Thursday, 23 March 2017

Approaching a Gallery

Images of WorkMake sure that you have good quality images taken of your work (35mm transparencies, digital images for CDs or email), after all, you will be competing with practitioners that have been in business for years and are firmly established as leading national and international designers. Sending poor images/presentations reflects very badly on your approach and your work.

Invest in a professional portfolio filled to the brim with beautifully laid out colour photography on a black background. Don’t walk into the gallery with a handful of snapshots.

Sending Biography and VisualsSend general descriptive information about yourself and your work to the gallery first. Then follow this up with a telephone call. Find out the contact name you need for the relevant department within the gallery. If you send something with no contact name your presentation can sit in a pending tray for months! Contact as many galleries as you can handle, rather than waiting for a reply from the first one on your list.

Research and Make Appointments
Don’t just turn up at a gallery with your work. Galleries plan their exhibition schedule at least two years in advance. They are busy most days with artists and dealing with clients so it is always best to make an appointment first.

Pop in regularly to your local galleries, or research on the internet, to get an idea of the kind of designers they display, and the style and quality of work on show.

Keep in TouchContemporary galleries are always looking for new original designers for their exhibition programme, so update the gallery regularly by sending emails, transparencies and CD (with images).

It is especially important that the gallery can see how serious you are about your work, how it develops in style and that you are still exhibiting and producing work 2-5 years later. Make sure your work is unique and difficult to duplicate. Keep your own designs and patterns dated and own the copyright to them.

Don’t give up. There's someone out there who will like your work. When you find gallery owners who are crazy about your work, stick with them.

When you have an offer of a show
Watch the papers for announcements of other openings at the gallery to see how well each opening is advertised. Ask around the arts community to see how well known the gallery and its owner are.

Check on the gallery/artist percentage agreement when calling each gallery. Your price to the public must be calculated based on this. Charge what the work is worth!

Check around with other artists represented by the gallery, asking them about promptness of payment by the gallery.

Be businesslike in all dealings.Prepare a contract, if the gallery does not have one, to cover mutual expectations. It should include who does what, e.g., mounting of the work, invitations to the opening, opening night, payment terms, artist’s residual and resale rights, etc.

Don’t be a pain to the gallery owner. Don’t pester. If you have to be anxious about the show, do it privately.

Enjoy the opening night!

Wednesday, 22 March 2017

Over Annealing

Sometimes the statement is made that you can never over anneal.  This statement is true only under certain circumstances. 

The statement is also dependent on the understanding of what anneal means.  Annealing is the process of stabilising the temperature, ensuring the piece is at the same temperature throughout, and then gradually cooling the piece to avoid heat shock.  This is to point out that annealing is both the soak and the slow cool.

Long Soaks
Long soaks at the annealing stabilisation temperature can be injurious to your piece if the temperature in your kiln is not even.  This can mean that one or more parts of your piece are at different temperatures. This sets up stress within it.

You can reduce the possibility of stress by placing the piece at the centre of the kiln or avoid placing the piece in the cool spots of the kiln. 

Cool Rates
Another method of avoiding locking in the stress to the piece is to reduce the cooling rate to less than normal.  This will reduce the temperature differential within the piece.

Mass Being Cooled
In all this you need to remember that the anneal cool rate is relative to the mass of material to be cooled.  Therefore, a thick piece needs a slower annealing cool than a thin one.

But it is not just the thickness of the glass to be cooled.  You need to think about the mass of the kiln shelf or mould that supports the glass.  An example is that glass on a ceramic shelf needs slower cooling than one on a fibre board shelf, because the mass of the shelf needs to be taken into account as well as the glass. Connected to this is whether the shelf is on the floor - slower cooling - or supported on posts, allowing air to circulate under the shelf.

Wednesday, 15 March 2017

Fibre board moulds

A publication on moulds from fibre boards is available from Stained Glass Supplies. This gives much more detail than this note can.  However, the basics are outlined here.

Commonly available refractory boards are:

·         Calcium silicate
·         Standard fibre boards
·         Armstrong ceiling tiles

They can be used bare (except Armstrong ceiling tiles) or hardened.

