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
24 Responses to “Success! Pink and Violet ^6 Glaze Test Recipes Part 2”
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I like the bottom right clover pink the best.
Nice! Very good results! Congrats!
Those latest glaze tests are great. I’ve been getting some fantastic purples in my slip tests I’ve been doing too. I’ve been using a combination of Mason stain Lobster and either cobalt oxide or cobalt carbonate. I get anywhere from deep royal purple to a lovely plum depending on what percentages of each I’m using.
For the expansion coefficients of clay, I’ll just tell you I’d be surprised if you are able to get this info out of the supplier. Those that I have talked to don’t know.
Even if you do find it out, you are going to have to test anyway. Do the tests described in the M^6 Glazes book and keep track of the calculated coeff. of expansion for your glazes. Maybe do the tests in the book where they describe the various expansion test glazes (p 67ish). Do you have the glazemaster software? If not I’d be glad to punch in your glaze recipes and tell you their calculated coeff’s.
OK I love the Mustard and the hot deep pink, I have idea what you are talking about but I wish I did. You make clay sound like Mr. Wizard made science sound fun. I do wish I understood more about yur work, but I can say that I love t, even the duds.
Next time, I will spell check…darn not having enough time! LOL
Thanks Janet – still looking at them before making a decision myself…
Lisa
Leigh, I’m using the trial version of Insight and the glaze expansion # is 7.29 I sort of thought that the clay co won’t give it to me either in the form of their recipe for proprietary reasons. Though, I have neither the time nor the inclination to make my own clay right now. I have some lobster in my locker – maybe I should try some tests of that too.
I hear ya Heather – for non clay people all this must sound like the speaker voice in Charlie Brown “wah wah wah wah”.
Yay for you! These are great. I’m jealous of these electric kiln firings… such fast results.
Good luck with the clay companies. I’d hope they would know. I had a c.04 glaze craze when I put cold water into the cup… guess it didn’t move with the clay, but I’m not using the glaze again until I have the time to reformulate it for better fit. (Getting some glaze software would help too.) So, no, you’re not being too picky!
I loved reading about this! I recently bought the book Mastering Cone 6 glazes and I’m slowly muddling my way through it. What a neat glazing adventure you are having. I love the colors you’re developing!
As long as you do a rigorous test for crazing, you don’t really need the numbers for the clay, and they probably wouldn’t do you much good anyway, I don’t think. It’s all going to vary to some degree based on batches and lot numbers of both clay and glaze ingredients anyway. Just find a range of coeff of expansions (for glazes) that works with your clay and use that as your starting point.
Not like I’m an expert or anything, so don’t take me too seriously
P
I’ve had such problems with this one glaze I’m using. I’ve tested a bunch though. LOL!
Way to go Cynthia!
Those Tony Hansen articles are great.
I can’t wait to see your final results – especially on those nesting bowls:)
Excellent colors! I’ve been lusting after those boxes of yours – they’ll be fabulous in chartreuse! Might have to custom order one after I get my house remodel done.
(Sent a long email to your builder with info about my desired expansion – haven’t heard back yet but am looking to get bids from at least 4 guys and he seems like a really good one. Thanks for the pointer!)
Yay! Well done Cynthia
You must be thrilled.
Nice that you’re able to run your tests through so quickly!
Hey Julie – I thought Mile Hi would know too since they formulate their own clays. Maybe no one has ever asked? I think the software has really helped me understand why a lot of this is important and while I had questions before, I didn’t really know where to look for the answers.
Welcome, Natalie! I’ve had MC6G since 2003 and all I ever really did was read the recipe section. In the past week, I’ve backtracked and wish I had read all this stuff from the beginning. Good luck with your glazing adventures
Leigh – you’re right about the testing. I guess I just have to do it the poor man’s way. Eh – we’re all experts at something, especially if it’s fresh
I appreciate all the things people have suggested since part of this clay journey is so self taught/learned by experience.
Thanks Andy – I love his site, his style of writing and the way he makes the technical more accessible.
You’re too kind, Lisa! I hope he gets back to you soon and I don’t have to eat my words…
Thanks Anne – I’m happy to have figured out the secret to the chrome/tin combo…but testing is not over yet. I’m going to retest the glaze using actual oxides. It would be way less expensive in the long run.
