Transcript of 1st Glaze Sharing Workshop –Judi Buchanan Begining Glaze Making

 

Judi Buchanan’s Glaze Workshop Handout

First you need to know my ONLY qualification for doing this workshop is an insatiable 40 year curiosity. I’m like a 3year old who never got past “Why? What if? And Can I? I invite you to join me in creative glaze exploration and offer basic information to give you a foundation to work from. I promise to avoid higher math and to begin at the beginning. Just think, I learned and did glaze experiments before pocket calculators and digital scales much less computers. I encourage any of you to chime in with questions, corrections or your own tips.

You can spend a life time collecting and trying glazes but I encourage you to test them before risking that gorgeous pot that would look so good with the glaze in the picture. An upright test tile will give you a chance to see what effect your clay has on the recipe and how important glaze thickness is for the effect you admire. Save the oops, that bowl that warped in the bisque, the jar you trimmed bottom out of and the pot you accidentally opened to the wheel head will make a great dome to do color tests on. Having test tiles available will make it easier to try things. My favorite way to make test tiles is to open 3 or 4 lbs. of clay to the bat. Continue opening to within an inch of the edge. Split the wall and raise the back wall 2 or 3 inches then pull the outer one to 3 to 5. You can cut a groove at the bottom to catch the glaze overflow. Cut into larger or smaller sections depending on what kind of tests you want to do. You can texture some so see how it will break over scrafito or apply slip or underglaze. The back of the back wall is used to record test info. Look at the test tile pics.

A few mixing tricks will help you be sure you actually followed the recipe. Put a copy of the recipe beside the scales and mark off the ingredients as you add them to the bucket because sooner or later the phone will ring or a customer show up and you won’t be sure exactly where you stopped. I have weighed the bucket contents to see what the total is, to figure out where I stopped. :>).

Keep records, make notes. 6 months or 6 years from now you’ll run into the test tile and will have forgotten how you did it. The most stable glaze in my studio (made 25 years ago) is labeled 75/25 but I have no idea what two glazes I mixed to get it. I recommend spiral notebooks of file card size.

Complete mixing is important, mix dry, then mix and sieve it wet. Remember it is easier to add more water to the finished glaze than get the excess out but here is a trick that can do it. After the water has risen to the top ( usually overnight ) sink a small plastic bowl up to the rim and let the clear water flow into it and suck it out of the bowl with a turkey baster. Don’t discard the water because you may need to add some of it back.

You joined this group to collect glaze recipes, so what can you learn from reading one? There is an amazing amount of information in those few lines. THE NAME: TEMPERATURE, Cone 6 or 10 , you’ve probably decided on the temperature you want to use: KILN ATMOSPHERE, oxidation or reduction. (Reduction is firing in a kiln that uses a fuel that not only uses up the oxygen in the atmosphere but steals the oxygen from the chemicals in the glaze. A special firing effect, such as salt, soda, ash, etc, is a subject better taught by some one else) SURFACE TEXTURE: These descriptions run from matte as rough as bisque surface through matte described as buttery to gloss so shiny as to be reflective. TRANSPARENCY: goes from completely clear to translucent to opaque. COLOR descriptions can be romantic as poetry or so limited as to tell nothing. You just hope you have a good picture.

INGREDIENTS:

SILICA is the base of all glazes. CLAY, the element ALUMINA, controls the flow of the glaze in the fire and the smooth application on the bisque. It helps suspend it in the bucket. The smallest particle clays shrink more as they dry so you need to recognize the clay in your glaze. Kaolin is the purest and most used. Ball clays are smaller particled and shrink more but are good for glazes to be applied to green ware and keep the glaze suspended in the bucket better. The smallest particle clay is Bentonite. It literally gels when wet. A 2% addition to the dry glaze mix won’t change the character of the glaze but don’t try to add it to wet glaze without dissolving it in warm water first. FLUXES: The basic elements most used as fluxes are: SODIUM, POTASIUM, BARIUM, BORAX, LITHIUM, MAGNESIUM, TALC, ZINC and CALCIUM, but we seldom base a glaze on the pure element but use natural earths that contain them. 6 Some I am familiar with are Gerstley borate, potash feldspar, and soda feldspar, and nepheline synite, cryolite, ravenscrag slip. OK. I didn’t mention frits. I personally don’t like frits. They are hell to keep suspended in the bucket, have a powdery surface on unfired ware and usually a narrow firing range. COLORANTS: COBALT(OXIDE OR CARBONATE), MANGANESE DIOXIDE, IRON, COPPER CARB.,CHROMIUM (Be very careful , this chemical has some bad effects) VANADIUM STAINS. COLOR AND TEXTURE MODIFIERS TITANIUM DIOXIDE OR RUTILE, TIN, ZIRCOPAX, ZINC

Ok get out a recipe, read it and tell me what I skipped.

