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Boro Room -- For Boro-related tips, techniques, and questions. |
2014-08-23, 2:41pm
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Bernhard Riegler
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Join Date: Jun 03, 2010
Location: Northland - New Zealand
Posts: 452
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Does anyone know this problem?
made this one yesterday, but I am so disappointed - there are patches of rough glass that are dull - almost like sand blasted. I felt it in the marble mold - it felt scratchy and I tried to flame polish it out, but with no success. Is my mold buggered or did I overwork my glass - maybe too hot? This is now the second time in a row that this happened. Does anybody out there know whats wrong? Checked my mold, but can't see any faults - feels smooth. I hope someone can tell me whats happening here. You can see it quite well in the second pic.
Best regards - Bernhard
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Bernhard Riegler - Bay of Islands - New Zealand
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2014-08-23, 2:47pm
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Ass-kicking Cephalopod
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Join Date: Jun 19, 2006
Location: Duh, Squidville
Posts: 9,523
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Looks like devitrification
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2014-08-23, 2:52pm
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Senior Member
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Join Date: Mar 07, 2011
Location: Northern California
Posts: 2,023
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Very common issue. I went through this as well for a while. This tends to happen in the mold where the clear lens meets a stiffer backing color. You may have just overworked it since you do not have a colored backing. I eliminated the problem by not overworking in the mold and more importantly I started encasing the backs in clear. If you encase be sure to overlap the clear lens a bit. I now do very little shaping in the mold and instead use heat and gravity and only go into the mold for the final shaping step before puntying. Also be sure the whole marble is at an even temp and give the glass time to skin up a bit before molding or marvering. Never go into the mold screaming hot. You should be able to clean this up with cerium and a bit of elbow grease. Ask me how I know
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2014-08-23, 2:53pm
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Senior Member
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Join Date: Mar 07, 2011
Location: Northern California
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Quote:
Originally Posted by squid
Looks like devitrification
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Not devitrification. Just overworked glass.
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2014-08-23, 3:59pm
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Bernhard Riegler
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Join Date: Jun 03, 2010
Location: Northland - New Zealand
Posts: 452
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Thank you for your help. Larry, I think you hit it exactly. You may not see it, but there is a little black backing - and come to think of it, I changed to a different black (very stiff one) and I have the problem since then. I never thought about it until you mentioned it. And coating it in clear would be a great solution - thank you!!! I have never heard about cerium before, but googled it - sounds super - hope I can get some here - and I will put the ellbow grease in . . . I was so devestated, because I made so many marbles and this has never happened before - all of a sudden it happened every time - and it was always with that different black backing - can't call it by name as it is unlabled. I was completely on the wrong track. First I thought it was the sparklers like Jackpot - then I thought I worked it too long (at least 2 hours in the flame) and finally I hit it with a very big flame to get it into shape. Wrong on all accounts . . . So good to have you guys out there helping - Thanks again
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Bernhard Riegler - Bay of Islands - New Zealand
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2014-08-23, 4:33pm
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Senior Member
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Location: Northern California
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Quote:
Originally Posted by Onekura
Thank you for your help. Larry, I think you hit it exactly. You may not see it, but there is a little black backing - and come to think of it, I changed to a different black (very stiff one) and I have the problem since then. I never thought about it until you mentioned it. And coating it in clear would be a great solution - thank you!!! I have never heard about cerium before, but googled it - sounds super - hope I can get some here - and I will put the ellbow grease in . . . I was so devestated, because I made so many marbles and this has never happened before - all of a sudden it happened every time - and it was always with that different black backing - can't call it by name as it is unlabled. I was completely on the wrong track. First I thought it was the sparklers like Jackpot - then I thought I worked it too long (at least 2 hours in the flame) and finally I hit it with a very big flame to get it into shape. Wrong on all accounts . . . So good to have you guys out there helping - Thanks again
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No problem. I work some continually for 3+ hours so I dont think working time has much to do with this. Opals dont like it but thats a subject for another thread I use the cerium polish on a flat lap at the shop but any wet buffing wheel arrangement should work. Someday I would like to collaborate as I have been admiring your marbles here for years.
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2014-08-23, 5:13pm
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Bernhard Riegler
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Join Date: Jun 03, 2010
Location: Northland - New Zealand
Posts: 452
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oh, thank you Larry, but I am in New Zealand . . . if you come for a holiday - would be awesome
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Bernhard Riegler - Bay of Islands - New Zealand
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2014-08-23, 8:49pm
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Senior Member
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Location: Northern California
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Quote:
Originally Posted by Onekura
oh, thank you Larry, but I am in New Zealand . . . if you come for a holiday - would be awesome
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I have done it through mail. Someday I would like to visit NZ. Only know of it from books.
