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Ian Currie Test Tiles Forums?

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Joseph I have about a half hour more plaster experience than you do.   I have only ever messed with plaster to make a few drying bats and damp box inserts.  The bat you see below is an old bat I used for drying clay, not a good one and not made out of anything more than standard plaster for drywalling and cornices from the hardware store.  Instead of "master mold", perhaps think "some material with carved indentations which I can press clay into to make duplicates".

 

Currie Tile Mold Whole Bat

Currie Tile Mold Close Up

 

I followed the instructions Currie gave in his book "Revealing Glazes" on page 136 fairly closely.  Making your blank tiles from a flat plaster bat ensures that every cell you put glaze into is going to be flat from the start.  This matters because glaze runs and pools in depressions and corners, leaving some parts of the cell inundated and other parts too dry.  Not a big problem in itself, only when you try to compare that cell with others nearby, or the same cell on another tile (made, say from another clay body).  And this is particularly a headache when the glaze you are testing only changes subtely from cell to cell anyway (eg, clear glaze testing).  

 

I think it is important to eliminate as many sources of variation as possible so that what you are really looking at in the results is changes in the glaze, not changes in the tile because of how you made it.  Greater comparability across cells and tiles equals more information.  The tile is simply a tool, and it makes sense to make that tool as good as it can be if you are going to use it over and over again.

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How do you use the master mould, roll a slab over it? I tried making one but it didn't work as intended and I went to cutting 5mm slabs from the bagged clay and stamping in the squares, cut to shape. Used to be about 10mm but I found I can get away with 5mm and stack 3 high without too much bending.

 

I disagree about his weights and measures, they can easily be halved. Hard to do more than that because then you need to take under 1ml of glaze for some squares. Per square I only use 1tsp (5ml~) glaze so having 43ml left over is a little too much for me. I would go lower than 24ml if I had a smaller more accurate syringe.

I put a slab of clay over the master and then roll over it with a rolling pin.  However, I have been a bit too skimpy on the clay and made the tiles too thin so I need to improve how I am doing this and make the thickness of the tiles more consistent.  I do not have a slab roller so I am making slabs by hand, which is not really working well. 

 

Finished (cone 10) thickness of some of the more successful tiles I have made seems to be around 5mm on the edges and somewhat thinner in the bottom of the cells.  If you see my gallery pictures on currie tiles I have had some tile stack disasters so I am now usually setting each tile on its own on a shelf.  If I make better tiles I may try stacking again. 

 

I prefer to stick with Currie's stock 300g batch weights for corners for a few reasons.  That amount gives me enough material so that when I add the water I can mix each corner batch properly with a stick blender at high speed (I find stirring with a spoon completely inadequate).  Too little slurry makes mixing difficult, and since I am often integrating native materials (Currie's technique really shines with native materials btw) the mixing step has to be thorough. 

 

Thorough and repeated mixing is also important when it comes to heavy materials like silica in some parts of the grid.  Again, having enough material to mix is important to make sure you are getting a homogenous sample out of the corner batch to put in each cell.

 

Joel do you still put in 48 ml per cup or are you using less?  Some of the 35 cups require an addition of no more than 2 ml of one of the corners and I find this quite challenging to measure out even with some of my smallish syringes...

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Thanks for all the good information. I guess I am going to have to get some plastic and get a mold made. I definitely will make it thick and I will have no problem using 300G batches. I too use a stick blender so that will work great. I will probably finish the book tomorrow and make plans for everything. I am going to do some basic test to get a feel for the process then I am going to jump into chemical reduction via silicon carbide. 

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I think I remember the problem with rolling my slabs now, stretching the clay always seemed to make it weak/tear. Stamping into a slab on a bit of wood made a better structure. The bottom of my rolled slabs were always bumpy too, it was probably a bad mould which made things worse.

 

I was having a look back through my notes and this was the only curry grid I could find, still the most recent edition. It looks like I was using 100ml total and if I remember that just covered the stick blender in a standard plastic jug. I obviously forgot my whole process to the 5by5 grid and I have taken out the two horizontal lines that when dividing by 4 would give under 1ml values. I haven't noted down the weight of materials in each jug but my last tests were all listed to 100g tickets so that must have been it. If you add up every test it makes 75ml so you get 25ml of each corner glaze to play/lose in sieving.

