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SunsetBay

Testing glazes and firing schedules--I'm overwhelmed!

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After a summer without enough pottery time, I finally got around to a glaze firing including some commercial glazes and a bunch of test tiles using glazes I mixed up myself. I've also been experimenting with firing schedules. Based on some previous experiments, I tried using the E3 schedule from John Britt's glaze book, only with the top temp changed to 2210 degrees F (based on advice from L&L's tech) and a 10-minute hold at 1900 degrees F (can't remember where I got that idea). The exported log file tells me the highest temp I reached was 2209. My cones tell me the kiln was at a hot ^5 (I've been trying to reach closer to ^6 in a kiln that has had a tendency to overfire). I'm not loving the results and I'm contemplating messing with the glazes and refiring the pieces I don't like that much.

I guess my main question is: When you move on to glazing actual pieces after getting results you like well enough on test tiles, what do you do when the final results aren't what you like? How many pieces do I dare risk with experimenting with firing schedules and temps? How do you do all that experimenting WITHOUT risking too many "real" pieces?

I'm starting to think I should chicken out and go back to only commercial glazes and my kiln's preprogramed "slow glaze" program. But I'm tired of brushing glazes and interested in finding the color and combos I especially like for myself. Not sure where to go from here.  Any guidance (or encouragement!) would be appreciated.

 

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Hi SunsetBay,

I have had some of the same problems with glazes over the years, and found a few things that made a difference in viewing the results of a Test fire.  How full was your kiln? This will often effect the glazes as there is not much conduction of heat in a kiln that is not full. One of my solutions also was to fire Test tiles and Test Shot glasses at the same time on one shelf level, with pots that I was not entirely worried over on another level. . . thus loading the kiln. The Test shot glasses allow me to see more of the surface and the inside outside effect of the glaze. You may try a firing of this sort to allow a better assessment of your tests.

 

best,

Pres

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12 hours ago, Pres said:

Hi SunsetBay,

I have had some of the same problems with glazes over the years, and found a few things that made a difference in viewing the results of a Test fire.  How full was your kiln? This will often effect the glazes as there is not much conduction of heat in a kiln that is not full. One of my solutions also was to fire Test tiles and Test Shot glasses at the same time on one shelf level, with pots that I was not entirely worried over on another level. . . thus loading the kiln. The Test shot glasses allow me to see more of the surface and the inside outside effect of the glaze. You may try a firing of this sort to allow a better assessment of your tests.

 

best,

Pres

I had all the test tiles on one shelf, but the kiln wasn't as full as I'd have liked--in addition to not having anything particularly tall in this load, I've been using new Advancer shelves, which leave me more room for another level than I'm used to, so I've been underestimating the amount of work I can comfortably fit into a glaze kiln! When I was loading the kiln, I thought about adding another shelf on top and just putting extra furniture on it, but  then didn't bother.

I intend to make a bunch of test shot glasses. I think I will also concentrate my glaze-search efforts on making test glazes, as much as I don't love the process, rather than continuing to try various combinations of commercial glazes. And for actual work, I'll just use the tried-and-true (if not super dear to my heart) commercial glazes. I guess that sounds like a plan.

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You might look up some of the glazes from Mastering Cone 6 glazes, and some of the glazes from Van Gilder, if you are not using any of these at this point. I fire glazes from both of these to a hard cone 6. Most of them are very durable, safe, and work very well if using dipping or spraying. I have used some of them for brushing also by working with a thicker version.

 

best,

Pres

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24 minutes ago, Pres said:

You might look up some of the glazes from Mastering Cone 6 glazes, and some of the glazes from Van Gilder, if you are not using any of these at this point. I fire glazes from both of these to a hard cone 6. Most of them are very durable, safe, and work very well if using dipping or spraying. I have used some of them for brushing also by working with a thicker version.

 

best,

Pres

I've tried some of them in the past but didn't fall in love. Except with a version of Van Gilder's oribe green that I mixed wrong and haven't been able to replicate! Lately I've been experimenting with John Britt's book EXPLORING MID-RANGE GLAZES and wondering if I should try seeing what's available on Glazy.org. (I've looked at the Ceramic Recipes here on the Ceramic Arts Network, but I've found it a bit difficult/annoying to navigate.) My goal is to switch to dipping, which is the way I learned. I am tired of brushing... 

Btw, thanks for your help! :-)

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17 hours ago, SunsetBay said:

I'm starting to think I should chicken out and go back to only commercial glazes and my kiln's preprogramed "slow glaze" program. But I'm tired of brushing glazes and interested in finding the color and combos I especially like for myself. Not sure where to go from here.  Any guidance (or encouragement!) would be appreciated.

