Kiln parts

written by Glass Fusing Made Easy

http://www.glass-fusing-made-easy.com/

Ok, so you have read about the different kiln parts, but what do they look like? I know that when you first hear about all the different parts, it can be quite confusing. When purchasing a kiln for the first time, you need to know what parts are needed and which parts you can do without.

This page will give your some graphic pictures of some basic parts, and what they are used for.


All glass fusing kilns have the same basic components:


Elements (high temperature coiled wire) are usually embedded into the walls and/or top of the kiln.


Fire brick insulation on the inside of the kiln top, walls and bottom.


Stainless steel cover on lid and outside of kiln.


Thermocouple – high temperature wires covered by ceramic rings and placed through a hole to the inside of your kiln.


Infinite Dial – some kilns just have an on/off switch, while others have settings from low to high.


This is a Jen Ken kiln. Jen Ken kilns come in many sizes. Lets look at all the kiln parts that make up this unit.

Kiln Lid:  This is the lid of the kiln. You can see how the fire bricks are lined up to make this piece.


This is a top loading kiln, with a hinge. The outside is made of stainless steel. There are no coils embedded into the lid of this particular kiln. You can see that there is a chain securing the lid from being moved too far back on the kiln. A handle is used to open this lid to gain access to the kiln.



Kiln Latch:  One of the kiln parts and features of this kiln is the latch. This allows you to lift the lid just a little to allow the unit to cool.



Infinite Switch and Pyrometer:  This picture shows the kiln parts known as the infinite switch, pyrometer , and light indicator.


The dial is used to control the rate of electricity to the kiln. It is not like a regular oven dial that you can set to achieve a particular temperature. How high or low you set this dial will determine what percentage of time the heating elements are on, and how fast your kiln will heat up or cool down. This switch is used to go from a setting of low to high. The simplest control method is still turning the kiln on and off along with frequent observation of the item being fired, and adjusting this dial as needed.


The pyrometer has the readable face on one end and the thermocouple on the other end. You can't see the thermocouple here, because it is inside the kiln. This unit directly reads the temperature of the kiln.


The infinite switch and pyrometer is a dial type control of your kiln. This method is the cheapest and simplest device available for constant monitoring the inside kiln temperature.


Using an infinite switch and pyrometer do require continuous supervision and adjustment to achieve the best possible results.


Always use a timer with an alarm, when using this type of control over your kiln.


The black rectangle you see on the top right side is a light that comes on to tell you that the kiln is on.





Peep Hole:  As you look around the side of the kiln, you will see the peep hole. When firing a piece, the hole is plugged with a peep hole plug. This is used for looking inside the kiln to check the status of your piece. Always wear safety glass when looking inside your kiln. The peep hole plug can also be removed for venting your kiln.

The picture above shows the peep hole and the peep hole with the plug inserted.


Inside the Kiln:  Ok, this is what the inside of the kiln looks like. You can see that it is built with fire bricks. You can see that the heating coils or kiln elements are in grooves in the fire bricks.



This picture shows a close up of the peep hole inside the kiln, and the coils going around the edges.



Kiln shelf and posts:  The kiln shelf is usually round or square. This kiln supports the round shelf. The shelf should be at least one inch below the thermocouple. This picture shows the kiln shelf and kiln posts. The kiln posts are placed under the kiln shelf inside the kiln.

Thermocouple:  A thermocouple runs from the pyrometer into the kiln. In a previous picture, I showed you the pyrometer on the outside of the kiln. The pyrometer has a thermocouple on one end, and it is inserted into the kiln. The thermocouple can become brittle from previous firings. When inserting the kiln shelf avoid hitting the thermocouple as it could break.



Hopefully by seeing pictures of the different kiln parts, you will have a better understanding of the different kiln parts and how they work.

Kiln Secrets, getting to know the types of units, and what to purchase

by Glass Fusing Made Easy

http://www.glass-fusing-made-easy.com/

Everyone should check out Glass Fusing Made Easy's webpage, it is wonderful and full of valuable glass art information.

