Glaze Making/ Testing Again!

[Rebekah Krieger]

Sorry If I sound repetitive. 

 

I FINALLY got around to watching John Britt's Glaze DVD.  My goal is to start developing a few of my own. (i would like to have a base of maybe 6 glazes that I use for my functional/ or signature pieces and then just use commercial glazes or underglazes for specific pieces if I don't want to create a glaze for) 

 

Anyways I watched Disc 1 and felt very excited about testing (colorant testing in a base glaze) .  I watched Disc 2 and now I feel very overwhelmed with all of the information I need to know to even begin. I absolutely suck at chemistry.  

 

Is there a bare bones beginner way to start learning this? The idea of doing the tiles with dollops of each material seems easy enough (except most of the materials seem to melt much higher than my kiln goes!!) And I wouldn't even begin to know what percentages to blend the materials.  I feel like the video was equivalent in teaching somebody how to read / phonics but I am not even at the stage of knowing the letters and sounds they make.  (i hope my reading analogy doesn't throw anyone off) I feel like a complete idiot.  

[High Bridge Pottery]

One thing to work at is glaze calculations, if you can't take a recipe and work it down into its components then it will be hard for you to ever understand what you are doing. I guess you can buy software or get a trial version to work it out but I find it is good to be able to do it out on paper.

 

http://digitalfire.com/4sight/education/understanding_glaze_calculation_an_aid_to_potters_126.html (part 2+3 but all of it is a good read)

 

Once you can do that, get one recipe and change a single variable to see how it changes a glaze to get a basic understanding of what does what. Start with messing with silica and alumina and some fluxes.

[Guest JBaymore]

I start my glaze calc students out with some "old" methods... and then lead them into molecular understanding and then into using glaze claculation software.  Works well.

 

First assignment..... research a glaze RECIPE (I immediately make the verbal distinction between a recipe and a formula... to set the stage.) in books or online (that fits the firing range used) that they LOVE, that is composed only of materials that we stock in the lab.  Bring in the recipe and images and share..... explain why they picked it and so on.  Then mix it up (that lets us get into how to DO that... stuff like accuracy of measurements and the impact of significant figures, use of lab tools, H+S procesures, and so on) and apply the glaze test to test cylinders (and record keeping and labeling). 

 

Then I have them research each of the raw materials in books and online.  Write me out (typed, etc.) a "book' on what they found out about the characteristcs of each raw material in their glaze recipe....chemical composition, what it comes from, where it is mined (if so), what oxides it supplies in the melt, what it does when mixerd in water, and so on.

 

Then I have them make a decision about changing one characteristic material from their list of ingredients.  Some pick different feldspars, some change from stuff like Whiting to Dolomite, some change the colorants, and so on.  It is their decision what to do.  (In the group setting... this lets me address a LOT of stuff to the group.)  Then I introduce the concept of scientific method (short version - change ONE thing at a time ....control all else), and a line blend and how that works.  They then set up a line blend system (11 points) and vary a SINGLE variable in that potential blend (sort of half of a blend....really just regular incremental stepped changes).  Next comes exchanging two items for each other.... a true line blend.

 

Eventually when we have fired results, and can look at an analyze them, we then look at what the material changes did to the oxides in the melt in each case.  Slowly we shift from a materials based approach to glazes to an oxide based approach.

 

15 weeks......... two - 3 hour classes a week, plus homework time.  By the end....... they can mix up glazes, organize tests, do recordkeeping, use Insight at a basic level.. .... and know what they are doing at a basic level.  (At NHIA we now just instituted Clay and Glaze Chemistry II in our curriculum starting in the fall BFA semester.... YES!)

 

Don't get overwelmed.  There is a lifetime of study ahead of you.  Take baby steps.  You'll get there.

 

best,

 

......................john

[Rebekah Krieger]

Thanks John! I wish there were local classes.  

[jrgpots]

I second the digitalfire site and insight.  Duncan Shearer has an intro to glaze chemisrty... http://www.duncanshearer.co.nz/glaze/glazechemistry.html . It's a bit basic.

 

Once you recognize the parts of the glaze, it's not so overwhelming. 

1. fluxes,

2. glass makers,

3. stabilizers,

4. opacifiers, 

5. colorants.