 

Why not try getting larger quantities of glazes and start dipping and/or spraying? We use 5 gallon buckets from Lowes. On the commercial side these run $60-$90 to fill and prob a quarter of that from recipe. It is a bit of an investment but actually much cheaper per pot so cheaper in the long run.

We use commercial and recipes (several from mastering cone 6 book that pres referenced) and I test all of my glazes on our standard cone 5 with 20 minute hold schedule we use on all glazes, commercial and house. Can't imagine trying to having multiple ones  as it would get hard to keep track of what gets glazed when.  

Spoon rest might also be a thought for a good form to test on. They are quick to throw and have a good flat surface as well as walls to see the how/if the glaze breaks.

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You might even consider a ^6 Pinterest search as this has worked for me in finding glazes that allude me in old recipes. I have found several there.

I use Variegated blue along with some of the VG glazes for my pottery. Maybe not the effects you are looking for, but they work well in either dipping, or spraying. The variegated blue is pretty neat with the VG rutile green over top.

 

best,

Pres

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49 minutes ago, Stephen said:

Why not try getting larger quantities of glazes and start dipping and/or spraying? We use 5 gallon buckets from Lowes. On the commercial side these run $60-$90 to fill and prob a quarter of that from recipe. It is a bit of an investment but actually much cheaper per pot so cheaper in the long run.

We use commercial and recipes (several from mastering cone 6 book that pres referenced) and I test all of my glazes on our standard cone 5 with 20 minute hold schedule we use on all glazes, commercial and house. Can't imagine trying to having multiple ones  as it would get hard to keep track of what gets glazed when.  

Spoon rest might also be a thought for a good form to test on. They are quick to throw and have a good flat surface as well as walls to see the how/if the glaze breaks.

Commercial dipping glazes just seem so expensive! I've been using Amaco Potters Choice and Celadons mostly, and on top of the extra cost, they claim the formulation of the dipping glazes doesn't allow for the same results as the brushing in terms of layering and the interaction between glazes. 

Just out of curiosity, what is your "standard cone 5 with 20 minute hold schedule," and what does that 20-minute hold do in terms of final cone results?

 

46 minutes ago, Pres said:

You might even consider a ^6 Pinterest search as this has worked for me in finding glazes that allude me in old recipes. I have found several there.

I use Variegated blue along with some of the VG glazes for my pottery. Maybe not the effects you are looking for, but they work well in either dipping, or spraying. The variegated blue is pretty neat with the VG rutile green over top.

 

best,

Pres

I tend to be drawn to blues and greens that run together nicely.  Do you have any pictures of VG rutile green over variegated blue?  Or any other suggestions? I'll try Pinterest, and check out other sites, as well. Thanks!

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29 minutes ago, Pres said:

Check out my blog site, most of the later stuff is using these along with the Cream Rust and white liner that I have modified.

 

best,

Pres

 

28 minutes ago, Pres said:

Also check out my albums.

 

best,

Pres

I'll do both, thanks! 

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3 hours ago, SunsetBay said:

Just out of curiosity, what is your "standard cone 5 with 20 minute hold schedule," and what does that 20-minute hold do in terms of final cone results?

 

ya know I have never brushed although my partner does here and there for some layering  effects on more time consuming pieces, so on price can't really comment with a lot of firsthand knowledge. We have a lot of 5 gallon glazes. probably 25+ mixed by a shop in Tacoma and I probably have 8-9 in house recipes I still do, although some we will just use up and we have new ones we want to mix and try. Its been a while since I actually mixed anything but our Val's turquoise (great glaze recepe)  Our red is a mass firebrick (amoco?) and a couple of Celadons my partner uses I think are mass produced. Yes it is expensive upfront but we consider glazes (once you have them :-) to be a very cheap part of the process.

Ya know we have a couple of kilns with Bartlet controllers and programmed in our ramp, 20 minute hold and controlled cool down years ago, settled on one and have always used it. If a mid fire glaze (commercial or in-house) doesn't work well with our standard glaze program we would just not use it. Some of our glazes we just use for accents for this reason until they are gone.

The hold is for a last cone of heat work to even out the melt. We think it helps reduce glaze defeats such as pin holes etc. That 20 minutes gets a half bend on the cone 6 cone in a cone 5 program.

The difference here is that we try to move a kiln load or two a week when we're clicking and that leaves less time to fuss with individual glazes and pots. Because of that my advice may be of less use to you.  Pres is a retired pottery professor and his advice is golden. 

