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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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An additive that will make a glaze crawl

An additive that will make a glaze crawl

Light magnesium carbonate has been added to a low temperature terra cotta white glaze (about 10%). It induces crawling. It also mattes the glaze because it sources MgO. “Snakeskin” recipes to produce this effect can call for much higher percentages, but of course, fired properties (like color, gloss, thermal expansion) will be much more affected.

Thursday 19th July 2018

When using stains, customize the percentage, host glaze and firing schedule

When using stains, customize the percentage, host glaze and firing schedule

These are G2926B clear glazes with stains added and fired at cone 6. The one on the left has 11% Mason 6021 encapsulated red. It is pebbling the surface (even with 2% zircon), it may be at the upper end of its firing range. Possible solutions are faster firing up and down to give the stain less ... more

Tuesday 3rd July 2018

The difference between a slip and an engobe

The difference between a slip and an engobe

L3685U slurry was applied to the insides of both of these mugs. But on the left it is a "slip", on the right an "engobe". Why? The left mug only has a thin layer, applied by painting a gummed version on (at leather hard stage). On the right a gelled slurry was poured into the leather hard piece, ... more

Tuesday 3rd July 2018

Terra cotta transparent glaze: Too thick and just right

Terra cotta transparent glaze: Too thick and just right

When clear-glazing terra cotta ware (Plainsman L215 here) an important issue is glaze thickness. The mug on the left was double-dipped (so suspended bubbles are present in the handle recess, thumb-hold and along its edges). The glaze needs to be thick enough so that it feels glassy smooth but thin ... more

Tuesday 3rd July 2018

Terra cotta with transparent glaze: At cone 04, 03

Terra cotta with transparent glaze: At cone 04, 03

The body is Plainsman L215 (bisque fired at cone 06). The glaze is G2931K. There is good reason to glaze fire to cone 03 instead of 04. Although these commercial underglazes work the same the clay fired at cone 03 is stronger and a deeper red color. But best of all, the glaze is more transparent ... more

Tuesday 3rd July 2018

Ravencrag rutile blue vs. Alberta Slip floating blue at cone 6

Ravencrag rutile blue vs. Alberta Slip floating blue at cone 6

Both have been applied at moderate thickness on Plainsman M325 (using a slurry of about 1.43-1.45 specific gravity, higher values end up getting them on too thick). The Ravenscrag version highlights contours better (the edges are black because of the black engobe underneath). It also produces the ... more

Tuesday 3rd July 2018

Manually programming a typical electric hobby kiln electronic controller

Manually programming a typical electric hobby kiln electronic controller

I document programs in my account at insight-live.com, then print them out and enter them into the controller. This controller can hold six, it calls them Users. The one I last edited is the one that runs when I press "Start". When I press the "Enter Program" button it asks which User: I key in "2" ... more

Thursday 28th June 2018

Thrown pieces made from pure Grolleg and EP Kaolin

Thrown pieces made from pure Grolleg and EP Kaolin

These have just been thrown on the wheel. They were slurried and dewatered to about the same water content and the same amount was thrown on a potters wheel to compare the plasticity. While the Grolleg is stickier and dewaters a little slower, it is not nearly as plastic. Curiously, New Zealand ... more

Sunday 24th June 2018

EPK fired bar (top) vs Grolleg at cone 10R. Why shrinking more?

EPK fired bar (top) vs Grolleg at cone 10R. Why shrinking more?

From these (SHAB test bars) EP kaolin appears to have a much higher fired shrinkage. But half of that happened during drying. Still, EPK shrinks 4% more during firing. Yet Grolleg produces more vitrified porcelains. The EPK bar also appears be whiter. Yet in a porcelain body Grolleg fires much ... more

Sunday 24th June 2018

Precipitate can forms in fritted glazes, remember to screen it

Precipitate can forms in fritted glazes, remember to screen it

Potters often store glazes for long periods so tiny spherical precipitate particles can form. These were found in a months-old bucket of G2926B (M370 clear) cone 6 clear glaze (about 2 gallons). These can appear over time, depending on factors like temperature, electrolytes in your water or ... more

Saturday 16th June 2018

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