There are a number of ways of applying kiln wash/ shelf primer/ batt wash - all are separators so the glass does not stick to the shelf - to achieve a smooth surface. Remember though there will always be some texture because of the particle size of the wash. So for the smoothest surface, use the finest powder you can find.
It also is important to prepare the mixture some hours before application to ensure all the particles of the powder are wetted. Immediate use often leads to a gritty surface.
Spraying the separator onto the shelves can give an even coating without brush marks, runs or ridges.
Applying the kiln wash with a very soft brush such as a hake brush in a variety of directions will ensure full coverage. There may be some brush marks.
To reduce the application marks further, you can brush or spray hot water over the still damp kiln wash. This helps to remove brush marks or the stippling that often comes from spraying.
Another way to reduce the texture after drying is to polish the kiln wash with a ball of old nylons or rub a flat piece of paper with the palm of your hand over the shelf. Remove the dust that may be left behind.
Sunday, 30 August 2009
Friday, 28 August 2009
Foil Lifting While Soldering
There are several possible reasons for this.
The main one is that the soldering is too slow. This causes the adhesive on the foil to fail before the solder has a chance to become rigid.
The foil may not have stuck to the glass firmly. Reasons for this are many, but some are:
- Dirty glass. Make sure the glass is washed and polished clean, especially if you have been grinding, when you need to get all the glass dust out of the pits on the edges.
- Oils from your hands. The oils can be natural or from hand creams. If you have oily skin or need to use hand creams consider cotton gloves for use when handling the glass prior to and during foiling.
- Inadequate contact between the foil and the glass. This can be from both the above, but can also be that the foil was not pressed firmly to all the sides and edges of the glass pieces.
The foil adhesive may be inadequate through manufacture or age. If a test piece does not feel tacky to your finger tips, it is not going to stick to the glass very well.
The main one is that the soldering is too slow. This causes the adhesive on the foil to fail before the solder has a chance to become rigid.
The foil may not have stuck to the glass firmly. Reasons for this are many, but some are:
- Dirty glass. Make sure the glass is washed and polished clean, especially if you have been grinding, when you need to get all the glass dust out of the pits on the edges.
- Oils from your hands. The oils can be natural or from hand creams. If you have oily skin or need to use hand creams consider cotton gloves for use when handling the glass prior to and during foiling.
- Inadequate contact between the foil and the glass. This can be from both the above, but can also be that the foil was not pressed firmly to all the sides and edges of the glass pieces.
The foil adhesive may be inadequate through manufacture or age. If a test piece does not feel tacky to your finger tips, it is not going to stick to the glass very well.
Monday, 24 August 2009
Grinding for Copper Foil
It is often thought that every piece of glass has to be ground to enable the foil to stick well to it. There are conflicting views about this. I am firmly on the side of not grinding. The impact adhesive on the back of the foil is thin and will not fill the depressions caused by grinding. It will adhere to a smooth surface more strongly than a rough one. Remember the purpose of the foil is to provide a surface to carry the solder. It keeps the foil in place until the solder bead is completed on both sides. It is not a permanent adhesive. So some of the discussion about which surface is best is academic.
There are ways of obtaining clean cuts that help avoid the need to grind.
Score with an even pressure. This helps the glass break clean with few shells or chips. If there are any overhangs, you can eliminate them with a quick wipe of the edge of the cut piece on the waste piece.
Ensure you hold your cutter vertically. This will encourage the break to be at right angles to the surface giving a clean smooth cut face.
The only NEED for grinding is to adjust an inaccurate cut. We all make inaccurate cuts from time to time.
There are ways of obtaining clean cuts that help avoid the need to grind.
Score with an even pressure. This helps the glass break clean with few shells or chips. If there are any overhangs, you can eliminate them with a quick wipe of the edge of the cut piece on the waste piece.
Ensure you hold your cutter vertically. This will encourage the break to be at right angles to the surface giving a clean smooth cut face.
The only NEED for grinding is to adjust an inaccurate cut. We all make inaccurate cuts from time to time.
Friday, 21 August 2009
Copper Foil Oxidisation
Protection of foiled pieces from oxidisation
If foiled pieces are going to sit a while before soldering, put them in a sealed plastic bag with the air squeezed out. This will prolong the time before the oxidization becomes a problem for the soldering process.