A question that will arise is whether to harden or not.  This depends on the durability you require.  A board that is not hardened does not require kiln wash when fired.  However, as it is soft it is easy to break.  A hardened fibre board mould always requires kiln wash or another separator.  It does become durable and almost rings when tapped once it is hardened and cured.  If the shape needs to be preserved for further use, hardening is advisable.

Working methods

Usually hand tools are all that are required to get the results required.


Do any work on refractory boards outdoors if possible, and with a respirator.  If you must do it indoors, have good ventilation, wear a respirator, and clean up with damp sponges or other absorbent material to avoid putting the dust back into the air.

Do you need to pre-fire fibre moulds?

Moulds that are small or thin do not erequire firing before using.  Thick and large fibre moulds do need to have the binders burned out before use to avoid carbon marks on the glass.

Sunday, 12 March 2017

Advice on Commissioning Craft

This is an outline of information you can give to a potential client to help them with the process of commissioning.

If you have always imagined owning something unique and original, or like to be distinctive and stylish and can’t find what you are looking for on the high street, then commissioning could be the way forward.

If you are nervous about taking the next step and uncertain what is involved, these are the key stages.
Step 1: What do you want?
Step 2: Research by looking at ideas and images that suit your imagination. Note who is working in that kind of style.
Step 3: Write a brief of what you have discovered and then discuss your ideas with the artist you have identified.
Step 4: Discuss the budget and get a written quotation.
Step 5: Agree on the time frame for progress and delivery updates. There are sometimes difficulties in making unique items.
Step 6: Communicate regularly with each other.

Remember, because the process is about communication, there is the potential for misunderstandings and differing expectations by the commissioner and maker. Make sure you have thought the process through before proceeding and ensure all aspects are clarified in writing before you begin - including the quotation, payment schedule, time frame, etc.

And finally…… Enjoy it

The opportunity to commission a piece is an exciting experience and can be rewarding to both you and the maker. As long as you are prepared, and keep communicating with each other, you will become the owner of a unique and special piece of work which will bring hours of pleasure and will be the envy of your friends. 

The full information can be downloaded from craftscotland

Polishing Brushes

The polishing brush should have moderately soft bristles. A long bristled shoe polishing brush can be used, although one that is a little stiffer does the job more quickly.

A shoe polishing brush

It is important to keep these brushes free of hardened cement, as a brush containing pieces of hardened cement will scratch the leads rather than darken them. As soon as the polishing is finished, inspect the brush for little balls of cement. Rubbing the brush against a clean rough surface will clean it while the cement is “wet”. Also running the brush at an angle on the sharp edge of your work bench will clear some of the cement adhering to the bristles.

A polishing brush with slightly stiffer bristles

If the cement hardens, you can clean the brush by crushing the hard balls of cement with a pair of pliers. Or you can just get a new shoe polishing brush.

Saturday, 11 March 2017

Drawing an Oval

Need to draw an oval for a panel? Here's how:
  • Calculate half the measurement of the longest line. In this example the long line is 340mm and the short axis is 200mm long.  So the diagonal is 170mm.

  • Measuring from the end of the shortest line, mark off this amount on the longest line, top and bottom. You can use a ruler or compass set to the correct length.
  • Insert a pin at both these points.

  • Place a piece of thread, string - or in this case a quick release tie - round one pin. Tie a knot in the thread at the far end of the longest line.
  • Put a pencil inside the loop. Pull the thread taut and begin to draw the oval.

For a leaded panel, the space occupied by the lead came will need to be accounted for in the measuring of the dimensions.

Wednesday, 8 March 2017

Grinding and Polishing - Grits

Grinding and polishing grits and their effects

60 grit belts and disks provide a very aggressive grinding action. This grit takes large amounts of glass away very quickly. It makes shells and takes chips out of the glass with anything greater than light pressure. You need to create a small arris to avoid the shelling before grinding the face.  The metric size is 0.2337mm.

