Ian Currie Test Tiles Forums?

[curt]

Very interesting that the best melting was at the high clay / high silica corner, where flux content is at a minimum!.  I would have thought that with whiting (a standard flux) you should have got good melting right up through the middle of the grid as well, because there are plenty of viable silica/alumina blends that will (should?) melt around that part of the tile (have a look at some of my gallery tiles).  Hmmm maybe something fishy there?...  Are you sure you put the right amounts of each of the corner glazes into the 35 cups?  I go slowly and talk to myself out loud, systematically reciting which corner I am coming from, and which cup I am going to, and what the amount of mls in the syringe is.  Somehow that seems to help when I am doing this, because it is EASY to get mixed up with, er 4 x 35 = 140 different additions. 

 

regarding the blue, is it possible there is some contamination there?  Shudder to think such a thing, but the blue only seems to really appear in the good melting flux corner.  In many of the unmelted cells it does not really look blue at all, except the ones right along the border (ie, 6. 12 17 and 28) between the high flux and dry zone.

 

If you are going to diversify fluxes, maybe one of the spars might be good , say neph sy or Kspar?

 

I always work with the 100g batches.  Partly this is because I do multiple tiles on different clay bodies,  and partly because I often want to go back and semi-dip test tiles in some of the more interesting cells. 

 

BUT,  I also save all the cups with the glaze blends in them until I am sure (ie post digesting firing results) that I don't want to go back and tweak all 35 with, say, some colorant, or rutile or titanium or something. Basically just guesstimate what you have left in each cup (if you used a syringe to apply to the tiles originally you prob have a good idea how much you used from each cup) and then add the same percentage of the additive to very cup (eg, 5% or 10% rutile) and go again!  I have not done anything with rutile myself (yet) but having looked at many of Ian Curries tiles, rutile seems to bring the thunder to many otherwise quiet glazes...

 

Also, don't forget that with a bit of careful thought you may well be able to recombine some of those cups to get a much bigger amount of some "average" glaze from the grid after you are all done testing that batch.  I have done this, and it worked out fine.

 

Just some ideas.  Have fun!. And keep those pics coming!

[High Bridge Pottery]

Maybe I made a mistake.

I don't know what you mean about the four glazes being in each cup. I went to http://ian.currie.to/cgi-bin/ian_calculation.html and added whiting with a value of 1 to flux one and recalculated it. I then made the batch size 10 and it gave me a table of 35 glazes. I weighed out all of these that it gave me and added them to the right square. I did see the bit above that gave me four glazes but I was a bit confused and they seemed to match with the data table.

 

This is the data I used. Was that the wrong way to do it? For example top left (1) is 6g whiting and 4g china clay. Then 2 is 5.4g whiting 3.6 china clay and 1 silica and so on till square 35 bottom right.. I did a little rounding but I wouldn't think that would matter too much if I kept it consistent.

 

The top right (5) has values of 3.5 whiting, 2.5 china clay and 4 silica.

 

[curt]

The calculations page looks right, just did it myself to be sure.  However, you did it the long way if you mixed 35 different glazes one at a time.   Curries method is one massive shortcut for turning 4 glazes into 35.

 

His innovation was to only have to actually mix four (largish) batches of glazes (the corners A B C and D), and from that get 35 different glazes by blending them by volume, transferring the right amount from each corner into each one the 35 cups. (!)  The key to this once you get the dry materials put together for each corner, you add water until each of the four corners has the same VOLUME (in millilitres).  Put another way, you shift from weight in grams for the dry ingredients, to millilitres of liquid when you add enough water to each corner glaze to make them all equal.  So what you eventually put in each of the 35 cups is slightly differing amounts of liquid drawn from these four corners of now liquid glaze slop (more on this further down). Have a look at the page below which is out of his book for the executive summary on mixing the four corner glazes (I suggest you stick with his 300 grams for the four corners, at least to start).  Then look further below to see what to do next.

 

 

NOW, print a copy of this next page below and put it on the table very close to where you have arranged the 35 cups exactly as they are shown here.   You will be referring to it constantly. This is the master map of what goes in each cup.  Each of the 35 circles is divided up into four quarters, showing you how much glaze to draw from each of the four corner batches to put in each of the 35 cups.  You will need a 50 ml syringe (no needle!) from your medical cabinet and you will use it to systematically draw out the right amount from each corner and put it in the 35 cups one at a time.  This may sound a bit complicated, but dry mixing up the four corner batches and getting them to equal liquid volume is the messing around part.  Once you get going with the syringe the whole process really flies. 