Another possibility is to tin all the pieces before putting them away in the plastic bag. Solder oxidizes more slowly than copper does.
If foiled pieces are going to sit a while before soldering, put them in a sealed plastic bag with the air squeezed out. This will prolong the time before the oxidization becomes a problem for the soldering process.
Another possibility is to tin all the pieces before putting them away in the plastic bag. Solder oxidizes more slowly than copper does.
Wednesday, 19 August 2009
Channels in Jewellery Items
The principle in forming channels in fused glass is to keep the space open with something that will survive the firing and can be easily removed.
You can use kiln washed wire, mandrels, or tooth picks which you can pull out after cooling. These tend to leave a residue of the kiln wash behind. So this is best used on opaque items.
You can use rolled or cut fibre paper, which can be washed out after cooling, leaving a clean hole. This is works well on transparent items.
Both these methods tend to leave bumps over the channel. So you can make a three layer piece. Cut the middle layer short enough to allow the element to keep the hole open (toothpick, cut piece of fibre paper, wire etc.) to be placed with enough overlap of the top layer to catch the bottom layer. In this kind of setup you need to make the top layer a bit longer than the bottom layer. Make sure you are generous in the length of the "hole keeper" so if the glass (now possibly 9mm) does expand you do not trap the material inside.
Of course on a three layer set up like this you could use thin glass which would give you about 6mm of thickness thus eliminating the spread due to volume. In this case you would need to use fibre paper or wire that is about 1.5mm high/thick. It is probably best to have a thin piece of glass on each side of the “hole keeper” to ensure the glass does not retreat due to lack of volume.
You can experiment with a layer of standard and two of thin in various combinations to find the one you like best.
You can use kiln washed wire, mandrels, or tooth picks which you can pull out after cooling. These tend to leave a residue of the kiln wash behind. So this is best used on opaque items.
You can use rolled or cut fibre paper, which can be washed out after cooling, leaving a clean hole. This is works well on transparent items.
Both these methods tend to leave bumps over the channel. So you can make a three layer piece. Cut the middle layer short enough to allow the element to keep the hole open (toothpick, cut piece of fibre paper, wire etc.) to be placed with enough overlap of the top layer to catch the bottom layer. In this kind of setup you need to make the top layer a bit longer than the bottom layer. Make sure you are generous in the length of the "hole keeper" so if the glass (now possibly 9mm) does expand you do not trap the material inside.
Of course on a three layer set up like this you could use thin glass which would give you about 6mm of thickness thus eliminating the spread due to volume. In this case you would need to use fibre paper or wire that is about 1.5mm high/thick. It is probably best to have a thin piece of glass on each side of the “hole keeper” to ensure the glass does not retreat due to lack of volume.
You can experiment with a layer of standard and two of thin in various combinations to find the one you like best.
Monday, 17 August 2009
Fusing straight lines
In addition to the "flip and fire" approach, there are a number of other factors that contribute to sharp, crisp lines in a piece made with strips of glass laid on edge and fused.
Smooth glass will fuse straighter than strips of textured glass. The individual strips fit closer together, leaving less room for lines to wander and create a wavy appearance.
The quality of the cut of the strip is important. Straight strips with right angle edges and no flares make for crisper lines.
The thinner the strips, the less opportunity for movement in the fusing. Ideally, the strips should be 6mm wide. This is the thickness that glass tends to take up when full fused. The greater the width beyond 6mm, the less likely the lines will be straight.
The viscosity of the glass affects the crispness of the lines. A glass that is less viscous will tend to be more wavy than a more viscous glass. E.g., black glass, a less viscous glass than white, will tend toward waviness more than the white. This is not a variation between manufacturers; it is a variation within a compatible range of glasses.
The firing surface will have an effect. Firing directly on a kiln washed shelf will give crisper lines than firing on fibre paper of whatever thickness.
Damming the composition before firing will produce straighter lines. The dam holds the strips in place during the heat up and restricts any flow that would be caused by strips thicker than 6mm.
Smooth glass will fuse straighter than strips of textured glass. The individual strips fit closer together, leaving less room for lines to wander and create a wavy appearance.
