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Tiles 16 and 17 above are the tiles 16 and 17 from the squares. They have melted more than the square, I think there was just too much glaze in the square to melt thoroughly whereas on the tile there is enough but not too much to get a full melt at the cone.

 

 

I don't quite understand this.  Why would thicker glaze be harder to melt?

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Sorry David my blabbing about alumina and silica was not related to your colourant tests. Will have to try some of those out for sure. I am trying to make my own test where the silica and alumina ratio will stay the same and the flux value will change. Found out it's a bit harder in practice as feldspar don't play nice. It brings far too much silica and alumina :(

 

I dunno Ray, maybe my thinking is wrong. I thought it didn't have enough time to melt the thicker glaze compared to the thin.

 

I am working night shift again tonight so I made this excel spread sheet. Pretty much does what Ian Curries page does except I can choose the values for each glaze.

 

All you need to do is add in the four glaze corner recipes, weight of dry glaze (blue boxes) and total ml of water and it works out the rest :D

 

post-23281-0-39585800-1433114887_thumb.jpg

 

 

post-23281-0-39585800-1433114887_thumb.jpg

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Ray, it would be hard to choose (yet) one glaze as the most useful I have got from Currie's grid method. I have used his approach with a variety of native materials of unknown composition and this has yielded at least two or three glazes of interest on most tiles. However, I have been too excited about churning through my stockpile of new materials with grids to spend much time (yet) following up on the likely prospects. That said, I am now following up on several of these prospects with test tiles, etc to see how they perform when scaled up. But your question is a good one and I will report back when I have a better answer!

 

I did promise to post some more tiles but I am travelling at the moment and will wait to do this until I get back to the desktop.

 

High bridge I like your thinking about trying to alter the fluxes instead of the silica or alumina. I would have thought that a precursor to doing that would be to identify the most useful silica:alumina ratio which you would apply everywhere. What most useful means is an open question. I am guessing for some here that means within functional limits, is that what you are thinking? I am just curious as to which ratio you will use.

 

I also wanted to address a potential point of confusion about what is going on with the fluxes in a Currie grid. It have seen it said in a few places (on the Matrix website help section, and also in John Britts high fire book to name two) that the Currie method alters silica and alumina while keeping fluxes constant. This is not quite right. The Currie method keeps the RELATIVE amount of one flux to another constant, but it constantly VARIES the amount of flux around the grid at the same time it varies the silica and alumina. So there are three variable changing at once, not two.

 

In corner C flux starts off at 100%, but by the time you travel from the lower left to upper right corner of the grid flux has decreased to 35% of the blend. I think these amounts are not accidental either. The silica, alumina and fluxes are kept in a region where they have a good chance to melt and form some kind of a glaze, functional or not, that will at least melt some and stay on the pot.

 

I think this is important when comparing the Currie method to triaxial methods, quadraxial methods, or other techniques that change more than one variable at once.

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Ah yes, I was thinking the flux stayed the same across the whole tile, probably looking at too many unity formula. It does keep the flux ratio to itself the same so maybe that was it. I wanted to see what different ratios of flux to each other would do.

                     Kaolin    Silica    Gilles-    Dolomite                        
Glaze A    31.2         44         74.8        0
Glaze B    35.8         51.7     41.7        20.8
Glaze C    60             90         0               0
Glaze D    41.3         61.5    0               47.2

 

These are the four glazes I ended up with. Think it is 8.33~ ratio and it does vary slightly across each glaze. There will always be quite a bit of CaO as the dolomite and GB both bring it. No idea what is going to happen but I will be glaze firing a few tests today.

Edited by High Bridge Pottery

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OK at long last some more tile pics...  Had to re-teach myself how to upload pics.  Again....  May include some other samples from this firing later.  Over all it was quite successful, primarily from a testing point of view.

 

Cone 10, LPG fibre kiln, more lightly loaded than usual. Heavy reduction from 900 to 1280, then a very clean, level, oxidizing soak for last 30 mins before shutdown.  Fast cool, down to 120 C 12 hours later.   Cone 10 flattened at the top, suggesting we probably went closer cone 11 (no peep hole up there!), with the bottom cone 10 (the actual cone we could see) stopped at 3 oclock, or half down. 

