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How Much Testing Or Tweaking Of Glazes Do You Do?

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#1 Marcia Selsor

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Posted 22 July 2014 - 07:04 AM

How much testing or tweaking are you doing? Do you use software or making educated guesses. Ian Currie's grid process is a good example of getting lots of info from simple alterations of materials.

If you are using software. What software are you using? What are you firing? What are you striving for?

 

Marcia



#2 Marcia Selsor

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Posted 22 July 2014 - 04:47 PM

Guess this question is a dud. Not one response. With all the discussions we have here about adjusting glazes, i thought it would be a good opportunity to share some ideas or methods of tweeking.

Example:

My glaze is runny. What do I do?

answer: add some stiffener. such as kaolin. Start with small variations around 2% at ^6

 

My glaze is crazing. How can I fix it?

answer: add a little silica. Start with about 2.5, 3, 3.5%

 

So what about adjusting colors?

Anyone?

 

 

Marcia



#3 Marcia Selsor

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Posted 22 July 2014 - 08:35 PM

Still no responses. Everyone must be working on shows.
marcia

#4 Biglou13

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Posted 22 July 2014 - 08:46 PM

I not so technical yet
I have changed firing schedule which has improved certain glazes.

I have glossy black that cannot be under fired, and likes a crash cool vs controlled, refiring gives it a different look, Iridescence

I have tried to make glaze less glossy by increasing the epk.

While,not a glaze thing I am testing absorption /vitrification of commercial bodies and self made bodies.
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#5 clay lover

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Posted 22 July 2014 - 09:02 PM

I don't tweak glazes, but I do a lot of testing.  I am still adjusting firing schedules for max performance of glazes I already feel good about.



#6 Min

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Posted 22 July 2014 - 10:17 PM

I do a lot of testing, tweaking and from scratch glaze tests.

 

I use glaze calc program Insight (level 2 access). If a glaze looks good on paper then I'll run it through Insight, if it still looks good for the clay I'm using then I'll make a test batch. After that I tweak it with Insight to fix what isn't working and run more tests.

 

I'm not looking for crazing on my functional pots so I test for crazing. Usually make the base without colorants then if it passes my craze tests I'll try with colorants and or opacifiers, taking into consideration that some colorants and zircopax will help with crazing if necessary. I oven test for crazing by heating the test pieces at 320F for 20 mins then plunging them  into room temp water, 3 cycles of this, then brush with sumi ink to check for crazing. 

 

I use triaxial blends for both changing the base glaze and colour trials. I also like doing line blends.

 

I pay attention to silica and alumina levels as I make mostly domestic ware. I have sent a few samples for leach testing to Brandywine Labs.

 

I'm currently buying 2 claybodies and usually mix them together in the mixer/pugger. I like and dislike qualities of both of them and blending them seems to even them out.

 

Is there anything we don't test and mess around with? Seems I'm always trying out something new.



#7 TJR

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Posted 23 July 2014 - 11:54 AM

Marcia;

I test and tweak glazes all the time. I am working on an ash glaze that runs like stink. I added kaolin to it in a line blend. Lost the rivulets and the shine, so I am disappointed. I always have glaze test tiles in my kilns. This might be a maturity thing. If you are still working on throwing skills, maybe you are not making glaze tests.

TJR.



#8 Marcia Selsor

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Posted 23 July 2014 - 12:19 PM

Yes, it may be a maturity thing or it may be that more people are using commercially accessible glazes. 

Not sure. I am always testing too but lately my tests are in alternative firings ideas. 

Good point TJR

 

Marcia



#9 Roberta12

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Posted 23 July 2014 - 01:17 PM

About the only tweaking I have done is with colorants.   But I also do change up  firing schedules/cooling times/holds/ temps and that sort of thing.  I would like to take a serious glaze workshop.   Or a workshop to teach me how to use the software.....   I recently have been using a different clay.  SB red by Laguna.   I really like it.   But I noticed that some of my glazes had some small pinholes.   I decided to try bisquing to a lower temp.  That seemed to help.  Now I am going to increase the hold on the glaze fire and see what happens.   That is the sort of tweaking I do. 