INGREDIENTS:

SILICA is the base of all glazes. CLAY, the element ALUMINA, controls the flow of the glaze in the fire and the smooth application on the bisque. It helps suspend it in the bucket. The smallest particle clays shrink more as they dry so you need to recognize the clay in your glaze. Kaolin is the purest and most used. Ball clays are smaller particled and shrink more but are good for glazes to be applied to green ware and keep the glaze suspended in the bucket better. The smallest particle clay is Bentonite. It literally gels when wet. A 2% addition to the dry glaze mix won’t change the character of the glaze but don’t try to add it to wet glaze without dissolving it in warm water first. FLUXES: The basic elements most used as fluxes are: SODIUM, POTASIUM, BARIUM, BORAX, LITHIUM, MAGNESIUM, TALC, ZINC and CALCIUM, but we seldom base a glaze on the pure element but use natural earths that contain them. 6 Some I am familiar with are Gerstley borate, potash feldspar, and soda feldspar, and nepheline synite, cryolite, ravenscrag slip. OK. I didn’t mention frits. I personally don’t like frits. They are hell to keep suspended in the bucket, have a powdery surface on unfired ware and usually a narrow firing range. COLORANTS: COBALT(OXIDE OR CARBONATE), MANGANESE DIOXIDE, IRON, COPPER CARB.,CHROMIUM (Be very careful , this chemical has some bad effects) VANADIUM STAINS. COLOR AND TEXTURE MODIFIERS TITANIUM DIOXIDE OR RUTILE, TIN, ZIRCOPAX, ZINC

The easiest changes are in color and texture. A test to give you an idea of the color possibilities is line blends done in a wide bisque bowl. (the kiln ogre can’t object because there can’t be any run drips on the shelves) Mix a 100gram batch or if you already have bucket of an untinted glaze measure out ¾ cup (that’s close enough to 100 g for our purpose) Divide it into 4 little cups, about 3 tbls. in each.

Choose 3 coloring oxides and one glaze modifier. Put ¼ the amount of oxide into the cup that you would use in a 100g batch. Choose a glaze modifier tin, Zircopax, or rutile for the 4th cup.

Label cups A, B, C. D. Stir well.

Do I need to post a list of usual oxide amounts? Since the tests are a dilution of the oxide percentages you probably want to use higher amounts of the colorants.

Now start making notes because you will have to interpret this code later.

On the lip, less than an inch apart write this code in underglaze or cobalt oxide wash, A- aab -ab – abb -B – bbc – bc – bcc – C – ccd – cd – cdd – D – dda – da – aad- A – aac – ac – cca – C D – ddb – db – dbb. Okay now you are ready to mix and apply 24 line blend tests.

I like to mix the blends on a water color palate but a plastic egg carton will work. Measuring the glaze into the wells is easiest done with a vet syringe but you could make a mark on an eye dropper and just put in one or two “marks”.

Make a good heavy stripe of glaze A below its mark. Mix 2 parts glaze A with 1 part glaze B, paint that stripe. Mix equal parts glazes A and B, apply stripe. Mix 1part A with 2 B, apply stripe. Paint stripe B and so on and so on around the bowl. A 9 inch bowl should have enough space for all 24.

You are probably not going to the actual percentage math until you see a blend you like but it is simple. A two part blend has diluted both oxides by half. A three part blend is just a little more complex best explained by example. Say blend aab is 2 parts 1% cobalt plus 1 part 4% copper, this equals 2% cobalt divided by the three parts of the mix or .66% and 4% copper divided by three or 1.33%.

When the bowl comes out of the kiln, MAKE NOTES, good or bad you may need the information. Who knows when you may need an ugly wrinkled gray for a Hippo :>)

When the bowl comes out of the kiln, MAKE NOTES, good or bad you may need the information. Who knows when you may need an ugly wrinkled gray for a Hippo :>) 10

Test your glazes over and under each other. Usually you will get more interesting patterns with a lower clay glaze on top but a stable matt might stay in a decorative pattern painted underneath.