 

 

 

If you do it this way you will have enough glaze to fill each cell adequately, plus add the extra little upside down y shape in a second pass.  This will give a much better idea of melting behaviour.

 

Good luck!

[High Bridge Pottery]

Thank you. It all makes a lot more sense now. There wasn't much explanation on the calculation page. Looks like I need to order some graduated flasks and a syringe. It hurt my brain weighing out like 100 different amounts.

[curt]

I can see how it might be a bit challenging to try and figure everything out from Ian Currie's calculations page.  Suggest you get his book Revealing Glazes if you are going to be doing more of this.

 

Not sure you why you need graduated flasks?  Would suggest you watch some of John Britt's teaser videos on glaze testing, as what I am about to describe is very similar to how he operates.   This whole exercise does NOT require any fancy equipment or have to be expensive.  Syringes can be gotten in bulk off of EBay cheap if you cant get them from your local chemist or pharmacy, and they can be used multiple times.

 

For the 35 cups, get small (say 200 ml) disposable (but you can reuse them) plastic childrens drinking cups.  Ideally they should be clear and have lines around the sides for visual measuring.  Also get some of the larger say 500 or 750 ml variety of these for mixing up slightly larger batches later, dipping test tiles, etc.

 

For mixing the corner glazes I use these recycled yogurt containers which we use at home, but anything will work as long as it is large enough to hold your batch and be able to mix it without spilling.

 

 

what you DEFINITELY need is a hand blender, stab mixer, whatever you want to call it.  I now do not know how I every lived without one of these.  They are BRILLIANT for quickly mixing any liquid batch from 100 mls up to about 10 litres.  You will want to have one of these to mix the corner glazes, although I always end up mixing my 35 cups by hand because they are a bit small for the hand blender. 

 

 

Go for it!

[High Bridge Pottery]

Sorry, I meant a measuring cylinder. That and the syringes should be delivered in the next few days. I do have the hand blender and some containers to mix the 4 glazes in.

 

Do you add anything to help suspend the pure flux glaze?

[curt]

Ah yes now I understand about the measuring cylinder, to get the volumes equalized, although to be fair any container will work as long as the volume mark you are aiming for on the side is the same for all four corners. 

 

Nothing else added to any of the corner glazes.    And yes it is a bit challenging to keep the flux corner (and the silica corner for that matter!) mixed with little or no clay in them. I give each a swirl or a spoon stir every few syringe suck-ups.  But the results of these extreme corners are eye opening and very informative even if you would never use them as a glaze (or would you???....hmmmm....  )

[High Bridge Pottery]

So a few more tiles been put through a firing. Fired to a hot cone 8.

 

I bought some Spodumene, thinking it would be a powerful flux but by itself some strange results.

 

Spodumene

 

Soda Feldspar

 

Soda Feldspar and whiting

 

GB

 

GB and Whiting

 

[High Bridge Pottery]

One question, why is my Gillespie Borate so bubbly. Fired to hot cone 8.

 

Sorry for the bad lighting on the above, here is a close up.

 

[curt]

That is great, thanks for the pics dump.  Plenty to ponder here, but just some quick reactions to start. 

 

Starting at the bottom, it looks like your Gerstley Borate and GB/Whiting worked well.  The pattern I see on those tiles looks familiar - dry clay-overloaded A corner (top left), a good melt zone running from C (bottom left) to B (upper right), and dry silica-overload D (lower right) corner.  This is reassuring in that it suggests the corners were all mixed correctly, as were the 35 cups  .  It also looks like you have been using more glaze in each cell because I can see many cells where your raised pattern has been submerged in melted glaze, also good.   Running your fingers across them will provide yet more info...

 

Gerstley Borate is such a wild card flux.  Boron is an aggressive melter, and starts melting early, it could easily be the source of micro bubbles and pitting.  I find similar pitting problems with rutile glazes, but titanium may be a culprit there.  Also, GB is notoriously unreliable regarding "other" materials that could be in it.  What the GB tile suggests to me is that a) you can get some cool borate effects along the silica/flux border (like your closeup pic) and I would look more closely at cell 10 on the GB tile, AND you could easily use more clay, since even your high clay corner (corner A) looks completely melted.  Overall this confirms to me that boron should be used carefully and sparingly at high temps.   The crazing suggests (unless you want crazing  that you should be tending toward the B corner because those glazes will be more durable...

