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Post by mohawkpiper on Aug 2, 2015 0:54:43 GMT -6
Hi Sherri,
I reduce a lot. More so than I do oxidation. I havent noticed reduction being the cause to crazing in the crystals. I get crazing in the crystals only with a 413 base and it happens in oxidation too. I havent related reduction to being the cause. I do know some people rub ink and whatnot in the crazing afterwards. Jon price does this. I havent done it so i cant comment really.
I reduce all over the place in my electrics with the alcohol drip. From 2000 F to 1800 F to 1500 F to 1300 F to 1150 F. So far i havent noticed a negative effect on the elements. And from time to time I'll do 3 or 4 reduction firings back to back in the same kiln. I usually reduce on the way down. Rarely do I do post fire. I feel like it's a waste of time to get similar results as opposed to reducing on the way down.
Currently I am exploring copper to quite an extent. I've heard the whole it burns out thing. Or it boils above said temp or whatever. So far I am not convinced of the boiling whatsoever and I am still pretty unsure it even burns out. Even at 2000F. I reduce copper at all those temps. Both hard and soft reductions. I get all sorts of effects but I believe what is happening is more dependant upon the rest of the chemical makeup of the glaze and the thickness of the final glaze at reduction time. Even when the bg is white with a red crystal I am still not convinced it is "burning out" to get the white. From time to time i put a test glaze of a regular 4% copper oxide glaze in there cuz it has a lot of copper so it is sure to do something if it is reducing. this is sort of to make sure the reduction is working because sometimes it doesnt seem like it with other glazes but low and behold the 4% copper turns ugly dark blood red black brown or whatever so i know they are reducing.
I can reduce copper at pretty much any of these temps and get some color in the ground. I can reduce copper at any of these temps and keep the ground green as if it didnt reduce at all. i can keep the crystal green in a reduction. Again I think it has more to do with what else is in there and the thickness of the glaze. I believe the "loss of color" is actually a deceptive quality of the glaze being reduced. I am not 100% sure but those are my beliefs.
Jose can comment more on what he is doing if he feels like doing so and I could be totally wrong because I do not actually know what he is doing but I believe he is playing more with titanium and iron than copper at 1850 and if he is playing with copper titanium does interesting things to it in reduction.
I have done a high temp reduction (2000) as a seperate firing only once and there was no copper in the glaze so i cant comment much on that but again i am still unsure the reduction is the cause of the loss of color. I havent tested the high strike thing (2000° reduction without the reduction) in oxidation to compare though.
Hope that helps.
G
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Kuba
Full Member
SztukKilka in Old Formu
Posts: 111
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Post by Kuba on Aug 2, 2015 4:37:42 GMT -6
Arnie or Greg, You should make a new topic about the reduction! I would do it myself, but I have nothing interesting to say yet... I just star to playing with reduction firing.
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Post by Arnie Benton on Aug 3, 2015 8:44:34 GMT -6
Hi Kuba -
You're right - more people seem to be trying reduction.
My experience is mostly with a specialized electric kiln that uses propane and a 'magic box' that keeps the flame inside and lets the CO seep through. I have no experience with any drip method. I've also done reduction in a gas kiln, but not for 5 years or so. So, I can contribute to a topic on reduction - it's similar to my working only with plates and bowls - I have to add an asterisk to my comments that this may apply only to horizontal surfaces. Never thought of that - I'm probably the only person on earth who reduces with an electric kiln with propane and a magic box AND only on horizontal surfaces. I guess that makes me a super specialist - either unique or weird.
Arnie
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Post by tileman2 on Aug 3, 2015 9:06:02 GMT -6
Hi Arnie:
Seems there have been alot of changes in the ceramic industry as of late. Cerox 506 supposedly is gone, unless Zochem decides to continue making it: but that is not what I am hearing. I was aware of changes in clay recipes, as I have heard complaints from time to time about changes in frit. Was contacted by my supplier wanting to know if I would run some zinc tests for a company that apparently was buying from Horsehead. I mentioned in another thread about testing increasing amounts of sodium and potassium (feldspar) in the glaze recipe. Being aware of the clay changes; was curious to see how each of these effected the glaze. A certain percentage is leached from the clay: so I was checking the effects. The oddity of this glaze: the smallest of issues can affect the outcome. Another question if I might: are you putting alumina or sand under your plates when you fire? One thing about tile; if they cannot move during the firing, they will crack, or crack the glaze. Really does not effect smaller tile; but the larger and heavier they get: the more dramatic it becomes. Great looking crystals on those last two plates!
Tom
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Post by Arnie Benton on Aug 3, 2015 9:24:22 GMT -6
Hi Tom - I haven't put anything under my larger plates - and I SHOULD AT LEAST TRY IT! And I WILL - pieces 12 inches diameter and over have split - I'll let you know -
Arnie
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Post by mohawkpiper on Aug 3, 2015 14:26:08 GMT -6
Arnie, you definitely are a super specialist. Unique or weird... either way, it's great and amazing!
