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Tips, Techniques, and Questions -- Technical questions or tips

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  #1  
Old 2015-07-29, 2:13pm
Carolyn Hipskind Carolyn Hipskind is offline
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Default Kiln Reduction?

I have a Skutt GM10F that's run without a problem for over six years. About 3weeks ago certain colors that are prone to reduce easily like(Effetre Dark Turquoise) starting coming out of the kiln with grey smutz on them. Talked with Skutt Tech Service & he talked me through a list of things to check but wasn't able to help solve the problem but said something is gassing-off in the kiln that's causing the glass to reduce. I've taken out all the rod racks, vacuumed the kiln, same kiln wash as always, removed the fiber strip that sits in the bead slot, haven't got new mandrels, no new bead release, lowered temp down to 925 degrees C, holding time only 2 hours before annealing down to 840C, hold for 35min. then off to room temp. Beads go in very bright and shiny & come out dirty. See picture included. The shiny ones were from the rod, same torch setting, etc. & placed on my desk. The dirty ones were annealed with the above schedule. Any other ideas before I buy a pyrometer & new thermal coupling? I am able to clean the smutz off with coke left to sit over night but it's just one more step I'd like to avoid.

PS: not able to load photo at this time.
**Edit but not able load image.

Last edited by Carolyn Hipskind; 2015-07-29 at 2:28pm.
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  #2  
Old 2015-07-29, 2:22pm
JavaGirlBT JavaGirlBT is offline
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Do you mean a silver-grey scum on the beads (reduction) or is it white and chalky (devitrification)? It sounds to me like you're talking about the grey schmutz rather than devitrification. Your kiln may have developed a reducing atmosphere. I'm not sure what you do for that. I know you can use charcoal in the kiln - just a few small pieces - but I can't remember if that's to create a reduction atmosphere or to cure one. Also you can soak the beads in coke or toilet bowl cleaner to get the grey schmutz off.
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Old 2015-07-29, 2:25pm
Carolyn Hipskind Carolyn Hipskind is offline
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You're right it's grey Schmutz. I have been able to clean it with coke but that's just one more step in the bead process. I'll have to edit my original post. Thank you.

Last edited by Carolyn Hipskind; 2015-07-29 at 2:29pm.
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Old 2015-07-29, 2:30pm
JavaGirlBT JavaGirlBT is offline
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Here's a post that talks about it and shows pictures.

http://www.lampworketc.com/forums/sh...+charcoal+kiln

Oh and you put activated charcoal in the kiln to create a reduction atmosphere, so don't do that. Someone mentioned vacuuming out the bottom of the kiln in case there's a stray piece of metal causing it. Maybe give that a try.
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Old 2015-07-29, 2:46pm
Carolyn Hipskind Carolyn Hipskind is offline
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I'll try vacuuming one more time. Thanks again.
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  #6  
Old 2015-07-29, 2:50pm
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I might suggest running the kiln empty and taking the temperature up to something like 1200 in an attempt to 'burn out' what ever might be cooking in there.

I was under the impression that a reducing atmosphere required a hot fuel with less oxygen than needed to burn off the all of the fuel. So I can not imagine how a fuel source would wind up in the kiln.

You don't have any leaking fuel lines do you? Maybe it is time a soap bubble test on your fuel lines and valves.

Another thought would be to let some air out of your kiln by holding the lid open a couple of millimeters with a stringer. That would be just enough to allow some circulation with out dumping all of the heat out of the kiln. It might make a difference but it might not.
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  #7  
Old 2015-07-29, 3:18pm
Carolyn Hipskind Carolyn Hipskind is offline
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I can do the bubble check easy enough. The tech said something in the kiln was off-gassing. There is a gap at the bottom of the bead door on these kilns that provides almost 1/2" without the kiln liner, which should be enough, don't you think? I'll try these suggestions & get back to you. It's almost 80C plus in my little studio right now so i might wait till it's cooler.
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  #8  
Old 2015-07-29, 4:28pm
2xMI 2xMI is offline
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You do mean Fahrenheit, right?
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  #9  
Old 2015-07-29, 4:47pm
Carolyn Hipskind Carolyn Hipskind is offline
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Yes, I meant Fahrenheit. It's more than 90+ F in my studio now as I'm ramping it up to 1200F to burn off anything that might be cause of the reduction of the glass. I vacuumed one more time carefully & found one small burnt spot on the bottom kiln plate. Scraped off best I could, didn't find any real particles but it was different in appearance. Tomorrow will tell.
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  #10  
Old 2015-07-29, 5:05pm
2xMI 2xMI is offline
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That's precisely why I stayed out of my studio today; way too hot! Good luck with the reducing issue.

