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Joseph Fireborn

Quick Question: Progressing From Test Glaze Batches To Production Batches

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So I successfully mixed some 400G test batches. I was very happy with them. But I have read that it would be foolish to jump to a 3000 gram batch right from a 400G test batch. Where is the middle ground? Do I move up to like 1500G batch and see if it looks the same? Then if thats good, go to a 3000-5000 gram batch depending on how happy I am with the glaze?

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1000g is about an ice cream pail of glaze. Once you start applying your new glaze to things larger than a test tile, you begin to notice things like how it applies, if it settles out in the bucket, and how far it really does run. If it presents problems, you aren't over-committed to a batch that you have to dispose of somehow, and you can still tinker with things.

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400 g is very easy to mess up test wise unless you are super careful . I would mix up that 1000-1500 batch for another test.

Back in my glaze calc class (1973-4) 500 to 1000 was the test batch size.Its amazing I have any memory at all of those times.

Mark

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You are much braver that I am. If/when I shift from that 500g test batch, I will move to a 2 Gallon bucket version (approx.2,500- 3,000g) and will stick with that size for a couple of batches and several firings.  Nothing becomes a 5 Gallon bucket size 10-15,000g until I am completely convinced that it is pretty predictable and that I intend to use a lot of it.

 

, it does make me feel better knowing that others share the same concerns about moving up from test batch sized mixes.

 

-Paul

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Guest JBaymore

You don't "know" that test glaze until you've use it is LOTS of tests and firings.  I'd say got for the 1000.... then got for 3000 if that 3000 is looking like what you want... then 5000.... and so on.

 

Use the need to have things to set the glaze ON as an excuse to make simple 1 lb. thrown cylinders as throwing development exercises.  If you simply must have some tangible product of those throwing exercises..... maybe make simple cylindrical flower vases or add a handle and make mugs (if the glaze is expected to be suitable for that).

 

Kill two birds with one stone.

 

best,

 

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

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I like base 10.

I mix up one paper coffee cup of test at 100grams. Then you can easily see what percentage of oxides, opacifiers, bentonite etc to add.

From 100 grams it's an easy jump to 1000 gr., which is an icecream pail. all you do is add zeros to all your ingredients.

Then, easy move to 10,000 grams which is a 5 gallon bucket.[add more zeroes]

Your test tiles should have a vertical aspect to them so that you can see if the glaze runs. I have all these beautiful flat glaze tests, but then you put them on a mug that has a crack in the bottom, and they run TWO INCHES down the side.

Ain't ceramics fun?

TJR.

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I made a 400G batch my first batch, and I put it on vertical test tiles, and I also dipped a few bud vases into it so I could get a better look at the glaze. I have the bud vases sitting on their sides right now with lemon slices sitting on them. So far no change in color or texture. Next will be sitting them in some dish detergent. If all goes well I will be moving up to a 1000G test batch this next firing. Thanks for everyone's help.

 

And yes! Ceramics is so much fun!

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Guest JBaymore

Remember that a 'lemon slice test' for glaze durability relative to any toxicity questions (if toxins are present in the formula) only tells you if it FAILS...... not if it passes.  It will also tell you about some visual erosion issues.

 

best,

 

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

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So I have the mastering cone 6 glazes book, and he runs through those test that I am going to run my test pieces through each time I make a bigger batch. However he says the only true way to test is to send off to a lab. When do I send a cup off to a lab? Is that what everyone here does for a production glaze? I mean I think the glaze I am using has very mild ingredients, or at least according to John Britts book, he stated that his whites were much less toxic than other glazes. Did I read this incorrectly? I am not really sure what ingredient to test for leeching in this glaze recipe?

 

Folk Art Guild White 

 

F4-Feldspar(Minspar 200) 

Spodumene 

Silica 

Kaolin 

Dolomite 

Gerstley Borate 

 

Red Iron Oxide

Tin Oxide 

Bentonite

 

 

SO MUCH TO LEARN! I feel overwhelmed sometimes. So thankful for all of you guys and gals helping me out along the way.

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Guest JBaymore

There are two general broad "quality issues" to think about with glazes on your work:

 

1. ) Visual/physical durability, archival integrity, customer satisfaction

 

2.)  Technical stability, legal conformity, liability

 

 

As far as potential toxicity goes....... if nothing in the glaze is toxic, then you do not have any liability concerns there if the glaze is not stable.  If you take a glaze that is not stable, and alter that recipe in some manner to add something that IS potentially toxic....... that story changes.

 

This has nothing to do with how a customer perceives your work to "stand up" (#1 above).    

 

Lab testing is for when you have resolved a lot of other stuff.  It is not expensive... but don't spend money ion it until it is time.  Learning to use software like Insight can go a long way to understanding the potential of a particular glaze under certain use conditions.  (Yes....... the road is long. ;) )

 

best,

 

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

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I like base 10.

I mix up one paper coffee cup of test at 100grams. Then you can easily see what percentage of oxides, opacifiers, bentonite etc to add.

From 100 grams it's an easy jump to 1000 gr., which is an icecream pail. all you do is add zeros to all your ingredients.

Then, easy move to 10,000 grams which is a 5 gallon bucket.[add more zeroes]

 

TJR.

 

 

It's easier for me to work in base 10 also. I also get used 250 ml saline irrigation bottles from work. Instead of discarding the irrigation bottles, I take them home. They are perfect for 100 gm tests.

 

Jed

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I like base 10.

I mix up one paper coffee cup of test at 100grams. Then you can easily see what percentage of oxides, opacifiers, bentonite etc to add.

From 100 grams it's an easy jump to 1000 gr., which is an icecream pail. all you do is add zeros to all your ingredients.

Then, easy move to 10,000 grams which is a 5 gallon bucket.[add more zeroes]

 

 

This works for some glazes, but none of the 15 glazes currently in use in my studio will go 10,000 grams to a bucket. They are all 8,500 to 9,0000 grams to 5 gallons. I found that my cone 10 glazes tended to fit the 10,000 gram rule better because they were typically lower in clay content than the cone 6 glazes I'm using now. But even some of my cone 10 glazes were 9,000g to a bucket, like those that were high in feldspar (50%) or iron oxide (10%).

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I like base 10.

I mix up one paper coffee cup of test at 100grams. Then you can easily see what percentage of oxides, opacifiers, bentonite etc to add.

From 100 grams it's an easy jump to 1000 gr., which is an icecream pail. all you do is add zeros to all your ingredients.

Then, easy move to 10,000 grams which is a 5 gallon bucket.[add more zeroes]

 

TJR.

 

 

It's easier for me to work in base 10 also. I also get used 250 ml saline irrigation bottles from work. Instead of discarding the irrigation bottles, I take them home. They are perfect for 100 gm tests.

 

Jed

 

My last batch of glaze tests in Tim Horton coffee cups-the bottoms fell out. So you are laughing. I teach high school, so not a lot of 250ml. saline bottles lying about.

T.

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You metric people! How dare you make more sense than the stupid system Americans use here!

*is American*

Man, Grype...you make 400g batches?! Chenoweth is right--you ARE brave! :) I never make batches outside of 5 or 1 numbers (like 500 or 1000). The potential for my guinea brain ruining the glaze is just too high. Some ingredients are way too expensive for me to risk--My shiny clear only has three ingredients, but every speck is precious when you're broke, lmao!

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