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I made some confirmationish discoveries with my currie grid test in results to SiC. I have said it before but I sort confirmed it today.  I have said in the past that glazes that have more flux s

Well, I got my slab roller setup this weekend and I went out and bought 2 dollars worth of kids play foam. I ended up building this:   Which is three square foams thick. The triangle on

I finally got round to using a couple of Currie grids in my last firing. I varied alumina and iron instead of adding kaolin and silica, so I hope no-one minds me posting in this thread. The tiles are

Posted Images

So I took a few pictures at different angles in my photobooth and the lighting just wasn't bright enough to show the detail of all the glaze surfaces. So I took it on the floor at an angle with a flash and it shows up better.


I don't know if the higher fluxes in the C corner caused the mason stain to fade or what. But the corners in the C barely show up any of the stain. The glossiest tile is number 32. No surprise there. The best two tiles are very close to the original number 18 and 23. I have posted the recipes for them below for comparison to the original which is from Matt Fiske. He is a glaze testing machine.


The original glaze is on the top thin on the left and thick drop in the middle. I think the best tiles are number 18 and 23. They are by very glossy and nicely melted.  I am about to mix up 18 and 23 and fire them tonight, and see if they hold true to the same thing. I am also going to decrease my slow cool because I have some crystal formations from the zinc in the bottom left, and a few in tile 18 and 23, I thought at first it was a defect until I saw the formation resembling standard zinc crystals. I don't know if I just didn't put the correct amount in the C corner or what, but I think I am going to make 4 100G batches of 18 and 23 and increase the stain on second batches of 23/24 and increase the stain to 2.5% to see the differences.


Currie Grid Test - Celadon

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Great, thanks for posting so quickly and congratulations, looks like a winner!


Did you simply forget to add stain to corner C? Looks suspiciously like that...with the no-stain portion fanning out from corner C... You could be right that something in the flux package is eating up the stain but I have never heard of that before and in any case the flux is not just in corner C it is in all corners in varying amounts.


Since the stain is pretty much inert I still advocate leaving it out for the Currie tiles. Unless there is some kind of special effect or mechanism you are going for which depends critically on the relative amounts of flux, silica and alumina (eg, Cory's Weird in his book) it is just a distraction Other than this, since it is a well controlled and well-travelled ingredient you already know what it is going to look like. And if you don't, once you get the base glaze right (the REAL challenge in my mind) you can just do a progressive line blend to dial up the right amount to taste. In your picture of the tile I find the color from the stain is obscuring the glaze surface, and the deeper the colour the more this is an issue (eg around the edges). the colour in the surface of the glaze kind of disappears.



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Yea. I didn't know if I should run it with the additions or not. Either way I found 2 beautiful super glossy tiles 18 and 23. So I am testing 4 variants of them right now. I just burnt up my 3rd stick blender in 2 years. So gotta hit up walmart tomorrow. I think this will be the final correct glaze. I don't know if it was 100% blended because my stick blender died and I tried to finish it by hand, but either way if it isn't I will just fire again. The new work that I am creating is so obscure that I have to have a perfect glaze that is very simple to make it balanced. I think this will be the trick.


On a side note I just had the best throwing experience of my life. Literally pure bliss. The perfect music came on pandora and I was able to let go of my thoughts and just create. Made some really beautiful pots that are definitely in the direction I am looking to go forward. I will probably have to tone it down a good bit for it to be household dinnerware, but I find its best to start far out there and tone down.


Thanks for all you advice and help on the grid stuff. It has already paid off with just that one tile. It had perfect gloss besides the small crystal formations. That was due to my slow cool though. I have removed that and I am naturally cooling past 1900F, which will be super quick in my little kiln. 


EDIT: oh and on the C having no stain. I did not forget it. I thought that same thing, but I kept the C bucket with the remaining glaze in it and its blue as blue can be. No way there isn't stain in it. 

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OK, a few more comments/questions/clarifications...