The quality of the cut of the strip is important. Straight strips with right angle edges and no flares make for crisper lines.
The thinner the strips, the less opportunity for movement in the fusing. Ideally, the strips should be 6mm wide. This is the thickness that glass tends to take up when full fused. The greater the width beyond 6mm, the less likely the lines will be straight.
The viscosity of the glass affects the crispness of the lines. A glass that is less viscous will tend to be more wavy than a more viscous glass. E.g., black glass, a less viscous glass than white, will tend toward waviness more than the white. This is not a variation between manufacturers; it is a variation within a compatible range of glasses.
The firing surface will have an effect. Firing directly on a kiln washed shelf will give crisper lines than firing on fibre paper of whatever thickness.
Damming the composition before firing will produce straighter lines. The dam holds the strips in place during the heat up and restricts any flow that would be caused by strips thicker than 6mm.
Saturday, 15 August 2009
Fusing Straight Lines
"Flip and Fire" is a term was devised by Brian Blanthorn to describe a process to achieve crisp details in the final piece.
The process takes advantage of two things - heat and weight. The glass on the shelf side moves less than the top as it is not quite so hot, and the weight of the glass above keeps the lines the way they were cut. The glass on the top of the piece begins to move first and fill the gaps that are left between the pieces.
The simplest method to achieve straight lines is to fire the piece with the final surface down to the shelf. After fusing, turn over and clean any surface contamination, usually by sandblasting. Wash and polish dry. Then fire the new surface to a fire polish temperature.
This technique works best on pieces that are of one uniform thickness.
The process takes advantage of two things - heat and weight. The glass on the shelf side moves less than the top as it is not quite so hot, and the weight of the glass above keeps the lines the way they were cut. The glass on the top of the piece begins to move first and fill the gaps that are left between the pieces.
The simplest method to achieve straight lines is to fire the piece with the final surface down to the shelf. After fusing, turn over and clean any surface contamination, usually by sandblasting. Wash and polish dry. Then fire the new surface to a fire polish temperature.
This technique works best on pieces that are of one uniform thickness.
Thursday, 13 August 2009
Transparency Sketches
Use matt finish acetate .25 to .12mm thick. This will later be fixed to Perspex for presentation.
You will need rigger brushes in sizes 0, 1, 2, and 4 for doing the lead lines and other areas of graphic delineation. In using these brushes for lead lines, you want to maintain a line that is consistently thick. It is a different feeling from general image making and you may want to try locking your wrist to maintain a greater consistency of pressure.The paint for the lead lines can be a calligraphy ink or a black acrylic paint. The lead lines and all other tracing is applied to the matt side of the acetate.
Once the tracing lines are all completed, start laying the colours on the backside, the smooth side. The brushes to use are bulbous pointed sables in sizes 2, 3, 5 and 6. The application is in a "floated" versus a "stroked" manner of application. Stroking has a tendency to hasten the drying resulting in streaking. You may find this a bit of a trick at first. It is advisable to place colour throughout the design so it has time to set up and dry a bit, as opposed to putting wet against wet.
When the colour has dried, one can emulate matting on the matt side with an ebony pencil. And if you want to take out some lights, that can be accomplished with carefully placed extender. The extender is also used to make the piece transparent and to emulate a variety of textures available in glass from reamy to seedy.
When the colours are dry, mount the sketch on 3mm Perspex to stiffen the presentation, provide weight and give the presentation with some "substance”. You can also add double matt board doors hinged with smooth electrical tape to keep the lacquer colours away from sustained sun. Also when open, they support the sketch during the presentation.
When putting matting boards around the presentation sketch, they should be much wider than a drawing or water colour so that ambient light from behind is modified by a greater expanse of black or dark matting board.
Edited from emails by Richard Millard
You will need rigger brushes in sizes 0, 1, 2, and 4 for doing the lead lines and other areas of graphic delineation. In using these brushes for lead lines, you want to maintain a line that is consistently thick. It is a different feeling from general image making and you may want to try locking your wrist to maintain a greater consistency of pressure.The paint for the lead lines can be a calligraphy ink or a black acrylic paint. The lead lines and all other tracing is applied to the matt side of the acetate.