 

Maybe I am a little tight with my ingredients  :lol: 12ml per glaze test and no more  B)

 

I only have the one cup for mixing tests and dump the left overs into a big bucket to dispose of. Sat in front of the sink with a table to the side and could run the test and wash the cup/syringe out without moving from my chair. If no sink get a couple of big buckets of water to rinse things out as you go. 

 

sml_gallery_23281_1027_15643.jpg

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I can't decide what to do. I want to get started right away. So I think I might just roll out a slab and stamp this first version and then get some plaster this week and get my plaster slab setting up.

 

Rolling a slab this large uniform is going to be challenging. At least I can put some of Akira's workshop to good use. He showed us the best way to roll slabs. Works well.

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Maybe I am a little tight with my ingredients  :lol: 12ml per glaze test and no more  B)

 

I only have the one cup for mixing tests and dump the left overs into a big bucket to dispose of.

So am I understanding correctly that you do not set out 35 numbered cups in a grid and fill them systematically with the right proportions of each of the four corner glazes?

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Yes that's right, I can't deal with the 35 plastic cups sitting around waiting for me to knock over/crack the cheap cups. I have also never found myself doing more than two of the same tile so the extra seems like a waste.

 

When running a test I have the 4 jugs (sharpie labels so you don't swap them by mistake) with spoons in for re-suspending, one plastic cup with teaspoon, the bisque test tile and syringe. That's it besides the bucket to dump leftover glaze. I will syringe up the ml of each glaze needed into the cup, give a two second stir and spoon out into tile, dump the leftovers then rinse and repeat. If possible don't syringe in alphabetical order as sometimes you can miss a rinse of the syringe as no contaminants are being added one way but they are the other. For each corner I spoon straight out the jug and don't even take the full ml needed so an extra bit of 'mistake' glaze left over.

 

Joseph it's best to get some drying and through a bisque as that can take a few days while you decided about the mould. I slice mine straight from the bag and get three tiles a slice. Use the cheesewire and two guides either side to run it along for even thickness. Lift of the top lump and stamp in the squares then cut off the excess. I do this on a bit of wood so no need to bend the thin tiles picking up and moving.

 

Stick to how he does it to start with, I just want to explain how it can be manipulated to suit your needs, if the 35 cups with 48ml works for you then keep going with it. 

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I think I am just going to make a thick bisque tile mold out of clay. I am going to get some thick pieces of wood and roll out the master mold out of clay 2'' thick, then let it dry slowly under plastic for a week or so between two pieces of drywall with weight on top of it to keep it flat, and carve the grid on it at the right time, then continue drying it slow and then run a long preheat and bisque it and use that for my master mold. Does this sound like a bad idea? I am not in hurry to get the grid up and going now that I have read through the book and understand the process better. I am more interested in getting a really good master mold to work from as I want this to be done as best as possible so that I can have good test. 

 

Thanks for all the help and comments. I am sure I will have more once I get to actually doing the process. Off to roll out 3-4 master mold blocks.

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Some of the 35 cups require an addition of no more than 2 ml of one of the corners and I find this quite challenging to measure out even with some of my smallish syringes...

 

 

I think I've mentioned this before, but you can simplify the measuring method Currie describes by doing two 7-glaze line blends from A to C, and B to D, followed by seven 5-glaze line blends between the glazes along the vertical edges of the grid. Not only will this cut down on the number of measurements, it also means the smallest volume you need to measure is 12 ml (assuming each of the 35 cups holds 48 ml)

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I got my grid created today. I made the squares 1.25 inches. I am not sure if after they shrink they will be less than an inch. Some of them got a little smaller then I wanted, but I will remake it again when I have time. I am going to continue drying this one under plastic between two boards to make sure it stays perfectly flat.  Although I doubt that matters that much as after I roll the clay on top of it I can just lay that flat and it should be ok. So maybe I am wasting time with it under plastic. I might just dry it between two boards and no plastic, thoughts?

