Friday, January 15, 2010

Test Tiles Part 2

Ok, months ago I promised a second post about test tiles and I'm finally getting around to writing it.

These are test tiles to show what different glaze combinations look like.  The problem is that for every glaze you have, the amount of combinations grows exponentially.  Wow, didn't think I'd spell that right but my spellchecker is giving the ok.

So if you have a total of three glazes, there are 9 possible combinations (if you include the same glaze for both layers as a combo).  If you have 4, there's 16 combos, 5 and 25 combos and so on and so forth.  Part of the reason for that is because you want to see how they combine when you apply one glaze on top of the other, as well as the other on top of the one glaze.  That is a whole lotta test tiles to make and fire!!

I have a ton of glazes.  Seriously, I buy glazes like a Sunday comic strip female buys shoes.  There is not enough kiln space in the world to test all of the possible combinations I could test.  So we're narrowing this down a bit and making one big tile to test several combos.

Pretty cool eh?

And before you tell me, yes, that one broke just before being glaze fired and I had to glue it together after the fact.  But it still gives me the info I need.

What you're looking at is a test tile of 4 different glazes in every possible combination they could have with each other. 

And here's what other information I've designed into the tiles.  I use several clays because I make a lot of agateware.  Each of my new glazes is tested with a white clay and a dark red clay.  But I've never tested with my recycled clay which falls somewhere in the middle.  So for my combo glaze tests, I use the recycled stuff!  So now I have a test tile of each of these colors individually on recycled clay.  See how they are labeled on the diagonal?  And each tile as a divot cut out of the center so I can see how the glaze combination breaks.  And while you can't see it very well, the lower left segment of each tile has a rubber stamp impression to see if a stamp would be visible under that combo.

Making these things -

Obviously I make a slab.  Usually a pretty large one. 

I press a wire shelving cube thingy (you know, those wire squares that you can attach to each other to make cube like shelves, really cheap and portable, common in college dorms) into the slab to make approximately 1 inch squares.  Then I carve off the edges and see how many squares in each direction I have.  If I have more columns than rows, I cut off a column to make it square.

Originally I was going to go for about 7x7 but I found that those broke really easily.  That's how I ended up with so many 3x3 kickin around.  The largest I've made that has survived as been 5x5 and that ended up splitting in the final glaze firing.  Still gives me the info I need though so it's all good.

Grab a tool and carve a diagonal divot through each row.

Hole punch a couple of holes at the top in case I want to string it up at some point.  Don't think I ever will, but you know, options are good.

Stamp each lower left portion of tile.

Let dry and fire.  If it breaks, try to salvage at least a 3x3 section if you can.  Very nice to have if you just want to check one or two glazes with each other.

So now you have your fired grids.  How do you keep track of what goes where?

It's imperative that each glaze is tested as both the top layer and the bottom layer.  Oh you don't think so?  Trust me, it is.  The same glaze combo might look completely different depending on which one is applied first.  Here are the two samples of Blue Hare Fur with Stellar Rust.  The one of the left is BHF under SR and the one on the right is SR under BHF.  If you only test one combo, you don't actually know what the two glazes are capable of doing together.

Ok, so back to keeping track.  I always paint my horizontal lines first.  So the horizontal lines will always be the bottom layer.  Then, I go back and paint my vertical lines. 

By doing this, I end up with this: 

Of course, you have to somehow mark the tile when you're applying the glazes so that when it comes out of the kiln, you know what combo is where.  I write the glazes in underglaze pencil along the top of the back of the tile.  But remember, when you flip the tile over, it's now backwards.  So as you write across the top, remember to write it as Glaze 4, Glaze 3, Glaze 2, Glaze 1.  So if you put your thumb on the front and your forefinger on the back, the appropriate label will match the tile you're touching.

Then go ahead and label the tiles on the diagonal. 

So now you can test your glaze combinations quickly, easily, and efficiently in terms of space and time.  All sorts of combos at a glance!

Oh, and I have all of my glazes listed in an excel spreadsheet heading both the columns and the rows.  So when I do a tile like this, I can mark off which combos I've already done. 

Hope this helps!



wow! i am impressed with how incredibly organized you are with your glaze tiles. i just made a bunch of tiles - started to glaze them, then never got around to firing them. i always just wing it - but this is inspiring me to actually be a bit more "scientific".


mv said...

::swirly eyes:: Wow! This sounds like a science experiment. Very cool! Although I got lost somewhere along the way when I started trying to imagine all the under and over combinations. It's great how you have photo examples, I think I'm *almost* getting it! It sounds scary but fun at the same time! :) Thank you for sharing!