Once the tracing lines are all completed, start laying the colours on the backside, the smooth side. The brushes to use are bulbous pointed sables in sizes 2, 3, 5 and 6. The application is in a "floated" versus a "stroked" manner of application. Stroking has a tendency to hasten the drying resulting in streaking. You may find this a bit of a trick at first. It is advisable to place colour throughout the design so it has time to set up and dry a bit, as opposed to putting wet against wet.
When the colour has dried, one can emulate matting on the matt side with an ebony pencil. And if you want to take out some lights, that can be accomplished with carefully placed extender. The extender is also used to make the piece transparent and to emulate a variety of textures available in glass from reamy to seedy.
When the colours are dry, mount the sketch on 3mm Perspex to stiffen the presentation, provide weight and give the presentation with some "substance”. You can also add double matt board doors hinged with smooth electrical tape to keep the lacquer colours away from sustained sun. Also when open, they support the sketch during the presentation.
When putting matting boards around the presentation sketch, they should be much wider than a drawing or water colour so that ambient light from behind is modified by a greater expanse of black or dark matting board.
Edited from emails by Richard Millard
Tuesday, 11 August 2009
Oxidized Copper Foiled Pieces
If copper foiled pieces sit out for any length of time after foiling they will oxidize. This means that the solder will not stick to the foil, as it requires a clean surface to attach to.
Clean the foiled pieces with fine steel wool, pot scrubber or flexible mild abrasive. Make sure you do not damage the foil or pull it up from the glass during this process. It is likely that the adhesive holding the foil to the glass is not as strong as it once was.
I do not recommend using a stronger flux to overcome the oxidisation, as this is often highly acidic and may damage the glass.
Once cleaned, you can flux the foil and proceed as normal.
Clean the foiled pieces with fine steel wool, pot scrubber or flexible mild abrasive. Make sure you do not damage the foil or pull it up from the glass during this process. It is likely that the adhesive holding the foil to the glass is not as strong as it once was.
I do not recommend using a stronger flux to overcome the oxidisation, as this is often highly acidic and may damage the glass.
Once cleaned, you can flux the foil and proceed as normal.
Sunday, 9 August 2009
Compatibility Tests
These procedures are based on the observation that glasses compatible with the base glass are compatible with each other. This means that you can test opaque colours’ compatibilities with each other by testing each of them on clear strips.
Annealing test
These tests must be combined with an annealing test. This conists of putting two pieces from the same sheet of glass together - so you now they are compatible - and firing them along with your compatibility test. Viewing the results of your annealing through the polarised filters shows whether there is stress left in your annealing. If there is, the compatibility tests are inclusive as there is no difference in appearance of stress whether from incompatibility or from inadequate annealing. Once you have the annealing right, you can then interpret the compatibility tests done at the same time.
Strip test
Cut a strip of base glass ca 25mm wide and as long as convenient for you or your kiln.
Cut clear glass squares of 25mm to separate the colours.
Cut 25mm squares of the colours to be tested
Start with a clear square at one end of the clear strip and alternate colours and clear along the strip finishing with a clear square.
Add a stack of two layers of clear to the kiln before firing. This is to test for adequate annealing. If the annealing is inadequate, then the whole test is invalid.
Test the result with polarising filters. Start with the clear annealing test square. If no stress is apparent, go to the test strip. But if stress is apparent, look to your annealing schedule as something needs to change. Usually the requirement is a combination of a longer soak at the annealing temperature and a slower annealing cool.
Look carefully for little bits of light in the clear surrounding the colour. These are indications of stress – the more light or the bigger the halo, the greater the stress.
You can use this test to determine if you annealing is satisfactory for larger pieces. In this case you should use at least 100mm squares. Stack them to the height of your planned project and dam them with fibre board or other refractory materials to prevent spread. Fire to full fuse and anneal. When cool check for stresses.
The tile method looks at compressive factors too.
Cut a 100mm clear tile
Cut two strips of glass 25mm wide and 100mm long for each test
Cut two rectangles of 25 by 50mm of the same glass for the two remaining sides
Cut a square of 50mm for the centre. The glass in the middle is normally the test glass. To be very certain of what has happened you can do the reverse lay up at the same time. You put coloured glass around the outside, but in this case the inside needs to be clear or transparent. At least one element needs to be transparent enough to view the stress patterns, if any. So you could have a clear middle and black exterior, and vice versa.