I just wanted to add a few things... I just re-read my comment today and thought that maybe it could have come off a little snobbish and that wasn't my intent....
I don't really know what is going on with all this. I am just making educated guesses based off of my own observations of my own pots. I only reduce with the alky drip so I can only observe from that... I am sure gas (and other methods) are different and do different things but at the same time I believe you can get similar results between the two at least with some glazes anyways by tweaking the glaze and thickness. That is based off of sharing and comparing images with others that reduce solely in gas.
Others claim copper boils out of the glaze or burns out of the glaze above said temperatures and that may very well be true. Maybe I haven't yet met that threshold, or I see it as something else, or the alky and gas interact differently... I just meant to say that I believe that it can be controlled not to do these things at higher temperatures. Not that it in fact never does these things at higher temps.
Oxblood glazes are a good example of copper being reduced even well above 2000F and not having the copper boil or burn out. I just mean that it can be prevented not that it doesn't happen.
Also, post fire reduction may in fact be what is needed for the look you are going for. Sometimes you can't quite achieve a look from straight initial reduction on the way down. I just meant for me, for the glazes I am working on, and with the ability to reduce on the way down, it makes sense to do that as opposed to spending time, energy and cost to do a post fire reduction when I don't have to.
Occasionally I will strike reduced stuff which if i were to just not reduce on the way down and do a post fire reduction it would kinda be the same. The reason I prefer reducing on the way down and then striking in oxidation later as compared to a post fire reduction is that I can reduce a little higher and/or strike a little lower and get slightly different looks, or I can reduce a whole bunch of stuff at once, then only strike certain things whereas a postfire reduction would sorta have the strike done to all the pieces being reduced. Or I can strike reduced stuff along with non-reduced stuff and not worry about the non-reduced stuff reducing.
G
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Post by Arnie Benton on Aug 3, 2015 16:47:16 GMT -6
Hi Greg -
I thought the Cu issue with above 1700 F reduction has to do with the Zn boiling out in a reduction atmosphere. Somehow one leads to the other - I guess I need to do some more reading.
We each speak from our experience and differences are interesting to me - to be explored. I hope I don't sound like I'm right and any one who differs is wrong. My conscious belief is that everyone is right and let's figure out what's going on.
Speaking of oxblood glazes - the stoneware glazes I used to produce reds in my gas kiln also turn red in post fire reduction, after 30 minutes or so - that surprised me. I've got some combination pieces with an oxblood glaze and a crystalline glaze - oxidation fired and then pf reduced .... if I can find any of them in my stacks and stacks of plates.
I have done it both ways - lofire reduction while cooling and pf reduction - bowing to pressure from my family I do a regular crystalline firing and then they can take out the pieces they love before I go any further. I can present your approach to them and see if they buy it - they like striking and etching so it could work!
Arnie
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Post by tileman2 on Aug 3, 2015 18:53:33 GMT -6
Arnie:
Just in the last few days I have come to realize why my posts seem so odd to most. It dawned on me most are firing vertical pieces, with their own unique parameters and variables. I only fire flat pieces; that have their own unique parameters and variables. Same glaze(mostly), but issues unique to the form. There are things you can do with vertical pieces that you cannot do with flat pieces; and vice versa. You are doing plates and very well I might add. So you are the real oddball: you have to deal with both issues. LOL.
Tom
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Kuba
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SztukKilka in Old Formu
Posts: 111
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Post by Kuba on Aug 3, 2015 23:45:58 GMT -6
I have question to experts in reduction firing I know that in reduction atmosphere, cones went down much faster, than in oxidation, so the heat work is different in same temperature. The question is how much different? What is the equivalent to 700C (1292F) in reduction to temperature in oxidation? In other words: If the glaze is getting softer in 700C (1292F) in reduction, will the same happen in 800C (1472F) or 900C (1652F) in oxidation?
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Post by Arnie Benton on Aug 4, 2015 7:24:59 GMT -6
HI Kuba -
I think the problem only comes with Fe containing cones, easily identified by the color. I've never bothered with cones with post fire reduction. That's heresy and I can hear the Furies getting ready to pounce on me, but I admit it and to avoid confrontation, ask for forgiveness. So, get white colored cones - the self supporting ones are more accurate because there's less to mess up than with cone packs which should probably be calcined first and the angle may not be exactly right.
