Posts Tagged “mastering cone 6 glazes”

Hybrid Leaf Vases

I liked making these 2 vases - the bases were made from slabs of clay and the wheel thrown neck was added after the hand built portion of the vase had set up (not quite leather hard) enough to withstand having the neck addition.  I also made a bisque texture plate using ginkgo leaves from the little tree I planted in my yard - though I haven’t used it yet.  The white glaze is new for me - it’s from Mastering Cone 6 Glazes by Hesselberth and Roy, pg. 108 “Faux Majolica”.  There’s a great interaction between the white and the aqua color glaze where they overlap that I really like.

In an effort to use and store a limited number of glazes and all the associated raw materials in my small garagio, I thought this white would be good as both a liner and I might like to try painting some stains on top in the future maiolica style.  I decided to be conservative and only made a 5,000 gram batch just in case I didn’t like it, but I have to say, it fires terrifically!

In regards to glazes, I decided to bite the bullet today and purchased the Digital Fire Insight Glaze Calculator after testing several different programs, even a free glaze calc program.  I’m all about free, unless it isn’t working for me and this one isn’t a terribly intuitive program - but that really applies to me only.  Maybe now that I have the glaze calculation program, I can add my glaze recipe page to my website.  I’ve been too lazy to format tables in word for my recipes and it would be really cool for others to see the analysis that accompanies each.

Square Bottom Mug - hand built from slabs of clay

I really like the way this mug turned out - round top, square bottom and the faux majolica MC6 glaze interacts nicely with this green one too! In an effort to move away from the templates that ceramicist, teacher and writer Annie Chrietzberg gave to everyone this past summer during a workshop I took here in Denver, I tweaked her template just a tad giving the mug a square base instead of a round one.  The tweak was minimal, but effective.

Speaking of Annie - I wonder if her ears are ringing right now…I enjoyed spending a couple of hours with her yesterday in my studio.  She’s warm, funny and very generous with her knowledge.  Oh Earth to Annie…thanks for stopping by!

Meanwhile, yesterday was hectic and I didn’t get a chance to do all my daily Internet activities such as responding to blog comments, answering emails etc.  In the am, I took my daughter to visit the Denver Center for International Studies, which is a 6th grade -12th grade public magnet school in Denver.  Denver residents are lucky to have school choice - but we are also cursed because choosing a school is like applying to college.  She will be starting middle school next year and we’ve narrowed our choices down to 4 including the one above, Denver School of the Arts, Morey Middle School which has a gifted magnet program, and one other neighborhood school.

My first choice for her is the international studies school - it’s so cool, they start studying a foreign language in 6th grade (French, Spanish, Italian, Chinese or Japanese) and they visit countries where their language is spoken starting in 9th grade.  Her first choice is Denver School of the Arts - but they only accept 20% of applicants.  Besides, does our family need more than one artist?  DCIS accepts about 50%, Morey is an automatic in - and the other school is just an extra for decision making purposes.  All 3 of these schools are urban & very diverse - and bonus upon bonus - they provide busing!

The downside to all of school choice is that applications are due by Dec. 12 for following year and include essays, interviews, teach recommendations, test scores - all for 6th grade!  It’s a little overwhelming for both of us.  I promised her that if she decides to go to DCIS, I’ll take classes in whatever foreign language she picks.  Wouldn’t Japanese be cool?  Of course I’d sign up to chaperon field trips whenever possible!

TGIF,

~Cynthia

Early this summer, I set out on a quest to expand my cone 6 glaze palette and since I’m attracted to vibrant colors, I decided to look for some candy colored hues such as pink, violet, and chartreuse.  I found success with Mason Stains as colorants in this pink base glaze #4 cone 6 glaze recipe I found on http://www.ceramic-materials.com.  After figuring out the cost per batch, I decided to try using chrome and tin oxide instead of Mason Stains to achieve a pink glaze and also to substitute some ingredients to make the cost per 10,000 gram batch less expensive.  My new criteria sent me off on another round of testing which I ended up abandoning to write some lesson plans in preparation for my teaching stints this last summer.

Cone 6 Pink chrome-tin combo

There is a slight error in this photo - there should be one more division of the glaze colorants lower right hand pile for the 6 part color progression glaze test.  In some ways, this glaze test was doomed to fail from the start because I lost the momentum of my glaze testing in July when I switched gears.