This test is a more time consuming process and you may wish to use it only for larger projects.
Also look at the use of polarising filters
Annealing test
These tests must be combined with an annealing test. This conists of putting two pieces from the same sheet of glass together - so you now they are compatible - and firing them along with your compatibility test. Viewing the results of your annealing through the polarised filters shows whether there is stress left in your annealing. If there is, the compatibility tests are inclusive as there is no difference in appearance of stress whether from incompatibility or from inadequate annealing. Once you have the annealing right, you can then interpret the compatibility tests done at the same time.
Strip test
Cut a strip of base glass ca 25mm wide and as long as convenient for you or your kiln.
Cut clear glass squares of 25mm to separate the colours.
Cut 25mm squares of the colours to be tested
Start with a clear square at one end of the clear strip and alternate colours and clear along the strip finishing with a clear square.
Add a stack of two layers of clear to the kiln before firing. This is to test for adequate annealing. If the annealing is inadequate, then the whole test is invalid.
Test the result with polarising filters. Start with the clear annealing test square. If no stress is apparent, go to the test strip. But if stress is apparent, look to your annealing schedule as something needs to change. Usually the requirement is a combination of a longer soak at the annealing temperature and a slower annealing cool.
Look carefully for little bits of light in the clear surrounding the colour. These are indications of stress – the more light or the bigger the halo, the greater the stress.
You can use this test to determine if you annealing is satisfactory for larger pieces. In this case you should use at least 100mm squares. Stack them to the height of your planned project and dam them with fibre board or other refractory materials to prevent spread. Fire to full fuse and anneal. When cool check for stresses.
The tile method looks at compressive factors too.
Cut a 100mm clear tile
Cut two strips of glass 25mm wide and 100mm long for each test
Cut two rectangles of 25 by 50mm of the same glass for the two remaining sides
Cut a square of 50mm for the centre. The glass in the middle is normally the test glass. To be very certain of what has happened you can do the reverse lay up at the same time. You put coloured glass around the outside, but in this case the inside needs to be clear or transparent. At least one element needs to be transparent enough to view the stress patterns, if any. So you could have a clear middle and black exterior, and vice versa.
This test is a more time consuming process and you may wish to use it only for larger projects.
Also look at the use of polarising filters
Wednesday, 5 August 2009
Applying kiln wash
Applying kiln wash to shelves and moulds has the same requirements.
The kiln was must be applied evenly.
You can use a soft bristled brush like a hake and trail on the kiln wash in four directions – top to bottom, side to side, and diagonally left to right and right to left.
You can also spray the kiln wash onto the shelf or mould. This can provide an even coating, but you must be careful to avoid puddling the kiln wash. Pause after each coat to allow the water to be absorbed before applying the next coat. Apply until the shelf or mould surface is not obvious through the kiln wash.
You can use a sponge to apply to flat surfaces. A light touch is required. You need to apply in various directions as with the brush.
Metal moulds are a special case. The water carrying the kiln wash will simply bead up or run off the metal. First clean the metal to get rid of oils and dirt – sandblasting will do well. Then you need to heat the metal to about 25C – 50C above boiling and brush or spray the kiln wash onto the mould, one coat at a time. Return the mould to the heat source and then apply another coat of kiln wash. Do this until you have an even layer of kiln wash. Be careful not to put so much liquid on the mould that it begins to run. If this happens, you really need to start again.
Apply the kiln wash thinly.
You need enough kiln wash to separate the glass from the carrying surface. Any additional kiln wash will not make for a better separation, but may begin to flake off the surface and adhere to the glass more or less tightly.
The usual recommendation for brushing is one part kiln wash to five parts water. I recommend ten parts water to one part kiln wash if you are spraying the kiln wash. If you have a really absorbent surface, such as a vermiculite mould, you can reduce the water to two and a half parts water to one kiln wash. All these measurements are by volume.
The kiln wash finish must be smooth.
There are several ways to smooth the surface.
You can rub your hand over the shelf or mould to remove high spots/streaks. You need to remove the dust before using though.
