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I am attemping to make a 5 layer project. I will have 1 patterned glass layers with 2 layers of clear top and bottom. I am planning to pre-fire 2 double layers (2 3mm sheets) first.
#1 Should I pre-fire the patterned layer to one sheet of clear, or fire the 2 sets of 2 clear layers and place the patterned layer in between on the second firing?
#2 If I fire the patterned layer to one sheet of clear, should the single clear layer go on the top or bottom of the stack for the second firing?
My intention is to have the finished piece 1/2-5/8" thick.
Thanks,
Roberta

..."intention is to have the finished piece 1/2-5/8" thick."

I could ask a million questions, but I will instead jump right in.

At 1/2-5/8" thick, I am assuming you will dam your project to prevent spreading.

Pre firing blanks helps in preventing bubbles, but if not fired properly can add their own set of bubbles. The patterned glass layer should definitely be pre-fired if it is to be in the middle.

You can complete your project in two firings. Pre fire two stacks of two layers of clear, and go ahead and place pattern layer on top of one of the stacks. You should block/dam the patterned stack if the volume is enough to make it spread when fired to completely flat. For your second firing, place the clear blank on top of the patterned blank, block/dam the stack and fire.

There are some tricks to blocking/damming. The fiber paper lining the sides should be 2-3mm shorter than the height of your expected finished piece. This prevents prickling, or sticking to the sides above the height of the finished piece, and aides in rounding your surface corners.

Hope this helps.

Rose Hawley
Dairy Queen
Art In The Dairy
Charlotte, NC

Thanks Rose.
Yes I plan to dam the piece. It's an odd shape so I plan to dam it using cut out fiber paper. Should this be 2-3 mm shorter than the finished piece, or the height of the finished piece?
Do I understand correctly that you are recommending pre-firing 1 - 2 layer and 1 - 3 layer stack( with a dam) and then stacking and firing the 2 together, with the 2-layer stack on top?

Roberta

Hi!

Dr. Steve Immerman, Clearwater Glass Studio, has a very detailed tutorial with lots of pictures and hints like how to line the fiber paper with thinfire.

Scroll down towards the bottom for free-form dams etc

http://www.clearwaterglass.com/Tutorial ... print.html

Bullseye also has good diagrams on their "Working Deep" tip sheet:

http://www.bullseyeglass.com/images/sto ... eet_03.pdf


Charlotte

Fiber paper protecting dams should (almost) always be shorter than the thickness of the finished piece. The only time fiber paper dams don't need to be shorter is when you're going to cut off the edges and coldwork anyway. This is because the glass has a tendency to settle, pushing out excess air between the pieces and compacting slightly. If the fiber paper is the same height as the pre-fired stack, the glass will slide down the paper as it compacts, leaving a scooped-out-looking edge with a lot of prickles on top. I generally cut mine 1 layer (3mm) shorter than the finished height.

Prefire your patterned glass sheet on one of the sheets of clear. If you prefire a 3mm sheet by itself, it will be too thin and pull in on the center edges, creating what's called the "dogbone" effect. The edges will be slightly thicker than farther into the sheet, and that contour will create a little air gap between that sheet and whatever's stacked on top. You're far more likely to get bubbles that way. Firing on a sheet of clear will give you 6mm, which will be flat and stable.

When I'm doing this, I like to overfire slightly, to make sure that the center is as flat as possible. I'm a huge fan of never firing more than I have to, so I'd just leave the other sheets unfired. Then stack them with your prefired sheet, dam it with firepaper, then fire once more.

The reason for pre firing is to eliminate trapped air. You can do what Monica said, pre firing only the designed piece, then stack with unfired layers for finish fire. I prefer to stack 'similar' items for easier programming. Morganica may be firing some of her glass less times, but she is combining more layers of different thicknesses, requiring slower ramps and bubble squeezes. I say go with your experience and/or education. Be willing to try something else, but realize you will need to change your firing schedule to accommodate.

And, yes to all of your questions. As I understand your original set up, you wanted the design to be in the middle of the 1/2 to 5/8 inches.

Good luck with your project.

Rose Hawley

I always think it's much easier to buy thicker glass to eliminate trapped air between layers.

William, you are absolutely correct!!!