80 grit belts and disks provide a slightly less aggressive grind. But you must push lightly until you get the shape you want. On a new belt this is a remarkably fast process. Eighty grit belts can also take chips out of the glass, so be careful. Again an arris will help avoid the shelling.  The metric size is 0.1778mm.

100 grit belts and disks can also remove glass quickly with a new belt. Work at 100 grit until you get the shape or the big scratches are all gone from the 80 grit. As the belt gets worn, you may want to push harder to get the desired shape, but let the belt do the work. The metric size of this grit is 0.1397mm.

120 grit belts and disks remove scratches and still do some refining of shape.  The metric size is 0.1168mm.

200 grit belts and disks remove smaller scratches only. The shape of edge can still be adjusted, but only slightly. The metric size of this grit is 0.0737mm.

 400 grit belts and disks begin the polishing phase. Look for bigger scratches that you may have missed. The use of paint markers will help in this. Cover the the dry surface with the paint marker before beginning the polishing. This will show up any large scratches remaining after the first pass with the belt. If you find these, move back up to the level of grit that would remove any of the visible scratches, then work your way down again. The metric size of 400 grit is 0.037mm.

600 grit is a polishing phase. Take your time and move a little slower. At this stage, all the larger scratches should be gone and you are only polishing. The metric size of this grit is 0.020mm.

You can proceed to finer grits if you wish - such as 1200 (0.012mm) - but 600 is a practical grit at which to switch to cork and pumice, rouge or cerium oxide.

Cork is the final polishing phase before getting an optical finish with cerium oxide. The cork will grab the glass, so hold it securely. It is the friction between the cork and the glass that actually does the polishing. But do not let the glass overheat.

Grinding method You should not push hard with any of the grits. If you find that you want to get the work done more quickly, then it's time to put on a new belt or go to a coarser grit to remove the glass. You can use older belts as though it is a finer grit. The belts with finer grits will usually last a little longer than the coarser ones because the work is less agressive.

The grits of 100 and coarser are for shaping the piece.  The one you choose will be related to the amount of glass to be removed.  

After achieving the shape desired, it is usual to half the size of the grit (or in grit sizes - double the number) at each stage.  So after 100 grit, use 200, 400, and 600 one after the other.  

Of course you can do all this work without machines.  These grit sizes are available as loose powders.  The methods of working with a slurry of water and grit are described here.

Make Your Own Stopping Knife

“Stopping knife” is a traditional term for an oyster knife with a weighted end.  This makes it a multi-purpose tool that manipulate glass, dress lead came, act as a fid, act as a putty knife, and become a hammer.  It also stands up on its own.  I find it the single most useful too in leaded glass panel construction.

This note is how to get from here:

To here:

The process relies on the low melting temperature of lead.  This means that you can use stiff paper wrapped around the handle of the knife to contain the molten lead until it cools.

Cutting the Handle
First you set the oyster knife into a vice and cut two dovetail joints at right angles to each other into the end of the wood handle.  This will insure the lead is firmly grasped by the wood and will not come loose during use.

I do this with a fine bladed saw such as a hacksaw, coping saw or even a dovetail saw.  There are Japanese saws that work very well too, but are not so widely available.

The top of the dovetail joint should be just a millimetre or two off centre. 

The angle should be about 30 degrees from vertical.  Saw down far enough to get a 6mm chisel into the space between the two angled cuts.

Chisel out the wood between the cuts.

Repeat for the second dovetail at right angles to the first.

Wrapping the Handle
Now you are ready to prepare the oyster knife to become the stopping knife.

Use paper of around 90 grams per square metre, such as cartridge paper to form the narrow cone - although photocopy paper will do in a pinch if you use several wraps around the oyster knife.  Set the knife at a slight angle on the paper.  

Secure the beginning edge to the knife handle with a bit of masking tape. 

Mark the paper 5 mm – 10 mm above the top of the handle.  This will be the fill indicator when pouring the lead.  If you over-fill the cone, the stopping knife will be heavy and uncomfortable to use.

Roll the paper around the handle to form the cone.  This cone should be as close to vertical as possible.  A wide based cone will, of course, provide stability, but it will add so much weight as to be uncomfortable to use.  It will also be so wide as be uncomfortable for the palm of your hand.