 

I have made up flash cards with the names of the glaze compounds with their "pottery name," common name and/or chemical name, catagory #1- #5, and a brief discription to help me know its properties and function.  They work for me.  It may help you.

 

Many of us are in the same boat.  The great news is that You are on your way..you are doing it.

 

Jed

[Bob Coyle]

The problem with glaze software is that it might get you close to what you are looking for but it probably won't get you there. You said you want six basic glazes but that is too many. start out very specific as to what your first glaze should look like and then pick an already existing glaze that (supposedly) gives you what you want at cone 6 Then, keep tweaking this glaze ONE COMPONENT AT A TIME as everyone has already stressed. till it starts to look like what you want. Make sure that you have plenty of each material you use. Don't buy 1/4 pound of rutile for your tests and then run out and have to buy from possibly a new batch for your production glazes. Variation in materials can negate all your hard earned progress.

When you get the first glaze to your satisfaction... move on to the next.

 

Every time you run a glaze test that doesn't work out... ask for help here or over on http://cone6pots.ning.com/   There is at least a thousand years of expertise in glaze development between these two sites.

 

Don't get discouraged. stay focused on specifics. there is no single answer as to how to develop a glaze. If you are really going to do this... WRITE EVERYTHING DOWN.

 

And what is really cool, is that sometimes you do an adjustment but it doesn't look like what you wanted in the first place but it is absolutely beautiful in it's own right.  Now you have another glaze that you can use.

[CarlCravens]

I really like Michael Bailey's "Glazes Cone 6" for understanding the fundamentals, the balancing act between glass formers, fluxes and stabilizers, etc.

[C. Banks]

glaze calcs bah

 

melt some stuff and see what happens

 

find some good glass and you're set

 

*I can only begin to aspire to a feeling for what to expect from the limited range of materials im somewhat familiar with. I only wish to suggest that although the science is absolutely useful the end result is still a combination of both art and science.

[Babs]

I'm with Bob here, It's amazing how the same base glaze with different additions of colourants gives varying results just by altering thickness of application, textured surfaces, etc.

Many potters have a very few go to flazes and only add to these from time to time.

BUT do learn the calc. now as it's more difficult and frustrating to return to after some success without!

[Mark369]

Here are some good books to read.

 The Potter's complete book of clay and glazes by James Chappel

Clay and Glazes for the Potter. by Daniel Rhodes

Ceramic Formulas: the complete Compendium by John W. Conrad

The Ceramic Spectrum by Robin Hopper

[High Bridge Pottery]

I agree, pick one base glaze and make it into 6 cool glazes

[Rebekah Krieger]

thanks everybody! I just need to order some dry materials now. I have had a shopping list for ages and haven't done it.  I also saw a cool video on surfaces and need to get some mason stains and gersley borate asap!  

[neilestrick]

Start with fusion buttons: Melt a little glob of each material on a tile. This will give you a good idea of how each material behaves in the glaze melt.

 

Then do line blends: 90/10, 80/20, 70/30......10/90. You could just do two materials, but you won't really get anything you can use. Instead, add some EPK and flint in there so you might actually get a useable glaze. I'd go with:

10% EPK

20% flint

70% flux material

Mix up 2 batches of this formula with different fluxes, like maybe a frit for one and a feldspar for the other, and do the line blend.

 

Then do a triaxial, where you use the same 10/20/70 formula for each corner.

 

Then do a quad blend, where you take a glaze from the line blend or the triaxial, and increase the alumina and silica across the grid. You'll need glaze formulation software or a good grasp of how to work unity formulas by hand in order to do this. Personally, I'm a fan of Hyperglaze.

 

Once you get something that works, run color tests. 

[C. Banks]

Maybe you have some stuff lying around.

 

Granite cliffs will have useful material at their base. Decomposing shells from old lake beds work for whiting. Volcanic ash, with a bit of flint/quartz, is fantastic substitution for feldspar. Limestone works for ... it's a source of calcium again iirc. Fine silt can work for slips and if you're lucky maybe that new road or old river bank cut into some nice clean local clay

 

Then there's toothpaste, baby powder, shampoo?, or sunscreen or ... stuff with zinc oxide and titanium dioxide anyway

 

You might already have seen the results from John Britt? Stuff that just makes a person smile.