 

I think this will be a good one enough to start, I am sure that I might make it better eventually. I am excited to get started with it.  I will fix the corners and stuff once it is more dry. I dont want to warp any of the cells messing with it before its almost bone dry.

 

If this ends up not working as I planned. I will probably just roll out slabs and let them dry for a day then stamp them as Joel does. Hopefully this will work though. I think an inch thick slab bisqued carved down on the sides a little should be able to be pressed down on enough to roll a soft slab of clay over it. If it snaps, stamps away!

post-63346-0-64504400-1464710170_thumb.jpg

post-63346-0-64504400-1464710170_thumb.jpg

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I tried drying several tiles between pieces of drywall once and about half of them cracked into several places. drying clay needs to have the freedom to shrink as it dries. Weight pressing down on it prevents this, and your tile may well come out looking like clay that has been dried on a plaster bat, ie, many cracks.

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Looks like it will work to me :D

 

I have never been able to use a rolling pin with clay successfully, either they are fat and wobbly or I rip it in half going too thin and sticking. Much easier to slice from two rail guides either side. One pull and you have the slab.

 

I have never wrapped the slabs up either, left on plaster or wood to dry in the open. My clay is very forgiving though 

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Any tips on the first trail of this thing? Should I start with a clear for kicks? Or just pick a glaze I want to work on? I am at the point where I am going to practice making jars, plates, and other things that I plan on selling in the future once I nail down my glaze lines. So while I am doing all this throwing and learning. I plan on using my kiln to be running these currie test. 

 

Also, how do you guys stack these in the kiln, do you use some wadding? Or do you just put some clay between them? I think the next version of my grid mold I will add 5 points that are lower than the rest of the grid so that when I roll my slab over them it will create stacking points that are above the glaze areas.

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The power of a Currie grid in my view is its ability to reveal what systematic changes in silica and alumina do to a given package of fluxes.   What you would probably like is a glaze which is going to give you some good variation across the 35 cells to demonstrate this.  

 

I would start with a glaze you use often, and you know how it behaves, and has raw materials which you regularly use.  Since that glaze is probably somewhere on the grid, you will learn a lot about how those materials work, and/or how you could tweak the clay or silica to get variations.  You could go for a clear, or a matte, or anything in between. 

 

Color adds an extra variable of visual distraction and obscures other things that you can and should be learning about the glaze, which is unhelpful when you are starting out, so I suggest you either pick an un-colored glaze, or leave the colorant out.  Once you know how the base glaze is behaving you can always add the colorant back in and go again.  And if the colorant is also a flux you will want to do this.   But for now the focus will be on surface texture, melt zones, matteing, crystallization more generally, how you clay and silica are performing, etc. etc..   One of the first things I discovered with several of my glazes is that there was a much better version of it elsewhere on the grid!!!  

 

Also make sure it is a glaze which has silica or quartz or flint (the main silica source is) and clay or kaolin (the main alumina source) as distinct raw materials in the recipe.  Put another way, do not choose a glaze (at least to start with) in which the primary source of either silica or alumina is already naturally combined with one of the major fluxes in the recipe.  For instance, a simple dolomite matte glaze may get all the silica it needs from potash feldspar, and therefore not even list silica as a separate ingredient.  Avoid these types of glazes to start with.

 

Make a separate grid tile with every clay body you use, and try to make sure that you have at least one clean porcellanous body and one dirty, irony body to see the (massive) impact that the clay body has on your glazes.  I usually try to do four:  one porcelain, one light stoneware, one semi-irony, speckled reduction body, and one dark, dirty, heavy-iron-spotting woodfiring body.  And if I have an experimental body I am working on that will be number 5.   Once you have mixed up the four corner glazes and then the 35 cups, to me it makes sense to get as much milage out of them as possible.

 

I would avoid stacking to start with.  Until you get the clay thickness of the tiles right it is too easy to get tile splitting, warping and other maladies which compromise the test you have worked hard to put together.  Porcellain in particular gets pyroplastic at stoneware temps, and if you look in my gallery you can see I was way to ambitious when stacking.  When I have stacked, since I did not design my tiles to have a prop in the middle, the props stick to the glaze below (which inevitably creeps up the side of the cell to the prop and glues it in places, then I either break the tile getting it off, or it leaves a little bit of broken prop obscuring the cells below it.  In order to examine my tiles in different light and at different angles, ideally I would not have anything vertical sticking up on my tiles at that I could not remove.