A glass kiln is an oven used for the glass fusing techniques. This is the most expensive item of all the fusing supplies. They come in a variety of sizes and shapes. If you are looking to purchase a kiln, check out the great table top units at Delphi Glass - Art Glass Tools & Supplies. These are fantastic for fusing at home as they run on your household current. They are usually lined with fire brick, which maintains the heat, and can support the objects being heated. The size is an important factor, because it limits the quantity and size of items that can be fired at one time. There are many parts to this heating unit. Long ago, objects were fired in an open fire. The heat could not be measured or regulate, and the effects of a direct flame made it unmanageable. Over time, it was found that if objects were fired in an enclosed space, like a brick oven, you could achieve a higher degree of heat, and a slower cooling of objects. Glass has seen a rebirth in the past few years. It is used as a building material, a surface to paint on, engraved, cut, blown, slumped and fused. Before purchasing, figure out the size that will fit your individual firing needs, whether you want a manual or a programmable unit , and find out what type of warranty comes with this appliance. Ask where and how you will get repairs done. What parts of the unit are replaceable and where you can purchase these parts. Once the unit has been purchased, get to know your firing kiln . This will come in handy in any future firings. Glass vs Ceramic Glass ovens heat single layers from the top, while ceramic units heat multiple layers from the side. Most glass projects are relatively flat, and with the heat radiating from the top, the entire face of the glass receives heat at the same time. This helps to keep the temperature differences within the glass uniform and helps to prevent cracking. You can still obtain these uniform heating results in a ceramic oven by slowing down the firing. An electric unit is the best for working with glass. The temperature can be regulated and controlled. They are also quiet, safe to operate, easy to handle, and fairly inexpensive to operate. There are numerous types of electric units on the market, in a variety of sizes and accessories. These ovens are usually insulated, so there is very minimum external heat, and with no or very little fire hazard. What Size to Purchase: Make a decision on how large the items are that you are going to make, that will help you decide the size to purchase. Find out the internal dimensions and external dimensions you need for the size of your desired projects. If you are going to use larger molds, will you have to fire on the bottom of the unit? You need at least 12 inches clearance around the outside, so figure out where you are going to place it and make sure it will fit in this area. Front load vs Top load:  A front loading firing kiln is great if you are going to be removing items from the unit while they are hot. This is great if you are planning on doing any enameling. A top loading kiln has either a hinged lid or one that can be lifted off with handles and removed completely. This is most commonly used for glass fusing. Electrical Outlets: Know your electrical outlets. If you are glass fusing at home, then you will want a kiln that uses standard 120 volt, 13 amp household current. You don’t want to have to do any rewiring to your home. It should have a three-prong plug and about an eight foot power cord. Manual or Programmable: A manual oven has an on/off switch and a dial to adjust the temperature. There is small light to show that the unit is on and operating. They come with a pyrometer so the inside temperature is shown at all times. A thermocouple runs from the pyrometer into the oven. It should protrude into the firing chamber about one inch. Remember, the pyrometer will read the temperature where the tip of the thermocouple wire is, so put it near your shelf. These are not that difficult to use and don’t require that much more time or effort than a programmable unit . Keep records of your firing. At first, set your timer for every 15 minutes, so you can see the rate of temperature for your particular unit. Keep records of the particular rates of temperature climb with each digit on your dial. Records will help you determine what works and what doesn’t work with each firing. Make detailed records of the total time it took from the start of your firing, to when you reached your desired temperature. These records will help you in future firings. Then in the future, you can set your alarm to go off just before you know your oven should be at a particular temperature, instead of having to check it every 15 minutes or so. Always unplug your kiln when you are finished firing. Be sure to set an alarm clock to remind you when switches should be changed. Brick or Ceramic Fiber: Firebricks are used as insulation in a brick oven. They heat more quickly and retain heat longer. These are great for glass fusing and annealing. More maintenance is needed because of the delicate nature of the fire bricks. The heating coils are placed in grooves in the fire bricks. If these coils should ever bulge out, they must be pushed back into place.  A ceramic fiber oven stays clean and is easier to maintain. The heating elements of these units are not exposed, because they are molded into the walls. Kiln Safety: Even though a kiln will fire to a higher temperature than a stove, the area around the unit is surprisingly cool during firing. Glass kilns are well built and don't radiate a lot of area heat. For safety purposes, the unit should not be placed within a minimum of 12 to 18 inches of any other object. It is recommended that the unit be placed on a flame retardant flooring. Some place the kiln on a stand on a flame resistant cement floor or fire board. Be careful when opening the lid while the unit is at a high temperature. The heat will escape and rise. If you have low ceilings, cabinets, shelves, or other objects close by the heat will hit these items and could start a fire. Always use common sense on what you have near or around the kiln. Be aware of where the heat goes when opening the lid during firing. If opening the lid while doing procedures like raking, etc. always unplug the unit before proceeding with the process. Make sure that the power circuits are up to supplying the kiln. If there is a question about the supply, have an electrician check things out. Furniture:  The furniture consists of a shelf and shelf supports. These items are made of a highly refractory fire clay. The shelf material is quite strong, and should fit your particular unit. There should be about 1 inch of clearance between the shelf and the wall of the oven. Furniture is inexpensive, easily available, and can be used over and over again. The shelf needs to be protected with either a wash, or fiber paper. Care and Maintenance:  When you first make your purchase, keep all the packaging material. If the unit needs to be sent back for repairs or replacement, you will be happy that you kept the original box and packaging materials. You first need to prepare the kiln and shelf for firing. Then you will be ready for a first firing of a fused glass project. Use the shelf and posts. Having your items on these shelves allows air to circulate around your item and makes it easier to remove the shelf from the kiln. Place the shelf at least one inch below the thermocouple when firing. Use protection on your oven and shelf. The unit needs to be coated with a wash. When coating the unit, it doesn't matter which wash you apply, just be sure to mix it about twice as thick as you would if you were using it to coat the shelves. Avoid getting any wash on the elements . Reapply the wash every few years. The shelf can be protected with either a wash or fiber paper. Repairing coils might seem like a tedious task. See how simply this can be done without having to send your unit out for repair. Periodically check and clean your thermocouple. This can be done using a damp cloth before firing your piece. Also check the position each time you start to fire. Try to avoid hitting the thermocouple with the kiln shelf, as it can be broken and damaged. Check for any dust on the floor of your unit. Vacuum if necessary. Dust can react with the color elements in your glass and result in foggy or burnt colors. For a small and inexpensive oven, try purchasing one that you can fire in the microwave . These are very limited in use and applications.