 

This Currie tile below has ash as the flux, and using basalt rather than silica, with the view that the basalt was mostly silica anyway.  In retrospect looking at how fluxy and crazed this tile is, the basalt must have acted more as a flux in the melt than it did on its own (which was not very much).  The original images were taken in very poor light and if they appear juiced up it is because they have had a bit of "work" done. ;)

 

Note to self: stop being so stingy with the clay and make tiles THICKER!

 

First the full tile.  The wild, untamed fluxes here have clearly been spitting in discontent at their poor treatment!

 

Currie Tile Ash May 2015

 
Now working around the tile clockwise starting with bottom left corner (Corner C) which is all ash

Currie Tile Ash May 2015 Corner C

 
Now moving to Corner A upper right which is high clay and no silica

Currie Tile Ash May 2015 Corner A

 
Now corner B which is high clay and high silica, with minimum flux.  Still looks VERY melted to me.... :lol:

Currie Tile Ash May 2015 Corner B

 
Finally down to the high silica, no clay corner at D.  Some interesting overload appearing, but the tile split and some of this very runny glaze melted right through to the shelf underneath (argh!) leaving unhelpfully little evidence in the cells themselves.

Currie Tile Ash May 2015 Corner D

 

Next time I may try using the basalt itself as the flux, then move on to some simple flux blends.  Ah, so many tests, so little time....

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The rutile and cobalt are definitely helping the melt. They are quite smooth but still matt, 16 more than 17. I think there is too much glaze in the squares as my tiles of the glaze came out with a better melt and it's the same recipe.

 

 

 

You'll get different results on flat tiles compared to vertical tiles. They're probably both melting fine, but many glazes behave radically different depending on whether they are puddling flat or allowed to flow. If you plan to make pots, then I would run your tests on vertical tiles so that you get a real sense of just how fluid the glazes really are. There's no sense wasting time with flat tiles if you're not going to use your glazes in that way in the end.

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Neil, not sure what you mean by "radically different"? Maybe you could give some examples? Other than how much the glaze will run on a long vertical surface I have not seen much difference in glaze performance between flat tiles and later vertical tests across the various tests I have run. The glazes pretty much look the same, melt the same, craze (or not) the same, etc. Different application thickness can produce different appearances (and runny-ness) but that is something else.

 

As I said when you made this point earlier in this thread, there are good reasons to use Currie method as is, including the fact that the standard Currie format already provides a few good indications of runny-ness if you know where to look for them. I think there is a time and a place for vertical test tiles, but using them to implement Currie's method rather than his purpose-made flat tile misses much of the unique learning opportunity that his format offers. That includes the ability to compare 35 closely related glazes that have been varied systematically and fired in the same place in the kiln under exactly the same conditions.

 

Maybe you have another way to do it, but it seems to me that the amount of raw materials needed to make 35 cups of enough glaze to properly dip vertical test tiles is many times the amount called for in Currie's technique. Since you will only be interested in a small number of these, most of those cups will be thrown away. This seems wasteful, since most of the same learning could occur with far less glaze.

 

I think it is fair to say that we all plan to utilise the results of our testing to make pots (otherwise it is just some kind of pointless academic exercise). However, to dismiss Currie's way of testing as a waste of time simply because you are not making flat pots misses the point - and the value - of his technique entirely.

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Neil, not sure what you mean by "radically different"? Maybe you could give some examples? Other than how much the glaze will run on a long vertical surface I have not seen much difference in glaze performance between flat tiles and later vertical tests across the various tests I have run. The glazes pretty much look the same, melt the same, craze (or not) the same, etc. Different application thickness can produce different appearances (and runny-ness) but that is something else.

 

As I said when you made this point earlier in this thread, there are good reasons to use Currie method as is, including the fact that the standard Currie format already provides a few good indications of runny-ness if you know where to look for them. I think there is a time and a place for vertical test tiles, but using them to implement Currie's method rather than his purpose-made flat tile misses much of the unique learning opportunity that his format offers. That includes the ability to compare 35 closely related glazes that have been varied systematically and fired in the same place in the kiln under exactly the same conditions.