A fun low tech way to create a new glaze is to mix two glazes together. Personally, I have never mixed two glazes that in some ratio didn’t make a better more stable or interesting glaze.

Come on lets play !!!!!!

 

Transcript of 1st Glaze Sharing Workshop  –Judi Buchanan Begining Glaze Making

–mark campbell

hello, It would be great if Judi explained how to read a recipe that is given….It really looks intimidating to someone who has never mixed her own glaze…

Judi Buchanan

Mark , do you have a simple glaze you could post? for me to explain?

–Mark Campbell;

Buck Cream Breaking red cone 6-7 G200 Feldspar 41 Silica 25 Gerstly Borate 22 Tin Oxide 13 Calcium Carbonate 9 Red Iron Oxide 6 Strontium Carbonate 3

–Judi replied;

Ok, Mark the title gives you color (cream breaking red) and come temp (6-7) no clue as to surface texture. First ingredient is G200 feldspar the amount 41% Silica is 25% Gerstley Borate is a flux chemical at 22% Tin oxide makes the glaze less transparent and a blue white color Calcium Carb is also a flux 9% red Iron oxide 6% is the colorant Strontium Carb 3% is a matting flux

–Mark asks;

what’s the difference between how the above recipe is written and the way this one below is written?

Frog pond green EP kaolin 31.7 3124 ferror frit 31 Wallastonite 23.2 Silca 14.1 .5% copper carbonite

–Judi Buchanan

I bet Frog Pond is the name of the pottery that developed the glaze green is the color.The first ingredient is Edgar plastic Kaolin 31.7%. The second is a frit that combines several igredients that have been melted together and then been finely ground. Walastonite is a replacement for calcium and flint. And the silica is the base of all glazes. The .5% copper carbonate is added to 100% for color.

June Kinsinger;

can you dip seperate test tiles so you will have a sample with the dip method, which is what I like to use, instead of a painted strip?

Judi Buchanan

a smooth painted double coat will give the same effect if you are doing several tests on the same tile but by all means dip a scrap piece to test the coating

June Kinsinger

great, thanks

Monica Grez Bauza

the firing shedule is so important??for example to hold the temperature at the end for 45 minutes???

–Judi Buchanan

Monica, not really unless the pottery is damp. a good test is to hold a mirror to the peep hole to see if it fogs up. Don’t kick up the temp until it doesn’t.

–Jackson Gray

What is the reasoning behind mixing the glaze ingredients dry – then again wet? I usually blend with a stick blender as I add them to a predetermined amt of water.

If you already mixed glaze and your sure of the amount of water..good deal.

Judi Buchanan

If you already mixed glaze and your sure of the amount of water..good deal.

BUt if you loose your place in the recipe, it sure is hard to make a correction.

Lee Jackson

We always do both. Dry mix and wet mix. Mostly to be sure of multiple ingredients being completely distributed. This also lets you have a backstock of dry mix to to hydrate to different consistencies which allows you various application techniques with the same glazes. Dip- brush- splatter- spray etc.

–Debbie Buco

How does Judi feel about crazing!?? Is it a flaw food safe etc?

Top of Form 1

Judi Buchanan

Since I am a functional potter I consider crazing a flaw.

–Kate Bertin

Terri, I was just reading a digitalfire post about food-safe glazes, and they state categorically that crazing IS NOT FOOD SAFE, as it provides a harbor for bacteria.

Mimi Champlin

Correct, crazing is cause for concern where there is food. Restaurants with dishes with crazing are required to replace them. I use crazed pieces only decoratively or for vases.

Bottom of Form 1

–Debbie Buco

Please ask Judi if she has any recipes for beautiful cone 5 blues greens or red!???? I know red is not easy at cone 5

Terri Kennedy

she will be posting some recipes soon.

Ellen Appleby

The recipe for raspberry in the Mastering cone 6 glazes book by Hesselberth and Roy is a chrome/tin red, and can be a very strong red like a reduced copper red – and works well at cone 5 especially if it is over a clear glaze. Just be wary as the colour will end up an other pots that have glazes with tin in them – can be great, but unexpected.

Debbie Buco

Thanks Ellen— I have that book and the raspberry is pretty. My memory of it is that is for nonfunctional work???? Is that right???