Dairy Queen wrote:The reason for pre firing is to eliminate trapped air. You can do what Monica said, pre firing only the designed piece, then stack with unfired layers for finish fire. I prefer to stack 'similar' items for easier programming. Morganica may be firing some of her glass less times, but she is combining more layers of different thicknesses, requiring slower ramps and bubble squeezes. I say go with your experience and/or education. Be willing to try something else, but realize you will need to change your firing schedule to accommodate.

And, yes to all of your questions. As I understand your original set up, you wanted the design to be in the middle of the 1/2 to 5/8 inches.

Good luck with your project.

Rose Hawley

Uhm...no. If you have good schedule practice to begin with, nothing changes. The programming would be the same. I'm not sure where you get the notion that two layers of plain, clear glass and three layers where the top is decorated are "similar."

Morganica,
Replace "similar" with pre-fired elements.
Please explain "good schedule practice" that applies to multiple set ups.
Rose

Oh dear. If I replace "similar" with "pre-fired elements" I still don't understand that sentence:

"I prefer to stack 'pre-fired' items for easier programming." Why is it easier?

And anyone who needs an explanation of good schedule practice probably shouldn't be offering schedule advice to newcomers. Nevertheless: Good schedule practice means understanding what you want the glass to do at every segment of the firing and programming accordingly. It's the opposite of the one-size-fits-all schedule that brings so many newcomers to grief.

So...anytime you stack pieces of glass for firing, you want to minimize air entrapment. That means you'll need a bubble squeeze (as well as a layup that minimizes the appearance of bubbles in the first place). That requirement won't change simply because you're stacking two 6mm and 9mm pieces of glass instead of one 6mm and three 3mm pieces.

Then if you have any prefired/thicker pieces of glass in the stack, good scheduling practice dictates a reduced ramp-up speed to ensure even heating of the thicker pieces on the way up, reducing the chance of thermal shock. If, in fact, the glass is thicker (as in your example) the ramp-up will be even slower, not faster.

And, finally, you'll want to choose an annealing schedule appropriate for the thickness and shape of the glass. It will be slightly longer for the 9mm stack with decoration because that's thicker than a 6mm stack.

From Morganica:
Uhm...no. If you have good schedule practice to begin with, nothing changes. The programming would be the same. I'm not sure where you get the notion that two layers of plain, clear glass and three layers where the top is decorated are "similar."

"I prefer to stack 'pre-fired' items for easier programming." Why is it easier?

Then if you have any prefired/thicker pieces of glass in the stack, good scheduling practice dictates a reduced ramp-up speed to ensure even heating of the thicker pieces on the way up, reducing the chance of thermal shock. If, in fact, the glass is thicker (as in your example) the ramp-up will be even slower, not faster.

And, finally, you'll want to choose an annealing schedule appropriate for the thickness and shape of the glass. It will be slightly longer for the 9mm stack with decoration because that's thicker than a 6mm stack.

And anyone who needs an explanation of good schedule practice probably shouldn't be offering schedule advice to newcomers. Nevertheless: Good schedule practice means understanding what you want the glass to do at every segment of the firing and programming accordingly. It's the opposite of the one-size-fits-all schedule that brings so many newcomers to grief.


Let me repeat: Be willing to try something else, but realize you will need to change your firing schedule to accommodate.

According to you, NOTHING Changes, but be sure t reduce your ramp up speed, and lengthen your annealing schedule. You are assuming the newcomers have good schedule practice. I asked the question to help newcomers, who don't have your 'good schedule practices.'

Once again, you have found a way to be rude to me, suggesting I not offer schedule advice, and discrediting my 'opinion,' while embracing it in your own words.

Dairy Queen wrote:I say go with your experience and/or education. Be willing to try something else, but realize you will need to change your firing schedule to accommodate.
Rose Hawley

Rose, Cynthia has given above and beyond to this board on so many occasions I can't even begin to count. I could easily take my print outs of 'Cynthia advice' and compile an incredible "Guide to Working with Kiln Glass" book. The fact that she was willing to spend even more time to answer your "Please explain" question shows that she's anything but rude.

I'm afraid it's advice like yours above that adds to the confusion a newcomer is likely already experiencing. When they want concrete help and understanding, being told "go with your experience" will only cost them money that they're probably sensitive to wasting.