Arnie
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Kuba
Full Member
SztukKilka in Old Formu
Posts: 111
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Post by Kuba on Aug 4, 2015 11:46:45 GMT -6
Hi Arnie, I also do not use cones in post firing...only have cones number 8,9,10,11 I have two thermocouples - one in the bottom and second near the top. If I use several shelves in gas kiln, the temperature can differ even in 80 degrees C between them. Without any shelves it is about 20-30 C differences at higher temperatures. P.S. But I still use the cones to check elements health and temperature uniformity in my big electric kiln.
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Post by Arnie Benton on Aug 4, 2015 12:18:19 GMT -6
Hi Kuba - The picture of the gas kiln you posted - I think the problem of uneven heat distribution is much worse in updraft gas kilns - with downdraft you can arrange shelves and wall off the flames to improve the heat distribution. Or am I seeing wrong or do you have another gas kiln? It would be easier if it was the cones causing the problem!
Arnie
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Kuba
Full Member
SztukKilka in Old Formu
Posts: 111
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Post by Kuba on Aug 4, 2015 12:22:08 GMT -6
I need to build big chimney, so it will suck some air and create proper flow. It should solve the problem...
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Post by tileman2 on Aug 4, 2015 15:54:36 GMT -6
Greg:
I noticed you mentioned an alcohol drip: that one is rather new to me. Just purchased 1.75 Cf Paragon for small tiles; but mostly for testing. The other reason, I special ordered hollow bunges so I can mess with reduction for the first time. So in your experience: which medium is the best for reduction? Alcohol. oil. ?? I am going to play with just 2%CU and maybe a touch of Fe or MNO for highlights. Recommendations- any additional safety issues I need to know other than venting? I have roof mounted exhaust vents, so that is not a concern. Arnie- Kuba- feel free to jump in with advice.
Tom
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Post by mohawkpiper on Aug 5, 2015 0:27:49 GMT -6
Hi Tom, There was a thread on the old forum that had a bunch of info on all this but I couldn't find it. Spent a little time looking. Anyways, I don't have a lot of experience with other methods of reduction. I don't know what to tell you. I like the alky drip because it is all I have done really and I am comfy with it. A while ago, when I knew much less about crystals and all, before I was reducing with alcohol, I tried reducing with oil a few times. I wasn't dripping it though. I was soaking wood pieces in it and throwing them into the peep holes on the cooling. I didn't like it. It was hard to control, and the oil was super messy. I guess if you drip it then it would be a different story. I like the alcohol because it is clean. Gas/propane is much more common. Maybe safer? I don't know. The alcohol drip.... I don't seal up my kilns real nice like some people do, i bet if i did it would help. I have one peep plug with a small hole in it that I use in the top peep hole for when I reduce above 1800*F. I get a nice flame coming out the peep plug. I partially use that flame as a guide along with other things I use as a guide. When I reduce at 1500*F and below having that open holed peep plug seems detrimental to my reduction, so I fully close all the holes. My smaller kiln (skutt 822) reduces better at lower temps than my bigger kiln (skutt 1027) prolly cuz it is sealed a little better and smaller. At the higher temps it doesnt make a difference it seems. As far as safety... I cannot comment on methods other than the alky drip... but for the alky drip so far it seems fairly safe. Once when I was teaching my wife to do it she opened the drip all the way instead of closing it at the start... it blew a few of the peeps out of the holes. So there was some sort of pressure/combustion in there that was a little scary. Some people have seen lids blown upward (not sure the reduction method) and I believe phil hamling blew a kiln entirely (propane or gas if i got that right) so it is definitely something to be cautious with. after my wife's peep blowing incident I now leave two peeps open when i start the reduction so there is less chance of pressure building then when I get my drip in place where I want it I then close those peeps. I have CO monitors in my kiln room... two of them... they show safe levels most anywhere cept directly above the kiln where the peeps are it is off the charts. My studio is pretty open though and practically outside. When I reduce above 1800 i notice no smells or anything but when I reduce below 1500 if it is on the medium to heavy side (for me) i get a nasty smell and sometimes it kinda burns your eyes like when cutting onions so I mostly stay out of the room when reducing below 1500. I also wear an organic vapor mask (not sure that even helps but hey, why not) when I reduce below 1500. Reduction methods are different. You may get different results between the two. I don't think any is best. It is just what you are more interested in doing i guess. Bill Boyd used to do the alcohol drip then got a fancy kiln that he can reduce with gas (or is it propane? Im not sure i know the difference ioye) and he says he will never go back to alcohol drip. So to each their own I guess. Guess you gotta figure out what will be best for you, or try several methods if you can. Been meaning to try gas just never have yet. Btw, you seen one of these already, but these are the exact same glaze (like same mixed batch) and glaze to similar thickness levels (average 9/100s inch at bottom and 32/100s inch at top) and both reduced but reduced differently. Check out how different they are... They had the same growing schedule but the dark one everything else in the kiln was growing rather fast so I killed the last two holds so you don't get those like you have in the lighter one. G
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