First and foremost, delighted you were able to see another nearby recipe that was better.  That is definitely the kind of payoff which justifies the effort.  Just out of curiosity, where approximately is the original glaze on this grid (if it actually appeared as a grid recipe)?  I can tell from the amounts of silica and alumina in the original recipe that it is probably somewhere closer to corner B, or possibly off the grid in that direction. If I squint my eyes and just focus on the color as compared to the daub of the original glaze at the top of the tile, I am thinking it is like the thick corner of cell 19.  Does that seem right?  I can see from the recipe that your tile is using slightly less stain in all cells than the original recipe called for. 


On a related issue, after looking at your daubs on the top of the tile,  I am thinking in the future I might take one of the "fringe" cells on every tile (say 35?) and just put the original glaze in it rather than Currie's number 35 (which, while interesting to look at, I am unlikely to use).  That way I would have a cell in which the original glaze was right there on the tile, applied in exactly the same manner as every other cell, just for comparison... 


Could you remind me are you firing to cone 10?  I think so, but couldn't see it anywhere....


What about dimples, bubbles, etc.??  Have they improved over the original in any of the cells (and particularly your favourite cells 18 and 23)? 


The surfaces of cells in the left hand column (alumina heavy) seem rough and uneven from the picture.  I know part of this is the normal effect of lots of alumina and no silica, but in cells 25 and 30 you can see the flux bunching up in the corners of the cells like usual.  Is that roughness in the rest of the column above the surface of the glaze, or the surface of the clay poking through?  Hopefully it is not really the clay coming through as that would mean there was too little glaze in those cells.  If there is too little glaze that really confounds application with glaze chemistry because the glaze surface in those cells becomes more about the glaze/clay interface layer, rather than the glaze itself.  One other thought is that since you have lots of zinc in this recipe maybe it is small chunks of that not fully melting.  Do you sieve your glazes or otherwise crush up the zinc?  Just curious. 


The whole disappearing stain mystery is very interesting.  I do not work with stains so I am really just speculating here.  The only think I can think is that since corner C has no clay in it, there is nothing to suspend the glaze ingredients in the slop, which means that you have to keep constantly stirring when you are applying. and if you didn't you might miss the stain.  However, that same issue would also have affected corner D, which also has no clay in it, and we can clearly see the stain there...  Hmmm.... The only other unusual thing about this glaze I can see is the high zinc content (compared to many other clear glaze recipes), but maybe others will have a different view.  I guess one test might be to take a syringe and plunge the nozzle right down to the bottom of the corner C bucket (without stirring C first), suck some up, and see what it looks like fired. 


As a general comment, I am not surprised you got a better glaze using more flux (and less silica and alumina).  The original glaze seems to be quietly just scraping in with regard to  adhering to "the limits" for silica and alumina.  Yet you seem to be getting a much better glaze using more flux..., but your glaze falls outside the limits.  I have had the same experience, and it is starting to bother me. Is your glaze functional? On what measures? etc. etc.  Going to have to get to the bottom of this story....again, that is for another thread.


Finally, let me say that I truly hope my comments are received by everyone reading this as they are intended, that is to say, constructively.  My aim is to contribute however I can to improving your process and outcomes, which in turns makes every tile you run more understandable and more useful for me and everyone else, and if you receive useful comments, even back to you.  Often in this business, it seems, it is just that one little thing that turns the whole show around...


Perhaps that is why I tend toward being a bit of a purist regarding Currie's technique.  It is not because I think he has a monopoly on good glaze testing.  His method is very powerful in the information it cay yield, but it is also more complicated to execute than most other glaze tests I know.   Since there is so much going on in a currie tile, the more consistently we follow his basic technique, the more we will be able to understand what the test is telling us.  When as individuals we start making changes to his methodology, then everyone else looking at it has to catch up to what changes have been made and what impact they might have before they even understand what they are looking at.   This takes a lot of time in back and forth Q & A for all involved. 

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@ Curt, I am just going to quote your questions for ease of answers.


First and foremost, delighted you were able to see another nearby recipe that was better.


I am not sure if the recipe is better, but it is glossier in my kiln schedule based on my clay. I can't imagine the author's original glaze isn't glossy seeing his work.


Just out of curiosity, where approximately is the original glaze on this grid (if it actually appeared as a grid recipe)?


