit will of course be mounded above the levelled surface, because of the air spaces between the frit pieces.

Example of a small frit mould

Irregular shaped moulds

The moulds which are irregular in shape or depth are more difficult to calculate. 

You can determine the volume by starting with a measured amount of water.  Quickly fill the mould to the surface, so that no water is absorbed into the mould. Empty the water from the mould into the drain so it does not become soaked. The difference between the starting and finishing amount of water is the volume of glass required to fill the mould. 

You can use that volume in cubic centimetres times the specific gravity (2.5) to get the number of grams of glass required.

However, it is much easier to put the frit into the water until the measure shows the same amount as before the mould was filled. Then you only need pour off the water and allow glass and mould to dry.  No calculation required.

Using Ceramic to Drape

Characteristics

Before choosing a ceramic shape to use in draping of glass, you need to consider the characteristics of the two materials.  This is one circumstance where CoE is actually useful. 

The expansion of the two materials is different. Soda lime glass typically has an expansion rate - in the 0°C to 300°C range - of 81 to 104.  Ceramic has an expansion rate - in the 0°C to 400°C range - of 30 to 64.  This is important in the final cooling of the project.  As the glass expands more than the ceramic on the heat-up, so it also contracts more during the cool.  This means that the glass will shrink enough to trap the ceramic or even break if the stress on the glass is too much. 

Shape

The shape of the ceramic form will have a big effect on the usability of it as a mould.  Ceramics with right angles between the flat surface and the sides will not be suitable for draping without modifications or cushioning.  The forms suitable for draping need to have a significant draft to work well.

Ceramic forms such as rectangles, cubes, and cylinders do not have any draft in their form.  

A cube shape unsuitable for draping

Ceramic cylinders with straight sides

Although rounded at the base, the sides are too straight to be a draping mould

The glass will contract around these forms until they are stuck to the ceramic or break from the force of the contraction around the ceramic.

You can experience this trapping effect in a stack of drinking glasses.  Sometimes one glass sticks inside another even though there is a slope (i.e., a draft) on the sides of the glasses. This happens mostly when you put a cold glass inside a warm one.  On cooling the warm glass contracts to trap the cooler one. You can separate these by running hot water on the bottom glass, so that it expands and releases the inner, now cool, one. 

Effect of Shape

The ceramic contracts at about half the rate the glass contracts (on average), unlike steel which contracts faster than the glass. This means steel contracts away from the glass, while the glass contracts against the ceramic, on the cooling.

Because the glass is in its brittle or solid phase during the last 300°C to 400°C, this contraction tightens the glass against the ceramic, causing stress in the glass, even to the point of breaking.

However, if you choose ceramic forms with significant draft, you can drape over ceramic.  This is possible when the slope is great enough and the form is coated with enough separator, to allow the glass to slip upwards as it contracts more than the form. Experience with different draft forms will give you a feel for the degree of slope required. 

 

These pyramid shapes have sufficient draft to allow the glass to move up the mould during cooling.

Compensation for Lack of Draft

You can compensate for the insufficient draft of ceramic forms by increasing the thickness of the separators for the form.  The hot glass will conform to the hot ceramic, so there needs to be a means of keeping the glass from compressing the form while cooling.  This can most easily be done by wrapping the form that has little or no draft with 3mm ceramic fibre paper.  It is possible to get by with as little as 1mm fibre paper, but I like the assurance of the thicker material.

Kiln posts wrapped in 3mm fibre paper and secured with copper wire

The fibre paper can be held to the form by thin wire wrapped around the outside of the fibre paper. The advantage of the 3mm fibre paper is that the wire will sink below the surface of the paper.  You can tie off the wire with a couple of twists.  Cut off the ends and push the twist flat to the fibre paper to keep the glass from catching onto the wire.  If you want further assurance, you can put a bit of kiln wash onto the wire.

Conclusion

The choice of ceramic shapes to drape glass over is very important.  It needs to have sufficient draft and separator to allow the glass to slip upwards as it contracts more than the ceramic during the cooling.  You often can use items with no draft if you wrap fibre paper around the sides of the form.

