Sunday, 29 March 2020
It is recommended to use a rheostat in circumstances where the soldering iron does not have an internal temperature control.
A rheostat is NOT a temperature controller.
Action of a Rheostat
A rheostat actually reduces the power supplied to the iron, thereby making it take longer to heat or re-heat after a period of soldering. Without a rheostat, if an iron is left idle, it will eventually reach its maximum temperature. This is usually too hot for soldering lead, but OK for joining other metals. With a rheostat, if an iron is left idle with the rheostat set to (say) '6', it will still reach its maximum temperature but very much slower than the one without a rheostat.
Action of a Temperature Controlled Iron
Temperature controlled soldering irons attempt to maintain a set temperature. This is controlled by the combination of the microchip in the iron and the tip. So to adjust your temperatures all you need is a few different tips. For example, a number 7 tip lets your iron heat to 700F degrees. For decorative soldering your need tips of lower temperatures, usually a number 6 or 600F degree is enough of a reduction for most decorative stuff. A number 8 tip (800F) will let you work at a higher temperature if you work quickly.
Differences in Soldering Speed
Using an iron without a rheostat, provided you work relatively quickly, you will probably be able to solder all the joints in a small or medium panel without stopping to let the iron 'catch up'. In this case the temperature is controlled by the heating power of the iron balanced by the cooling effect of making the soldered joints.Using an iron with a rheostat, you will need to slow down a little if you are to do that same panel without stopping to let the iron re-heat. In this case the temperature of the iron is controlled by the (reduced) heating power of the iron balanced by the same cooling effect of making the soldered joints.This difference is caused by the fact that a temperature-controlled iron, if it is left idle, it will quickly reach its maximum operating temperature - just as quickly as an un-controlled iron of the same power. When you start soldering, the cooling effect will trigger the temperature controller to provide full power until the operating temperature is reached again.
Advantages of a Temperature Controlled Iron
You can buy an iron (not temperature controlled) and a rheostat but buying tips for the temperature controlled iron is cheaper. The big advantage of the temperature-controlled iron is that you know it will never get too hot for the work you are doing, and that it truly provides that 100 watts (or whatever) power to keep it hot even when you are soldering at top speed.
For example a 75 or 80 watt iron is sufficient to begin soldering with, but it will continue to get hotter, as it has no temperature control. An iron of this type should be used with a rheostat in order to prevent overheating while it is idling.
Historically soldering tips were copper, placed in braziers. One tip at a time was used; when the heat had transferred from the tip to the solder (and depleted the heat reserve) it was placed back in the brazier of charcoal and the next tip was used.
Much later gas irons were in common use. These used a gas jet to heat the soldering bolt/tip. They are very fast, but require significant amounts of experience to properly regulate the temperature.
Currently, electric soldering irons are used; they consist of coil or ceramic heating elements, which retain heat differently, and warm up the mass differently, with internal or external rheostats, and different power ratings - which change how long a bead can be run.
The soldering iron used must be of a high enough wattage to readily melt the solder and be able to reheat fast enough to maintain the necessary melting temperature. The tip can't be so small it can't maintain the heat and not so big it covers much more area than wanted.
For soldering leaded panels a 100w iron with a 3/8" temperature controlled tip that maintains a constant 370°C (700° F) is suitable.
For copper foil a higher temperature controlled tip is used. This normally runs at 425°C (800°F). Sometimes a tip of ¼” is used where more delicate beads are being run. But there is little difference in the resulting bead - only that the smaller bit takes slightly longer to heat up.
If a lot of soldering is required that has sustained heat requirements, you might consider a 200W iron. These can deliver heat more quickly and evenly than those with lesser wattage.
In the cases of irregular openings, you can trim the edge cames if you have used 12mm (1/2”) or more wide came. The quickest way of trimming cames to fit the opening is to use a rasp or “surform” tool. The open nature of the teeth, allows the lead to fall away. It is much quicker than using a lead knife, and it puts less pressure on the panel.