 

Maybe you have another way to do it, but it seems to me that the amount of raw materials needed to make 35 cups of enough glaze to properly dip vertical test tiles is many times the amount called for in Currie's technique. Since you will only be interested in a small number of these, most of those cups will be thrown away. This seems wasteful, since most of the same learning could occur with far less glaze.

 

I think it is fair to say that we all plan to utilise the results of our testing to make pots (otherwise it is just some kind of pointless academic exercise). However, to dismiss Currie's way of testing as a waste of time simply because you are not making flat pots misses the point - and the value - of his technique entirely.

 

How much a glaze behaves on a vertical surface is a HUGE issue. It determines how it will break on texture, how it will behave with other glazes, how it must be applied, how much underglazes will bleed, where in the flow that crystals form, variations in mattness/glossiness, milkiness due to thickness, etc, etc, etc. Respectfully, to say that there's little to no difference between vertical and flat tests is inaccurate. I get what you're working on here, but I think that a lot of it of it is simply academic, because until you put the glaze on a vertical surface you're just guessing as to whether or not it will actually work for you.

 

I don't agree that you'll get more accurate results because the grid puts the tiles all very close together. It's not hard to fit 35 tiles close together on one shelf, even in a small kiln.

 

In regards to wasting materials because the flat grid uses small amounts, yes, that's true. But I think that running tests on tiles that you know aren't going to produce anything useable, like all flux, or little to know alumina or silica, is just as big a waste.

 

My point is that the Currie grid can be quite flexible. It can be used for color tests, or for adjusting the fluxes or alumina or silica for a specific glaze, or for creating glazes from scratch. I get that you're using it just as Currie defines it, but that's not set in stone.

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I like the basalt tile :D do you have a picture of how it melted on its own? Interesting idea to use it instead of silica. Is the glass really that green in real life?

 

Sorry Neil but I don't really like the idea of making 35 different tiles and having to move them/lay them out/knock over :huh:  Man I hate it when one drops to the bottom of a full kiln  :angry:

 

I agree that the currie method is much more academic and there is knowledge gained outside of the scope of what you could possibly need for a functional glaze. I have begun to see it much less as a method and more of a graph. You can choose where the graph of your materials goes, within the parameters you set. Right now I don't know what I am looking for and really exploring what is in my store cupboards and how it melts. I will definitely be using more vertical tiles as I progress towards something functional but it will be a smaller sample size than 35! Now I am thinking of ways I could have the best of both worlds. A Hybrid of flat and vertical tiles.

 

I had some good results from my Si/Al ratio tests varying the flux but I seem to have left my SD card in the studio :(

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Neil, I did not say that there is no difference between flat and vertical tests (you are misquoting me).  What I did say was that in my tests I have not seen that much difference, particularly for the kinds of issues I am focusing on with unknown materials.  That said, lets examine each of your situations in turn, because I think a number of things are being co-mingled here. 

 

Breaking on texture:  if you are familiar with Curries method you will know that his tiles will provide some indication of breaking.   Suggest you have a look at Currie's book "Revealing Glazes" before making a conclusion on this.  That said, breaking is certainly one of the things I would be looking to get additional information on in second-round testing with larger format test tiles or test pots.  

 

Application: This is a user issue which needs to be fine tuned to everyone's specific situation.  Currie cannot really help you with that (although it does provide clues), nor was it intended to.

 

Underglazes:  again, this is a separate testing (and design) issue at the individual level, not a Currie issue.  You can certainly put a small dot or stroke of underglaze (or any coloring stain or oxide) in each cell of a Currie tile, and it will provide some color response and probably even some bleeding information, but if underglazes are a key part of your work of course you would want to do additional testing.

 

Cyrstalline Glazes:  The Currie technique can be used to test crystalline glazes, but if fine tuning where crystals form in the flow of glaze down the pot is critical to you then of course additional testing (probably a whole lot of it) will need to be done.  Again, this is obviously not something Currie's method was designed to do.

 

Glossiness/Matteness:  What makes you think Currie method cannot help with this?  I have plenty of glossy and matte cells on most every tile.  Sometimes it is a thickness issue, sometime it is a chemistry issue.. If you are talking about when the glaze flows and gets thinner or thicker and glossier and matte-er, well in my experience this is often a subtle pot specific issue which depends on a whole lot of things including firing, kiln placement and where the butterfly flapped its wings yesterday.   Not going to expect anything definitive on that from ANY testing method.

