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Tony Hansen's Thousand-Post TimeLine

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


A flameware recipe after mixing it. Are they kidding?

This is a flameware, made from a recipe promoted by a popular website. Are they serious? How could you throw this? Maybe it is possible, but we need an explanation. How could the page fail to mention how coarse this surface would be? How porous and weak ware would be? We find many body and glaze ... more

Monday 27th March 2017

This leaching mug needs a liner glaze. Seriously!

Three cone 6 commercial bottled glazes have been layered. The mug was filled with lemon juice over night. The white areas on the blue and rust areas on the brown have leached! Why? Glazes need high melt fluidity to produce reactive surfaces like this. While such are normally subject to leaching, the ... more

Monday 27th March 2017

Two glazes. One crawls, the other does not. Why?

The glaze on the right is crawling at the inside corner. Multiple factors contribute. The angle between the wall and base is sharper. A thicker layer of glaze has collected there (the thicker it is the more power it has to impose a crack as it shrinks during drying). It also shrinks more during ... more

Monday 27th March 2017

Potters can learn from how glazes are fit on ceramic tile

These are thermal expansion curves for body, engobe and glaze (from a dilatometer, a device that measures it against increasing temperature). The upper line is the body. The center line is the engobe. The lower line is the glaze. The ceramic tile industry is very conscious, not only of glaze-fit but ... more

Monday 27th March 2017

Two stains. 4 colors. Will the guilty oxide please step forward.

We are looking at two pairs of samples, they demonstrate why knowing about glaze chemistry can be so important. Both pairs are the same glazes: G2934 cone 6 matte and G2916F cone 6 glossy. The left pair has 5% maroon stain added, the right pair 5% purple stain. The red and purple develop correctly ... more

Monday 27th March 2017

An engobe is shivering off the rim of a low temperature mug

Classic terra cotta bodies are not vitreous, so engobes used on them need to have similar low fired shrinkage. But when terra cottas are fired above cone 04 they start to mature and fired shrinkage increases quickly, flaking off engobes that do not have sufficient added frit (to increase their ... more

Tuesday 7th March 2017

A glaze incompatible with chrome-tin stains (but great with inclusion stains)

Left: a cone 6 matte glaze (G2934 with no colorant). Middle: 5% Mason 6006 chrome-tin red stain added. Right: 5% Mason 6021 encapsulated red stain added. Why is there absolutely no color in the center glaze? This host recipe does not have the needed chemistry to develop the #6006 chrome-tin color ... more

Monday 6th March 2017

Tuning the degree of gloss in a colored matte glaze

Matte glazes have a fragile mechanism. That means the same recipe will be more matte for some people, more glossy for others (due to material, process and firing differences). In addition, certain colors will matte the base more and others will gloss it more. It is therefore critical for matte glaze ... more

Monday 6th March 2017

How to test compatibility between engobe and terra cotta body

Slips and engobes are fool-proof, right? Just mix the recipe you found on the internet, or that someone else recommends, and you are good to go. Wrong! Low fire slips need to be compatible with the body in two principle ways: drying and firing. Terra cotta bodies have low shrinkage at cone 06-04 ... more

Sunday 5th March 2017

A settling, running glaze recipe gets a makeover

The original cone 6 recipe, WCB, fires to a beautiful brilliant deep blue green (shown in column 2 of this Insight-live screen-shot). But it is crazing and settling badly in the bucket. The crazing is because of high KNaO (potassium and sodium from the high feldspar). The settling is because there ... more

Monday 13th February 2017

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What people have said about digitalfire

• First I'd like to thank you about your site. It's outstanding site.

• 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.

• Thank you so much. This is what a good business looks like; great product, immediate response from the owner no less, and over the top service.

• I normally do not comment on articles I find, but this is amazing. Thank you so much for providing this information! I am a ceramics student in my BFA year, and this is the most comprehensive and helpful information I have found on creating a porcelain casting slip.

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

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

• What a lovely surprise to find you online. As I've changed to Broadband you were allowed through and I'm really pleased. I'm quite sure your site will be a source of much inspiration.

• First I want to thank you for creating and maintaining your web site. I started as a potter and moved into ceramic engineering over the course of my career and your web site has helped me all the way. Currently I am working on digital ceramic ink jet printing.

• I have been thinking to thank you for the great help your interest in ceramics continues to inspire in my studio.

• I want you to know how much it means to me to have you help with my questions. I have been doing pottery for over 20 years and never new this stuff. I feel so responsible for my glazes leaching and stupid to not have known, and the stress or waiting for the lab test results has been eating me up.

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