You can smooth the surface using a rolled up nylon stocking. This relatively open weave allows the powder to be captured in the material. It works well on irregular surfaces like a mould. Again you must clear off any remaining dust.
Another way is applicable to flat surfaces. After applying the kiln wash, but before it has dried, make sure the surface is level. Then brush or spray on a layer of hot water. This both puddles and evaporates quickly, leaving a smooth surface on thinly applied kiln wash. If the kiln wash is thick, the drying process will leave cracks as in a dried out river bed.
The kiln was must be applied evenly.
You can use a soft bristled brush like a hake and trail on the kiln wash in four directions – top to bottom, side to side, and diagonally left to right and right to left.
 |
| The pigmented kiln wash turns white, indicating that the shelf has been fired |
You can also spray the kiln wash onto the shelf or mould. This can provide an even coating, but you must be careful to avoid puddling the kiln wash. Pause after each coat to allow the water to be absorbed before applying the next coat. Apply until the shelf or mould surface is not obvious through the kiln wash.
You can use a sponge to apply to flat surfaces. A light touch is required. You need to apply in various directions as with the brush.
Metal moulds are a special case. The water carrying the kiln wash will simply bead up or run off the metal. First clean the metal to get rid of oils and dirt – sandblasting will do well. Then you need to heat the metal to about 25C – 50C above boiling and brush or spray the kiln wash onto the mould, one coat at a time. Return the mould to the heat source and then apply another coat of kiln wash. Do this until you have an even layer of kiln wash. Be careful not to put so much liquid on the mould that it begins to run. If this happens, you really need to start again.
Apply the kiln wash thinly.
You need enough kiln wash to separate the glass from the carrying surface. Any additional kiln wash will not make for a better separation, but may begin to flake off the surface and adhere to the glass more or less tightly.
The usual recommendation for brushing is one part kiln wash to five parts water. I recommend ten parts water to one part kiln wash if you are spraying the kiln wash. If you have a really absorbent surface, such as a vermiculite mould, you can reduce the water to two and a half parts water to one kiln wash. All these measurements are by volume.
The kiln wash finish must be smooth.
There are several ways to smooth the surface.
You can rub your hand over the shelf or mould to remove high spots/streaks. You need to remove the dust before using though.
You can smooth the surface using a rolled up nylon stocking. This relatively open weave allows the powder to be captured in the material. It works well on irregular surfaces like a mould. Again you must clear off any remaining dust.
Another way is applicable to flat surfaces. After applying the kiln wash, but before it has dried, make sure the surface is level. Then brush or spray on a layer of hot water. This both puddles and evaporates quickly, leaving a smooth surface on thinly applied kiln wash. If the kiln wash is thick, the drying process will leave cracks as in a dried out river bed.
Monday, 3 August 2009
Devitrification
What is it? When does it happen? Why does it happen? These are frequent questions.
Devitrification is the beginning of crystallisation of the surface of the glass. It can look like a dirty film over the whole piece or dirty patches. At its worst, the corners begin to turn up or a crackling can appear on the granular surface.
Devitrification occurs in the range 650° –750°C. This means that you need to cool the project as quickly as possible from the working (or top) temperature to the annealing point.
There is evidence to show that devitrification can occur on the heat up and will be retained in the cooling. Normally this is not a problem as the advance on the heat up is relatively quick through this range.
The devitrification seen in typical studio practice – especially among novices - results more often from inadequately cleaned glass than from excessive time at a particular temperature or down through the devitrification range.
Temperature range for devitrification
Homemade devitrification solution
Devitrification is the beginning of crystallisation of the surface of the glass. It can look like a dirty film over the whole piece or dirty patches. At its worst, the corners begin to turn up or a crackling can appear on the granular surface.
Devitrification occurs in the range 650° –750°C. This means that you need to cool the project as quickly as possible from the working (or top) temperature to the annealing point.
There is evidence to show that devitrification can occur on the heat up and will be retained in the cooling. Normally this is not a problem as the advance on the heat up is relatively quick through this range.
The devitrification seen in typical studio practice – especially among novices - results more often from inadequately cleaned glass than from excessive time at a particular temperature or down through the devitrification range.
Temperature range for devitrification
Homemade devitrification solution
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