 

Roberta



#10 Tyler Miller

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Posted 23 July 2014 - 02:11 PM

I do a fair amount of glaze testing and tweaking.  My approach is to "shotgun" a triaxial/line blend by zeroing in on several different possible blends put through a glaze simulator (Insight, usually), and then I put all those potentially useful blends onto test tiles and fire them.  I select from those what I like best, then start testing on smaller forms before committing to big pieces.



#11 dhPotter

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Posted 23 July 2014 - 06:34 PM

Being extremely new to pottery(less than 5 months), but having an analytical background(day job of 30 years as a programmer) I have been testing glazes like crazy. 90 or so tests. My thought was to get a palette of glazes then start throwing forms. I mix my own glazes using Tony Hansen's Insight software. Having researched the heck out of glazes and materials, I didn't like what was being said about Gerstley Borate not being consistent and not being mined any longer. I decided to replace Gerstley Borate with Boraq. I use the software to enter the GB glaze then substitute Boraq comparing them side by side to see if the numbers are the same. If not, then start tweaking the Boraq side to get close or real close. It is not just a few numbers to get the same - it is nearly all the numbers. I always fire the GB glaze to compare against the Boraq glaze. None of the glazes I use have GB. The 90 or so glaze tests were overwhelming but John Britt's DVD really helped in the method used.

As someone who never took chemistry in HS or college, without the glaze software I would be lost. The glazes I have been using are from many books, web sites, magazines. If I see something I like then I try it. It hardly ever looks like the original. It has recently come to my attention to use Frits to replace the GB. However, I am satisified with the Boraq for now.

Ron Roy's "Mastering Cone 6 Glazes" is my go to book. I use some of their glazes, Waterfall Brown and Verigated Slate Blue. Also, Bill Van Gilder is another contributor to my palette like Licorice, Cream Rust, Raspberry Red, Rutile Green. From the Insight website, Butterscotch.   

The greatest surprise is the layering. At first, I only layered colors that would go with each other. Now, I try layering any color over any color because it rarely turns out the way you think; and the colors are out of this world with marbling, varigation, rivulets! I have a Floating Red that is a deep brick red. But layer it over Licorice and it becomes a bright red with yellows and greens and blues all mottled together. Both glazes are stable, they don't move. However, layer them and they run all over the place. Got a good dose of grinding shelves 1 weekend!

In programming we are given a set of operation codes, it is up to us to put them together to make a meaningful, user-friendly program. The same in pottery. We are given the raw earthy materials, it is up to us to make something useful  or beautiful or ugly or colorful. The sky is the limit.

So many options: different clay bodies, forming methods, glazes, glazing methods, firing methods. Whew!  

I cannot believe how pervasive red iron oxide is. It gets on everything. The wife was wiping down the staircase handrail and there was red iron oxide on the cleaning rag.



#12 Babs

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Posted 23 July 2014 - 08:43 PM

Depends on my schedule, and as I came into ceramics with no tuition , just reading and reading and reading, I have been testing and tested!

Glaze education if it was available nearby, I would pay for.

I do line blends and have a great book by an Aussie whose name is not in my brain today but he reduced greatly my fear of stuffing around with glazes.

Have been gaining a confidence in the formulation of glazes and knowlege of the properties of the glaze ingredients, but when pottery is something STILL fitted around other things, it is so easy to go with the known and loved..

Note to self, discipline required, allocate one month where all I do is test and work with glazes, Hmm where shall I stick that note?



#13 Pres

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Posted 24 July 2014 - 02:07 AM

I test variations of the same glaze by changing one variabble in small increments to see what happens. After I find something I like I test that with vinegar, and dishwasher solutio-idividually. Then send out.

However, because I like to inglaze I have tried mixing opacifiers for better color response. Zircopax-tin, zinc-tin, etc. Still plaing, but closer towhere I want to be.

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#14 High Bridge Pottery

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Posted 24 July 2014 - 07:40 PM

Nowhere near enough  :huh:  :(

 

I have found a few glaze recipes and made them. Looked into RO tables and tried messing about with a few numbers to change the glazes. Never been too precise about it. Tried to solve crazing by changing out some high expansion flux for lower expansion with some success. Manipulated the silica/alumina ratio to get a matt glaze.