Mimi
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  #11  
Old 2015-07-29, 5:56pm
Carolyn Hipskind Carolyn Hipskind is offline
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Thanks for the replies, esp. Ellen & Phill. I live in Pacific NW & the moss on my back dries out at this temp. & it's not a good thing.
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  #12  
Old 2015-07-30, 12:52am
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Cracking the upper lid of the kiln would allow any gases in the kiln to go upwards incase the gap at the bottom of the bead door plus the heat inside is trapping fumes. Warm fumes may be trapped under the lid otherwise.

Got to admit this is new one on me.
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  #13  
Old 2015-07-30, 10:38am
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It sounds like you're doing everything you can with the kiln. If that doesn't solve the problem (and I hope it does), take a look at your oxy and gas. Do you have an oxycon? It is working correctly? How is your fuel tank? Low? Sometimes schmutz comes up from a low tank. Have you replaced your fuel hose recently (few years)? Do you need to? Try hanging it to see if any sludge comes out? Regulator set right?

But honestly, dark turquoise can be boogery anyway. If you've been getting no reduction up until now, you've been pretty lucky. I usually get at least a little bit.
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  #14  
Old 2015-07-30, 1:12pm
Carolyn Hipskind Carolyn Hipskind is offline
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I have 2 oxygen & have changed filters on both & washed out the other filter in the door plus vacuuming. No change. Put full tank on, tanks are both about 1 year old & we have them refilled locally, no change with full tank. Hoses are 6yrs. plus but I'm willing to change them out. I did the bubble test on them but no leaks. Regulator is set according to manufacture. Flame is set for neutral. The thing is beads are bright & shiny going into the kiln but come out with schmultz after proper anneal time. Yesterday I ramped empty kiln up to 1200 for 2 hr. This kiln model has a bead door to put mandrels & without the kiln strip there's 1/2" space. The other door opens like a refrigerator so I'm not able to prop it open - well I guess I could but I didn't. This AM I made more test beads & put them in an empty kiln at 960F for an hour & at 840F to anneal for 35Min. & now it's down to about 440F so I'll be able to see if it helped to heat it up hot. One thing my husband mentioned was to vacuum after high heat but it was too late as I'd already started to ramp it up. We'll see. I also get reduction but have had pretty good luck if I pay attention to flame setting & distance from the flame.
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  #15  
Old 2015-07-30, 3:27pm
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this always happens to me with the turquoise, light and dark, also dark sky blue and sometimes purple. Even if I "wash" them in a low propane flame. Love to hear if you can work something out. Might just be the nature of the beast. Although, I do see there have been different versions of light turquoise, and one was VERY prone to that gray stuff. Not sure about the newer version as I have just gotten it.
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  #16  
Old 2015-07-30, 5:39pm
Carolyn Hipskind Carolyn Hipskind is offline
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Today I made test beads, 2 of each, one I left on my bench, one went into the kiln. Colors were Effetre Dk. Turquoise, Dk. Sky Blue & Copper Green. The ones on the bench are true to color, the ones in the kiln had schmutz. Not able to figure out how to reduce the size of my photos small enough to upload on this forum. Computer challenged. The kiln was bare of any racks, etc. There is still a reduction atmosphere in my kiln. I could accept thinking it might be my torching error but I've not had this problem until the last few weeks. I've had things reduce in the flame, devit in the flame, pitt in the flame but not in the kiln. Last thing I am willing to try is new hoses & then a pyrometer & new thermal coupler as they're both 6yrs. plus in age. Not willing to give up these colors of glass or soak every bead in coke or similar product. Thanks for all the tips & suggestions. I appreciate it very much. Phill if you have any other ideas, please let me know.
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  #17  
Old 2015-07-30, 6:38pm
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Perhaps a batch anneal in someone else's kiln?

I really am at a loss. I have not worked with these colors myself so I have reached the end of my guesses for the moment.

