Hanging Sun Catchers

Unless you are using some manufactured system or a frame, the most frequent way to provide hanging points is to create a loop from copper wire.

Hangers should originate in a solder bead that goes some way into the piece. The loop's tail should lie a significant distance into the solder line to ensure it does not pull the piece apart. If this is to remain invisible, some planning will be required to allow the small extra space between the foiled glass.

The loops for hanging a piece of any size should not be soldered to the perimeter foil without reference to the solder bead lines, as the adhesive and foil are insufficient to hold the weight of the piece without tearing.

Here the hanging loops could have been moved just a little to engage with the solder joints at the left ear and at the tail to make stronger hanging points

Here the hanging points are at the solder joints giving strong hanging points

Reinforcement of free hanging or projecting elements can be done by placing wire around the piece with a significant excess going along the perimeter in both directions. The supporting wire can go into the solder line, if it is a continuation of an edge of the free hanging piece.

In this case a twisted copper wire around the perimeter gives strong hanging points

The strongest method is to wrap the wire around the whole perimeter of the piece. Choose easily bent copper wire. This will be pretty fine, but when soldered, will be strong enough support the whole piece.

The hanger can be made by leaving a loop of wire free. This way you can hang from any convenient place on the perimeter. This loop can be made by a single 180 degree twist in the wire, or by bending a loop into the perimeter wire. In all cases you will need to tin the wire to blend it with the rest of the piece.

This perimeter wire can be simply butted at the start/finish of the wire. It could be overlapped, but this is unnecessary on any piece where this method is adequate for support. The start can be at the top or bottom, although I prefer the top, so the wire is continuous from loop to loop. The reason for continuing beyond the loops is to provide support to all the edges of the sun catcher.

This single point hanger is at the strong point of the piece

The left hanger is strong, but the right is weaker than if it had been attached to the right of the body

This piece needs wire around the piece, especially to stabilise the tail and ears

Cleaning Magnets

When making frit in steel containers the metal fragments need to be removed using magnets. It can be very difficult to get the fragments off the magnets.

A solution has been suggested. Put the magnet into a small plastic bag before use. After cleaning all the metal from the frit, take the bag to the bin and remove it from the bag. The metal fragments will drop off into the waste bin, leaving a clean magnet.

Single Layer Firing

Preparing a Single Layer for Further Kiln Work

There can be circumstances where you do want to fire a single layer in building up your project. This is more often difficult on rectangular than round pieces.

Some of the considerations are:

Temperature

Heat work

sizing

Cleaning after firing

Firing a 3 mm piece to anything over a laminated tack fuse normally leads to the edges drawing in creating a “dog bone” effect and often leading to bubbles in the interior at higher fusing temperatures. So one approach is to fire at low temperatures and accept relatively sharp edges on the piece.

Diagram of the full fused results of different thicknesses 

However the concept of heat work can help in this situation. Glass reacts to the accumulation of heat, so that slow advances or long soaks can achieve the desired results at a lower temperature without – in this case – getting the “dog bone” effect. This does require a bit of experimentation. Keep good records of all the stages of experimentation as the effects achieved with various combinations of temperature and time will come in useful later.

It is possible that using the concept of heat work will not be sufficient to achieve the desired results. Then you need to consider placing your design in the centre of a larger piece. Fire this to the lowest possible temperature to achieve your results and then cut the fired piece to size. You will need to fire polish or cold work the edges to get a suitable finish on the edges.

The central white piece shows the results of single layer firing that could be altered by the above technique

If you are going to re-fire any of these single-layer pieces, you need to clean them very well. Any dust or other contamination will be incorporated into the final piece. This is especially true if you are combining a flip and fire technique with this single-layer firing.

Slump Point Test

A slump point test is useful when you wish to determine the approximate annealing point of an unknown glass. The methodology follows:

Prepare a strip of the glass 305mm x 25mm. Suspend this strip above the shelf on 25mm pieces of kiln furniture. Leave a 275mm span between the kiln furniture. A piece of kiln furniture also needs to be placed on top of the glass to keep it in place.

Example of an extreme case of testing for slump point

Fire at 200C per hour to ca. 550C, then fire at 50C/hour to about 700C. Observe frequently from 600C. Record the temperature when the middle of span touches the shelf.  This is also the slumping temperature of the glass when fired this way. 

Subtract 40C from the “touch down” temperature for the approximate annealing point temperature.

Ceramic vs. Glass Kilns

The purposes of these two types of kiln differ, so insulation properties differ too. Ceramic kilns have high density brick insulation to retain the heat and slowly cool the contents from the top temperature to avoid breakage. Glass kilns have light weight insulation – whether brick or fibre - to cool quickly from the top temperature to avoid devitrification.

