Low Fire Friday - A brief into to glazes and glaze mixing

Glaze – A Brief Intro

A glaze is glassy substance that has been adhered to the surface of ceramics through firing. It is made up of a glass former, a stabilizer and a flux. 

 The glass former is the glass. Typically this will be in the form of silica/flint

The stabilizer is what keeps the glass from completely running off of the ceramic piece.

Alumina is the main stabilizer and is found in clay.

The flux is an oxide (generally Alkaline) which causes ceramic fusion when combined with other oxides and heated.

Glaze recipes are usually written as a list with ingredients totaling 100%. This base glaze is usually clear/white. Any colorants, opacifiers, suspenders, and gums are written below the 100% line and are added as a percentage of the total glaze.

Base 4
Base Glaze	Frit 3195	65
	Gerstly Borate	10
	Wollastonite	15
	EPK	10
		100
	Bentonite	2
Colorants
Dark Brown	Red Iron Oxide	10

Glazes are usually measured and mixed by weight. However, any unit of weight can be used as long as it is constant throughout the entire recipe. I weigh my materials out in grams and typically mix a 500g batch (about the size of a large yogurt container). This means that I would multiply each material the recipe by 5. 

So, I would actually be measuring and mixing the above recipe like this…

Base 4
Base Glaze	Frit 3195	65	325g
	Gerstly Borate	10	50g
	Wollastonite	15	75g
	EPK	10	50g
		100	500g
	Bentonite	2	10g
Colorants
Dark Brown	Red Iron Oxide	10	50g

Water is added until the desired consistency is reached. This is a matter of preference and application technique. I brush my glazes on super, SUPER thick, so my glazes are usually about the consistency of Greek yogurt.

I hope this answered a few of your questions and will help get you started if you're new to glaze mixing. If you have any other questions, please feel free to comment or email me. 

Cheers!

Meagan

Low Fire Friday - Base 3

Recently, I've been doing a lot of tests and line blends looking for a reliable, food-safe, base glaze that works well with Mason Stains. And I think I just may have found one that suits my needs!! 

Base 3 has a glossy surface, though not super crazy shiny. It's a bit semi-opaque with lower percentages of stains, and becomes opaque when higher percentages are added.


 


Base 3 - Cone 04

Frit 3134       75
EPK             15
Silica             10
__________________
                   100

Bentonite         2%

For color add...
The Mason Stains I've tested are:

• #6236 - Chartreuse
• #6026 - Lobster
• #6379 - Robins Egg
• #6025 - Coral Red
• #6201 - Celadon

The test tiles pictured have line blends of these stains. A line blend is an easy way to get fairly quick results when testing colorant/stain in a glaze.

I mixed up a 100g batch of Base 3 for each of the above Mason Stains. (That's five separate 100g batches.) For each batch I started by adding 1% Mason Stain, or 1g. Then, to test how the glaze would look with 3% Mason Stain, I added 2g. Yes, only 2g because my 100g test batch already has 1g in it. For a 5% Mason Stain, I then only needed to add another 2g, and so on. It can get tricky so I always write all this down before I get started. Between each addition I brush a stripe on my test tile before moving on and adding more Stain.

I tested each Stain at 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, and 20%. Some of the differences are too subtle to see in these images, but are more viable in person. 

This will give you a nice range of color saturation for each Stain. From these results you can decide what you like and do further testing if desired.

So, for example, if you like the color/look of the third stripe from the left on the Celadon Line Blend, then you would mix up the Base glaze with the addition of the 2% Bentonite and then 5% Mason Stain #6201 - Celadon.

I've labeled each image with the Mason Stain used and tried to test all colors on both red and white clay. (Though you can see the state of some of my test tiles is a bit rough and I'm missing red clay samples for the Lobster Stain and Chartreuse Stain.) 

Lots of testing, but if you're (crazy) like me, you love this part of the process! If you've got questions, just leave a comment or shoot me an email.

Well, happy glaze testing.

Meagan

Low Fire Friday - Lizard Skin Glaze

Lizard Skin - Cone 04

Magnesium Carbonate 40
Lithium Carbonate       15
Borax                          10
Gerstley Borate           20
Silica                             5
Nepheline Syenite        20
___________________
                                  110

For color add...
Light golden brown/dark yellow ochre: + Rutile 5%

NOTES:

Lizard Skin has a sandier, crunchier texture compared to the smooth satin beads of the Low Fire Crawl Glaze. Again, apply it THICK.

With this glaze, I've had the best results using it immediately after it has been mixed. Probably from the Borax (which is water soluble and evaporates changing the composition of the glaze) and from the Neph Sye (which causes the glaze to settle like a rock making remixing difficult.)

Newest Wall Sculptures - Spring 2012

Is tomorrow really, June 1st? Where does the time go?

In late March I was contacted by Harris Warren Gallery in Wake Forest, NC and arrangements were quickly made for a June exhibition. Well, here we are - Goodbye Spring. Hello Summer. It's been a whirlwind, but I'm proud to say that I completed 4 new wall sculptures for my show "Variegated Disposition" opening next Friday, June 8, 2012.

Anthocyanin, earthenware, 27” x 38” x2", May 2012

Continuation, earthenware, 31" x 35" x 2", May 2012

Dissipate, earthenware, 30" x 12" x 2", May 2012

Provide, earthenware and cast glass, 27" x 15" x 2", May 2012

 In addition to these, I'll also have 4 other works on exhibit. If you're in the area, please stop by.

Oh yeah, and there's one other work in progress...

 Baby #2 (aka "Peanut") is due in September.

What an exciting Spring it's been indeed! Now onto surviving the hot Summer months of Florida!

Cheers!
Meagan

Low Fire Friday - Recycled Raku (Guest Artist John Britt)

This month's Guest Artist is none other than the Glaze Guru John Britt. 

I took John's Basic Glaze Chemistry and Raw Materials workshop a few years ago, and let me tell you, it was AMAZING! This man is a walking glaze encyclopedia! I didn't think it was possible to learn so much information in such a short amount of time. Before I took John's class, I could follow a glaze recipe (ie measure and mix the listed ingredients) but if something went wrong, or I wanted to change something, I had NO IDEA how to proceed. It was like baking without knowing what flour, sugar and baking soda do. But after John's class, I had a much, much clearer understanding of what was happening and a great foundation for building my glaze palette.

Just a few of the Cone 04 glaze tests from John's Basic Glaze Chemistry Class

John has been a potter and teacher for over 26 years. He lives in mountains of western North Carolina although he grew up in Dayton, Ohio. John is primarily a self-taught potter who has worked and taught at universities, colleges and craft centers across the country, including the Penland School of Crafts where he served as the Clay Coordinator and then, as the Studio’s Manager.

He is the author of the “The Complete Guide to High-Fire Glaze; Glazing & Firing at Cone 10” which was published by Lark Books in 2004, was the juror for the book; “500 Bowls”, Technical Editor for “The Art and Craft of Ceramics”, and has written numerous articles for ceramics publications including: Ceramics Monthly, Ceramic Review, Studio Potter, Clay Times, New Ceramics, Ceramic Technical and The Log Book.

He is currently a studio potter in Bakersville, North Carolina and teaches glaze chemistry, throwing, glazing and firing workshops.

Here is the glaze (and fun story) that John is sharing with us today...

Recycled Raku

 


This is one of my favorite chairs. I formed it with the wire cut method, where you take a block of clay
and cut out the chair shape. (http://www.youtube.com/watch?v=gvfyD5xJobI)

Then I bisque fired the chair to cone 05. Then I rakued it with the glaze Raku Turquoise:

Raku Turquoise (From Chappell’s Book)

42.5 Frit P-25
27.4 Frit 3134
14.0 Silica
9.8 Lithium carbonate
6.3 EPK

4.5 Copper Carbonate
2.0 Bentonite

Then what happened is that the front legs broke off as I was putting it in the Raku cans to smoke it. So after about a half of an hour I open the cans and the legs were kind of stuck together and messed up a bit. But rather than throw entire chair away I separated and reglazed the legs but refired them in an electric kiln to cone 05. This made the legs a copper blue while the main chair was more turquoise and copper.

I then glued them back on and this became my favorite chair because it had the interplay of the
different glazes within the same piece.

Low Fire Friday - Bleeding Cake Glaze (Crunchy texture)

Another reliable glaze that works best if applied thick. Bleeding Cake is an opaque glaze with a crunchy, sandy texture.
 

Bleeding Cake - Cone 04

Volcanic Ash 33
Borax            20
Sand*           16   * (I use the fine grain hobby sand from Michael's or other craft store)
Grolleg          11
EPK              20
____________
                   100

 

 

[dark blue, moss green, brick red, yellow ochre]

 
For color add...
Dark blue:  + Cobalt Carbonate 3%

Moss green:  + Chrome 1%

Brick red/warm brown:  + Red Iron Oxide 15%

Golden/Yellow Ochre:  + Rutile 8%
 

Low Fire Friday - Todd's Texture

Todd's Texture - Cone 04

Gerstley Borate 30
Zircopax           40
Whiting             20
EPK                 10
______________
                       100

 [Base, mint green, light turquoise, turquoise]


For color add...
mint green:   + chrome oxide 0.5%

light turquoise:  + copper carbonate  1%

turquoise: + copper carbonate 5%



[Detail, light turquoise]

PS - Anyone happen to know who Todd is? I got this recipe off of a list from somewhere years ago, and have no idea who he is. But he makes a great glaze!