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2014-08-23, 10:40pm
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Bernhard Riegler
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Join Date: Jun 03, 2010
Location: Northland - New Zealand
Posts: 452
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and it happened again . . . no backing this time - guess I am boiling the glass
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Bernhard Riegler - Bay of Islands - New Zealand
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2014-08-24, 12:00pm
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I'm kinda biz-EE
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Join Date: Aug 08, 2007
Location: Arlington, TX
Posts: 3,610
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I'm going to throw this out as something you can try because I do it. I use graphite molds for beads and I do heavy production. What I have found is that even with good quality graphite it sheds. I couldn't see it but suddenly all my beads were coming out scummy. I took a bit of paper towel and some cheap medicinal alcohol (the stuff they sell at the drugstore) that I clean my glass with and cleaned out the mold with that. It came out horribly black the first couple of swipes but then cleared up. When I did my next set of beads, no scum! I periodically clean my molds out in this manner and I haven't had the problem anymore. Of course, let the alcohol evaporate before you use it and don't do this to a hot mold.
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2014-08-25, 10:21am
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Senior Member
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Join Date: Nov 06, 2005
Location: Austin - Texas
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yes, keep your molds very clean. Dust and carbon can do this to you. Also, don't work so hot. you can usually see it before you put it into the kiln, and then you have three options. First option is to put a dark backing over it. Second, get another rod of clear and wipe off the devit, and reshape. (you will be able to see the devit since it will look foggy, and not all nice and clear.) Third, put it in the kiln anyway, and then hit it with some 600 grit when it cools, clean it up, reheat it in your kiln and then reshape and fire polish in the flame. Good luck! Oh, and from time to time I get clear glass that just seems to be a little more fussy, so it could be that as well.
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The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing. ---- Albert Einstein
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2014-08-25, 3:41pm
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Senior Member
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Join Date: Mar 07, 2011
Location: Northern California
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Looks like back and front are assembled? Is there fume at the equator? This one is more extreme then the others. I slso wipe out my molds with alcohol before every use.
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2014-08-26, 1:16am
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Senior Member
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Join Date: Sep 13, 2012
Location: Albany, NY
Posts: 172
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That is very extreme. It really does look just like you've sandblasted the backside. I gotten little spots like this but the area you've got I think has to be from something other than your mold. How long has this been happening?
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2014-08-26, 4:29am
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Bernhard Riegler
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Join Date: Jun 03, 2010
Location: Northland - New Zealand
Posts: 452
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This has been happening for the last 4 marbles, but the very last one was ok, but it was a different design where everything is covered in clear. I don't think it was the mold - has to be the design, as the fuming came right out to the equator. Maybe some got on the surface of the marble and kind of smeared in the mold. I got me some 1200 sanding paper and cerium oxide and tried to polish it out, but what a job. I guess I need to use some kind of polishing machine for that.
And, Larry, the marble was not "assembled - all done in one piece, but I added clear and it probably pushed out the "burned in" fume. My mold was cleaned out - that was the first thing I tried - even sanded it with 600 grit sanding paper and then polished it with a cloth. I could not see/feel any damaged spots, even looking with a jewelers lupe. What I still don't know is, what does "boiled" glass look like? I did use a lot of heat on them . . and can it be repaired afterwards with polishing? Does boiling add bubbles? What I have is no bubbles, just pitted like sand blasted with very, very fine grit.
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Bernhard Riegler - Bay of Islands - New Zealand
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2014-08-26, 12:09pm
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Senior Member
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Quote:
Originally Posted by Onekura
This has been happening for the last 4 marbles, but the very last one was ok, but it was a different design where everything is covered in clear. I don't think it was the mold - has to be the design, as the fuming came right out to the equator. Maybe some got on the surface of the marble and kind of smeared in the mold. I got me some 1200 sanding paper and cerium oxide and tried to polish it out, but what a job. I guess I need to use some kind of polishing machine for that.
And, Larry, the marble was not "assembled - all done in one piece, but I added clear and it probably pushed out the "burned in" fume. My mold was cleaned out - that was the first thing I tried - even sanded it with 600 grit sanding paper and then polished it with a cloth. I could not see/feel any damaged spots, even looking with a jewelers lupe. What I still don't know is, what does "boiled" glass look like? I did use a lot of heat on them . . and can it be repaired afterwards with polishing? Does boiling add bubbles? What I have is no bubbles, just pitted like sand blasted with very, very fine grit.
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exposed fume can be a problem. It changes the viscosity of the glass just like color can and it burns easily. burning/Boiling can create very fine bubbles which then look like haze. None of this is really a form of devitrification. The cerium must be used on a wet buffing arrangement. Easiest would be a dremel like hand tool with a felt Bob. Make a slurry with water the consistency of sour cream and apply it to the felt and polish. I use a felt pad on a flat lap. Encasing the marble in clear really does cure a lot of issues.
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2014-08-27, 5:24am
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Member
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Join Date: Jan 12, 2012
Posts: 79
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Ive had that same prob seems like forever and just in spots on things.
Ive never tryed this but i was thinking i am going to try to polish it out with tooth paste... has anyone ever tryed that??
Just a thought.