Considerations

Controllers are necessary for controlled soaks and cooling on glass kilns. Much simpler controls are sufficient for ceramics firings. So a ceramics kiln needs to have a controller added. This is a significant cost. If buying a ceramics kiln new for glass work, ensure it has a controller that can be used for glass.

A bathtub or coffin type kiln with controller

Heat distribution is different in the two. Glass kilns are shallow to get even heat distribution to the surface of the glass. Ceramic kilns have elements around the sides and frequently in the top, but may not have any in the door, if it is not top loading. This means the heat distribution in a ceramic kiln is not as even as in a glass kiln, which is not a problem for ceramics as so much heat is retained at the target temperature, it equalises as the kiln cools.

Ceramic kilns with elements on sides rather than top

Loading

Ceramic kilns up to 450 mm deep tend to be top loading, the ones with greater depth tend to have doors. Glass kilns are shallower and tend to have top – just the lid opens - , clamshell – the lid is the whole chamber which opens giving direct access to the floor of the kiln - or bell type – where the lid also forming the chamber is lifted from the base of the kiln and often the base is on wheels so another base of prepared work can be wheeled into place for firing before the kiln has completely cooled.

Large top hat kiln showing direct access to the kiln floor

Baffles are required in ceramic kilns because the heat is greater nearer the elements on the initial advance in temperature. These baffles avoid premature sealing of the edges of pieces causing large bubbles.

Firing on multiple levels is possible in ceramic once you have built up the experience.

Schedules have to take into account the greater mass of insulation in ceramic kilns.

Kiln with fibre insulation all around

Annealing and cooling tends to require different strategies to encourage the ceramics kiln to cool fast enough in the devitrification range, but can have the power turned off earlier after the annealing soak, because of the slower cooling.

Large front loading ceramic kiln

Ceramic kilns are ideal for casting.

Cost – ceramic kilns tend to cost less than glass ones and second hand ones have been more widely available. That may be changing now with the increasing popularity of glass fusing. 

The electricity costs are marginally higher in ceramic kilns than glass, because the mass of brick to be heated up is greater..

Space - Ceramic kilns tend to take up less floor space because they are deep or tall rather than broad.

Small top loading kiln with combination brick and fibre insulation

Removing Kiln Wash

Kiln wash can get stuck on items for a variety of reasons. 

A variety of ways to remove the kiln wash are:

Grind the kiln wash off with diamond hand pads, or small rotary tool with wet sandpaper. You can then proceed to continue to grind with successively fine grits until a polish is achieved, or you can fire polish after a thorough cleaning.

Example of scrubbing kiln wash off

You can sandblast off the kiln wash and then proceed in either of the fashions above.

You can soak small pieces in tri-sodium citrate and then if necessary scrub with a wire brush – a brass wire brush is preferable to steel one to avoid scratching the glass.

Another solution is to place small items in an ultrasonic cleaner basket with water and a little soap or proprietary cleaner. Leave for an hour or two and they should be free of the kiln wash.

A link to some methods of cleaning shelves is here.

Grinder Chipping Glass

There are a number of reasons that may cause the grinder to chip the glass surface. Some of the things to check are:

Too much pressure

It may be that you are pressing the glass into the grinder head too hard. The grinder head should do the work. Firm rather than hard pressure should be applied. If the grinder slows, it is an indication that far too much pressure is being applied.

Insufficient water supply

There may be too little water reaching the head to lubricate the diamonds and keep the glass cool. If you are getting a white paste or a powder on or near the glass, you need to increase the water supply.

Worn or damaged grinder bit/head

Inspect your bit carefully for smooth areas showing that the diamonds have been worn away. Also look for dents, and other irregularities on the surface, indicating that the bit is damaged. Any dents or smooth places on the bit cause a vibration that is similar to a tiny hammer tapping the edge of the glass.

Grit size

It is possible that you may be using too coarse a grit on the grinder bit/head. The more coarse the grit is the larger the chips will be taken off the edge surfaces. Smaller grits take smaller chips off the edges, and so are less obvious.

New bits

Examples of the range and grit differences in grinding bits

If it is a new bit that is causing the chipping, consider dressing it. New bits often need to be dressed – removing protruding diamonds, or cleaning and exposing new ones on a worn bit. To dress the bit you can grind some scrap glass, brick, or use a dressing stone to lightly grind some of the abrasive material away. This most often settles the bit and avoids chipping.

Cutting thick glass

Use the correct angle of cutter wheel for the thickness. 

Use a similar pressure to cutting 3 or 6 mm glass. It is natural to think that as the glass is thicker, you need to use more pressure. The different angle of the cutter wheel is designed to transfer the standard pressure more directly downward.

Use cut runners made for thick glass to help break the glass. Run score from both ends of the score, especially on curved scores.