Probably 19. It seems the closest in hue and surface to the original.  


 I am thinking in the future I might take one of the "fringe" cells on every tile (say 35?) and just put the original glaze in it rather than Currie's number 35 (which, while interesting to look at, I am unlikely to use).  That way I would have a cell in which the original glaze was right there on the tile, applied in exactly the same manner as every other cell, just for comparison... 


I am going to build a new grid this week. I plan on adding a grid at the top of the tile Grid 0. This will be my original glaze for cases where I am working on a glaze I already have. I am also going add places stacking them on the 4 corners and one in the middle. I haven't drawn out the sketch yet, but I definitely want to stack them for room once I start filling my kiln full of wares while I test at the same time. If I had a testing kiln I wouldn't worry about this as much, but I want to continue testing while I fire my production work, so I need to stack them 3 high at-least. 


Could you remind me are you firing to cone 10?  I think so, but couldn't see it anywhere....


Cone 6


What about dimples, bubbles, etc.??  Have they improved over the original in any of the cells (and particularly your favourite cells 18 and 23)? 


There are no dimples in tiles 18 and 23. 23 is of course smoother than 18, but either are a large improvement over the original in my environment. There was some crystal growth from the zinc, my schedule has a few holds on the way down from my previous work. I have removed them, so I am assuming the firing that is cooling right now shouldn't have any of these zinc crystals starting. But besides those there was nothing I didn't like about the surface. The glaze has microbubbles in it, but I like that part about the glaze, I want that in this particular glaze because you can't see it unless your looking at the pot up close and I think people would enjoy it. I know I do. 


The surfaces of cells in the left hand column (alumina heavy) seem rough and uneven from the picture. 


That must be the picture, because they are smooth and pretty silky feeling really. I was surprised at how they were not as rough as I was expecting. As far as the other concern, there is plenty of glaze in the grid. I checked with a needle tool several times to make sure I was 2mm deep. I also when filling the tiles would work around the corners in a square pattern, then when I got to the middle I would keep filling it until the tile almost overflowed. Then after it dried I would go back and put more in the bottom right corner. If you could hold the tile you could see that it is thick, its hard to picture it being so white. I do sieve my glazes. My zinc oxide is very soft from US Pigment. Its a fine power, I have never had a problem getting it to mix in well. On smaller batches I stick blend it for a long time, then I check application on a test tile, if I see any bumps of material I sieve, then blend again. Usually I don't have to sieve. I do however always sieve production batches.


The whole disappearing stain mystery is very interesting. 


I honestly have no idea what the heck is going on here. I was very careful since this was my first time to accurately stir everything as much as possible. What is even more interesting is when I was finished with the tile. I was looking at the shades of the grids. The bottom left was the most blue because it didn't have any clay in it changing the color to a darker greyish.  See attachment. 




If you look here, I am sorry the quality is so low, camera phone. The bottom left is in the bottom right corner of the picture. It is more blue than the entire rest of the grid! I know I stirred it all well, because I tilted every cup as I was mixing before I went to syringe it out. I also had the syringe in my hand so as soon as I finished stirring I went in for the mix, this way it didn't settle fast. 



The original glaze seems to be quietly just scraping in with regard to  adhering to "the limits" for silica and alumina.  Yet you seem to be getting a much better glaze using more flux..., but your glaze falls outside the limits.


According to the Roy-Hesselberth limits, all three of the glaze falls within their limits for cone 6. 23 is pretty close to being out of the limits but is still inside of them.

Roy-Hesselberth is AL203: .25-.5, and SiO2: 2.5-4 (unless I am wrong this is what digital fire list inside of insight.) This will be a functional glaze. I have tested my cups with all the standard testing I can do for wear and tear on the original glaze formulation. I will test again if I end up using this newer recipe. So far I haven't had any changes in surface from vinegar or dishwasher detergent. I have also done the whole ice water oven test stuff and no visible instant crazing or pinging. There isn't much to worry about in the toxicity of this particular stain. I have researched those oxides on digital fire and in product usages. Plus I am using it at a very low % here.