Odd Schedules

Schedules appear on the internet which do not seem to have a logical sequence in the firing schedule.  Some have multiple soaks at intervals up to 540°C.  Others have kind of dance toward the top temperature – slow, quick, slow.  Some initially cool at a given rate and then slow to about half that initial rate.

Multiple soaks

These schedules have been referred to as catch-up schedules.  They tend to look something like this:

200°C to 150°C for 20 minutes

250°C to 300°C for 20 minutes

300°C to 590°C for 20 minutes

50°C   to 677°C for 30 minutes

330°C to 804°C for 10 minutes

AFAP   to 482°C for 60 minutes

60°C   to 370°C for  0 minutes

Off

The justification for the first two soaks is given as allowing the glass to catch up to the air temperature.  It would be much safer for the glass to have a moderate steady advance in temperature rather than risking the heat shocking of the glass.  You could achieve the same work in the same amount of time by altering the rate of advance to a single one of 198°C to 590°C.  This achieves the same temperature in the same amount of time, but has less risk of heat shock, as there is a steady input of heat.  

Secondly, if the glass can survive the initial rate of heat up without breaking, there is no need to soak at an arbitrary temperature.  The first relevant point where a change in temperature makes sense is above the softening point, which for most fusing glasses is about 540°C. The equivalent softening point for float glass is about 700°C

Slow, quick, slow

This kind of schedule alters rates up and down with little justification as far as I can see.  This is an example:

139°C  to 560°C  for 30 minutes

222°C  to 621°C  for 30 minutes

139°C  to 786°C  for 15 minutes

9999 to  515°C  for 120 minutes  

60°C   to 427°C  for 10 minutes

115°C  to 350°C  for 10  minutes

The question for me is why the slow down to top temperature. There is a lot of heat work being put into the glass, so that the higher top temperature may not be required.  The slower rate from 621°C does allow a form of a bubble squeeze to occur, but is not the traditional one.  A 139°C rate from 621°C to 677°C with a soak would be faster than usual, but may be acceptable.  I would prefer 50°C per hour with a 30-minute soak at the end.  Then advancing at 300°C per hour to top temperature.  The anneal soak and cool of this schedule are acceptable, even though different than I would do it.

Erratic Slumping Schedule

The fusing schedule above was followed by this slumping schedule:

83°C to 148°C  15 minutes

167°C to 590°C  10 minutes

83°C to 720°C  10 minutes

222°C to 410°C  120 minutes

83°C to 427°C  10 minutes

This schedule seems to have a catch-up phase in that it goes at half speed for the first 148°C and then doubles the speed to 590°C (a little above the brittle phase of the glass).  It then slows the rate and continues that to a very high slump temperature.  It is, of course, necessary to have a slower rate of advance in the slumping than the fusing, as the piece is now thicker. Slowing the rate of advance as much as in this should be able to achieve the slump at around 620°C (100°C) less than the target temperature used by the schedule. 

Once the top temperature soak is finished, a very slow cool to the annealing soak is used in this schedule.  This is not ideal as it invites devitrification to form.  The kiln and its contents should be allowed to cool as quickly as possible to the temperature equalisation soak at the annealing point.

The schedule then uses an annealing soak temperature 100°C below that used for the fusing. This does not make sense. The annealing soak should be at the same temperature for both firings.  The length of the soak is not in question, but the early turn off the kiln at 427°C is questionable. The anneal cool of the fused piece extended down to 350°C.  The anneal cool on slumping should be almost the same as the fuse.  Almost all anneal cools extend to 370°C at least.

Anneal Cools

Some anneal cools have erratic rather than progressive cooling.  In this example the early part of the schedule is eliminated:

……………..

AFAP to 482°C 120 minutes

110°C to 427°C 0 minutes

55°C to 370°C 0 minutes

200°C to 100°C 0 minutes

off

Here the schedule is faster in the most critical part of the anneal cool than in the next, cooler part.  This will not provide as good an anneal as if the first two segments after the equalisation soak were reversed.  Start slowly in the anneal cool and then you can speed up (approximately twice the previous segment rate) on each of the following segments.

Rationale

This critique of the schedules above is not to batter anyone.  It is to make clear that there needs to be a conscious rationale for each of the segments in relation to the others.  If you take a schedule from a source, it is a good idea to see if there is a reason for each segment and how it relates to the next. 