 

Milkiness from thickness:   This is exactly one of the reasons to do Currie testing.  It clearly provides information on this.  Obviously in a live-fire situation this issue is going to be intermingled with application technique, specific gravity, etc.  Again, these are user variables, not Currie variables.

 

So IMHO most of the issues you are raising are not reasonable demands to place on the Currie method, even though his tiles CAN provide some information on most of them if you know what you are doing.  

 

No testing method is a panacea, but that does not mean it is a waste of time.  Even you have observed previously that Currie's method provides a tremendous amount of information.  I would add that if you know how to use it, the Currie method can inform ALL the glazes in your studio (not just the one you are testing) because they all probably mostly use the same raw materials. That is the kind of learning we should be focusing on here, not picking holes in it.  Perhaps I am misunderstanding, but I feel like you are spending a lot of time here trying to dismiss, distort or otherwise undermine this testing technique whlle the rest of us are trying to learn about it and share information and images and experiences and make a POSITIVE contribution which benefits all.  

 

Of course you can tweak or alter Currie's technique to test anything you want, but once you change it enough it is not really a Currie test anymore, but probably some kind of quadraxail, triaxial or or other method, or your own concoction.  No problem with that, but there is already a lot going on in a standard Currie grid.  I would suggest that anyone looking to extract maximum value from this technique concentrate on learning everythying it has to offer first, before making major changes.

 

I think everyone understands your preference for vertical test tiles.  As I have said, I regularly use vertical test tiles myself for all sorts of things and I am sure many others here are the same.  However, like Currie tiles. they are only one of the arrows in the quiver, and there is no need for anyone to have to choose one over the other.  They all have their place.  I think the reason many people are following this thread is because most people ARE NOT familiar with the Currie technique and how it is done, but would be interested in knowing more about it and maybe even joining in the discussion. So can we please focus on Currie tiles and what they CAN offer rather than what they cannot?

 

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Highbridge, here are some undoctored photos of the test tile.  That emerald green was due mostly to the excess collagen, er, saturation provided to me by Apple (blame Tim Cook!),  Purely for illustrative purposes and to highlight what was going on in the tiles.  Sorry I will try to be less heavy handed with color in the future! :blink:

 

Here is an unaltered photo taken in overcast conditions.

 

Ash Basalt Currie tile In overcast daylight

 

Here is a similar photo, but just adjusting AE slightly (no other changes!)  To my natural eye, I think the best way to describe the color is:  have you ever seen a car window shattered?  It is that color of green/blue if you can imagine it.   I am still thinking about what is the ash and what is the basalt here.

 

Ash Basalt Currie tile AE adjusted

 

Finally, here is a shot of the basalt on its own.   It behaved very differently than in the glaze, needless to say.  Although I am pretty sure I used sub-80 mesh basalt in the glaze, and what you see in this pot is 40 mesh.  Yep, its true I think, size matters. :o

 

Basalt test

 

I have also thought about how one might create more vertical surface on the standard currie tile without sacrificing its other attributes.  However, introducing verticals in each cell interferes with your ability to hold the tile up to the light and compare glaze surfaces in adjacent cells.  That may not sound like a big deal, but subtle variations from cell to cell are some of the most important info I get in my tests, and I am still discovering minute differences which make me change my mind about which is the best cell even after 6 or 7 examinations.  So I haven't yet left the standard format.  Open to ideas though.

 

Please do share your Si/Al tests when you have a moment.  Very interested to see them.

 

I would hasten to add that I do not think of Currie tiles as an academic exercise.  Academic exercises are generally only for the consumption of other academics who are also carrying out there own academic excercises.  If we are lucky the result of all these exercises is that small drops of useful information for mere mortals eventually flows out of the academic pipeline years later.  (apologies in advance to any moderators who are also academics  :unsure: ). 