Finally, let me say that I truly hope my comments are received by everyone reading this as they are intended, that is to say, constructively.  My aim is to contribute however I can to improving your process and outcomes, which in turns makes every tile you run more understandable and more useful for me and everyone else, and if you receive useful comments, even back to you.  Often in this business, it seems, it is just that one little thing that turns the whole show around...


I don't think anything here was negative at all. I fully appreciate the comments. It is like having a personal tutor!  B) ... and negative comments are very good for learning anyways, so if you have them I want them.


Without this forum and the people in it, I don't think I would have even continued with ceramics. There is just so many daunting problems to figure out and without the experience of everyone on here I doubt I would have gotten past a majority of them. I fully give this forum credit for a large majority of my ability to do what I do in ceramics being self taught and only in it for 2 years. I am very happy with my knowledge level and abilities. I work very hard and I am always in the garage tinkering and testing things so I enjoy a good conversation about things like you did above. I can't wait to really get into the deep dark world of silicon carbide reduction. Pulling out grid after grid and finding a few millimeters of a part of a tile I enjoy then basing the next tile off that single grid is going to be very interesting. 


I do agree that I should have left out the stain, although the stain/flux issue is quite interesting. Either way I thank you and Joel for all the help here. I have a ton of testing that I want to do and I will post all my results like I did above except hopefully with a better picture. 


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I think this is how I am going to do my next grid mold:


Dark black areas are extra deep so that they create raises that the tiles can rest on when stacked. The diagonal lines are the places that are dug out, but not as deep as the dark spots. this is so I dont have any more problems with the tile getting sloped on the edges. the actual tile ends around the far black lines. Similar to what you have curt.


The only thing I am questioning is the 4 props in the middle. I don't know if it is taking up to much of the grid 18. I was thinking about making the tiles a tid bit bigger than 1 inch to compensate for this, and also just to give more information and leave more room for the running man. 


Tile 0 is for the original glaze if I am working from a previous one. 


The notes section is to write down the original glaze recipe used. I don't want to keep track of the title of each glaze on paper corresponding to the currie test. so I decided I would make a place to write with an underglaze pencil the notes of the tile. Basically the information that I put into the currie form for the output. 





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Don't know if this is of any interest/help but I remember an old J. Am. Ceramic Soc. article on silicon

carbide reduction. Among other methods they added SiC into a slip which they bisqued before

applying the glaze. Seems that the SiC only decomposed when it was wetted by the molten glaze.


It might be one way of getting uniform SiC action for all the sub-tiles on a full-tile, and using the same

glaze batches on several full-tiles with different SiC content in the slips.

... But harder to use dancing men, etc.

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There is quite a bit of zinc and this could be where the colour is disappearing to along with the calcium. I have been thinking about the chemistry of it all and got lost along the way  :huh: It is a good idea to add the oxides/stains if it is going to be that colour as it does impart something to the melt and the chemistry will change the colour.


Curt I am with you about limit formula not adding up with experiments. I am starting to think there is a lot more weight towards what raw ingredients you use than I thought. I would also like to say thank you for bringing the topic up :D even if there never is a whole forum dedicated to the idea this thread has produced a lot of good knowledge for me. I still remember being stupid enough to weigh out 35 different glazes for my first tile  :lol: who knew, volumetric blending...


Joseph, I would try a square stamp then you can just leave the gaps for the props. I measured the thickness of one of my tiles and I am getting 4mm (1/8 inch) thick once fired. I certainly have some older tiles three maybe 4 times as thick but I think with a stamp you don't stretch the clay, only compress, then you can go much thinner. Slice straight from the bag with a cheesewire thin sidebars combo.


Give the glaze a typecode in insight and add that to the tile. T001, T002... T00n. Then there's no need for the full recipe.

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So i just pulled out some pots from the kiln and pots in the 23 glaze have less color than the 18 tile. Which is the same on the grid test, so something is in fact getting rid of the color of the stain. The 2.5% mix is about the same as the 1.75% mix on the original glaze if that makes sense.