Dairy Queen wrote:
Let me repeat: Be willing to try something else, but realize you will need to change your firing schedule to accommodate.

According to you, NOTHING Changes, but be sure t reduce your ramp up speed, and lengthen your annealing schedule. You are assuming the newcomers have good schedule practice. I asked the question to help newcomers, who don't have your 'good schedule practices.'

Once again, you have found a way to be rude to me, suggesting I not offer schedule advice, and discrediting my 'opinion,' while embracing it in your own words.

Thanks, Val (considering how much I love your work, wow...that's really flattering).

Rose, I'm not trying to be rude, I'm trying to obtain an explanation for your frankly confusing and sometimes misleading advice. I agree with Val.

Let's take this in order. What I said was, "If you have good schedule practice to begin with, nothing changes." Good scheduling practice dictates that you match the schedule to desired changes in the glass. That doesn't change just because you're stacking more glass.

Specifically: You will need a bubble squeeze whenever you want to prevent bubbles in a stack, whether you're stacking two sheets of glass or ten. You don't suddenly add a bubble squeeze because there are single sheets of glass in with a double--because the squeeze is already in your schedule. Nothing changes.

Second, thicker glass must be heated more slowly because it's a poor conductor of heat and it's going to take longer for a thicker piece of glass to heat evenly and prevent thermal shock. Again, if you've got good scheduling practice you've already got an adequate ramp-up for single/double layers...so your ramp-up won't need to change. If you've stuck a 9mm-plus thickness of glass in that stack, you'll need to slow down..that's a change.

Finally, I never did see your explanation of why it's easier to program a prefired stack than a stack of unfired and prefired glasses. Again, if you have good scheduling practice, there's no difference.

mor,
Is there no room in your brain for a different opinion? If not, you have no room for growth. Last time we disagreed, I had to bring in Ted from Bullseye to explain where you were incorrect. This Board is an absolute waste of my time. I am no longer following.

Thanks to everyone for your help. I fired the piece using Cynthia's method and was successful. My reasoning for this was that my kiln has both side and top elements. My dam was made of fiber paper which I believed would be an insulator. I thought that having the one single layer on the bottom, less heat, and the two single layers on the top, more heat, with the prefired layer in the center made the most sense for equalizing the heat during firing. I still have to coldwork my edges because the shape was complicated and my layers were not precisely uniform. I plan to use my grinder to smooth the edges and firepolish the piece. Coldworking is also a new challenge for me. Any advice on this next phase would be appreciated.
Thanks,
Roberta

Morganica wrote: - - - -
When I'm doing this, I like to overfire slightly, to make sure that the center is as flat as possible. I'm a huge fan of never firing more than I have to, so I'd just leave the other sheets unfired. Then stack them with your prefired sheet, dam it with firepaper, then fire once more.

Cynthia,
What do you mean by 'overfire'?, time-wise? how much more time do you spend, probabley at process temprature.
You do not mean a higher temp. by 'overfire', right?


Thanks,
Havi

rfreedfl wrote:Coldworking is also a new challenge for me. Any advice on this next phase would be appreciated.
Thanks,
Roberta

You're going to want to do some research before popping that back in the kiln to fire polish, as it'll likely spread. I had some five-layer pieces I needed to cold work by hand for the same reason.

Valerie Adams wrote:

rfreedfl wrote:Coldworking is also a new challenge for me. Any advice on this next phase would be appreciated.
Thanks,
Roberta

You're going to want to do some research before popping that back in the kiln to fire polish, as it'll likely spread. I had some five-layer pieces I needed to cold work by hand for the same reason.

Is'nt it possible to firepolish AND dam , so that it will not spread [understanding that the edges WILL have to be polished, ]


Thanks,

Havi

Havi wrote:

Valerie Adams wrote:

rfreedfl wrote:Coldworking is also a new challenge for me. Any advice on this next phase would be appreciated.
Thanks,
Roberta

You're going to want to do some research before popping that back in the kiln to fire polish, as it'll likely spread. I had some five-layer pieces I needed to cold work by hand for the same reason.

Is'nt it possible to firepolish AND dam , so that it will not spread [understanding that the edges WILL have to be polished, ]


Thanks,

Havi

That was my concern when I needed to do it; if you take the glass hot enough to gloss up, it would likely take on texture from the dams.