 

We are not in that camp.  Any experimentation we do must contribute - directly or indirectly - to our making as a matter of some urgency (within our lifetimes even!  :lol: ).  I find that the information I get from Currie tiles has a direct bearing on my current making agenda, so much so that I am willing to take time out from making to do them.  In my case, with many totally untested native materials, I cant really see much alternative, other than random tests that lead nowhere except to kiln meltdowns.  Currie tiles informed by the current generation of glaze software provides real time information which focuses my testing and ultimately means less wasted time and materials, and better pots! or at least I think so... ;)

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Ok here are the two flux tests. Made four glazes with as close to 8.2-8.3 silica/alumina ratio. Corner C is only kaolin and silica.

 

Found out it is hard to keep the ratio the same when most flux come with a butt load of silica and alumina. To keep it simple I started with Gillespie Borate going up the Y axis and either Dolomite or Talc along the X axis.

 

Not sure why I didn't do one with whiting but that is next on the list.

 

With Flux test 1 it increases in MgO (Talc) along the X and KNaO/CaO/B2O3 (Gillespie Borate) up the Y axis.

 

gallery_23281_912_204933.jpg

 

Flux test 2 has CaO/MgO (dolomite) along the X and KNaO/CaO/B2O2 up the Y axis.

 

gallery_23281_912_46684.jpg

 

It seems impossible to do many more of these as adding feldspars seems to mess everything up but I will keep trying a few more. Not sure how the flux compares between the two in amount but I think they are kind of close. It is interesting to see how matt the Mg can go compared to Ca and Mg. The fourth row down is a good one to compare.

 

gallery_23281_912_23777.jpg

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Good pics.  Are you indoors using normal light or adding some additional light?

 

Could you please remind me what cone you are firing at?  Also, are you using that spreadsheet you made up to determine the amounts in each cell?  Is what you have in the C corner really all silica and clay and no flux at all?

 

Like you surprised that the Mg is doing so little with the Talc.  In fact in your bottom Row 4 comparison it actually looks like as you increase MgO the melt deteriorates from left to right!  I find that surprising, but as you said you are adding two parts silica for every one part MgO in talc, so it must just be a case of extreme silica overload in the bottom right part of that grid.   Eventually the G Borate starts to get things going but I guess it takes alot to make up for all the extra silica...  Looking at the surfaces, so you think there is any payoff in terms of, say, a higher quality surface, or maybe less crazing (cant see any of that in these photos) from the talc presence?   MgO will probabaly improve glaze fit, which should result in less crazing. 

 

I guess the Dolomite is better, certainly from a melting perspective, but its high LOI is the downside.  Half of it goes up the flue!  But again, how is the quality of the glaze and the glaze surface?

 

If I had to choose I would say it was number 12 on the talc tile in terms of quality of melt and smoothness without any discoloration.  I am a bit more confident of this choice even though I do not have the tile in my hand when I note that the best melted cell in row 5 is number 22, two directly below my best pick.  This kind of confirms the silica overload thesis and says to me that somewhere around column two is where the ideal eutectic is taking place with talc and the other fluxes.

 

On similar thinking I would choose cell 10 on the dolomite tile, given that I can even see early indications of melting down in corner D.

 

Asking the question another way, if you pick the two best cells from each of these tiles and compare, which flux combination is best?

 

As an aside, the hazy, dental white you are getting in some of the better melted cells (eg, Talc 16 or Dolomite 17 reminds me of the look I get with my Boron fritted cone 10 clear I am working on).   I am always suspicious of boron in high fire because it starts to melt so early...

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These ones are taken at night under the ceiling lights (long fluorescent tubes)

 

Firing to cone 9 :D but cone 10 has moved a little, so what 9.5 - 10. I did use the spread sheet to get a few of the amounts out and run them through calc software to make sure the Si/Al ratios were the same. Now I am at my laptop in the studio I can give you some values.

 

Flux test Gillespie Borate and Dolomite

  Kaolin   Silica  Gillespie Borate  Dolomite
A  31.2      44           74.8           0
B  35.8      51.7         41.7           20.8
C  60        90           0              0
D  41.3      61.5         0              47.2

Here is my calc software results for glaze A, B and D in that order, had to copy and paste B into the pic.

 

gallery_23281_871_5704.png

 

Flux Test Gillespie Borate and Talc.

  Kaolin   Silica  Gillespie Borate     Talc
A  31.2      44           74.8           0
B  36.9      36.3         51.2           25.6
C  60        90           0              0
D  49.4      23.0         0              77.6

Glaze A is the same as the test above so calc below is for glaze B and D.

