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Tony Hansen's Thousand-Post TimeLine

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


An extreme extremely runny glaze at cone 6. Is there a cost?

This recipe melts to such a fluid glass because of its high sodium and lithium content coupled with low silica levels. Reactive glazes like this produce interesting visuals but these come at a cost that is more than just the difficulty in firing. Recipes like this often calculate to an extremely ... more

Sunday 4th December 2016

The blue color in this porcelain develops more as maturity increases

These fritted porcelain bars are fired at cone 06, 04, 03 and 02 oxidation (bottom to top). The body contains 0.2% blue stain. Notice that almost no color develops at the lowest temperature. Glass development is needed.

Friday 2nd December 2016

A tiny percentage of blue stain in a porcelain has amazing power

The top porcelain bar has only 0.07% Mason 6336 blue stain added (vs. none in the bottom bar). This is a low fire frit-ware body fired at cone 03 in oxidation. At a slightly lower percentage (e.g. 0.05%) this porcelain will have the same color as a cone 10 reduction one (when covered with a transparent glaze). However adequate glass development is needed before the blue color develops.

Friday 2nd December 2016

Maroon and white mug before and after firing: What a difference!

The outer glaze is Ravenscrag GR6-E Raspberry, the bright maroon color is a product of the surprising interaction between the 0.5% chrome oxide and 7.5% tin oxide present. That small amount of chrome is only enough to give the raw powder a slight greenish hue, hardly different than the clear liner. ... more

Friday 2nd December 2016

Is Lincoln 60 really a fireclay? Simple physical testing says...

Materials are not always what their name suggests. These are Lincoln Fireclay test bars fired from cone 6-11 oxidation and 10 reduction (top). The clay vitrifies progressively from cone 7 upward (3% porosity at cone 7 to 0.1% by cone 10 oxidation and reduction, bloating by cone 11). Is it a really fireclay? No.

Wednesday 23rd November 2016

Reduction Polar Ice vs. Oxidation Polar Ice

Polar Ice (Plainsman Clays) has been fired to cone 10R (left). This is beyond the recommended cone 6 range, but it worked well in this instance. The result is even more translucency and a translucency of a different character: blue! This looks much more like real blue polar ice.

Monday 14th November 2016

Outside tenmoku glaze meets inside transparent in a straight line at the rim

An example of how a liner glaze can meet another at the rim of a piece. This it quite simple to do. The technique is especially practical where mug walls are thin and cannot absorb enough water to dry the glaze after immerse-dipping. It is essential where the outer glaze is potentially leachable, or ... more

Saturday 12th November 2016

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

Saturday 12th November 2016

A fluid melt glaze bleeds much more into adjoining ones

The outer green glaze on these cone 6 porcelain mugs has a high melt fluidity. The liner glaze on the lower one, G2926B, is high gloss but not highly melt fluid. Notice that it forms a fairly crisp boundary with the outer glaze at the lip of the mug. The upper liner is G3806C, a fluid melt high gloss clear. The outer and inner glazes bleed together completely forming a very fuzzy boundary.

Saturday 12th November 2016

Can a cone 6 functional glaze having only whiting and feldspar melt enough?

This flow test compares the base and base-plus-iron version of a popular CM recipe called "Tenmoku Cone 6" (20% whiting, 35% Custer feldspar, 15% Ball Clay and 30% silica, 10% iron oxide). Although iron is not a flux in oxidation, it appears to be doing exactly that here (that flow is just bubbling ... more

Saturday 12th November 2016

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What people have said about digitalfire

• Great site btw. Besides getting married its the next best thing I did.

• I have only been involved with ceramics and glazing for about a year now, and I'm hungry for knowledge. The wealth of information you have on your site and in your products has just been great.

• Wow. Thanks. That is so great. I also thank you for making so much material available on your web site. You obviously care deeply about the craft and teaching others.

• I have not been pottery long and I have decided to try to make my own glazes. Your web site is great. I like your cone 6 base glaze.

• 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.

• Just wanted to share the good news with you. Couldn't be doing it without all the help you have given us over the years!

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

• Also, as a side note, this website is an excellent resource and I appreciate the fact that all this info is available on the web! Not only that, but I have found the information to be accurate, dependable and thorough, which is difficult to find anywhere.

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