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Colorants in a Currie context are any oxide or other ingredient (eg, stain) added whose main intention is to change the color of the glaze.  In terms of how to add them, I think what he does is mixes up the 35 cups and then simply adds an identical percentage to all 35 one at a time.   The idea (I think) is that if you have done the volumetric mixing correctly, each up has an equal gram amount of dry material in it.  When you know this, you can add a percentage of dry material.  

 

Another way to do this is to make one grid without color, then come along and add color to all 35 and make another grid.  Interesting to compare them. 

 

As I mentioned above, where this gets complicated is where the colorant is also an important flux, in which case the glaze may look very different if you leave it out.   Copper oxide, iron oxide, etc.. are examples of this. 

 

Kind of gets down to the recipe in question and what you are trying to learn from it as to whether or not to have colorants in and when...

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Curt,

 

Thanks for the awesome response. I will look through some of the past glazes I have used a lot and see if I can find one without any colorants. I don't think I have used many that didn't use some form of iron, zircopax, or tin. However I am sure I can find something that meets these requirements. I do have a glaze which I have used hundreds of times but it contains RIO and Tin. However I wouldn't mind seeing different variations of that. I am currently only working with one clay body, however I do have some porcelain lying around from some test I ran, so I will do that. 

 

I think I might mix up the glaze without colorants and then do another with colorants. He explains it in chapter 7, but I am having a hard time understanding the maths. I will just have to read over it a few times. That would probably be the best way to start. Take my classic cream white and mix it without the RIO and Tin, then add it to each cup for another tile. 

 

If I am going to be mixing enough for multiple, I am going to have to get a new measuring cylinder, mine only goes to 200 ml. So I am going to have to get one multiples I think so that I can accurately measure under 500, under 1000, under 1500. 

 

As far as the cups for the 35 glazes, did you buy heavy duty ones that are clear and just wash and use them over and over or do you just use cheap throw away cups. I am trying to find some wide based ones so that I can fit my stick blender in them. 

 

So much stuff to figure out! It's so exciting, probably another 3-4 days before my mold is dry enough to bisque fire. I think I am going to go ahead and make another mold. one like this one which has a place to prop the other molds on top of it later one once I figure out the thickness needed.  http://ceramicartsdaily.org/ceramics-monthly/wp-content/uploads/sites/6/2015/09/Screen-Shot-2015-09-17-at-3.29.39-PM.png

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I bought the larger, clear cups and reuse them.  Make sure are clear.

 

If it is just a little tin (say a minor flux) then probably OK to leave in, but if you are adding enough to deliberately opacify then I would treat it as a colorant. 

 

Zircon is tricky.  So refractory that it is an anti-flux.  Would treat it as a colorant and leave it out in the first instance.

 

Iron, well, as discussed above....

 

Are you using the calculation page from Currie's website? 

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I have plenty of IFB so they get sawed up into lego sized props. Sometimes they do end up in the glaze but works 90% of the time and you can snap most of the brick back off to use again. You can see the leftovers in this tile, although I used it for 5 line blends instead.

 

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Not sure about adding colourants to 35 glaze cups, sounds tedious and missing the point of volumetric blending. If I remember you can multiply ml by 0.8 to get an estimate of dry weight at 1.5sg. To get 1% you need 0.384g so is far too small. Saying that I have mixed up a batch of glaze and then taken about 50ml off to add 1, 2, 4, 8, 16% of one ingredient and it worked well.

 

I think a better way to see the currie grid is the glazes a, b, c and d. They are your corner points on this graph paper. He chooses to plot silica along the x-axis and kaolin up the y axis with a background of flux. It is a very useful test to run but not the only parameters you can set.

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Joel,

 

In his book he has a lot about mixing colorants into the whole grid test. It makes sense the way he explains it, but I haven't tried it yet. He is big about taking the time to mix up large amounts of the 4 corners then using it to make multiple grid tiles and adding different amounts of colorants to other ones besides the first so that you get a base, then see how the colorants change the melt etc etc. 

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