Disguising Joints in Fusing

One advantage of fusing over leading or copper foiling is that shapes impossible to cut as a single piece can be made from multiple pieces. However these joints often show up in the finished work.

You are always more likely to have the joints show when the cut coloured glass is on the bottom. The infra-red heat of the kiln elements goes through the clear glass to the coloured below, allowing it to soften first. As the glass underneath softens and pulls in, it allows the top glass to sink into the space. Upon cooling the seam is kept open even sometimes showing a clear line at the joints.

Putting the clear as the base and the jointed pieces on the top has a better chance of having the joints fully fuse together. There is no glass above to spread the pieces apart.

When you need the joints to be concealed, you can put a line of powder the same colour of glass over the joint. This line should be slightly rounded above the surface along the joint to account for the reduction in volume as it fuses. When it is two colours meeting, using powder of the same colour as the darker glass is most successful.

Fusing to a contour fuse for 10 minutes is normally hot enough, but taking the piece to a flat fuse – again for 10 mins - will certainly be enough to fully melt the powder into the joint.

Installing Leaded Glass in Stone

Side rebates
One side of the rebate (or raggle) in stone should be deeper than the other. This allows the panel to be slotted in and then slid back into the shallower rebate. Which side the deep rebate is on is not important, but you must determine which is the deeper and its minimum depth all along the raggle.

Adjusting the placement of the panel
To help move the panel from side to side stiff oyster knives and lead knives are important. This allows you to get behind the edge and slide the panel to the side, especially when it is sitting on top of another panel to make the fine adjustments to get the lead lines flow correctly.

In some circumstances, especially when installing a single panel, it is necessary to bend the leaves of the lead toward the installation side. After placing the panel, you then fold the leaves out one at a time into the raggle slot.

Top and bottom rebates
For the top and bottom rebates it is important that the top is the deep one. You insert the panel up into the slot a the top and let it settle into the bottom rebate. The panel should be completely covered by the stone.

Extra came
In all installations into stone, you should carry extra came of at least 12mm (1/2”) to solder round the panel when the stone work is not as accurate as it should be, either through workmanship or weathering.

Wedges
Have some little blocks of wood and some whittling tool to hand to wedge the panel in till mortared. It is possible to use little scraps of lead for the purpose. These wedges don't need to be that robust, they are just there to hold the panel in place until the mortar is in.

Mortars
Mortars for stone should be of lime cement, or sand mastic. Don't use silicon, you'll never get it out again! Also don't use putty as this stains some types of stone and the oils leech in to the stone, causing the putty to dry and therefore the window ceases to be watertight.

Brushes for Painting

A quality paint brush will have hairs that form a point and have a good spring to them - they bend while painting but return quickly to their original shape. A good brush will also hold lots of paint and deliver that paint evenly throughout the stroke. Brushes usually have a number to indicate their size - the larger the number, the larger the paintbrush. The larger the brush the wider the line that can be produced, although with a light touch a fine long line can be made because of the pointed nature of the brush.

The best brushes are made from natural hairs, although there are brushes made from a combination of natural and synthetic materials which are adequate.

Sable hair brushes are considered to be the best for painting. The hair comes from a variety of pine martin and the Kolinsky sable from Siberia is considered the best. These brushes are more expensive than others, but are soft and flexible, hold their paint well and can make an expressive thick to thin line.

Ox hairs are normally used for making rigger brushes. This is a round brush with long hairs, said to be used to paint the lines of ships' rigging in the past. The hair is strong and springy making it useful for long lines and thicker paints.

Squirrel hair brushes are useful for applying paint in broad, thin layers for matting.

Goat hair brushes are normally known as hake brushes. These are a traditional, oriental style brush. It lacks spring, but forms a good point and so is useful to cover larger areas quickly with a gentle touch.

Pony hair is made into short round brushes used as soft stipplers.

Hog hairs are made into hard, very economical brushes. They come in flat and round shapes. They are most used for stippling and can be trimmed, shaped, used, and abused for years.

Badger hairs are thicker at the end and thinner at the root, creating a conical shape. These soft brushes are used to blend paint once it has been spread on the glass. The brush is swept across the surface of the paint to blend or move paint and remove stroke lines.

Glass Shifting on Mould

There are a number of things to investigate if your blank is shifting on the mould during firing.

Is there a heat differential?

Glass absorbs heat at different rates depending on colour and type meaning that one part may begin to move before another. The solution to this is to slow down the rate of advance to allow all the glass to gain heat at the same speed. It may also be useful to slump at a lower temperature.

There also may be a heat differential within the kiln. You need to run a check on the heat distribution of your kiln to be sure where the (relatively) hot and cold areas of your kiln are. Bullseye published Tech Note no.1 on how to do this.

Not perfectly balanced on the mould?

Glass can be placed just off square or level and that can allow it to start slumping unevenly. Measurements and observation can help to get the glass placed squarely on the mould. Also a small spirit level placed on the glass can tell you if the glass is level within the mould.

The mould may not be level.

The kiln, shelf and mould should each be checked for level in all directions. The kiln level can be established and can be assumed to be level until it is moved. The shelf level should be checked each time it is moved. The mould level should be checked each time it is used.

Is the glass overhanging the mould?

Glass overhanging the mould rim can hang up on some of the edges more than others. Check the rim of the mould for any rough areas and smooth them. If you do have glass overhanging, you should slow the rate of advance to allow the edge of the glass to tip up and begin to slide down into the mould. If the problem persists, make the glass blank smaller, or support the overhanging glass with a collar.

Is the glass heavier on one side?

The glass may be uneven thickness and so heavier on one side. The heavier area of the glass will begin to slump first and so promote movement of the whole glass in an asymmetrical manner. The solution to this is to fire slower and to a lower temperature.

Do you have a wonky mould?

The mould can be imperfect. So you need to check the mould for accuracy. I have a slumper that has one side lower than the other three. Being aware of this, I can place the glass so that it is still useable. Measuring the mould in all directions will help determine its symmetry.

If all these things have been investigated and the solution not found, it is possible to create a bevel on the bottom edge of the glass so that the edge sits in the mould at the same angle as the mould. This provides a larger contact point for the glass and mould than just a thin edge. This appears to allow the glass to move evenly during the slump.

Of course, a major solution is to observe the slump.  Peeking into the kiln at the beginning of the slump soak and frequent intervals after that will show if the piece is slumping evenly or not.  If it is uneven, you can put on the appropriate protective gear and with gloves on your hands, shift the glass to be set evenly in the mould.

The major solutions to avoid uneven slumping are:

• Avoiding the hot and cool parts of the kiln
• Making everything level
• Careful placement on the mould
• Slower rates of advance
• Lower slumping temperatures
• Observation

Using Space on Shelves

Often there is unused space on the kiln shelves when you are firing a project. With a bit of planning, you can make use of the spaces for a variety of things.

Frits fired on fibre paper

Bowl made from frit balls

You can place piece of frit in the clear areas to make frit balls.

You can make colour tests on plaques of glass to see the results of strikers, powder combinations or results of various depths of colour.

Compatibility tests can be done with pieces of glass of which you are not certain.

simple stress testing set-up

Strip of fired glass samples for testing

Results - those with halo are stressed

In the same way, annealing tests can be conducted.

You can fire small pieces of jewellery at the same time as your larger pieces.

You can also prepare elements for incorporation into other fusing projects and lay them out in the open spaces on the shelf.  Your use of the spare space is related both to your imagination and to your future projects.