You can unwrap the paper and start over if the cone becomes too wide.  The key is to start the wrapping just before the handle begins to taper toward the end of the handle.  The other way of looking at it is to attach the paper just as the expanding taper stops.

Try to keep the paper cone as smooth as possible.  This will form the shape of the lead end of the handle.  You want it to be as circular as possible without dents or angles.

If the paper cone is too long, you can cut it shorter with scissors or a knife.  It does not need to be a smooth cut, as it will not affect the poured lead.

This shows the fill line inside the cone before pouring the melted lead.

Pouring the Lead
I use a small old cast iron pot to melt the lead.  I place this over a camping gas burner to provide the heat.  I promise that I did straighten the stabilising legs before lighting the camping burner.

Put some old lead came into the pot to be melted.  While this is coming up to heat, place your wrapped oyster knife in a vice with heat resisting materials around the site to catch any spills.

Put sufficient lead into the pot, as there will be impurities floating on top and the lead will cool quickly when taken off the heat.  The photo below shows the amount of lead used.  This 100mm diameter pot has lead barely covering the bottom.  You do need enough lead to complete the pour at one go, as a second pouring will not stick to the first adequately.

The photo shows the last piece of came just about to be melted.  This is the time to begin the pour.  If the lead is too hot, it burns the wood creating gases and multiple bubbles splashing hot lead and leaving an unpleasant surface for the tool

As the last piece of the came melts and leaves its impression as the piece on the left, it is time to pour.

Pour at a steady rate into the paper cone until you reach the height indicator you previously marked in the paper.  When you stop pouring, set the pot on a heat proof surface.  You will notice some smoke and browning of the paper.  That is normal.  This picture shows the effect of the hot lead on the paper once the smoking has finished.

This photo shows the inside of the cone while cooling.  The cooling process will take about an hour.  You will be able to check, by touching the paper, how hot the whole is. 

Finishing the Handle

When the whole is cool, you can unwrap the paper from the handle.

This shows the roughness of the handle end.  This is due to the bubbling from the scorching of the wood and paper.

When the paper is removed and the lead is fully at room temperature you can use a rough file to remove the bubbling and to round the edge of the lead.

Unwrapped and waiting to cool.

This shows the rough surface and edges of the freshly poured lead base.

Smoothed base and rounded edges.

The oyster knife has been transformed into a stopping knife and is ready to use.

Wednesday, 1 March 2017

Thinking About Design

To think about design, you need a vocabulary to describe the object. This needs to be combined with a structure of principles. What follows is an outline to structure your thinking about design.  This is based on the writing of Burton Wasserman in Spark the Creative Flame, Making the Journey from Craft to Art, by Paul J Stankard, 2013, pp. 25-27.

First there is the language to structure the conversation about design. The elements of this are “… point, line, plane, texture, colour, pattern, density, interval, … space, … light, mass, and volume”

Then there are principles of good design.  They relate to:
  • ·         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.

These five principles of design together with the vocabulary of elements assist your critical thinking about expressing your design and realising it in the best way you can.  This thinking can be applied usefully to the critical appreciation of others’ works.

I have grouped the elements according to the principles that seem most applicable as follows.  This organisation is not prescriptive. It merely helped me to think about using the language when viewing my own or others' work.

Design Language   

Vocabulary                                 Principles of Good Design

Point                                           Unity 

Colour                                        Balance   

Texture                                       Rhythm             

Density                                       Emphasis 


Wednesday, 22 February 2017

Flip and Fire

"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.

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. 

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 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.

Solder for Zinc

A number of people seem to have difficulty soldering zinc around their projects.  This is because zinc transmits the heat quickly – more quickly than the tin/lead solder – requiring more heat to be put into the process.  There is a solder that can make this process easier as it is designed for soldering zinc.

“Galvanite is a lead-free galvanizing solder formulation designed specifically for high quality repairs to galvanized steel surfaces. Simple, effective and easy to use, in both manufacturing and field applications. It metallurgically bonds to the steel, for a seamless protective barrier.”