Ellen Appleby

No – H & R take great pains to make sure their glazes are food safe – they discuss this at the beginning of the book as I remember.

Debbie Buco

Awesome!!! I’m in a car driving home from Chicago!!! Thanks!!!

So excited judi uses cone 5 glazes. Would she be willing to share her favorite recipes with us!?!? I also fire laguna b mix to cone 5. Thanks!

Judi Buchanan

Yeah, the most stable white glaze…I refered to in the workshop

SMooth buttery opaque ^5 -6 ox. it has saved many a bad pot by dunking a badly blistered pot.

this glaze does not run…at all.

I’ve used it to paint designss under other glazes and on top of other glazes.

it is great for painting with majolica techinques

Gertsly borate 30.8

Silica 30

Zircopax 7

kaolin 10

Whiting 9

custer feld 8

titanium diox 2

rutile 2.4

Cindy Douglass

Is this page not the workshop? What/where is that white glaze referenced?

Cindy Douglass

Thank you.

–Don Oliff

Would mixing the chemicals with distilled water make a big difference in the glaze performance?

Judi Buchanan

Only if you have VERY hard water.

tiny differnces in the chemicals make a lot less difference than you think.

recipes are not always the same for everyone, different waters, chemicals, firing conditions, matter more.

of the possible variations, water is probably the least worrisome.

–June Kinsinger

Mimi, does she have a listing of chemicles with corresponding “like names”? sometimes I have the ingredients but under a different name? It would be great to have the listing to post in our shops. Just a thought…

Judi Buchanan

the main example is flint is silica and sometimes in europe it’s quartz

okay, I’m gonna look and see if I have a list of subs for you.

Okay, very few chemicals are exact subs for one another.

the clays vary in their charteristics…so you can only exchange balls’ clay, like OM4 , tennesee ball clay

you might also exchange it with kaolin, which is pure alumina, but that will change the glaze charateristics

–Alisa Fritz Kuniya

Can you ask Judi if she has a Tomato Red recipe in Cone 6 oxidation?

Judi Buchanan

No, I just use underglazes and clear…most reds aren’t red at a higher temp.

Monica Grez Bauza

the firing shedule is so important??for example to hold the temperature at the end for 45 minutes???

Judi Buchanan

Monica, not really unless the pottery is damp. a good test is to hold a mirror to the peep hole to see if it fogs up. Don’t kick up the temp until it doesn’t.

don oliff

For “Once-Fired” pieces would you adjust the glaze in any way?

Judi Buchanan

yes, replace kaolin with a ball clay that will shrink at the same rate as the clay.

Mimi Champlin

how do you know what that would be?

Judi Buchanan

You have to test that, it’s different with every clay.

You will have to make a shrink rule to see the shrinkage of your particular clay.

–Carolyn R. Sleeper

I’ve never used, but I want to experiment with Mason stains. Can I just use my favorite glaze, white satin matt, and add small amounts to get the color I want?

Judi Buchanan

Caroline, If the satin matt has tin or zircopaz you need to leave it out or cut way back they will make the color very pale. You may even have to go to 10 or 15% in a white matt glaze. It is easier in a clear.

Carolyn R. Sleeper

thanks.

don oliff

I usually spray my pieces with multiple thin layers. If the layers don’t dry fast enough I use a small propane torch to speed the process. Would you expect this to affect the glazes?

Judi Buchanan

no, as long as you don’t dry them so fast the glaze doesn’t pop off. hahaha

Cindy Douglass What percentage of time and raw materials do you devote to testing of glazes?

Judi Buchanan

very little in the way of materials, because I mix and test 100 gram batches

time is in vary small segments so I don’t know how to count it…very few kiln firings that don’t have a test or two in it.

I have always given myself the month of january to play with new shapes, forms and new glazes.

because I consider expierimenting “play time”. hahaha

Mimi Champlin

This is the recipe referenced by Judi for those of you who were confused, cone 5 ox, heals all wounds! Does not run. Gertsly borate 30.8 …. Silica 30.2……Zircopax 7.6…………kaolin 10………Whiting 9………custer feld 8………..titanium diox 2.4……rutile 2

Judi Buchanan

says, I will be on the group, for a night or two, if anyone thinks of any questions, direct them through mimi or terri and I’ll get to them as quick as I can.

  1. No comments yet.
  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: