Javascript must be enabled in the security or content
settings of your browser for this site to work properly

To learn more about cookies search for HTTP cookie at

Click here for information about DIGITALFIRE Corporation

Tony Hansen's Thousand-Post TimeLine

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


How can you test if an engobe fits your clay body?

This is part of a project to fit a fritted vitreous engobe (slip) onto a terra cotta at cone 02 (it fires harder there). Left: On drying the red body curls the bi-clay strip toward itself, but on firing it goes the other way! Right: Test bars of the white slip and red body compare their drying ... more

Thursday 27th October 2016

Glossy blacks are best made adding a black stain to a quality base transparent

The glaze on the left is called Tenmoku Cone 6. It is 20% calcium carbonate, 35% Custer feldspar, 15% OM4 Ball Clay and 30% silica, 10% iron oxide. If you have any experience with glaze you will note two things that a fishy here: There is no boron, lithia or zinc sourcing material. How can this melt ... more

Thursday 27th October 2016

Low fire nirvana: Use commercial underglazes but make your own clear over glaze

Decorate ware with the underglazes at the leather hard stage, dry and bisque fire it and then dip-glaze in a transparent that you make yourself (and thus control). These mugs are fired at cone 03. All have the same transparent glaze (G2931F), all were decorated with the same underglazes. Notice how ... more

Wednesday 26th October 2016

Are frits partially soluble? Yes, many are.

These 1 mm-sized crystals were found precipitated in a couple of gallons of glaze containing 85% Ferro Frit 3195. They are hard and insoluble. Why and how to do they form? Many frits are slightly partially soluble and the degree to which they are are related to the length of time the glaze is in ... more

Wednesday 26th October 2016

With porcelains, poor plasticity gets worse at the leather hard stage

This porcelain becomes quite brittle as it gets stiffer making it difficult to make these cuts in the foot ring. This creates extra sponging work when it is dry. It also means that dry strength will be low. Porcelains do not need to be this way, plenty of white burning bentonites are available (although they increase cost).

Tuesday 25th October 2016

Laguna B-Mix on Steroids! I have wedged in 10% and 20% Plainsman P.E.S.

Both pieces have a transparent glaze, G1947U. The bar in the front is PES (Performance Enhancing Substance)! PES is made from 50:50 Plainsman A1 and St. Rose Red, it behaves like a red fireclay. BMix has some specks anyway, so why not concentrate them into some awesome aesthetics? The addition does ... more

Tuesday 25th October 2016

Now that is a translucent porcelain!

These are two cone 6 transparent glazed porcelain mugs with a light bulb inside. On the left is the porcelainous Plainsman M370 (Laguna B-Mix 6 would have similar opacity). Right is a zero-porosity New Zealand kaolin based porcelain called Polar Ice (from also)! The secret to ... more

Tuesday 25th October 2016

Alberta and Ravenscrag Slips on two cone 10 reduction whiteware bodies

Laguna B-Mix (left) and Plainsman H570 (right). They are fired to cone 10R with pure Ravensrag Slip on the inside and a 50:50 mix of Ravenscrag and Alberta Slips on the outside.

Tuesday 25th October 2016

Can a decal firing melt a glaze? Yes!

Typical zero-boron high temperature glazes will not soften in a 1500F decal firing. But low temperature glazes will (especially those high in boron). Even middle temperature ones can soften. G3806C, for example, is reactive and fluid, it certainly will. Even G2926B, which has high Al2O3 and SiO2, ... more

Monday 24th October 2016

Cone 6 rutile floating blue effect lost. Then regained.

Left: What GA6-C Alberta Slip rutile blue used to look like. Middle: When it started firing wrong, the color was almost completely lost. Right: The rutile effect is back with a vengeance! What was the problem? We were adjusting firing schedules over time to find ways to reduce pinholing in other ... more

Thursday 20th October 2016

Test, Document, Learn, Repeat in your account at

Login to your online account

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

Conquer the Glaze Dragon With Digitalfire Reference info and software

Still available for Mac, PC, Linux

Interactive glaze chemistry calculations. Download it from the Files panel in your account at (no extra charge).

How to reach us

From within your account at or

What people have said about digitalfire

• I have used this site on numerous occasions for glaze information and always get a personalized answer, quickly, and plenty of help. They go above and beyond the call of duty!! They are a excellent website for potters!!

• 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.

• Great site you have here, I am the ceramics tech at the University of .. the info. on your site is a great help to my students.

• I have used your web sight to help with information for teaching Glaze Formulation. I have sent my students here.

• I have found the glaze information on your site really helpful for quite some time now. I like the way that there is an emphasis on problem solving and understanding how things work, rather than just offering recipes that might work.

• Your website has become an excellent resource for students and professionals alike, congratulations.

• Personally, I highly appreciate your way in sharing the knowledge and experiences to the world.

• Your web is great!

• 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.

• Thanks for the great resource Digitalfire is. I could not make our studio glaze without it.

To see more (at random) refresh this page

DigitalFire Logo

1 - 530 Allowance Ave, Medicine Hat, Alberta, Canada T1A 3E3
(403) 527-7508
Privacy Policy