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I was wondering what temperature you guys take the kiln to in order to properly firepolish a piece. I make mostly fused glass cabs for use in my wire wrapped jewelry. Will firepolishing restore a piece that has cracked, and needs to be re-fired? If not, then at what temp should I try and "heal" the glass? I am just now getting some decent pieces out of the kiln, which are properly annealed and really pretty to look at. I'll be needing periodic advice from you more experienced glassers in order to "graduate" to more predictable results. BTW: The silica sand and plaster mold ideas were WONDERFUL! I fired my molds yesterday, and got some very pretty results. Thanks for all the advice......

I find that I can get a good firepolish at 1350 degrees with a 20 minute hold.

To heal a crack, you have to go back to full fuse (1490-1500). But, if the crack is from incompability it will probably come back after refiring.

Steve

Thanks for the response. I do not think the crack is from incompatibility, as all glass was 90 COE. Think it was maybe temp shock. Sometimes I am too impatient, and open the kiln way too soon. How long should I hold the temp for firepolish? I will try and heal that piece the next time I do a full fuse with other pieces. Thanks for the advice!

Molly just remember that because something doesn't crack when you take it out of the kiln too soon doesn't mean it won't crack. If you create stress in the piece it may not show up right away and you could sell something to someone which will crack a day, a week, a month or a year later. Its hard to wait (its something everyone has to learn the hard way with glass I think) but its important if you are going to be selling your work.
Amy
P.S. Not trying to be preachy--I just learned this the hard way!

Molly, what silca sand and plaster mold method worked best for you? Yo

Hi Molly,

I fire polish using visual observations. Fire polishing depends on the glass type, the colour of the glass, the proximity to the heating elements and the rate of heating. So it is difficult to say that one temperature works for all situations.

Firepolishing is one of the critical signs that glass is beginning to tack fuse.
If you want clean crisp edges and details when tack fusing (which I prefer) then I heat to the lowest temperature possible.I look for three critical observations: ground edges start to look watery (aka fire polishing); 2) the edge between the top and the side of the class starts to round ever so slightly; 3) glasses with slightly lower melting temperature (i.e. black) start to bleed into the glasses with higher melting temperatures.

If you can't make these observations directly on your project try placing some scraps of the glass used in the project directly in front of the peep hole on the kiln.

Having said this I find that 1325F works well for Bullseye glass. I guess the point I am trying to make is that you can look in the kiln and see how the piece is responding to heat. Fascinating!

Hope this helps.

Cheers,

Bob

Thanks for all the great replies! YoDuh....I use a mix of about 2 parts sand to 1 part plaster. I Added enough water to make a "clay like" paste. It set up very quickly, so I had to work to form the mold really fast! I got the "recipe" from here on the boards. Do a search for "silica" "mold" "plaster", etc. You should find it. Someone else might have a better recipe, as this wat my first attempt, but it worked like a charm, and the molds are holding up beautifully! I make some molds out of clay too, but I had to wait a week or 2 for them to dry enough to go into the kiln, and I got impatient.
Speaking of impatience.....Thanks for the advice about waiting for the kiln to cool to room temperature before opening. I used to open in about 8 hours, which was causing thermal shock. I now wait 12 hours, and no more busted pieces! I am simply annealing "naturally"...by letting the kiln cool on it's own to room temp, so all I can do is HOPE my pieces do not break. I have kept all of them so far, and no breakage....but when I start to sell them, what can I do to assure they will NOT break? I want to be sure of selling quality jewelry.....Any ideas?

Firepolishing depends upon the kiln type, depth, size and finish. I firepolish in my Jen-ken at 1425 for 7-10 minutes when I what a smoothly rounded surface without too much shape loss. I will go to 1415 for 3-5 mintes when I want to preserve the crisp top edge. These numbers don't work at all on my Even-heat so you've got to experiment . . .

Andy

molly wrote: I am simply annealing "naturally"...by letting the kiln cool on it's own to room temp, so all I can do is HOPE my pieces do not break. I have kept all of them so far, and no breakage....but when I start to sell them, what can I do to assure they will NOT break? I want to be sure of selling quality jewelry.....Any ideas?

I'm no expert on jewelry sized glass but I'm guessing you still need to anneal properly--as long as you do that you should not have any breakage. Time is not limited for glass with stress in it to show itself. Pieces can break decades later. So just make sure you are annealing for the right amount of time and then you won't have to worry about it.
Cheers!
Amy

Amy: As of yet, I do not have a controller. It is supposed to arrive any time now. What temperature should the glass be held at for annealing, and how long? I figured that slowly ramping my kiln down would do the trick, and even after that, it takes about 12 hours to cool to under 100 degrees. Any advice as to where to "soak" the glass for a good anneal?

It depends on the type of glass you are using. Bullseye recommends 960 for their glass and the amount of time you hold depends on the thickness of the glass. Check here for listings of times for different thicknesses http://www.bullseye-glass.com/techinfo/anneal.html Again I don't know if making small things changes the equation--lots of people on the board make jewelry so hopefully one of them will chime in here. Hope you get your controller soon--I couldn't live without mine!
Amy

Thanks for all the advice, and Amy,Thanks for the links to the bullseye charts! Theya re delightfuL! I think my stuff is being annealed though, as the chart says a 1/8 inch thick piece should be soaked at 960 degrees F. for 15 minutes, and so on. If it takes my kiln 13+ hours to cool from 1500 to a little above room temperature, I should theink the annealing would be MORE than done! Am I wrong? Anyone? Thanks for all the info. Now, if I could just find more time to experiment, but I have a full time "real" job...LOL! But I admit to dreaming about glasswork off and on all day. I even check this bulletin board each day on my lunch hour!

molly wrote:I was wondering what temperature you guys take the kiln to in order to properly firepolish a piece. I make mostly fused glass cabs for use in my wire wrapped jewelry. Will firepolishing restore a piece that has cracked, and needs to be re-fired? If not, then at what temp should I try and "heal" the glass? I am just now getting some decent pieces out of the kiln, which are properly annealed and really pretty to look at. I'll be needing periodic advice from you more experienced glassers in order to "graduate" to more predictable results. BTW: The silica sand and plaster mold ideas were WONDERFUL! I fired my molds yesterday, and got some very pretty results. Thanks for all the advice......

Here is some technolgy relavant 2 U

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In archives

Brian

Hi all

Ok, so I know different kilns fire at different rates and in different ways but has anyone ever firepolished in a Paragon GL24 and, if so, at what temp.

Thanks

IJ

ijeffery wrote:Hi all

Ok, so I know different kilns fire at different rates and in different ways but has anyone ever firepolished in a Paragon GL24 and, if so, at what temp.

Thanks

IJ

I go to 1300, for varying times, depending on the type of glass.

Jim

Jim,

Thanks for the help - I'll try that temperature when I next need to polish.

Regards

Ian J