It composition is 50% tin, 49% zinc and 1% copper.  It becomes solid at 200C and liquid at 300C.  This makes it a high temperature solder for stained glass purposes, but will give a firm attachment between the zinc and the solder or lead came it surrounds.  The high temperature aspect means you need to keep the iron on the zinc rather than the more easily soldered metals or the glass.

Wednesday, 15 February 2017

Single Layer Slumping

Almost all glass can be slumped as a single layer, whether produced for kiln working or not.  A few are extra sensitive at even slumping temperature and change character at around 630C-650°C, but all others can be slumped.  This posts concentrates on slumping of single layers of non-fusing compatible glass, but most of these elements can be applied to fusing compatible glass too.

The things you need to take care about are:
  • Temperature
  • Soak Times
  • Edges
  • Devitrification
  • Annealing
  • Testing
It certainly is possible to slump single layers. The resulting glass will be slightly less robust than two or more layers of glass, but simply because it is thinner.

The temperature that you use needs to be high enough to allow the glass to take the shape of the mould, but low enough that the glass does not distort or stretch and thin.  This is a balance that you can achieve through observation of the firing. 

It most often is best to use the lowest practical forming temperature that you can.  Practicality here is about how long you want to wait for the glass to conform to the mould.  It is possible to take the glass to about 580°C and soak for multiple hours, but not very practical.  It does depend on the glass as to the temperature to be used for the slump.  There are two sources here that can help: the slump point test  and this table of glass characteristics

Soak times
A practical soak time will be 30 – 90 minutes, which will avoid marking the underside of the glass.  This means that the temperature will need to be lower than the softening (or slump) point of the glass. Your slump point test will tell you the temperature at which the glass begins to deform.  That is the best temperature to use.  If it is taking too long, advance the temperature by about 10°C.  If you used the table of glass characteristics to find a softening point, reduce that temperature by about 30°C as a starting point.

The temperature that you will choose to use is not high enough to allow the edges to change as they would in a fuse.   This means that you need to have the edges exactly as you want them in the finished project.  This will require cold working by hand or machine.  Neither will take a long time, but require the correct tools. This post gives you the comparison of fused and cold working methods.

While most glass can be slumped you need to be careful with opalescent glass, as it can devitrify easily.  Most wispy glasses are fine, but the more opalescent wisps they have, the more difficult there may be.  Streaky and single colour glasses are usually fine. 

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.

You will find some manufacturers’ glasses are less adaptable to kiln forming than others.  So, it is best to run tests on the glass before committing to larger projects.

Remember TADSET - temperature, annealing, devitrification, soak, edges, test.

Wednesday, 8 February 2017

Vinegar for Cleaning

Cleaning glass with acids causes corrosion of the surface of the glass.

So many people mention using vinegar to help clean the ground edges. I can't resist commenting. Vinegar is acidic. Glass is alkaline. Leave the glass in the vinegar too long and it will affect the surface of the glass.

Sometimes it dulls. Sometimes it corrodes to give a mild iridised appearance. The acid removes the alkaline materials – potash, lime, etc. – leaving a pitted surface at the microscopic level.  Left long enough – hours rather than days – the surface will begin to appear dull due to the pittiing. It is at this stage that it is easy to introduce contaminants which may later form nucleation sites for devitrification.

If you must use vinegar, rinse with it. Do not soak your glass in a vinegar solution.

Alkaline cleaners

Two alkaline substances that are used to clean glass are baking soda and ammonia.  Both are effective cleaners and do not have a reaction with the glass as they both are alkaline. The glass can be left to soak for a brief time in a solution of these chemicals, although I would not be happy with an open bath of ammonia.

But the effective part of what people are doing to clean the edges is the scrubbing. Scrubbing the glass powder out of the pits left by the grinder is what really works.  When leaving the glass in a bath of even plain water, you are giving the powdered glass the opportunity to settle into these pits.  Once settled into the pits, the powdered glass can become like cement to remove.

Mechanical cleaning

You could have a much better effect if you scrubbed under clean water before placing in a bath of water with grinder lubricant.  This material promotes a gel like glass residue. This gel prevents the glass becoming caked like cement.

