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Tony Hansen's Thousand-Post TimeLine

I am the creator of Digitalfire Insight, the Digitalfire Reference Database and Insight-live.com. ... more

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Three visual glaze mechanisms make this piece unique

Three visual glaze mechanisms make this piece unique

Mechanisms" are specifics about the glaze application or preparation process, the materials, the chemistry or firing schedule that produce a specific visual effect. This is fired at cone 10R. It is made from a buff stoneware, Plainsman H550, and has L3954N black engobe on the inside and part way ... more

Saturday 16th February 2019

Possible to grind your own ceramic grade rutile?

Possible to grind your own ceramic grade rutile?

Yes, the granular and powdered grades are the same material. But grinding it is very difficult. Commercial ceramic grade powder is minus 325 mesh, the companies doing this obviously have very good grinding equipment. They also have patience because even in this efficient porcelain ball mill, 90 ... more

Wednesday 13th February 2019

When to use a hydrometer and when not to

When to use a hydrometer and when not to

If a glaze has already been mixed and gelled to give it thixotropy these things won't bob up and down to home in on the right level. If the glaze is watery enough there are other issues. The one on the right has a 1.0-1.7 scale. Since most pottery glazes need to be 1.4-1.5 specific gravity (40-50 on ... more

Tuesday 12th February 2019

More problems measuring glaze specific gravity using a hydrometer

More problems measuring glaze specific gravity using a hydrometer

First, the hydrometer is long, the only container I have is this graduated cylinder. I had to fill it just the right level so it reads near the top. OK, fine. But the hydrometer needs to bob up and down to find home. However this glaze has a creamy consistency, that prevents free movement. OK, I ... more

Tuesday 12th February 2019

Same glaze/body. One fired flawless, the other dimpled, pinholes. Why?

Same glaze/body. One fired flawless, the other dimpled, pinholes. Why?

The difference is a slow-cool firing. Both mugs are Plainsman M340 and have a black engobe inside and partway down on the outside. Both were dip-glazed with the GA6-B amber transparent and fired to cone 6. The one on the right was fired using the PLC6DS drop-and-hold schedule. That eliminated any ... more

Wednesday 6th February 2019

Do ceramic material powders go bad?

Do ceramic material powders go bad?

Many minerals are just ground up rocks, they were in the ground for millions of years (e.g. kaolin, feldspars, ball clays, bentonite, calcium carbonate, dolomite, talc, kyanite, wollastonite, etc), so the powders should last millions of years as well. Some are powderized man-made glasses and ... more

Wednesday 6th February 2019

Cracking casseroles. Why?

Cracking casseroles. Why?

The cracks happened on heat up (since they have opened up wide). A combination of issues contribute. The kiln shelves heat-sink the wide flat bottoms, vessel walls are thick, there is some unevenness of wall thickness and only a 30-minute hold at 220F to remove glaze water from the bisque (that ... more

Monday 4th February 2019

Vitrification can be obvious by simple visual inspection

Vitrification can be obvious by simple visual inspection

The unglazed surface of the left piece has a sheen, it is a product of glass development during firing to cone 6. That body is a 50:50 mix of a cone 8 stoneware and a low fire earthenware red (a material that would normally be melted by this temperature). Together they produce this dense, almost ... more

Monday 4th February 2019

Measuring glaze slurry specific gravity

Measuring glaze slurry specific gravity

This is the easiest way to measure the specific gravity of a glaze if it is not in a container deep enough to float a hydrometer (or if it is too viscous to enable free movement). Just counterbalance the empty graduated cylinder to zero (you can buy these at amazon.com), fill it to the 100cc mark ... more

Monday 4th February 2019

The matteness this glaze develops is dependant on the cooling rate

The matteness this glaze develops is dependant on the cooling rate

This is the G2934Y matte cone 6 recipe with a red stain (Mason 6021). The one on the left was fired using the C6DHSC slow-cool schedule. The one on the right was fired using the drop-and-soak PLC6DS schedule. The only difference in the two schedules is what happens after 2100F on the way down (the ... more

Monday 4th February 2019

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Chemistry plus physics. The on-line successor to desktop Insight. Get an account for as little as $15. It does so much more.

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What people have said about digitalfire

• Again, thanks for being such a resource to potters over the years!

• THANKS so much for all of the information you share at no cost. It really helps me. I feel a little guilty for not subscribing to Insight, but I am working toward that. You have truly changed the way I think about glaze, and I appreciate you. thanks. future subscriber/fledgling potter

• You have been more than helpful and I will recommend your site to all of my pottery friends. Once again a big thank you.

• I am very much appreciative of the work you are doing.

• Hi Tony, First, your website is the most knowledgeable and accurate information available on the internet today. THANK-YOU!

• I'm only just beginning to learn about pottery and glazing. I have learned more from your website than anything I have read!

• I have had previous communication with you Tony, and want to say that you do a great job. Very informative. All of my former students are aware of your expertise.


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What people have said about Insight-Live

• Thanks for doing the timeline. I’ve told you before but it never hurts to say it again, this is great stuff and I get so much info from your posts. Extremely valuable!

• I have went to this website for technical info for over 4 years now :) IT is absolutely amazing!!!

• You are a real gem, your work really help me a lot.

• It's very impressive work you do. Thanks you for providing it.

• I wanted you to know that, you have a fantastic program. Every serious potter should use it. And it would be a good starting curriculum for high school and college to learn from. Thanks for, I would imagine, many hours in developing time. Kudos sir. I hope, by God's good will that I will be able to enjoy it for any years to come.

• I teach glaze technology at ... the information that you display on your this website is absolutely fundamental for my teaching.

• Yet again, you provide a quick answer not easily found elsewhere (a bowl was befuddling me with wall cracks that never made it to any edges.)


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