I don't want to stamp tiles I think that sounds like more work than rolling them out, now that I figured out how to roll them it only takes me like a minute to create a tile. I would rather get my master right so that all my results are the same as well. 


I didn't think about the typecode for insight, that is a good idea. 

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Ok  :D I will shut up about the stamp :( .


Did you mix up a fresh batch for the two tests? It is certainly something strange. I have started getting into acid, alkaline and amphoteric thinking for glazes. Probably because I made it through chapter A of the potters dictionary :lol: Acids seems to be the glass formers, alkaline the flux and amphoteric a bit of both depending what else is there. The lack of silica I think is making something swap how it would normally act in the melt. Can't say I fully understand where I am going with this and the glaze just seems to have a lot of alkaline stuff in.


Most limits seem around the same, little more here, little less there.

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Yes I mixed up 4 batches. Some with the old % and some with .75% more.

The .75% more resembled the old glaze in color.

I think stamps are fine with ur method of slicing off clay. I am making bigger tiles than my clay so I can't do that as easy, so I might as well roll them which I have gotten pretty fast at. Going to make a new mold tomorrow I think.

Got a bunch of test tiles under a fan for a bisque tomorrow. Going to test application for the 4 mixes and get a new stick blender.

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Hi, re SiC in a slip.

Full details in

http://onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.1932.tb13930.x/abstract (but the full paper is behind a pay-wall)

... I have a copy somewhere, but not readily accessible.


Some details are in a patent available at


... which gives 2% SiC in the slip.

IIRC the original article used the technique in both low and high fire.





Memory slowly returns. I said much the same thing, in more detail when I had a copy of the paper to hand.

See post 7 of http://community.ceramicartsdaily.org/topic/4341-silicon-carbide-in-glazes/


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Thanks for all the information. I will get to this stuff in the coming months. My plan right now is to continue on the path I am on and get grids setup for this type of testing once I am filling my kiln with production ware i will have a place for a stack of 3 currie grid test. The idea of the slip is interesting. So many things to try. When I get to it I will be sure to purchase that paper. Thanks for that link. 

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OK, re-entering the thread, a lot has happened in the last 12 hours!


Re my previous post, my bad on the limits, Joseph.  I was comparing your recipes to cone 10 limits in Insight, assuming (wrongly) that's where you were firing at.  Of course it makes more sense now and I take your point that at Cone 6 your glaze is OK on that count.  However, that said, I still think there is a major issue to be resolved with glaze limits and glaze functionality, and Joel I am glad to hear that I am not the only one troubled by this.   I would love to launch into a good discussion of this, but will save my thoughts for another thread.  For the moment when I look at limits I use the ones in my desktop copy of Insight as a matter of convenience, but I am increasingly sceptical of them with every test I do, and am badly in need of some recent, more scientific backing for their legitimacy.


Currie Tile Design:   


I believe that the reason the currie "tile" is not simply a series of 35 independent vertical test tiles, and why it is superior to most other forms of glaze testing is this: having 35 very-similar-but-systematically-altered glazes all close together on one object on the same plane and the same orientation maximizes our human potential for comparison.  And given the high degree of subjectivity in this whole business, that is exactly what is needed. Tilting all 35 glazes at the same time in just the right light lets our brain cells divert all their energy to processing visual information from the glazes themselves, rather than the surrounds.  This sets us up to be able to answer the ultimate human question: "compared to what?"  Yes this glaze is good, but compared to the one next door is it better or worse?  And let's remember that color is only one aspect of a glaze.  Texture, smoothness, bubbles, durability, pitting, etc, etc, are also very important for any kind of functional surface and we need to be able to compare those things as well.  


So what does this have to do with tile design?  Well, I think the overall aim with a currie tile is to create a testing surface which replicates as many features of the situation for your pots without compromising the kind of information the test is designed to deliver.  At a practical level this means the same clay body as your pots, same firing conditions as your pots, same thickness of tile as the thickness of the walls of your pots, etc.,  Obviously we are firing on a flat surface not a vertical pot wall, but we can still replicate some of the "verticality" environment with tile features like small raised mounds, striding men, scratch tests, etc.  However, the main game is still the outcomes of the chemistry at this point (I agree that vertical test tiles come later). 