Use a soft brush to polish lead came. Don't pick out the cement until the polishing is done, as it provides the colour for darkening and polishing the lead and solder joints. The action with the polishing brush should be gentle and rapid, much like polishing shoes. If the shine does not come, you can use a very little stove blackening (carbon black mixed with a little oil) If you use a lot, you will have a big clean up job. A little stove blackening spreads a very long way.
Before turning the panel a final time, put down paper or cloth, to avoid scratching the solder joints while polishing the other side. The result should be shiny a black came and solder joints that does not come off the way a final buffing with stove blackening does.
Finally, pick out any remaining cement.
Rest horizontally with weather side down for traditional installations. If the panel is going into a double or secondary glazed unit, you may want to reverse this. The reason for having the smallest exposed cement line on the outside is to allow the water to run off the window with the minimum of area to collect. In a sealed unit or for secondary glazing, you may want to have the smallest amount of cement showing inward for appearances, as there is no weathering reason for the traditional method.
Rest for a day. Pick out the cement again. If the cement was stiff enough, there should be no need to do any more picking at the cement after this.
After the pushing the cement under the cames on both sides, flip the panel over and begin a firm rubbing to push addidional cement into the gaps between the lead and glass on this side. Sprinkle the used dust from the bench top over the panel and rub in all directions. This begins to set up the cement by helping to provide a stiff skin over the more fluid cement. Brush until the whiting is largely off the panel. Turn the panel and do the same for the other side. Several applications of whiting/sawdust are required to give a sufficiently thick skin to reduce the amount of spreading, leaking or weeping cement.
Once both sides have been done a couple of times, begin to concentrate the brush strokes along the lead lines rather than across. This will begin the cleaning phase and also begin to darken the came. Repeat this on the other side.
After a few turnings, most of the cement will be cleaned from around the leads. Don’t try to get all of it away, you will need that colour for polishing. The glass will be shining, and any felt tip marks you made on the glass will have gone too. Clean up the dust from the panel and bench in preparation for polishing.
Cementing panels is as old as leaded glass - about 1,000 years - so it is a time-proven process using simple materials. The object of cementing is to make a leaded panel weather/water tight and sturdy. It can be messy and dusty, so putting on an apron and a dust mask are a good idea.
Start on the side that is already facing up after soldering. This normally will be the rough side. This way you do not have to move the panel much until it has stiffened with the addition of the cement.
Cover all open bubbles, rough glass (waffle, ice, etc.) and all painted glass with masking tape. Put the tape over all the relevant areas of the panel, then use a sharp knife (X-acto, scalpel) to cut the tape at the edges of the came. The cement will go under the came, but not into the texture of the glass. This will make the clean up of the glass much easier after cementing.
You can purchase commercially made lead light cement or you can make your own.
With the panel on the bench, put a dollop of cement on the glass and rub it in all directions with a stiff, but not hard, bristle brush to force it under the lead.
Turn the panel over to cement the second side the same way as the first. If the panel is a large one, you may want to use a board to support it in these early turning stages. No gaps can be tolerated in the cementing. Cement leaking out the other side is good evidence that all the gaps between the glass and the came are filled. Again, after cementing, sprinkle new whiting/sawdust over the second cemented side and rub it gently into the exposed cement.
Friday, 27 March 2020
GuidelinesThere are no all-encompassing reinforcement rules. There are however some basic guidelines:
- Restrict non-reinforced panels to between 2 and 4 perimeter metres (a rectangle of 1 by .5 meters up to a square of 1 meter).
- An abundance of horizontal or vertical lead lines within the leading concept are most likely best served by a vertical reinforcement system.
- A diagonal or bent reinforcement bar dilutes its reinforcement capacity in proportion as it deviates from the straight. Such supports serve to merely stiffen the section.
- Know that most reinforcement systems provide only lateral reinforcement.
- In most architectural situations which adhere to sections of 4 perimeter metres, reinforcement will usually be 12” to 18" apart in vertical accommodations, with an average around 15".
- Placement of reinforcement should be established on the initial scale layout in which the design is to be done. It should not be an addition after the whole is designed. That increases the likelihood that the reinforcement will be an intrusion upon the design.