 

gallery_23281_871_3247.png

 

The talc is definitely doing something along the bottom row but not much melting. Seems to me like everything has about the same flux but I am not sure. Having the same SiO2 and Al2O3 unity values, does that mean the same amount of stuff? I am still not sure sometimes what the numbers mean but I think that is right. They are all pretty close. Going to see if I can come up with another test without using GB.

 

I really like around square 15-20 on the talc tiles, something interesting happening around there. Anywhere around the top left the Gillespie Borate seems to take over the glaze and they all look quite similar. All the squares on the top half are very melted. Having no Dolomite seems to stop some of the bubbling but the GB seems to add small bubbles to the surface as well.

Edited by High Bridge Pottery

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That is the kind of learning we should be focusing on here, not picking holes in it.  Perhaps I am misunderstanding, but I feel like you are spending a lot of time here trying to dismiss, distort or otherwise undermine this testing technique whlle the rest of us are trying to learn about it and share information and images and experiences and make a POSITIVE contribution which benefits all.  

 

Of course you can tweak or alter Currie's technique to test anything you want, but once you change it enough it is not really a Currie test anymore, but probably some kind of quadraxail, triaxial or or other method, or your own concoction.  No problem with that, but there is already a lot going on in a standard Currie grid.  I would suggest that anyone looking to extract maximum value from this technique concentrate on learning everythying it has to offer first, before making major changes.

 

I think everyone understands your preference for vertical test tiles.  As I have said, I regularly use vertical test tiles myself for all sorts of things and I am sure many others here are the same.  However, like Currie tiles. they are only one of the arrows in the quiver, and there is no need for anyone to have to choose one over the other.  They all have their place.  I think the reason many people are following this thread is because most people ARE NOT familiar with the Currie technique and how it is done, but would be interested in knowing more about it and maybe even joining in the discussion. So can we please focus on Currie tiles and what they CAN offer rather than what they cannot?

 

I am in no way trying to dismiss this method. I apologize if you feel that way. High Bridge noted that he was having different results on his flat tiles vs his vertical tiles, and I made a comment pertaining to that issue. But when you responded that you "haven't seen much difference" between flat and vertical tiles, I felt that will lead people who are not very experienced with glaze testing to think that is the norm, which I feel it is not. And that is my point, nothing more. You asked me to give examples supporting that point, which I did. To then claim those examples do not pertain to the definition of a Currie test does not make them invalid. Glazes do behave very differently depending on whether or not they are fired vertically or flat, and I feel flat tiles are very limiting in how much information they give about a glaze.

 

I studied Curries method in grad school, and I have used it off on on for the past 20 years, and I think it is very worthwhile. I apologize if you got any other  impression form my comments. But even if I did not think it was worthwhile, or if I had ideas on how it could be improved (which I do), this is a public forum and it is important that anyone be able to add to the conversation, whether it fits your definition of what you think the thread should be or not.

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When I am testing new glazes I progress from standing test tiles, placed over a tray the first time to small bowls before proceeding to use the glaze on anything of great value.  Not only do you need glaze information on how it will react vertically, horizontally, where it breaks, but also where it pools.

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Here is a rerun of the whiting and soda feldspar tile with 5% rutile and 1% cobalt carbonate in each glaze. I love the green/grey specks the whiting seems to add.

1559744_454094574768102_4924970215501689393_n.jpg.426391ed3f73f8946e78c3bfdafe9b0f.jpg

Square 16

11052427_449804955197064_6340063153242847603_n.jpg.6499083eff484a18a86747ea31c33fb9.jpg

Edited by High Bridge Pottery
Old photos missing, think I put back the right ones.

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Yes, loving that number 16, very nice variegated effect.  Would be interested to see how you apply that in a pot decoration situation.  

 

Yes, hard to make out from the pics what is going on around that talc area you mentioned.  Looks like some decent melting with a slightly sugary surface?  I guess the talc gives you a low LOI way to add the magnesium which should decrease the bubbling associated with the dolomite, although you loose the calcium.  Maybe try a talc wollastonite combination?  You still have the silica to deal with, but both those are pretty low LOI materials.