Example of cut runners for thick glass

Alternatively, turn the over and use hammer and rounded screw driver to run the score (similar to tapping method for thinner glass). Place the screw driver blade directly over the score line and tap it with a hammer. This will start the run. Continue it by placing the screw driver over the score at the end of the open score and tap again to continue the run.

Air Brushing on Glass

Raphael Schnepf Workshop

Air brushing onto glass is a little different than onto other slightly absorbent surfaces. As glass cannot absorb the moisture from the material being sprayed, the medium needs to be allowed evaporate. This means that each layer of paint must be allowed to dry before the next layer is applied. If too much liquid is applied to the glass, it will bead up giving a stippled appearance to the finished result.

There are some things that can help to give an even application of the paint or enamels to the glass.

Clean the glass very well. After thorough cleaning and drying, use some of the paint to rub the glass. As the paint is a slight abrasive, it cleans off anything the other cleaning methods could not get off.

Add a drop of washing up liquid to the mixture of paint and medium (liquid). This breaks the surface tension of the medium and reduces the tendency to bead up on the glass.

Use alcohol part or all of the medium. This reduces the evaporation time. Also apply in a warm rather than cold place. You can use a hair dryer on low speed and power to assist the drying.

Apply in thin even layers, allowing the paint to dry between applications.

Open the air brush trigger before reaching the edge of the area to be painted and close it after reaching the other edge. Any overspray can be cleaned up as in any other painting.

A slightly larger opening at the nozzle is required on the air brush than for other paints, but you have to be careful to avoid opening it so large that you get the spitting of large drops of paint onto your surface.

Because you are putting very small particles into the air you need to observe various precautions. You need to have a dust mask on at all times you are air brushing. You should do this in a spray booth with extraction if possible. If not, you need a well-ventilated area and very good clean up afterwards.

Avoiding Large Bubbles

“I tried small projects and they turned out fine. I have a 12" square with an emblem in the centre and a border set in slightly from the sides. Most of the glass is only the one layer. Both firings produced huge bubbles in the areas where the glass was only one thickness.”

Scale does matter. What can be done at a small scale does not always transfer to a larger scale without alteration.

 

The first problem this project created was using only one layer as the base. Glass has a surface tension which means that it tries to become 6-7 mm thick, which is twice the thickness of a single layer. As it thickens at the edges, it traps the air under other parts of the glass, and as the glass continues to soften the expanding air bubbles come up through the thin parts of the glass.  Using two layers of glass with the design on top will ease the problem.

 

The design is the second problem. The weight of the border makes it even more difficult for the air to get out from under the glass.  Although having two layers of glass will reduce the problem, think about ways to make the border incorporated with the second layer of glass, so the weight of the glass at the perimeter is not greater than the interior.

 

The third problem is that there is not a bubble squeeze in the schedule (indicated elsewhere in the query). The soak of 10 minutes at 538ºC/1000ºF is not necessary. You do need a soak at a point between 620ºC/1148ºF and 677ºC/1250ºF - this is the bubble squeeze temperature range. It is also the slump temperature, so you can determine what the bubble squeeze should be for your glass by what the upper slump temperature is.

 

The bubble squeeze can be accomplished by a half hour soak at the slump temperature, or by a slow rise from 50C below the slump temperature – taking an hour or so, depending on the size of the piece.

 

A fourth problem is the that the separator is kiln wash, and the edges of the glass conformed to the kiln wash, resisting the movement of air from under the glass.

 

You may need to change to fibre paper for single layer pieces, as that allows more air out. Shelf paper may be enough, but you can also put it over 0.5 mm fibre paper for greater air release. Alternatively, sprinkle powdered kiln wash over the fibre paper and smooth it if you don't want to use Thinfire.

 

Lastly, try to avoid the factory set schedules in your kiln's controller, as they are generally set for 6mm thick pieces.

 

Look at the glass manufacturer's website. Bullseye, Spectrum, Uroboros, and Wissmach give basic firing schedules that work with minimal adjustment. I don't understand why kin manufacturers don't simply refer to the manufacturers’ sites to give their customers good advice, instead of the pre-programmed stuff.

Orientation of Cutter Heads

In addition to the alignment of the cutter, you need to be sure you are moving the cutter forward in the way it was designed. If you look at the cutter from the side you will see two things. The most obvious one is that the angles of the cutaway on the head are shallower at the front and steeper at the back. In addition if you look carefully, the axel for the wheel is slightly forward of the centre line of the whole cutter.

Cutters aligned to score to the left

So it does not matter where the fixing screw on the head is. It may be at the front or at the back. What matters is the cutaway at the back which allows the cutter to be used with a shallower angle, than if reversed. This is most obvious on wide cutter heads.

Cutters arranged to score to the right