I worry about any feature which is materially different from the environment my pots face (other than the verticality issue).  For instance, I worry that the thermal mass of the kiln shelf under the tile will mean slower cooling - and different colors? - for my currie tile than a pot wall would face.  I worry that the cells of a tile which are closer to the kiln elements will get different heatwork than cells which are closer in to the center of the tile (or othewise farther away from the kiln elements.  I worry that when I put a prop in the center of a currie tile, that it, too, has a thermal mass which subtlely changes the heatwork on the cells around it.  I also worry (and am just annoyed) when bits of the prop break off on the tile and cannot be removed without risking breaking the tile (says someone who has glued several tiles back together).  I worry that all of these things interfere with me getting the best situation for comparability between cells. 


How would I redesign my tile?  I would probably start by getting a setup which allowed me to produce tiles of any thickness I wanted, and then get a thickness of tile purpose-built for the situation of the glaze I wanted to test.  For example, my smaller, more-delicate pieces of functional porcelain will have much different thickness - and require much different glazes and application - than my larger composite and coil built pieces meant for the wood kiln.  I am thinking about how to use a slab roller (which I do not have at the moment) or similar mechanism for impressing currie tiles of very consistent thickness and density. 


I am also thinking about props for between currie tiles in a stack.  For the reasons mentioned just above, I would love to fire all my tiles so that both sides of the tile have air around them, and then I would not even put a tile directly on the kiln shelf.  I would probably design the places for the props to be as small as possible, and I would be looking at using pre-existing standardized props of some kind.  Those three-legged firing stilts with pointy ends for minimizing contact with the pots seem almost ideal, as they minimize contact with the tile (minimizing thermal mass transfer) and also minimize the surface area for fluxy glazes to crawl up on to - or worse - spit up on to.  But one would need to have the supply of these three legged things in hand and play around with the tile design to place them in the best way possible.  And Joseph, I would not have one prop in the center, I would have two of them along the center line, but spread out from top to bottom.  Keep them away from the center of the tile where you are likely to see some of the best cells (18, 23, etc) just in case there is a mishap.  I would put small indentations for the props to sit in, so that every prop is perfectly below the one above it, and almost "clicks" into place when you are stacking them so that they do not move around. 


This picture below shows how wrong a stack can go, And I now believe more props is better than less.  One wants that tile to stay PERFECTLY FLAT without having to make it artificially thick to do that.  When tiles melt and warp, glaze flows to corners and sides, dramatically reducing the potential to compare different cells.   



I have found I can always use a glaze pencil to write on the back of tiles to record recipes, clay body types, firing conditions, etc.. But of course this needs to be done before applying glaze to the tiles.  Otherwise, you can always come back and write with a permanent marker on the tiles, which actually works a bit better in my experience.


Still thinking, but that is plenty for now I am sure you would agree...

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  • 6 months later...

Was going to post these in the recent oilspot thread, but since they ARE Currie tiles.... The pictures are not that great, so it may help to click on them and look at them with more magnification.


This is a basalt glaze I have been experimenting with lately. Was not looking for oilspots, got them more by accident. For you currie tile aficionados out there, I apologize that these images were uploaded upside down, so that the lower left hand corner of the currie tile is actually in the upper right in these photos. (Edit: whoops, now it looks like the photos are right side up!, so the lower left hand corner is in fact the normal cell 31) Also sorry that my other experiment of using a piece of old kiln element as a makeshift prop for one of the tiles did not work. Stacking currie tiles is not something I have mastered yet as one look at my gallery will reveal....


Both tiles fired in oxidation at cone 10 in the same firing. Interesting to see the impact of changing the amounts of silica and clay on the size and look of the oilspots.


This first one is on a whitish stoneware body.

Cone 10 Currie Tile with Oilspots On White Body - Oxidation


The second one is on an irony body. both tiles were in the same firing. The body type did seem to make a subtle difference, my best guess is because of the iron in the body adding to the iron in the glaze.



Cone 10 Curie Tile with Oilspots On Iron body in Oxidation

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