Khan
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2014-08-27, 5:49am
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Member
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Join Date: Jan 12, 2012
Posts: 79
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There is a great discussion of this white haze in the Glass Lathe Tips and Tricks page on Facebook just yesterday... and Mike Souza had some very interesting comments to make about this and how to avoid it... at least i think its the same thing. I
Im going to copy paste what Mike said... i hope he doesnt mind. He knows so much about glass its incredable so i always listen when he speaks....I wish he would write a book!!!! it would be a god send to the glass community!!!!
anyway here is what he said.
Mike Souza said..." This white haze is actually sodium that has boiled out of the glass in your melting region and reconstituted from the vapor phase (at the high temp) back into a solid phase at a lower temp. It is most visible along the strain area of the glass, because the sodium oxide continues to cools back to a solid at this area. As it does so, it sublimes and builds up onto the surface as a powder. It sticks to that specific region of the surface, as a deposition, (much like the fuming process) at a narrow temperature range, just below the annealing point. In cooler areas, it tends to get to stay airborne and can easily be wiped away. To reduce or remove these effects there are a number of things that can help. 1.) Widen your hot zone. So as you melt the glass keep the the surrounding areas hot with a Bunsen burner or gas/air annealing fire and look over your didymium glasses to monitor the fires for sodium glare. The trick is to keep the strained area of the glass hot enough to absorb rather then sublime the phase sodium. And at the sametime, try not generate or boil out more sodium. 2.) Before you cool your piece, try to burn away the sodium/oxide during your flame annealing process. If possible, try and vent the piece you're working on, to allow air inside as you flame anneal. This can help the complete oxidation of the sodium..3.) In cases of water jackets or vacuum jackets, flush pure oxygen through the outlets prior to an annealing run in the furnace. The thing to keep in mind is that if you're seeing a lot of sodium bloom, the glass is really saying "Help me! I'm ready to crack.!" You're imposing a lot of strain because of the thermal contrast or you're melting the glass at too high of a temperature.. What's often overlooked, is that you're also boiling away a very important element out of the glass and physically changing the property of the glass...This is why we always see faint lines when we seal two identical glasses together. That interface or surface of the glass is not entirely homogenous to the bulk glass..."
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2014-08-27, 7:28am
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Member
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Join Date: Sep 24, 2013
Location: Austin, TX
Posts: 87
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Khan, that's a great find! It's funny because when I saw Bernhard's photos, I thought it looked really similar to the pitting effect you get if you put baking soda on glass and torch it. Sounds like that's essentially what it is!
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2014-08-27, 4:24pm
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Senior Member
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Join Date: Mar 07, 2011
Location: Northern California
Posts: 2,023
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Quote:
Originally Posted by khan
Ive had that same prob seems like forever and just in spots on things.
Ive never tryed this but i was thinking i am going to try to polish it out with tooth paste... has anyone ever tryed that??
Just a thought.
Khan
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Toothpaste? Never tried it. Let us know how it works out.
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2014-08-31, 6:44am
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kinda torching....
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Join Date: Mar 26, 2013
Location: Pennsylvania
Posts: 301
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Yea Souza is right as always! lol you are defluxing the glass and the haze is glass tyats no longer moxed properly. Only options really are to avoid it, remove it, and some people have had sucess sprinkling either table salt or borax into tye flame with tye hot piece your working right behind in the flame. the goal is to fume the fluxing agent which woud be the sodium/salt onto the problem areas.
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2014-08-31, 7:49am
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Senior Member
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Quote:
Originally Posted by jhamilton117
Yea Souza is right as always! lol you are defluxing the glass and the haze is glass tyats no longer moxed properly. Only options really are to avoid it, remove it, and some people have had sucess sprinkling either table salt or borax into tye flame with tye hot piece your working right behind in the flame. the goal is to fume the fluxing agent which woud be the sodium/salt onto the problem areas.
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De fluxing, burning, boiling.....Its all the same but not necessarily the problem here.
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2014-09-01, 3:16am
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kinda torching....
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Join Date: Mar 26, 2013
Location: Pennsylvania
Posts: 301
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Then what do you think it is?
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2014-09-01, 2:35pm
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Senior Member
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Quote:
Originally Posted by jhamilton117
Then what do you think it is?
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Read both mine and bernards posts again. Can be multiple causes for something like this and most marble makers have worked through at least a few of them. Some of what is here is boil but some I suspect is not. Hate to see him quoted out of context and archived here.
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2014-09-02, 1:32am
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Naysayer
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Join Date: Sep 22, 2009
Posts: 1,203
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Bummer, those are so pretty too.
Just want to say I have seen this posted on the other side of the fence in the soft glass part
http://lampworketc.com/forums/showthread.php?t=210906
So was hers boiled? She was on a hot head!?
Maybe some Cerium Oxide and buff it out?
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2014-09-02, 6:45pm
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Quote:
Originally Posted by Ravenesque
Bummer, those are so pretty too.
Just want to say I have seen this posted on the other side of the fence in the soft glass part
http://lampworketc.com/forums/showthread.php?t=210906
So was hers boiled? She was on a hot head!?
Maybe some Cerium Oxide and buff it out?
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I remember that thread. That is some very ugly clear
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