- Very tall or wide windows should have an armature of some sort. This is commonly "T" bars for the panels to rest upon without transferring their weight to the panel below. Other more complicated armatures can be seen in large windows, such as at Canterbury Cathedral.
With diamond and other quarry lights, reinforcement placement cannot always be equally spaced. In such instances, it is probably best to have the shortest distances between the reinforcement at the base of the section where the weight creates the greatest likelihood of buckling.
Dressing the cames gives a slight bevel or ramp for the glass to slide over the edge of the came and into the channel of the came. You can dress the whole length at once, or as you cut the pieces off from the main length. Dressing shorter pieces is less likely to bend the came.
Of course there is a second stage of dressing the lead came upon completion of the soldering.
Leaded light panels often require additional support against wind pressure or vibration. Whether this is needed depends on the size and location, e.g. if in a door or a ventilating window that is constantly being opened and shut. Large leaded glass windows need some bracing against the force of wind and rain. This can be achieved by using one of the following supports:
- Saddle Bar
- Reinforcing Bar (Rebar)
- Steel Core or Steels
- Zinc Section
Saddle Bars are the strongest method of support and are used in large external windows for preventing panels from bowing inwards. They resist wind pressure in exposed situations. Saddle bars form part of the latteral support structure of the window. These bars are attached to the panel with copper or lead ties. These ties are soldered to solder joints across the narrow width of the panels. The bars are fixed to the perimeter of the opening either by the mouldings or by being inserted into holes in the frame. The sides of the opening provide the ancor points for the bar. The panel is fixed to the bar by twisting the ties around it.
|A saddle bar fixed in position at the side and the ties being twisted around the bar.|
Sometimes the opening is divided by sideways "T" bars. Generally the leg of the "T" faces outwards and the panel is set onto the ledge formed by the leg of the "T". This leg often has a series of holes drilled in the leg, for pins to be inserted to hold the panel in place until the sealant has cured.
|An example of "T" bars being used on a small side opening window|
Rebar is another external support. It generally is a zinc coated steel strap about 2mm by 10mm and asl long as needed to cross the panel. This tends to be soldered directly to the panel at the solder joints either on the inside or outside. One advantage of this material is that it can be bent to conform to the lead lines of the panel. In consequence it is not as stiff as saddle bars are.
Steel cores take two forms - either steel-cored lead or steel strips fitted into the lead cames when leading. The steel cored lead came is less available nowadays. They are mainly used in domestic glazing where support is required particularly in leaded lights with diamond panes when they are inserted in continuous diagonal leads. The steel cores are not adaptable to significant curves.
|Steel cored lead came cut away to show the steel core|
Zinc section came is often used to frame a panel that is not glazed into a window or frame. It has been used in the past for both straight and curved lines. Using it for curves requires a came bending machine to give good, regular curves. It gives a panel strength for ease of handling, but does not resist sagging or bowing at the centre. The other disadvantage of zinc is that it corrodes much faster than lead.
|Image showing a variety of zinc came|
Wednesday, 25 March 2020
Natural Cooling Rate of the Kiln
|Kiln Name:||Cooling Rate|
Wednesday, 18 March 2020
|Two heights of new cocktail shakers|
|A well used cocktail shaker with kiln wash|
|A kiln post wrapped in preparation for firing|
|Two short kiln posts after firing|
|A single layer that has begun to stretch at the shoulder of the former|
|These two were fired at the same time. The back one is larger than the front|
Wednesday, 11 March 2020
|Example of vacuuming around elements|
|Example of vacuuming lid without elements|
Check on the kiln furniture – including shelves, boards, supports. Are they kiln washed and without scrapes, scratches, gaps? Has the kiln wash been fired to full fuse temperature? In both cases, clean the used kiln wash off the shelf and renew.
Check on the conditions and placement of the thermocouple.
Check on the elements. Some may be sagging or hanging out of their channels. Use tweezers to bring the coils closer together. This shortens the length of the element and it then can be pushed back into the channel. It may not have to be done after each firing, but checking will catch things before sagging becomes a major problem.