 

Have some plans to do a lot more testing soon, once I bisque the test tiles...

 

Good idea with the opacifiers, I use some tin and zinc in my recipe.



#15 JBaymore

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Posted 27 July 2014 - 04:36 PM

Unfortunately this kind of understanding takes time.  Particularly since the firing schedule/profile is such a big part of the results.  Plus you have a whole heating/cooling cycle of time lag between every iteration of testing.  It is just like pretty much all other parts of the art form........ each one has a good solid learning curve.  That is why it will NEVER be boring ;) .

 

FYI......... as far as glazes go...... a 15 week, 6 hour class time per week, plus outside homework and testing time college materials course will get the typical relatively motivated student so that they understand the glaze slurry mixing aspects, the raw materials sources for oxides, the chemistry aspects, and core firing issues at a BASIC level.   As well as using Insight glaze calculation software at a basic level.  Basic body information is covered as well, but we start with a focus on glazes/glass/ceramic chemistry. This class (along with the kiln design and operation one) are both required courses.  That is what we consider the minimum to graduate with a BFA tacked on after your name. 

 

We just added a Materials II level course as an elective option for those that are interested in pursuing more.

 

best,

 

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

 

PS:  Personally I am always messing around with something experimentally.  But rarely does it go into production on my own work.  Been using the same main stable of glazes for 35 years or so.  Just added a new Hare's Fur tenmoku to the line... I think.


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#16 Pres

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Posted 27 July 2014 - 04:49 PM

Ah, to have the luxury of the time, opportunity and money that was there when I went to school in the last century! :lol: I am still looking for a good work shop close to me that I can get into on a commute, or live in basis. I do believe that I have come to understand much more than I think, but it is always nice to be assured after putting several hours of work into a classroom situation. The other part of my problem is that I have been to the front of the room for so long, wonder if I could sit through a poor presentation without saying something. B)


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#17 High Bridge Pottery

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Posted 03 August 2014 - 09:42 AM

Never done a melt test before. Actually really enjoyable.

From right to left: cornish stone, potash and soda. Under that 50/50 mix with quartz and below that 50/50 mix china clay. The two on the far left is quartz top and china clay bottom.

I need more small bowls :D
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#18 Denice

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Posted 03 August 2014 - 10:48 AM

I'm like most of you just some tweaking, layering and lots of testing.  First thing I bought when I got out of school was a test kiln.  Since I work with C6 oxidation  I do a lot of firing adjustments, I don't own any computerized kilns but I have a nice dual pyrometer set up.  Denice



#19 Chilly

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Posted 07 August 2014 - 07:47 PM

Never done a melt test before. Actually really enjoyable.

From right to left: cornish stone, potash and soda. Under that 50/50 mix with quartz and below that 50/50 mix china clay. The two on the far left is quartz top and china clay bottom.

I need more small bowls :D
attachicon.gifimage.jpg

I used a large flat slab of clay and impressed lots of dents into it using a ......  can't remember what, but a bit smaller than the size of a film cannister.  Numbered each dent and put a half teaspoon of raw material into each dent.  Worked well. 

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#20 Wyndham

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Posted 10 August 2014 - 06:16 PM

Testing is part of every firing, gas, electric, anybody I can get a piece into their firing.

My gas firing is the most active for testing because I can expect some major changes with small ingredient changes.

Test for changes in % of copper in copper reds as well as fluxes in those glazes.

With the thread on the temoku & leaf bowl discussion, I have some thoughts that I want to see where that may go.

If all I have to do was glaze mugs with the same glaze day after day, I'd go crazy......

 

I got the testing bug when I used to rummage through Harding Black's boxes of glaze test and notebooks full of his cryptic recipes and comments.

Toward the end of his career, I asked him about a test bowl of his that was great but not marked with any info. It was both a funny and sad moment because his memory was starting to fade.

When I asked,He said, "that's  beautiful , who made it?"

So many test, so little time.

Wyndham







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