Please do tell us if you figure something out.
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  #18  
Old 2015-07-30, 7:06pm
Carolyn Hipskind Carolyn Hipskind is offline
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Good suggestion. I will let you know if I can figure out anything. The Tech at Skutt had no answers either. Thanks again for all the interest & suggestions. Carolyn
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  #19  
Old 2015-08-03, 12:26am
Ravenesque Ravenesque is offline
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I think this happened to someone else, I recall mentions of non stainless bead racks or other metal in the kiln making it happen....I saw that you took everything out but it could still be in the brick etc

search around here though, I do recall posts about this, hope you get it figured out.
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  #20  
Old 2015-08-03, 1:41am
De Anza Art Glass Club De Anza Art Glass Club is offline
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In my opinion, there is no need to replace the thermocouple, unless you believe that the thermocouple is the component that is contaminated. If you really want to replace the thermocouple, you might look on eBay, since I know someone selling equipment from a fusing studio has listed one (both a Skutt thermocouple and also an extension cable). If the pyrometer for a one time use to check temperatures when troubleshooting this particular problem, perhaps you could ask to borrow one from someone on this site.

I would recommend also posing the question on sites like Warm Glass and even Bullseye. Even though they use a different brand of glass, they still might have some suggestions on kiln operation for you.

Regarding the gap at the bottom of the bead door, I don't believe that is sufficient for ventilating the kiln. The goal is to get some air moving through the kiln. and I believe with the GM-10, the only option is to keep the main door cracked open. Or perhaps try heating the kiln to temperature, turning the kiln off, and then opening the door fully to get rid of the unwanted fumes (or gases) so they don't just redeposit on the inner surfaces of the kiln when they cool. (Well, I know you don't want to dump all that heat into your studio, but I don't think you have a choice.)

Consider your glass inventory. Could it be possible that you have started using new batches of glass?

Macintosh or Microsoft Windows? Try opening the picture file by double clicking. Once with picture is open, there might be a "Tools" menu at the top of your screen, and you might have a drop down menu option that says "Adjust size".

Last edited by De Anza Art Glass Club; 2015-08-03 at 1:50am.
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  #21  
Old 2015-08-03, 6:18pm
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Assuming your on a PC; Click on the Go Advanced button on the bottom of the page where you type your response (don't forget to type your response). Scroll down to where it says Manage Attachments.

Now you Upload a File (pix) from your computer. Click on Upload and your done. When your text posts, it will have the pix attached to it - automatically resized.

(Green text is what the button says that you're supposed to click on.)
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Last edited by Listenup; 2015-08-03 at 6:23pm.
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  #22  
Old 2015-08-05, 6:39am
Carolyn Hipskind Carolyn Hipskind is offline
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Kay Powell - For some reason when I Upload a File it does not automatically resize it.
An error notice comes up that the file size is too large. I'm on a MacBook Pro. Thanks for you help! Carolyn
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Old 2015-08-05, 6:47am
Carolyn Hipskind Carolyn Hipskind is offline
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I ramped my kiln, empty, up to 1200F one more time. Propped open the door about 3mm & ran it for an hour. After cool down I vacuumed the interior & made test beads. This AM they came out with just a small amount of reduction down in some grooves of one design. Problem greatly improved!!!! I'm going to do this one more time but will follow Phill's idea once kiln is up to temp to shut it off & leave the door open. I'm really happy about this turn of events!
Now I'll work on resizing photos. Thanks for all your help.
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  #24  
Old 2015-08-05, 10:47am
De Anza Art Glass Club De Anza Art Glass Club is offline
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On a MacBook Pro, double click on the picture file, and the picture should open in the Preview app.

There will be a "Tools" menu at the top and an "Adjust size" drop down menu. Make sure the "Scale proportionally" option is checked. Reduce with Width or the Height. There is a comment box on the bottom with "Resulting size".

The maximum width and the maximum height is 640 pixels, and the maximum file size is 78.1 KB.

Last edited by De Anza Art Glass Club; 2015-08-05 at 10:50am.
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Old 2015-08-05, 2:20pm
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I like to use the "attachment" paperclip that comes up when I click the 'Go Advanced' button.
It downsizes everything for me without my having to remember the numbers of the limits.


They tell me memory is the second thing to go as you get older.
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Old 2015-08-05, 3:14pm
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Quote:
Originally Posted by Speedslug View Post
I might suggest running the kiln empty and taking the temperature up to something like 1200 in an attempt to 'burn out' what ever might be cooking in there.

I was under the impression that a reducing atmosphere required a hot fuel with less oxygen than needed to burn off the all of the fuel. So I can not imagine how a fuel source would wind up in the kiln.

You don't have any leaking fuel lines do you? Maybe it is time a soap bubble test on your fuel lines and valves.

Another thought would be to let some air out of your kiln by holding the lid open a couple of millimeters with a stringer. That would be just enough to allow some circulation with out dumping all of the heat out of the kiln. It might make a difference but it might not.
this is comical
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Old 2015-08-05, 8:46pm
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Thanks. That helps me a lot. I can see where it balances what you have added to the conversation a lot.
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