A final scrub to thoroughly clean before assembly is a good idea. Each piece should be polished dry with lint free cloths or uncoloured absorbent paper.  If any particles cloth or paper are left behind, they will burn away long before devitrification can begin to form.

Of course, the best solution is to grind with 400 or 600 grit.  This is fine enough that there is not enough powder left to promote devitrification.

Wednesday, 1 February 2017

Devitrification on Ground Edges

The first element in preventing devitrification is cleaning.  Making sure all the edges of the glass are clean will help.  OK, you have cleaned the edges well after grinding. You still get detrification, so you want to know

Why do ground edges get devitrification? 

To answer this question, you need to think about how glass behaves in the kiln. As it heats up the glass expands, pushing the cut edges into the separator on the shelf. The pits caused by the grinding have not yet become fire polished.

When the glass retreats on cooling the pits in the edges of the glass, although very small, pick up some of the separator. These small particles act as the nucleation points for the crystallisation of the glass which is generally called devitrification.

The glass of a single 3mm layer retreats further on a single piece than on a 6mm piece. This rolls the devitrified glass upward onto the upper edge of the piece.

Prevention of devitrification of the ground edge is to have the pits in the glass edge finer than the particles of the separator. This is more than just washing the glass immediately after grinding to remove the glass powder from the grinding scratches.  Yes, this will reduce the chance for devitrification, but not totally prevent it.  As noted above, the pits in the glass will pick up particles of separator on expansion, giving nucleation points for the devitrification.

Further coldworking beyond the initial grinding is required to reduce the devitrification possibilities.  This involves using finer grinding bits or smoothing by hand with finer grits.  This does not have to take long, as the shape has been achieved by the grinder.

The logic of prevention is to have the glass edge smoother than the particle size of the separator, so the finer and smoother the separator, the smoother the surface of the glass edge must be.  

But my devitrified edge was on top of other glass

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 for Screen melts

In creating screen melts, the steel or other support left in the project can leave such a degree of stress that the piece will began to fracture over time.  The use of thin stainless steel rods as used in mandrels for bead making is an alternative, as they can be pulled out.

The separator used on the mandrel can be bead release.  If you have it that will work very well. This illustration shows a bead maker coating a mandrel from a bottle of mixed bead release.

If you do not have bead release on hand, you can use kiln wash.  To give the thick coating required to easily pull the steel out you need to mix the kiln wash differently. 

The normal mix of kiln wash would be 5 parts water to one of powdered kiln wash.  As you want this to be thicker so it will stay on the mandrel, you can mix it in a 3:1 ratio.  This will be sufficiently thick to keep it running off the mandrel and be able to extract it after kiln forming.

Mandrels prepared for bead making.  In coating them for a melt, you need to have the whole length coated.

To avoid the mess of pouring the wash over the mandrel, you can fill a stringer tube with the mixture and dip the mandrel into it. You can place the end of the mandrel into a polystyrene insulation block or a bit of clay to let it dry as done by bead makers.

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

Assessing Pre-programmed Schedules

Many kiln manufacturers are shipping their kilns with a set of programs already entered and saved into the controllers. 

You might think that all these pre-set schedules would all be the same, as the range of glass to be considered is relatively small. Yet, the range of schedules for the same glass varies from one manufacturer to another.  Yes, you may respond, but every kiln is different.  Well, I’d say, the variation is within a product line as much as between kiln manufacturers.

Assessing the installed schedules

What this means is that you need to assess the schedules that come with your kiln, rather than simply accepting what has been placed there.  There are a few things that can be looked at to assess whether you wish to rely on these pre-set schedules or not.

Differences between fast and slow fuses. 
  • ·         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?

Differences between tack and full fuses
  • ·         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?

Differences in slump 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?

Differences for different manufacturers’ glasses
  • ·         Are there different schedules for Spectrum, Wissmach, Bullseye, etc. fusing glasses?
  • ·         Are float glass schedules any different for rates, soak times, annealing points?

Printed schedules
  • ·         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?

The more “no” answers you get to these questions, the less you can rely on the installed schedules.