Replacing the thermocouple on a Skutt kiln, video

This is a very valuable video for any Skutt kiln owners.

Click here to view the video showing how to replace a Skutt Kiln's thermocouple!

Kiln problem, messed up thermocouple

Today I had our Evenheat kiln all set up to start fusing a piece that we're working on, but when I went to turn on the kiln and start up the program, the Rampmaster II controller said FAIL!  I also noticed that the kiln was displaying the temperature inside of it at times as high as 2000-3000 degrees.  Since the kiln was completely cool at that time and the location where it's at is only about 70 degrees, something major was wrong.

our Evenheat kiln setup

Like always I went searching online for an answer to this issue.  We are in the process of moving our store, Harrach Stained Glass out of state so I have packed away the kiln manuals and paperwork.  For some reason there isn't a lot of info on this issue online.  The Evenheat webpage doesn't give me a whole lot of information either.  Luckily it did have an error code section so I found that FAIL, is the code for a thermocouple issue.  I also thought I'd check to see if I blew the fuse on the side of the controller but I still can't figure out how to remove the darn thing!  The cap on the fuse seems to be frozen.

Anyway, the best I could come up with was that the thermocouple is the culprit.  Last week I removed my kiln shelf when working on a tall fused piece, so perhaps I bumped the thermocouple while removing the shelf.  The thermocouple is that little part, inside the kiln, that sticks out into the interior side of the kiln by the rampmaster.  I did discover that there is a thermocouple cement that I can buy from Evenheat!  And I'm going to look for it and buy it asap.

thermocouple seen on lower section of kiln in picture above

 thermocouple seen sticking into kiln on the right side in picture above

Yea, the kiln is actually back up and running.  I wiggled the thermocouple and tried to lightly push it back into the kiln wall and suddenly I noticed that the temperature reading was once again reading the correct room temperature.  Basically, now I've been keeping a close eye on it this morning to make sure it doesn't go haywire and perhaps overheat.

kiln in process of heating, thermocouple seen on right

Our studio has had this Evenheat Kiln for more than ten years and this is the first time we've ever had any problems with it.  If anyone is ever wondering what kind of kiln to purchase, we highly recommend Evenheat Kilns!  We don't know what we'd do without this workhorse kiln!  We love it.

Below we posted the link to the RampMaster II manual.  

Evenheat Kiln Inc. RampMaster II Glass Manual

What is a kiln's thermocouple?

by Glass Fusing Made Easy

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

A thermocouple is the twisted soldered metal pieces on the end of a pyrometer.

It is a temperature sensor used to measure the heat of the air inside a kiln.

It is placed inside the kiln either through a pre-drilled hole for this purpose or through the peep hole.

This device consists of two different metals.

These are joined together at one end, and that end is placed inside the kiln.

When the connection of the two metals is heated a voltage is produced.

The voltage is measured and converted to a temperature reading.

This reading is then displayed on the readable face of the pyrometer. 

For the best results on your reading, always leave about one inch of room around this twisted soldered metal.

Placing it closer to your shelf or glass can cause the temperature to read inaccurately.

Do not allow the wires touch any live heating element wire.

These devices can be used over a wide range of temperatures.

From the vast changes in temperature, this piece can be come brittle.

Try to avoid hitting it when inserting objects inside the kiln.

Although small, they are very inexpensive, hardy and consistent devices.

Time and high temperatures will cause these to wear over time.

If it appears corroded or crusty, it may be time to replace the piece.

They are also interchangeable and have standard connectors, which makes them simple and inexpensive to replace.
Changing this device when it has failed or become corroded can make a large difference in the accuracy of your firings.

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-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!