·        The scheduling must take account of the nature of the glass.  Glass is a poor conductor of heat and needs steady moderate input of heat.

·        Glass is brittle until approximately 55°C above the annealing temperature when you can accelerate the rate of advance.

·        Time is required to allow air out from between the layers of glass. This usually done in the range of 620°C to 675°C and is known as the bubble squeeze.

·        You need to go relatively quickly through the devitrification range of temperatures – approximately 700°C to 760°C - both up and down.

·        Glass needs a temperature equalisation soak at the annealing point (or nearby) related to its thickness.

·        The rate of cooling needs to be progressive.  The first 55°C below the annealing soak is the most important.

·        Cooling rates must be related to thickness.

·        The second cooling rate can be up to double the initial one.

·        The final cooling rate can be double the previous one.

·        The rate of firing will affect the required top temperature.

Factory Installed Firing Schedules

Factory installed schedules are a quick starting point for the novice kilnformer.  

Many kiln manufacturers install schedules in the controllers of entry level kilns.  Some install them in larger kilns too.  They will work for for gaining basic experience of kiln operations.

However, these schedules are not universal.  Each maker programmes schedules according to their understanding of a mid-range firing schedule for various processes. 

An example of some installed programmes from Scutt

This means that when referring to an installed programme on your controller, you need to give the full schedule so others can understand.

Why?

Not only because a tack fuse schedule may be to a different temperature, but also a "fast" schedule as programmed into one kiln might be quite different to one in another.

This matters, because how fast you get to the top temperature affects what temperature you need to use. You will probably experience the difference in final effect between a fast and a slow fuse to the same temperature.  If you haven’t seen it yet, try both schedules on the same layup of glass.

You will see that a fast rate of advance to a tack fuse will give a much more angular appearance, while a slow rate of advance will give a much more rounded appearance.  This is the effect of heat work, which is essentially the effect of the combination of temperature and time.

The longer it takes the glass to reach a given temperature, the greater the heat work.  Longer times to the top allow the use of lower temperatures. 

The consequence of accounting for heat work is that a simple top temperature cannot be given.  It is not just that kilns are different, but that the amount of heat work put into the glass will change the top temperature required for a given look.

The Purpose of Flux

The primary purpose of flux is to prevent oxidation of the base and filler materials in the short time between cleaning and soldering. Tin-lead solder, for example, attaches very well to copper, but poorly to the various oxides of copper that form quickly at soldering temperatures. This applies to lead and brass too.

Flux is a substance that is nearly inert at room temperature, but it becomes strongly reducing at elevated temperatures, preventing the formation of metal oxides. Secondarily, flux acts as a wetting agent in soldering processes for lead, copper and brass.

Without flux the solder does not firmly attach to the lead or copper foil and often forms sharp peaks.


See also
Flux, an introduction
Fluxes, a description
The Purpose of flux
The action of fluxes

Soldering fluxes

The Action of Fluxes

All common untreated metals and metal alloys (including solders) are subject to an environmental attack in which their bare surfaces become covered with a non-metallic film, commonly referred to as tarnish. This tarnish layer consists of oxides, sulfides, carbonates, or other corrosion products and is an effective insulating barrier that will prevent any direct contact with the clean metal surface which lies beneath. When metal parts are joined together by soldering, a metallic continuity is established as a result of the interface between the solder and the surfaces of the two metals. As long as the tarnish layer remains, the solder and metal interface cannot take place, because without being able to make direct contact it is impossible to effectively wet the metals surface with solder.

The surface tarnishes that form on metal are generally not soluble in (and cannot be removed by) most conventional cleaning solvents. They must, therefore be acted upon chemically [or mechanically] in order to be removed. The required chemical reaction is most often accomplished by the use of soldering fluxes. These soldering fluxes will displace the atmospheric gas layer on the metal’s surface and upon heating will chemically react to remove the tarnish layer from the fluxed metals and maintain the clean metal surface throughout the soldering process.

Chemical reactions
The chemical reaction that is required will usually be one of two basic types. It can be a reaction where the tarnish and flux combine forming a third compound that is soluble in either the flux or its carrier.