 

Edited by Stephen

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7 hours ago, Stephen said:

ya know I have never brushed although my partner does here and there for some layering  effects on more time consuming pieces, so on price can't really comment with a lot of firsthand knowledge. We have a lot of 5 gallon glazes. probably 25+ mixed by a shop in Tacoma and I probably have 8-9 in house recipes I still do, although some we will just use up and we have new ones we want to mix and try. Its been a while since I actually mixed anything but our Val's turquoise (great glaze recepe)  Our red is a mass firebrick (amoco?) and a couple of Celadons my partner uses I think are mass produced. Yes it is expensive upfront but we consider glazes (once you have them :-) to be a very cheap part of the process.

Ya know we have a couple of kilns with Bartlet controllers and programmed in our ramp, 20 minute hold and controlled cool down years ago, settled on one and have always used it. If a mid fire glaze (commercial or in-house) doesn't work well with our standard glaze program we would just not use it. Some of our glazes we just use for accents for this reason until they are gone.

The hold is for a last cone of heat work to even out the melt. We think it helps reduce glaze defeats such as pin holes etc. That 20 minutes gets a half bend on the cone 6 cone in a cone 5 program.

The difference here is that we try to move a kiln load or two a week when we're clicking and that leaves less time to fuss with individual glazes and pots. Because of that my advice may be of less use to you.  Pres is a retired pottery professor and his advice is golden. 

 

Okay, so at what temp do you program that 20-minute hold?

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the hold is once it reaches programmed high. I have seen a broad range of ranges quoted but the 20 minute hold on our kilns bends the cone 6 cone half way, programmed to cone 5. When you add a hold the heat work at that top temp continues the cone rise. If you did a cone 5 firing and had it hold for an hour you would likely bend a cone 7. Never tried having it hold at a ramp temp. Some specialized glazes may benefit from that to get a particular appearance. We do it at the end to even out the melt, let the glaze soak so to speak.

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If you want crystals, not like GlazeNerd's, in a matte look up Steven Hill's firing schedule. It really doesn't affect glossy glazes. He does fire to a cone 7, but as CAD Stephen has said, you can regulate that with the top temp hold. I would suggest to do what GlazeNerd has suggested. At 2050 until top temp, slow the firing down to 125*F per hour. I slow it down to 108*F to match the Orton SSB cone chart suggestion. This slowing down will allow pinholes to disappear. When the temp reaches 100*F less than top temp, I hold for 20 minutes to further smooth out pinholes. 

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On 8/14/2018 at 1:44 PM, SunsetBay said:

How do you do all that experimenting WITHOUT risking too many "real" pieces?

Piles of pinch pots.

Yes, so many choices, so little time. Since I'm still a relative newb to clay, I end up with a lot of unused bisque. If you're experimenting you might end up with odds and ends sitting around too. That said odds and ends on random clays don't often have the same results as glaze does on a pot, which they're designed for. I was about to throw out a certain store bought glaze because it just never did anything on a flat test tile. I decided to glaze a simple slab vase with it instead because wth I wanted a rustic look anyway, and suddenly it's the most beautiful glaze I've tried and I'm trying to learn to mix it myself. So when I really want to test something now I've learned to use little pinched bowls, with holes punched near the rims so they can be optionally hung; always at a premium for space in my studio. 

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I make two rounds for test tiles for glaze I’m making from a recipe where I see just a test tile as reference. 

Round 1 - Typical thrown or slab built test tile (thanks to John Britt) quick check on expected characteristics. I keep using that design. 

Second round - Small bud vases and small bowls with different clay bodies. I keep these as my reference pieces esp for glazes where gravity plays a big part. They do occupy a lot of space but they give me so much more info. The best part, if I don’t want them and they are decent looking they make good gifts. 

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I have a thread somewhere about small bud vases. But they make excellent test pots. Make them have ridges at the bottom to catch running glazes. You get to see how it does over a curve, over ridges, down the side and on the lip at the top. There isn't a better pot to test with IMO.

These are made with a very small amount of clay, you can fit a ton of them on your shelves, and they have self catching ridges on the bottom to catch those naughty glazes that run when you least expect it. They are about as big as your index finger tall. You just pull a small cup, and then bend the clay over into your finger and then form a lip, takes a few seconds.

Here is an example of what I am talking about:

18512646_444034779281943_917751642338204

 

Edited by Joseph Fireborn

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Joe, the test bud vases remind me of bud vases I used to make years ago. They were breasts, thrown, placed on a board, and then tapped the board for a little sag shift. They sold pretty well the one time, and at the same time, most of the purchasers were women. Just saying, but that was a long long time ago.