Kiln-pressed glass (a process that makes kiln glass look like it was mouth blown) no photos available

Are you tired of typical, two and three layer fully fused glass art?

Have you have ever wished you could create the watercolor-like effects that are typical in blown glass – but seem impossible to achieve in fused glass?

If so, this unusual and original glass fusing tutorial is for you.

The technique is one we call “kiln-pressed glass” and it is something we’ve developed at Helios over the past year.  We doubt we’re the first to do what we describe, but we’ve never seen it discussed elsewhere and we are pretty sure that nobody else has documented and shared the technique before now.

Kiln-pressed glass is so full of potential that we want to share it so that we can see what others are able to create with it.   Here’s just one example of what’s possible.   It is the piece that we create with the tutorial:

To help you fully appreciate kiln-pressed glass, we’ll start with a brief review of how glass melts and why it is difficult to create thin fused glass objects.

Surface Tension

All liquids have surface tension – the attraction between molecules that, on the surface of a liquid, causes the liquid to behave as if it had a thin skin.  Surface tension, for example, is why water drops on a slick surface will “bead” up.

Surface tension strength is different for different liquids.  Mercury, for example, has very strong surface tension.  Acetone, in contrast, is very weak. The strength of the surface tension of glass at 1500° F is somewhere between the two.  The strength of the surface tension determines the natural height of the liquid when allowed to spread.

For glass at 1500° F, that height is about ¼ inch (6 mm) – which is the same height as two standard layers of glass.  Understanding how this impacts the results when fusing is one of the most important lessons a fused glass artists can learn:

• If your project has less glass than in two complete layers (for example, a single layer with only a few design elements), the edges of the base glass will begin to pull up as the glass tries to achieve the ¼ inch thickness.
• If your project has close to two complete layers (for example a single layer of  glass with a complete second layer of design elements), the glass will flatten when fully fused – but will maintain its overall shape.
• If you have more than two layers of glass, the glass will spread when fully fused (unless you contain it with dams)

Here’s a simple illustration showing the above three examples:

But what if you want a fully fused design – but you want it to be a single layer thick?

One solution is to fuse the thick project and then grind it down with coldworking equipment, such as a reciprocating lapidary grinder like this one:

That approach requires expensive equipment, a lot of time, and you end up wasting a lot of material by grinding it away.

With kiln-pressed glass, you probably already have everything you need, the work is all done in the kiln, and there is no wasted glass.

Curious how it works?  Just click the “Overcoming Surface Tension” link below and we’ll get started!

Overcoming Surface Tension

The basic idea behind kiln-pressed glass is that we can defeat the surface tension and create thin glass by squeezing it from above using weights.  The basic setup looks like this:

As shown, the glass is placed between two kiln shelves and weights are placed on top.  Small fiber strips placed in the corners act as spacers to prevent the glass from being pressed too thinly.

The concept is surprisingly simple but the results can be spectacular.