 

The soda spar whiting combo is intriguing.   Cell 17 is particularly engaging (as cell 16 hints) because it seems to offer some interesting texture and partial melting which could be explored further.    You seem to be getting good melting, even in the top (high clay) row, although the crawling starting to appear there shows that you cannot go too far up (although cell 4 just seems to get away with it!)

 

You are getting some interesting halo effects on the clay around the cells on the tiles using whiting.  I have not seen this but perhaps others have.  I have read that Calcium does not melt well below Cone 8, although having another flux should work toward melting better.  Particle size of the whiting may also affect the melt.

 

Not sure about the spodumene, would have expected some kind of melting but it all looks very dry, as if no eutectic was hit anywhere.  And that strange curly egg shell effect at the bottom, hmmmm.....   Some bubbling almost like off-gassing under a soft shell at some point during the firing.  The clay seems like it settled down the top part of the grid though.

 

What were your reactions?

[High Bridge Pottery]

One thing I did change about the method was to half the amounts, I know there is probably a little more error in getting 1ml of glaze but it saves on the ingredients.

 

It is Gillespie Borate but I don't know how much difference that makes. The flow from clear to this purple then white is really interesting. Cell 17 on the soda and whiting was one that caught my eye too. It looks very interesting (top right below). It seems to have some of that purple/blue/green from the first whiting tile in the same area.

I am not sure if it is the whiting making the flashing or it just happens to be a coincidence that they also developed soluble salts on the surface. 

I have always been drawn to whiting as a flux. The Spodumene was really unexpected, it was also the hardest one to keep suspended in the pure flux glaze. I will need to try mixing that with these other ratios and see what difference it starts making compared to the original.

 

 

Really enjoying the process, got it down to 50-60 min. 

I think next time I make the tiles I will leave space for small firebrick props.

 

[curt]

Great closeup pics, very clear.

 

Seems like (from digitalfire - thanks Tony Hansen) that Gillispie Borate is a constructed Gerstley Borate replacement.  Probably more reliable than Gerstley Borate itself then!

 

The raw (uncalcined) spodumene I get is like sand.  Yes, would be very hard to get it to stay suspended in the glaze slop.

 

Good to hear it is going well.  Interested to see how you use the results of these tests.

 

Yes, I have to work on my propping as well!  More props for each tile I think....

[neilestrick]

Gillespie Borate is a blend of the minerals found in Gerstley Borate. So it's very similar to Gerstley in behavior, but more consistent. I have found it to be a stronger flux than Gerstley. I can usually reduce the amount in a glaze that calls for Gerstley by 3-5%, sometimes more.

[High Bridge Pottery]

So I did a little more testing with square 16 and 17 of the 50/50 soda feldspar and whiting tile.

 

I find it interesting how different the two test are when they are quite similar in composition. Added rutile and cobalt carbonate. Sorry for the different lighting on each  I am a bad photographer.

 

 

[curt]

I am loving 16. It delivers what 17 seemed like it should have. Are they smooth/matte? Or very rough to touch? And is 17 crawling or is that just the application?

 

In retrospect and looking back at the original tile, it could be that there was too little glaze in 17, because the cells just above and below 17 seem to have melted well - just like 17 did on the test you just did. If there was too little glaze in that cell, then the clay underneath could have been coming through and intermingling with the glaze, giving a slightly drier surface than the glaze has in reality (ie, the way it looks on the test you just did). Just a thought....

 

I have been busy in the studio and will post some more currie tile pics soon.

[High Bridge Pottery]

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.

 

Here is a comparison between tiles 16 and 17 50/50 soda feldspar and whiting, with the bottom row square 16 from just whiting flux. Need to keep looking around this area a bit more.

 

[David Woodin]

Have you ever tried taking a glaze that you use and run the Currie method on it? You may be surprised that there are many more good glazes in the grid.  Also there are some other very good ways to test colorants.

David

[High Bridge Pottery]

I haven't actually tried that yet, thought it would be best to start of simple and learn what each of my ingredients can do.

 

After seeing how much adding rutile and cobalt can change the glaze I need to start doing full grids with added colourants etc. What are the other good colourant tests?

[rayaldridge]

I would say titanium and anything else.  Cobalt, copper, iron, manganese, chrome, tin, zirconium.  Maybe vanadium and nickle.  And of course stains are a whole other world.