 

best,

Pres

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I have never tried to sell any of them. I'm sure they would sell if you made them well. I just throw them quick and dirty to get the pots made for the second glaze test after the original tile. 

Testing is all about having multiple stages of tests and results. If you go from tile to big pot your destination will sometimes be not a happy place. 

My other advice is to open your kiln with an open mind. This will help your frustrations. I used to mix glazes open the kiln and get a result that wasn't what I was after. I would instantly be frustrated and completely ignore how good the actual result was if I looked at it independent of my desires. Now some of the best glazes I have ever made are all those frustrated glazes that I hated when I opened my kiln.

So just a few things to think about. Testing is such a lengthy process both mentally and physically.

Take good notes.

Edited by Joseph Fireborn

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pres, photo, please.  

when i transferred to manhattan in 1985, i walked all over discovering the city.  a gallery on madison ave had a whole window full of breasts on various pieces of sinks, furniture and stuff made by a woman potter who lived only about 10 miles from my home in virginia.  cannot remember her name today, anyone know?   can still see herpink victorian house  when i go through Hillsboro occasionally.

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So I'm thinking this will be my new experimental plan:

Make a bunch of test tiles and small test cylinders (cups, yunomi, vases, whatever).  Make other pieces as usual.  Test glazes first on tiles and small cylinders, while using "tried and true" glazes on pieces that I don't want to risk (even if I dream of them looking more wonderful with my own glazes!). Try out so-far-successful test glazes on pieces I feel I can risk. And on and on, following the same cycle. Try to keep a balance so that each glaze firing includes a variety of tests as well as hoped-for "good" pieces.

Does that make sense? 

But this still doesn't solve my problem about how to test firing schedules. How would I incorporate that?

 

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When I took a workshop with Akira Satake, he said to the class, "try to always fire 95% of the work in your kiln to sale, and have the other 5% to continue to develop your line and test new things so that you don't get bored." I think his advice is very good if your selling work for a living. 5% of your kiln is probably just the perfect amount for a few test tiles and new ideas every load. 

But as far as your progression of pieces yes, I think that is about perfect: tile -> small cup -> seconds pot of your normal work -> actual pot for sale.

Testing firing schedules is a whole different ballgame. I wouldn't recommend adjusting your schedule while you are also doing testing. Only change one thing at a time.  Trust me, I spent so much time changing so many variables that I got confused and depressed many a times chasing results. 

If you really want to test schedules, make very minor changes each time for the specific results that you want. In general the longer the firing and the slower the cooldown the more variation in results you will get, this can be good and bad. Some glazes that are formulated on the border/poorly might all of the sudden become super dry/crystal and some glossy glazes might go matte. It really just depends on each particular glaze and how close they are to the border of being glossy/matte etc. Only you will know once you start testing them out.

If you have a schedule that your firing stuff your selling with, I would start by testing all your glazes with the schedule, as you can make money while testing. 

Last but not least, glazes don't travel well, so don't be upset if you followed the same exact schedule, recipe etc and get a completely different result.

Good luck and let us know how it goes.

 

 

Edited by Joseph Fireborn

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14 hours ago, Joseph Fireborn said:

Testing firing schedules is a whole different ballgame. I wouldn't recommend adjusting your schedule while you are also doing testing. Only change one thing at a time.  Trust me, I spent so much time changing so many variables that I got confused and depressed many a times chasing results. 

I think that is what has been happening to me--just thinking about making so many changes! I think I will take  your advice and go back to the schedule that seemed to be working, test new glazes, and go on from there.

14 hours ago, Joseph Fireborn said:

When I took a workshop with Akira Satake, he said to the class, "try to always fire 95% of the work in your kiln to sale, and have the other 5% to continue to develop your line and test new things so that you don't get bored." I think his advice is very good if your selling work for a living. 5% of your kiln is probably just the perfect amount for a few test tiles and new ideas every load. 

If you have a schedule that your firing stuff your selling with, I would start by testing all your glazes with the schedule, as you can make money while testing. 

At the moment, I don't sell that much; I'm not a production potter, it's been more of an avocation for me, and somehow this summer got too busy to keep up with pottery.  I would like to get myself on more of a schedule in the studio though, and go back to where I'm making more, as I seem to have done a few years ago. So...making money is not the primary goal at the moment. When I need to get finished stuff out of the way, then I'll need to sell! But I think I will take  your advice and go back to the schedule that seemed to be working, test new glazes, and go on from there. 

Thanks for your insight and advice!

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