Setting Up the Glass

The setup for our project is includes a lot of clear glass and some strategically placed transparent colors.  One of the best parts about kiln-pressed glass is that transparent colors that often seem too dark to be useful in typical fused glass projects dilute to wonderful hues in kiln pressed glass.

When stacking your pieces of glass, make sure that there are three or more equal high points.  This ensures that the top kiln shelf is level when placed on the glass.

Although not required, the base piece of glass makes it easy to build your piece and move to the kiln.  It will also help you to achieve the smoothest possible surface after firing.  In this example, the base is about 6 inches across.

Place your setup on a freshly primed (kiln washed) shelf as shown:

Note the fiber paper strips that have been placed near the edge of the shelf.  The height of the fiber paper (once fired) will determine the thickness of your final piece.

We are now ready for the top shelf and weights.

Setting Up the Weights

Coat your second shelf with shelf primer and place it (primer down) on top of your glass as shown:

Make sure that the shelf is either below the thermocouple (the small metal rod that sticks out of the wall of your kiln) or, if it is above the thermocouple, that there is no chance of it hitting the thermocouple as the glass melts and the shelf moves down.

If you have stacked the glass as described, with there being at least three, equally tall stacks, the shelf should be level.

Now place your weights on top of the shelf.  Old pieces of kiln shelf, high density fire bricks and kiln furniture are all suitable.  Do not use stones!  Stones can contain water that expands when heated, causing the stone to explode.

Here’s our top shelf loaded with weights:

We are ready to go!

Close the kiln and fire as explained on the next page.

Firing

Here is our firing schedule for our kiln-pressed glass:

Segment	Ramp	Target	Hold
1	300° F / hr	1225° F	3 hours
2	FULL	1500° F	1.5 hours
3	FULL	900° F	2 hours
4	100° F / hr	700° F	none

The long hold at 1225° F allows the glass to compress, eliminating much of the trapped air and helping the shelf to stay level as it drops.

The long (90 minute) fuse ensures that the glass is fully pressed so that the shelf rests on the fiber spacers.

Our annealing (from 900° F to 700° F) is fairly aggressive – that’s because our glass is exceptionally thin so there is little reason to be worried about heat differentials.

After 700° F, we can let the kiln cool naturally.  Thanks to all the extra mass provided by the weights, cooling will be very slow.  You can vent the kiln at 500° F and open it fully at 300° F without worrying about thermal shocking the glass (again – because it is so thin).  At 200° F, remove all the weights and shelf to allow the piece to finish cooling.  Be careful when taking out the weights – they will often be hotter than the ambient temperature of the kiln.

With the weights and top shelf removed, you should see something like this:

Congratulations!  You’ve completed your first kiln-pressed glass or follow this next step for more effect!

Adding More Glass

We don’t have to stop with a single pressing.  With additional glass and pressings the results can get pretty spectacular.

Here’s our setup for the second pressing.  Note that we have sandblasted the surface of our first results to ensure we’ve removed any residual kiln wash.

Here’s a close-up:

In addition to more color, we’ve also made careful choices about adding some clear pieces to the mix.  The clear glass will cause the color glass to spread more, thinning it out, and diluting the color.  Using clear glass this way can provide wonderfully subtle color variation and create vibrant watercolor effects.

We repeat the same setup and firing schedule as with our first pressing, slump the piece over a handkerchief mold for the results shown on the next page.

Finished Project and Tips

Kiln-pressed glass has endless possibilities and produces work unlike most of what is being created by fused glass artists today. 

To help you on your way, here are some tips:

Glass reactions (the color changes that occur when certain glasses are fused together) tend to be intense in kiln-pressed glass.  You can avoid this by placing clear glass between the reactive colors.  You can see this in the finished piece above – reds, yellows, greens and blues all overlap without creating browns that would typically occur when mixing these colors.

As mentioned in the article above, many of the transparent colors available today are very saturated and appear almost black without a light behind them.  When thinned during in a kiln-pressed glass project, these same colors often produce gorgeous hues.

Pay attention to how glass spreads when pressed – usually from the center out to the edge.  With practice, you can be increasingly deliberate with your design.

Use a scale to determine how much glass you are going to press.  If you use too much glass, it will squeeze out from under the top shelf.  One square inch of a single layer of fusible glass weighs about 0.2 ounces (5.5 grams).  You can use this value to determine how much glass is needed for a given size – or, you can simply use our Pot Drop Calculator to do the work for you.

Thank you Helios Glass for sharing this great tutorial for Kiln-pressed glass on Fusedglass.org http://fusedglass.org/learn/project_tutorials/kiln_pressed_glass_finished_piece_and_tips  We can't wait to try it!