- · Unity – all the elements form a whole.
- · Balance – note, not only symmetry, but a distribution of elements that allows each piece to appear to be in its proper place. Imbalance provides dissonance and tension which can be the purpose of the piece, of course.
- · Rhythm – this can be repetition with or without variation. This provides energy, animation to the piece.
- · Emphasis – or contrast between a main element and the rest. This can be size, colour or placing.
- · Harmony – all the elements work together to form a whole.
Wednesday, 1 March 2017
Wednesday, 22 February 2017
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.
|This piece has been assembled with the final upper surface on the shelf and the base sheet placed on top.|
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.
|The same piece fire polished after cleaning the fused glass.|
This technique works best on pieces that are of one uniform thickness.
There are other factors at play in obtaining crisp lines.
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 when they are placed on edge. 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.
Wednesday, 15 February 2017
- Soak Times
Another element in slumping glass not formulated for kiln working is the annealing of the glass after the slumping. The annealing temperature can be estimated as 40C below a low temperature slump of a 280mm span of glass. The slump point test mentioned earlier will help determine the annealing point. You need to soak for a time - maybe 30 minutes - at the estimated annealing temperature and then cool slowly in case you have miscalculated on the annealing temperature. In any case, a long slow anneal cool will pay dividends in a more robust glass.
Remember TADSET - temperature, annealing, devitrification, soak, edges, test.
Wednesday, 8 February 2017
Wednesday, 1 February 2017
The follow-on question is about why devitrification occurs on ground edges that are not near the kiln shelf. There are two elements to consider.
It is claimed that the fumes of the binder burning off can settle in the pits of the ground glass, providing those nucleation points for the glass crystalisation. The suggested solution is to vent the kiln to about 400C to allow the combustion fumes out of the kiln rather than keeping them inside the kiln.
The second and more certain element is that the grinding creates microscopic pits and fractures in the glass where the powder from grinding settles. Almost no amount of cleaning will completely remove this residue from the tiny pits and fractures resulting from grinding.
There are at least two solutions to this cleaning problem. Don't grind unless absolutely necessary - groze instead. The second is to lightly cover any ground edges with clear powder frit. You could of course consider ultrasonic cleaning or power washing, either with a dishwasher, or outdoor power washer. Both these seem to be so completely out of proportion to the problem, that I have never used them.
Tuesday, 24 January 2017
|Mandrels prepared for bead making. In coating them for a melt, you need to have the whole length coated.|
Once dry, you can arrange these coated mandrels in any shape of grid you choose. Lay them across your supports whether fibre board or brick with about 25mm on the support at each end. Lay all of one direction down first and the follow with the second, or more layers. Place you glass on top of the grid created and fire.
Wednesday, 18 January 2017
- · What are the initial rates of advance, are they different?
- · Where is the bubble squeeze, is there one?
- · Are there different rates of advance from bubble squeeze to top temperature?
- · If you can compare their larger and smaller kilns, is there a difference in schedules?
- · Are the top temperatures different for tack and fuse?
- · Is there more than one tack fuse temperature to allow for various levels of tack from lamination to fully rounded?
- · Is there a difference in soak times at the target temperatures?
- · Are there low and high temperature slumps?
- · Is there a difference in temperature or time between various slumps?
- · Is there any allowance for span or size of mould?
- · Does depth of the mould make any difference to the schedule?
- · Is a difference for the depth of the mould offered?
- · Are there different schedules for Spectrum, Wissmach, Bullseye, etc. fusing glasses?
- · Are float glass schedules any different for rates, soak times, annealing points?
- · Are the schedules printed in the kiln handbook or manual?
- · Are you given clear instruction on when to alter the programs?
- · Are you given clear instruction on how to alter the programs?
Wednesday, 11 January 2017
Wednesday, 4 January 2017
Wednesday, 28 December 2016
Wednesday, 21 December 2016
I am advocating the use of a feature almost all controllers have. The Delay function. On most controllers, it is the first thing that comes up on the display. We mostly ignore that and proceed to the first ramp. We set the controller to fire immediately, so that it will be done overnight and we can look in the morning or when we come back from work. That way all the waiting for the piece to be finished can be eliminated. We can go to work or to sleep knowing that the firing will be done when we can get back to the kiln.
“I need a life. I have to work. I have to sleep. I can’t be around my kiln all the time.”
The legitimate responses to the idea that you should be around to observe the work at critical temperatures are that “I need a life. I have to work. I have to sleep. I can’t be around my kiln all the time.” This is where the Delay function comes to your aid. You can use the Delay function to make sure the firing is at the critical point for observation at a time that is convenient for you. This way, you do not disrupt your normal life. Your social life can continue and you can get some sleep too.
If you are looking to get an exact tack fuse profile, the schedule will be a little more complicated. Say you want a rounded tack fuse that you think will be achieved at 750C in 10 minutes. The schedule might look something like:
You may feel that you are going to lose a firing by using the Delay function. You often can peek into the kiln in the morning to see how things have turned out by using the overnight firing. But there normally is still more cooling down time required.
This little extra planning is rewarded by the ability to see what is happening in the kiln, so that you can adjust during the firing, rather than having to do a firing again, or in the worst case, completely re-make a piece after a disaster.
Wednesday, 14 December 2016
The long established practice of glass workers has been to give the glass an arris at the end of each grinding stage before they change to a finer grit. This small area of angled glass, allows the continued smoothing of the glass without creating such a sharp edge that the glass there is not strong enough to resist the grinding action.
You will notice on a bowl or other rounded vessel, that the chips are almost always on the outside. The inside of the rim normally has an oblique angle to the rim, and the outside an acute angle. The explanation is held in the angle. As the rim is ground down, the outer acute angle becomes very thin as well as sharp. At some point the glass is thinner than the grit used to grind the surface. This causes little chips of glass to break off the edge.
Wednesday, 7 December 2016
At low temperatures it cannot quickly form exactly to the mould. It falls first in the middle. Because the glass is not very plastic, the edges rise up from the mould at first, because the weight there is not great enough to allow the unsupported glass to bend. The edges stay in line with the beginning of the bend in the middle. (apologies for the quick and dirty drawings)
It only settles back to the rim with the heat work of the slump as the slumping soak continues.
· Low temperature reduces the mould marks on the back of the glass.
· Fewer stretch marks are in evidence.
· Low slumping temperatures with long soaks reduce the uneven slump that is sometimes in evidence with deeper moulds.
· Low temperatures allow different colours to heat more evenly.
· Low temperatures reduce the thinning effect of a high temperature slump.