It seems to me that clay would be a bit different here on it’s expansion than in a wetter climate, so I’m thinking it may be a moot point for the manufactuer of the clay since you are using it in high altitude and dry climate. Of course that is just me, a total “wah, wah, wah,” person when it comes to knowing this stuff.
I think it is neat you are doing such diverse stuff in your teaching and your experiments. Rock on Cynthia!
Hey Mary – thermal expansion has nothing to do with climate, but rather how the clay and glaze fit together once fired. If you feel like reading more… http://ceramic-materials.com/cermat/education/198.html
Cynthia – You are so industrious! I really admire your hard work to develop new glazes. I am soooo lazy around the chemistry and testing. You’re an inspiration!
Congratulations, all your hard work is really paying off. I just love those bright colors. Oh, that violet is to die for – I could just see one of your floral pendants in that color.
For your testing of test tiles, do you use a test kiln (a smaller one) that you fire?
Thanks for all the links to articles and books, these will be really helpful to me when I start my own testing of Cone 6 glazes.
Can’t wait to see some of your pieces with your new glazes.
Wow, so much to learn! I understood some of it
I’m hoping it will all make more sense to me once I start my classes.
Patricia – I go through my own stages of laziness myself. I guess, I finally just realized that I needed some more colors. Now I’m possessed and am on a mission.
Thanks for your comments, Linda! I’ve kept the little test batches to use on the pendants. They’re all at full saturation, but will work great for the little things. I hate to waste the tests. Yes, I use a little test kiln, an Aim 88t 8″x8″x9″ 120 volt/15 amp cone 10, with infinite switch and Kilnsitter ($320.00) or with a Kilnsitter with timer ($365.00) It’s cool since it fires with a regular outlet. The downside, is that when I fire in my Skutt 1027, the results could be different. I’m guessing they’ll be better since I do a more controlled firing with soak etc.
Congrats on finding classes, undaunted – very exciting!
You are so organized and efficient. You’re my hero. Those test tiles came out wonderfully. Enjoy your successes.
Beautiful colours!!
I was searching for information about \’Painting Interior Decorating\’, and this your page (\’! Pink and Violet ^6 Glaze Test Recipes Part 2 at Colorado Art Studio\’) was in search results. Not sure why it appeared, but your site is still interesting to read
Did you ever do a retest of your Duncan Cover Coats and did you ever photograph the overifred test tiles? I am going through a similar process and would love to see the results of the first test and if you ever did a second test!
Did you use the cover coat on greenware or bisque? And did you use a clear over them…if so what was the recipe or brand.
Thanks for your hard work and diligence! You’ve helped many of us along on our journey!
Hi Carol -
“Did you ever do a retest of your Duncan Cover Coats and did you ever photograph the overfired test tiles?”
No, but I’m going to. I’ll probably test to cone 6 and cone 10. I will also expand the test to a vertical surface – and use a cone 6 porcelain and white stoneware (since that’s what I use at home). For cone 10, I’ll test on porcelain and also a white stoneware – not sure which ones yet, because I’m still learning about reduction firing and which clays I like using. I can fire to cone 10 at the Colorado Potters Guild where I’m a member.
I have used cone 10 Babu porcelain and I just picked up a 25lb bag of Zen porcelain that I’m anxious to try out. I know the guild has biz bod, bmix, dover and some other white stonewares – as well as babu, p-60, coleman, and jiki porcelains. I just have to find a couple of cone 10 clays that I like to use.
I just took a quick look at the Mile Hi Ceramic’s catalog and if I were willing to fire to cone 8 in my electric kiln, I could use the clays above – since they’re formulated for cone 8-10, but then I’d have to change all my glazes…
“Did you use the cover coat on greenware or bisque?”
Bisque fire tiles.
“And did you use a clear over them…if so what was the recipe or brand. ”
For my Duncan CC tests, I used 1/4″ flat test tiles and glazed 1/2 the tiles with a homemade clear and left half unglazed. Here’s the link to the tests http://coloradoartstudio.com/2008/07/10/duncan-cover-coat-results/
My recipe for clear is one that’s floating around in cyberspace. This was taken from a notebook binder that Lana Wilson gives workshop attendees.
Gerstley Borate: 50
Kaolin: 20
Silica: 30
It’s brushable – though gets cloudy when applied too thickly.