Cone 6 pink chrome tin combo ready to be fired

I don’t think I had anything to lose by proceeding with firing the test tiles even though I can’t say for certain which recipe I was using because it was not labeled - I could only make some assumptions based on my chicken scratch.  This test series also illustrates the need for taking good notes and accurate labeling in the studio.  The less than stellar results could also have something to do with the ingredients I substituted.  I still have another 2 batches of the base glaze to test, but since I’m not really 100% sure what these recipes are, I’m tempted to start over.  While I was in the heat of testing in July, I thought I would remember my reasoning and steps crystalline clear - big mistake.

Labeling my tests more accurately

So, in an attempt to be more organized in the studio - I added the date that I actually fired the tests on the reverse of each tile, along with the name of the (assumed) base glaze, numbered tiles 1-6 , clay body, temperature of clay - the latter three are scratched into the clay body before bisque firing and the former are written with a glaze pencil.

Cone 6 pink base chrome tin combo results

Results - blah.  I’m not sure if it’s the right recipe, the chemical make up of my substitutions or that my scale is off.  I had a dickens of a time measuring out .2 grams of chrome - it’s such a strong color.  After looking at the original recipe and then the “Raspberry” glaze recipe in Mastering Cone 6 Glazes, I know the proportion of chrome to tin was probably wrong.  .2 chrome - 7.5+ tin oxide would yield a decent result I think….

There is a little pink visible in the test tiles with higher amounts of tin and chrome

The latter 3 tiles are the only ones to show a hint of raspberry color - and these are the ones with the highest concentration of tin.  One interesting bit of info gleaned is that test tile #3 2nd photo up is close to the chartreuse color I’d like to use - much softer than what I achieved with Mason Stains.

Kiln is firing too hot

Another bit of information that I suspected, but have now confirmed is that two of my three of my kilns are firing hotter than cone 6.  Last time I visited Mile Hi Ceramics, I picked up some boxes of self supporting cone 5, 6 and 7 pyrometric cones.  Check out cone 7 - it’s touching the kiln shelf - the trio of cones should look like this instead.  These were placed in my test kiln which has a kiln sitter that turns off the kiln when it’s reached temp.  This past weekend I also tested my ancient Paragon - and it also over fired.  I haven’t tested my new digital Skutt 1027 yet, but will have the opportunity to do so next week sometime.  I almost have a full load to glaze.  Tips anyone?

Meanwhile, according to my studio log, I spent 12.5 hours out of my goal of 20 hours a week in the studio in the last 7 days.  I consider this a success considering that I was a substitute teacher 2 of those days and have reserved Sunday for family and getting ready for the following week.  This next week should prove more fruitful.

With that said, I’m signing off for the day,

~Cynthia

This is a continuation of my last post.

Mason Stains in ^6 Glazes

In my second round of testing, I was optimistic that I’d found the holy grail of base glaze recipes to achieve a pink ^6 glaze - but I was mentally prepared to open the kiln this morning and find nada.  Imagine my surprise and delight, when I opened my kiln and found these gorgeous tiles!  After loads of research and internet sleuthing, I happened upon this article by Tony Hanson that included a recipe for a base glaze good for chrome/tin colorants on the ceramic-materials.com on Sunday morning.  I quickly made up 3 test batches of the base glaze and fired up my little test kiln yesteray with anticipation.

To be expected, color developed much better after using a higher percentage of colorant.  I decided to try up to 12% stain this time just to compare with my tests a couple of days ago where I used up to 10% stain.  Truth be told, 10% is plenty - but I wanted to see if it made any difference.  It looks like color doesn’t start to really develop until tile 3 which would be 25% of the total amount of stain used (in this case, 25% of 12 = 3% of the total 100 gram recipe which results in a very pastel color).  I’m guessing that when I test some blues & greens, I will need even less colorant since cobalt and copper are much stronger colorants.  Also, I’m going to try redoing the pink glaze using chrome oxide and tin with the new base glaze.   Yesterday, Annie generously forwarded another chrome/tin compatible recipe to try and my friend Mary Cay emailed me this morning reminding me about a recipe that she included in the materials from a glaze workshop I took with her last year.  Thank you to both of you!

