System 96 Trouble Shooter

System 96® Troubleshooter

Q I'm having problems trapping unwanted air bubbles.

A Air bubbles are trapped between layers of fused glass when the edges of the layers seal before the air has escaped. Spectrum sheets are very smooth and flat; there are no natural avenues of escape for air (the ridged textures of table-rolled glasses often act as "vents" in the firing process). Knowing this, there are a number of techniques that can easily be employed to control or prevent trapping air:

Slow down your heating process after you reach 1050° F (500°C). Proceed slowly through the slumping temperatures up to 1250°. The increased time allows more air to escape from between the glass layers before the edges seal it in.

Create natural avenues of escape by using smaller pieces in your design. Every intersection of glass pieces is a natural vent for trapped air. A larger piece of glass can be split for venting purposes, yet still appear as one piece in the final, fired project (assuming full fuse temperatures).

Place a "lift" between two layers to create a vent. A tiny scrap of clear (or color similar to project) glass can be placed at the project edge, between two layers, lifting the upper layer to allow air to escape. The "lift" should be invisible in the final, fired project.

Try using ceramic paper on the kiln shelf instead of kilnwash. This permeable product will allow air to escape from below as well as above.

Q Why am I having trouble with the kiln wash sticking to my piece?

A More than likely, your firing temperature is too hot. Try experimenting with your fuse cycle. Either go to a higher temperature for a shorter amount of time or try a lower temperature for a longer period of time.

Q How can I get "fire polished" edges?

A Spectrum glass needs to be fired at 1350° F for about 10 minutes to fire polish edges.

Q How can I prevent bubbles from forming between the kiln shelf and the bottom layer of glass?

A This problem is gas. Small amounts of moisture in the kiln shelf or shelf primer may be turning to steam at high temperatures. Or, some organic material (dirt, filings or other debris) are burning and gassing off at fusing temperatures. First, try using firing paper between the shelf-primer and the glass. This product is air-permeable and will allow more air to escape than direct-shelf contact.

Next, try increasing the time spent around 250°F (hold it there for, say, 1/2 hour). By this point, the moisture has turned to vapor. Holding the temperature there for a brief period will allow this vapor time to find it's natural avenue of escape.

If you still have a problem, there is probably some chemical reaction taking place between the kilnshelf and the shelf primer. The reaction, which will be occurring at higher temperatures (1100-1300°F) is giving off a gas, which is creating the offending bubble. Solution? Again, first try taking it slower between 1100 and 1300°F. Spend an hour making that ramp. If that doesn't work, then try

a. a different shelp primer
b. a new batch of your existng shelf primer
c. a new kiln shelf, preferable made of a different material

Q I am re-melting Spectrum glass and using it for blowing. Is there any danger from breathing the fumes?

A It depends on when you choose to breathe the fumes! During the re-heating process, at temperatures of 2450-2500°F (required to re-melt our glass), there will be some measurable "gassing-off" of volatile materials. Commonly, this gas is directed from your furnace or melting chamber up and out a flue designed for this purpose. At these temperatures, if you hold your face over the flue (or the molten glass) and breathe deeply, you are in danger of both ingesting some nasty stuff and burning your face off.

However, this does not normally present any danger to the hot shop, since, as stated, fumes created during melting should not be directed into the studio.

Most studios blowing glass, casting glass or otherwise forming re-melted Spectrum glass are most concerned with fumes they might encounter at forming temperatures, typically in the vicinity of 2100°F. There will be no measurable gassing-off of ingredients at forming temperatures. At higher temperatures (lower viscosities) materials volatilize that at lower temperatures (higher viscosities) remain inert. Think of water: at boiling temperatures steam is produced. Steam is not produced at lower temperatures, though the material is still very hot.

Also, once hot glass is exposed to air (at forming), a surface "skin" is immediately created that adds another layer of protection against any gassing.

Q I'm having some trouble with orange glass turning red when its fired, or red glass becoming darker or more opaque.

A Some color chemistries are inherently less stable than others. Reds and Oranges in particular are "striking" colors - the more time they spend at high temperatures, the more their color will "develop." Some "striking colors" are more sensitive than others, and some production runs of a glass will be more or less sensitive than other runs of the same glass. Here are some things you can do:

Test! Simple testing will tell you what, if any, color shift to expect from any glass. When you know what to expect, you can't go wrong. (See discussion on testing in Common Questions.)

Use the striking characteristics to your benefit. If you have some red glass, for example, that you have learned will strike darker, you could choose to save that glass for lower-temperature projects. Or, plan your project to take advantage of the deeper red color created by the striking process.

Limit the time your project spends at its highest temperatures. Many experienced kilncrafters favor the "Quick Cool" or "Flash Vent." Once your project has reached the state or stage you desire, turn off the power, open the kiln (8 seconds for fusing, 3 seconds for slumping) then close. Keep the door closed for a couple of minutes, then flash again. Repeat until 1050°F is reached. Then close the kiln and anneal. This simple process vents high heat and effectively "freezes" your project at the state you have chosen. And, by immediately cooling after your project has reached the state you desire, you minimize color change due to striking.

Q I have seen color streaks in some of your solid opal colors. Sometimes they disappear when I fuse, sometimes they don't. Should I be doing anything different?

A We make every effort to keep these streaks to a minimum. They are areas of slightly darker color or slightly higher density, a common problem in opal glasses that is more noticeable in our flatter, smoother glass sheets. We think we can eventually learn to prevent the problem altogether, but for now, the easy answer is to turn the sheet over. The streaks are generally only on one side of the glass sheet.

Q Why is some of the Spectrum System 96 glass "rougher" at the edges than in the middle? Are these roll marks? Will these marks "fuse out"?

A During forming, some of our glass runs colder at the edges than in the middle. The texture you see is simply the result of this chilling. At full fuse temperatures, this texture will smooth out. Here are some other options:

Put the "rougher" side down in your project; allowing it to pick up the kilnshelf texture and effectively disappear.

Trim away the areas you don't want to use in one project and save them for use in another.

Q I am seeing what looks like devitrification on the edges of some of my projects. I thought your glass wouldn't devitrify.

A Spectrum System 96 products are devit resistant, not devit-proof. Comparitive testing has shown spectrum System 96 glasses to be less prone to devitrify than other "tested compatible" products. Virtually any glass will devitrify if held long enough below its liquidous temperature. The edges are usually the most sensitive areas, because they are "cut" exposed, not shielded by the natural "skin" of the glass. For similar reasons, crafters cutting with a bandsaw have more edge-devit problems than those who score & break, and those who grind their edges with a grinder are still more likely to experience edge-devit. This has nothing to do with COE or glass type.

Experiment with your time-temperature relationships. Devit is easily avoided with System 96.

Consider using a light coat of overglaze on the edges, if that seems like a better solution. We recommend Fusion Headquarter's "Fuse Master Super Spray." It has been tested extensively on Spectrum products and has also been approved for food bearing surfaces by meeting the American Ceramics Association standards for leachable lead.

Q What about the famous Borax overglaze you used to recommend?

A The Borax overglaze is simple, cheap and gets excellent results. BUT, it will not stand weathering. Exposed to outdoor conditions or moisture (like repeated washings) it will eventually lose its shiny surface. The formulation and instructions can be found here.

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	Q	I'm having problems trapping unwanted air bubbles.
	A	Air bubbles are trapped between layers of fused glass when the edges of the layers seal before the air has escaped. Spectrum sheets are very smooth and flat; there are no natural avenues of escape for air (the ridged textures of table-rolled glasses often act as "vents" in the firing process). Knowing this, there are a number of techniques that can easily be employed to control or prevent trapping air: Slow down your heating process after you reach 1050° F (500°C). Proceed slowly through the slumping temperatures up to 1250°. The increased time allows more air to escape from between the glass layers before the edges seal it in. Create natural avenues of escape by using smaller pieces in your design. Every intersection of glass pieces is a natural vent for trapped air. A larger piece of glass can be split for venting purposes, yet still appear as one piece in the final, fired project (assuming full fuse temperatures). Place a "lift" between two layers to create a vent. A tiny scrap of clear (or color similar to project) glass can be placed at the project edge, between two layers, lifting the upper layer to allow air to escape. The "lift" should be invisible in the final, fired project. Try using ceramic paper on the kiln shelf instead of kilnwash. This permeable product will allow air to escape from below as well as above.

	Q	Why am I having trouble with the kiln wash sticking to my piece?
	A	More than likely, your firing temperature is too hot. Try experimenting with your fuse cycle. Either go to a higher temperature for a shorter amount of time or try a lower temperature for a longer period of time.

	Q	How can I get "fire polished" edges?
	A	Spectrum glass needs to be fired at 1350° F for about 10 minutes to fire polish edges.

	Q	How can I prevent bubbles from forming between the kiln shelf and the bottom layer of glass?
	A	This problem is gas. Small amounts of moisture in the kiln shelf or shelf primer may be turning to steam at high temperatures. Or, some organic material (dirt, filings or other debris) are burning and gassing off at fusing temperatures. First, try using firing paper between the shelf-primer and the glass. This product is air-permeable and will allow more air to escape than direct-shelf contact. Next, try increasing the time spent around 250°F (hold it there for, say, 1/2 hour). By this point, the moisture has turned to vapor. Holding the temperature there for a brief period will allow this vapor time to find it's natural avenue of escape. If you still have a problem, there is probably some chemical reaction taking place between the kilnshelf and the shelf primer. The reaction, which will be occurring at higher temperatures (1100-1300°F) is giving off a gas, which is creating the offending bubble. Solution? Again, first try taking it slower between 1100 and 1300°F. Spend an hour making that ramp. If that doesn't work, then try a. a different shelp primer b. a new batch of your existng shelf primer c. a new kiln shelf, preferable made of a different material