 

I think from the format of your chemistry results you are using Insight?  When you are trying to adjust (stabilize?) the silica and alumina I would try looking at your corner recipes with the calc type on Mole% rather than RO unity.  RO unity is good for flux adjustment in a glaze, but makes the silica and alumina look like they are not changing much when they actually are (even though the Si:B:AL ratio does gives some reflection).  I find it a lot easier  and more informative to be comparing molar percentages to give an overall picture of the glaze at a higher level.

 

I think the boron is having a very dominant impact with your GB.  Look how different the Si:Al and SiB:Al ratios are.  Two big numbers up with Glaze A on boron alone.  That strikes me as a lot, although to be fair I don't use much boron in my own work.

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I will take a look at mole% next time I am in the studio. I did a larger test with number 16 and it ran in places, very strange. Got one slightly stuck to my shelf.

 

I have now run out of test tiles bisque :( going to have to make some more.

 

Here is a test I did with zinc along the x and talc up the y, I also started with corner C as a mix of stuff but I don't remember at home. Will post later on. The whites I seem to love on the left always seem to mark, seems to just be part of them being very crystalised. High zinc has made the glass crawl a lot.

 

gallery_23281_912_45936.jpg

 

Here is another more standard currie test but again I don't have the recipe at home with photoshop.

 

gallery_23281_912_176709.jpg

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Here are a couple of tiles I put up recently but didn't comment on. 

 

This is local barytes.  First tile is in oxidation and second tile is in reduction.  Clay not identical (ran out of bisque tiles!) but very similar. 

 

Probably the most interesting thing is that there was almost no evidence of melting anywhere in oxidation, except perhaps around cell 32 and then only a very little. 

 

Barytes Currie Test Tile Oxidation May 2015

 

However, in reduction the result was very different with good melting across most of the tile with the exception of the high silica column.  I am thinking that much (most?) of this melting is due to the iron content, which works as a flux in reduction, but would welcome any alternative theories.   I know there is also a little strontium in this material.

 

I have zeroed in on tiles 12 and 23 on the reduction tile as likely suspects to investigate further.  12 is very nice matte surface, and 23 and its neighbors give a nice jet black, particularly where thick.  Next step is to put these guys on some vertical tiles and/or small pieces and see how they behave...

 

Barytes Currie Test Tile Reduction May 2015

 

 

 

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You also have multiple variables with the two test tiles . . . one fired in oxidation in electric kiln to cone 10; the other fired in heavy reduction in gas kiln with a hold.  The oxidation tile was fired in a test kiln, so likely a fast rise to temperature and fast cool . . . unless you used a digital controller to follow a normal firing schedule. 

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Had to google the barytes. Says it's Ba,Sr(SO4)? Probably always going to be iron in anything, I am sure you are right and it is helping everything along in reduction. I like the high silica corner, a few look very stoney then going into this very dark glass.

 

I have been far too lazy about making myself a ball mill but there is always so much to do. One day soon.

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yes, I have thought about the cooling cycle and wondered if I should be seeking to control it ALL the way down as opposed to just firing down for the first 100 degrees of so and then shutting down and letting it cool as fast as it wants to.  I do use a digital controller on the electric kiln and a carefully controlled cool down schedule is not out of the question. The gas kiln is harder because there is no automated control function.  I would have to stand around and manage the firing down process myself.  

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Regarding Barytes, yes I am going after that dark glass in the current round of testing.  Cell 23 seems a good place to start, but I think the trick will be to get just enough melt flow to get the great surface but not so much that it runs off the pot. 

 

The rather vertical nature of the melty zone on the bottom tile suggests the control over the silica content will be oh so important in that quest...  More on this later. 

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yes, I have thought about the cooling cycle and wondered if I should be seeking to control it ALL the way down as opposed to just firing down for the first 100 degrees of so and then shutting down and letting it cool as fast as it wants to.  I do use a digital controller on the electric kiln and a carefully controlled cool down schedule is not out of the question. The gas kiln is harder because there is no automated control function.  I would have to stand around and manage the firing down process myself.  

 

You only need to cool down to approximately 1450F. Beyond that there's no real benefit. If I were doing it, I would try to estimate the cooling cycle of the gas kiln with the electric kiln controller. You could probably get similar results with only 2 or 3 cooling steps.

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