An example of this type of reaction takes place between water-white rosin and copper oxides. Water-white rosin, when used as a flux is usually in an isopropyl alcohol carrier and consists mainly of abietic acid and other isomeric diterpene acids that are soluble in several organic solvents. When applied to an oxidized copper surface and heated, the copper oxides will combine with the abietic acid forming a copper abiet (which mixes easily with the un-reacted rosin) leaving a clean metallic surface for solder wetting. The hot molten solder displaces the rosin flux and the copper abiet, which can then be removed by conventional cleaning methods.

Another type of reaction is one that causes the tarnish film, or oxidized layer to return to its original metallic state restoring the metals clean surface.

An example of this type of reaction takes place when soldering under a blanket of heated hydrogen. At elevated temperatures (the temperature that is required for the intended reaction to take place is unique to each type of base metal) the hydrogen removes the oxides from the surface, forming water and restoring the metallic surface, which the solder will then wet. There are several other variations and combinations that are based on these two types of reactions.

Acids commonly in fluxes

Flux as a temporary protective coating
Once the desired chemical reaction has taken place (lifting or dissolving the tarnish layer) the fluxing agent must provide a protective coating on the cleaned metal surface until it is displaced by the molten solder. This is due to the elevated temperatures required for soldering causing the increased likelihood that the metal’s surface may rapidly re-oxidize if not properly coated. Any compound that can be used to create one of the required types of chemical reactions, under the operating conditions necessary for soldering, might be considered for use as a fluxing material. However, most organic and inorganic compounds will not hold up under the high temperature conditions that are required for proper soldering. That is why one of the more important considerations is a compound's thermal stability, or its ability to withstand the high temperatures that are required for soldering without burning, breaking down, or evaporating.

When evaluating all of the requirements necessary for a compound to be considered as a fluxing agent, it is important to consider the various soldering methods, techniques and processes available and the wide range of materials and temperatures they may require. A certain flux may perform well on a specific surface using one method of soldering and yet not be at all suitable for that same surface using a different soldering method. When in doubt it never hurts to check with the flux, or solder manufacturer for recommendations.

Courtesy of American Beauty Tools


See also:
Flux, an introduction
Fluxes, a description
The Purpose of flux
The action of fluxes
Soldering fluxes

Flux

Flux is a material that provides a “wetting” action between the metal (lead or copper in our case) and the solder.


There are various types of flux. Some are of more use in some circumstances than others. Among them are:

Tallow
This normally comes in a candle-like stick. It is made from rendered animal fat. Although this may put some vegetarians off, it is one of the best fluxes for leaded glass work and will work for copper foil, but is not generally preferred.  It is relatively natural, does not contain chemicals, and does not require re-application if left for a while. Over generous application does not produce any problems during the soldering. It just leaves more solidified tallow to clean after soldering. The cleaning normally requires a mild abrasive such as a brass or fibreglass brush to get the cooled tallow off the piece.

 




Oleic acid and other safety fluxes
Many of the safety fluxes are made of oleic acid (sometimes called stearin oil). These fluxes do not produce chemical fumes in the soldering process. They are easy to clean up with detergents and warm water. Safety fluxes require re-application if left to dry, as they are only effective while wet. Putting too much on leads to boiling off the liquid, making holes in the solder joint or line.

An example only.  There are many water soluble paste fluxes available

Chemical Paste fluxes
These fluxes come in a variety of compositions. You need to be careful about choosing, as some are very difficult to clean off the glass or solder line or joint. They do produce chemical fumes, so a fume mask is advisable while using this kind of flux. The paste does not require re-application if left, so the whole piece can be fluxed at once.

Acid fluxes
Acid fluxes such as the kind that is in the core of plumbers solder are intended to clean the joint at the same time as acting as the wetting agent. These are not recommended for stained glass work as they can affect the glass surfaces, especially irridised glass. They do produce fumes that require the user to have on a fume mask while soldering. The ease of cleaning relates to the particular composition of the flux, so testing samples is required before application.

See also:
Flux, an introduction
Fluxes, a description
The Purpose of flux
The action of fluxes
Soldering fluxes