[David Woodin]

I usually make a 20 grid but 35 grid would work fine. A = base glaze + 8% Iron Oxide: B same base glaze + 8% Iron Ox.& 10% rutile;

C same base glaze no colorant: D 10% Rutile.  This gives a line blend from A to C for iron; A to B iron stays at same value but it cross blends with Rutile :C to D line blend for Rutile: This line blend cross blends with iron B to D.  This is impossible to explain but the top row 1 thru 4 Iron is 8%, but 2 to 4 rutile is #2 = 3.33%R + 8% Fe,# 3= 6.67% Rutile + 8% Fe, # 4= 10% Rutile + 8% Fe.  Anyway it is a good method for testing 2 colorants and depending on your base glaze you may get some rutile blue. take a look at www.matrix2000.co.nz

David

[rayaldridge]

If you really want complication, you could do sets over high iron slip.  I get a nice titania blue applied over a slip of my porcelain body plus 10 percent red iron.  It breaks dark red-brown on the edges.  But a light spray of high-iron glaze over the same glaze is a sort of oatmeal-colored  hare's fur with pinkish edges, if that makes any sense.

 

It's all more complicated than anyone realizes, I think.  While I greatly admire the thoroughgoing scientific approach exemplified by Ian Currie, I fear my own is more of a scattershot in the dark technique.  This eventually works, given enough time, energy, careful attention, and luck.  I think the main thing, no matter what approach you use, is to pay very very close attention to the results you get.

[curt]

 @ High Bridge  "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."

 

Not sure I understand, can you clarify? I would have thought more glaze = better melt?  too little glaze would mean that what you are seeing is mostly the clay-glaze interface, which would almost certainly look different than the glaze itself?  Maybe I am missing something...

 

I think the philosopny behind Ian Currie's technique is to try and uncomplicate an inherently complicated activity.  There are so many variables which can affect the outcome that it kind of makes sense to nail down some of them in a controlled manner and see what happens with gradual changes of a couple of variables in a systematic fashion.   That is why he keeps the flux package constant and only changes silica and alumina. 

 

You can add extra ingredients (ie, colorants and additional fluxes) but each of these will add an additional layer of complexity which will need to be understood and decoded, and may obscure other things that are going on that the grid is meant to (and able to) reveal.  Starting from the other end, his technique can certainly be used to pull apart existing glaze recipes in an illuminating way, and even to help fix broken glazes.

 

It seems to me that using an iron slip, assuming it is thick enough, is really just like using a different clay body.   Although we would be unlikely to be using a clay body with 10% iron??  In any case, all good, as long as one is able to identify and appreciate what variable is generating the variation.

 

Daves 4 corner line blend technique is different than a currie grid because currie actually varies the silica and alumina slightly even in a column or a row.  You can see this in the figures in his book "Revealing Glazes".  I have not read it anywhere but I think this may have to do with useful silica alumina ratios, which are more a diamond shaped grid than a square grid as with the materials which contain these ingredients.

 

Ray, yes it is complicated, and that is why, particularly when using unknown materials (where currie's technique provides tremendous power) I quickly realized that the scattershot technique had the potential to wander around a good while and still have nothing to show at the end!  Paying very very close attention to the results at the end is a lot easier when as few variables as possible are changing... IMHO.

[rayaldridge]

Curt, you're right of course.  I think I've been very lucky, which is not something you can count on.  40 years of flailing with glazes, has, however, yielded some good results, though I'm sure it wouldn't have taken so long had my methodology been more rational.

 

What's the most useful glaze you've found through the Currie method?

[High Bridge Pottery]

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.

 

After your post about the variables I started thinking what if I could change the flux and silica/alumina so I could vary two fluxes and keep the silica/alumina the same. One problem is if the flux contains silica/alumina After swapping the values in each glaze they probably contain too much flux so I halved them and re totaled it to 300. Probably a crude way to force it to work but I spent a while on the maths and couldn't really work out a way to do it. Might have to buy his book.

 

I made a test tile with whiting and soda feldspar but then realised I will have far too much silica/alumina with the feldspar. Going to work more on it today. 

[David Woodin]

The Currie method is great for revealing what other glazes you might have in the grid from a known glaze.  So he takes a known glaze and makes extreme changes in the Alumina/ silica.  But if you want to make a glaze from scratch take a look at Robin Hoppers book "The Ceramic Spectrum"  The information I posted was a method to look at two colorants and actually uses the same % as the Currie grid after you make the 4 corners using a known glaze.  You don't do anything with the alumina or silica.

David