	Q	I am re-melting Spectrum glass and using it for blowing. Is there any danger from breathing the fumes?
	A	It depends on when you choose to breathe the fumes! During the re-heating process, at temperatures of 2450-2500°F (required to re-melt our glass), there will be some measurable "gassing-off" of volatile materials. Commonly, this gas is directed from your furnace or melting chamber up and out a flue designed for this purpose. At these temperatures, if you hold your face over the flue (or the molten glass) and breathe deeply, you are in danger of both ingesting some nasty stuff and burning your face off. However, this does not normally present any danger to the hot shop, since, as stated, fumes created during melting should not be directed into the studio. Most studios blowing glass, casting glass or otherwise forming re-melted Spectrum glass are most concerned with fumes they might encounter at forming temperatures, typically in the vicinity of 2100°F. There will be no measurable gassing-off of ingredients at forming temperatures. At higher temperatures (lower viscosities) materials volatilize that at lower temperatures (higher viscosities) remain inert. Think of water: at boiling temperatures steam is produced. Steam is not produced at lower temperatures, though the material is still very hot. Also, once hot glass is exposed to air (at forming), a surface "skin" is immediately created that adds another layer of protection against any gassing.

	Q	I'm having some trouble with orange glass turning red when its fired, or red glass becoming darker or more opaque.
	A	Some color chemistries are inherently less stable than others. Reds and Oranges in particular are "striking" colors - the more time they spend at high temperatures, the more their color will "develop." Some "striking colors" are more sensitive than others, and some production runs of a glass will be more or less sensitive than other runs of the same glass. Here are some things you can do: Test! Simple testing will tell you what, if any, color shift to expect from any glass. When you know what to expect, you can't go wrong. (See discussion on testing in Common Questions.) Use the striking characteristics to your benefit. If you have some red glass, for example, that you have learned will strike darker, you could choose to save that glass for lower-temperature projects. Or, plan your project to take advantage of the deeper red color created by the striking process. Limit the time your project spends at its highest temperatures. Many experienced kilncrafters favor the "Quick Cool" or "Flash Vent." Once your project has reached the state or stage you desire, turn off the power, open the kiln (8 seconds for fusing, 3 seconds for slumping) then close. Keep the door closed for a couple of minutes, then flash again. Repeat until 1050°F is reached. Then close the kiln and anneal. This simple process vents high heat and effectively "freezes" your project at the state you have chosen. And, by immediately cooling after your project has reached the state you desire, you minimize color change due to striking.

	Q	I have seen color streaks in some of your solid opal colors. Sometimes they disappear when I fuse, sometimes they don't. Should I be doing anything different?
	A	We make every effort to keep these streaks to a minimum. They are areas of slightly darker color or slightly higher density, a common problem in opal glasses that is more noticeable in our flatter, smoother glass sheets. We think we can eventually learn to prevent the problem altogether, but for now, the easy answer is to turn the sheet over. The streaks are generally only on one side of the glass sheet.

	Q	Why is some of the Spectrum System 96 glass "rougher" at the edges than in the middle? Are these roll marks? Will these marks "fuse out"?
	A	During forming, some of our glass runs colder at the edges than in the middle. The texture you see is simply the result of this chilling. At full fuse temperatures, this texture will smooth out. Here are some other options: Put the "rougher" side down in your project; allowing it to pick up the kilnshelf texture and effectively disappear. Trim away the areas you don't want to use in one project and save them for use in another.

	Q	I am seeing what looks like devitrification on the edges of some of my projects. I thought your glass wouldn't devitrify.
	A	Spectrum System 96 products are devit resistant, not devit-proof. Comparitive testing has shown spectrum System 96 glasses to be less prone to devitrify than other "tested compatible" products. Virtually any glass will devitrify if held long enough below its liquidous temperature. The edges are usually the most sensitive areas, because they are "cut" exposed, not shielded by the natural "skin" of the glass. For similar reasons, crafters cutting with a bandsaw have more edge-devit problems than those who score & break, and those who grind their edges with a grinder are still more likely to experience edge-devit. This has nothing to do with COE or glass type. Experiment with your time-temperature relationships. Devit is easily avoided with System 96. Consider using a light coat of overglaze on the edges, if that seems like a better solution. We recommend Fusion Headquarter's "Fuse Master Super Spray." It has been tested extensively on Spectrum products and has also been approved for food bearing surfaces by meeting the American Ceramics Association standards for leachable lead.

	Q	What about the famous Borax overglaze you used to recommend?
	A	The Borax overglaze is simple, cheap and gets excellent results. BUT, it will not stand weathering. Exposed to outdoor conditions or moisture (like repeated washings) it will eventually lose its shiny surface. The formulation and instructions can be found here.