I also retested the chartreuse stain using the pink base glaze #4 (used with the pink and violet stains sucessfully) from Tony Hanson.  I’m interested in have 1 or 2 base glazes so that I only have to buy minimal ingredients in bulk for future use.  And, I had a thought…  I plan on using a combination of 2 different glazes for my work.  For example, glaze the exterior of a cup violet and the interior chartreuse.  My thinking is that if violet is a chrome/tin glaze that can have no zinc, magnesium and needs calcium - then some funky stuff might happen where the violet and chartreuse glazes meet.  But, not if they’re the same parent base glaze (or so goes my rational).  I may be wrong and I plan on calling Mason Color later today to ask some questions.

There is a slight color difference between the 2 glazes.  The one tested in the last post is more green, whereas the one with the pink base glaze #4 truly is more mustard yellow.  If that’s what I’m going for, I could simply use rutile as the colorant at a lower cost than the mason stains.  I suppose this is the whole point of testing; to see what can be learned and how to apply the knowledge effectively.

Thermal Expansion and Clay/Glaze Fit

I still need to find out a little bit more information too, before I mix up big batches of glaze.  Kris left a comment on my last post about the thermal expansion of the clay body I use.  If the clay body and the glaze’s thermal expansion don’t jive, crazing and a host of other issues could crop up down the road.  Funny, thing is that I was just reading up on this last night in  Mastering Cone 6 Glazes, Chapter 5 “Fitting Glazes to Your Clay Body”.  I need to call Mile Hi Ceramics this morning when they open and find out what the thermal expansion is for the 2 clay bodies I generally use - Ash (^6 white stoneware) and Aspen (^6 porcelain).  If the glaze is too big for the clay body, shivering results.  If the clay is too big for the glaze, crazing results.  Shivering is not cool - chunks of glassy glaze falling off the ware.  Crazing (fine crackling) is sometimes desirable for some potters, but isn’t really a good attribute for functional ware that comes into contact with food.

Update: Neither of the people I spoke with at Mile Hi Ceramics know the thermal expansion of their clay bodies - I was told to call back when the owner is in. Boohoo.  Am I over thinking this?

Using Underglazes to ^6

I did come upon some other interesting test tiles in my studio a few weeks ago while cleaning.  These were tests that I had mis-fired last year involving Duncan Cover Coat Underglazes.  I was doing these tests to provide my kid’s clay classes reference color chips.  The kids always wanted to know what the various colors were going to look like when fired.  My mishap was due to my Aim cone 10 test kiln over firing due to a couple of very careless mistakes.  I  put a small pyrometric cone 6 in the kiln sitter, loaded the kiln, turned it on, ramped up the heat on my predetermined schedule.  My mistakes: I wasn’t around when it was supposed to turn off and when I opened the kiln in the morning I realized that the kiln had totally over fired because one of the shelves was touching the kiln sitter.  I’m not quite sure what temperature the kiln reached - the pyrometric cone was totally melted and black (normally white after a succesful ^6 firing) and the kiln fires to cone 10.  It’s a good possibility that these tests were fired to cone 8-10, depending on how long it took the pyrometric cone to melt allowing the sitter to turn the kiln off.

I used cone 6 porcelain test tiles and though they didn’t melt or even bloat, they all have a sheen to them like glaze in all the unglazed places.  So, why am I telling you this?  Because I found out that Duncan Cover Coats can be fired quite high and retain their colors.  When I get around to photographing them, I’ll post those results.  Underglazes would certainly be an option for me to use as a colorant under a clear glaze.  I should redo these tests firing them to cone 6 and compare the results.  I have everything from yellow, organge, red, violet, light and dark blues, green and black in my “failed” tests.

I originally wanted to toss these test tiles since I was angry at myself for my mistakes, but held onto them for some reason.  There’s something to learn in both our successes and more often in our mistakes.  Zen master is teaching me again

So - I’ll post those tests later this week for you.

Meanwhile, I’ll be teaching a kid’s class at the Art Student’s League of Denver starting next Monday called, “Mixed Media Marionettes”.  The class is now full and is for grades 3-5 but, lucky for me I will have an assistant to help.  I will be spending part of my time this week making the proto-type and lesson plans for the class so I’m well prepared.  I pulled my daughter’s wood marionette down from her bedroom ceiling ceiling the other day and am studying its construction so I can successfully recreate a working one next week with the kids.  I’m also deliberately working fast since we only have 5 days to work on these.  3 with wet clay and the other 2 decorating, assembling and hopefully playing with them on the last day.

Whew… have a good day,

~Cynthia