7 sources, every one opened at its publisher — including the European directive, read from the directive itself rather than from anybody's summary of it. A glaze defect is not a bad recipe. It is a mismatch — and the two commonest defects are that same mismatch in opposite directions. As a kiln cools, the glaze and the clay underneath it both shrink. If the glaze shrinks more, it ends up stretched across a surface that will not come in with it: left in tension, it cracks. That is crazing. If it shrinks less, the body contracts out from under it and squeezes it: left in compression, it lets go and flakes off. That is shivering. One axis, two ends, and the cure for one is the cause of the other. Which is why applying the wrong fix does not merely fail — it walks the glaze off the far end of the tolerance. The chapter that will save the most firings A crazed pot comes out of the kiln and the instinct, everywhere, is to change the schedule. Cool more slowly. Add a hold. Drop and soak. It does not work, and the source is blunt about it: glaze fit "can rarely be fixed by firing differently (that just delays it)". Fit is a property of the two materials, not of the journey. A slower cool postpones the moment the glaze gives way — sometimes past the point where you unload the kiln and call it a success. The stress is still there. It is released later, on a shelf, or in a customer's hands. Delayed crazing is the normal case, not the exception. A piece that leaves the kiln clear and crazes a fortnight later has not developed a new fault. It has finished expressing the one it already had. A cone is not a temperature The Orton Foundation defines heatwork as "the combined effect of time and temperature on the ware you are firing". A cone reads the whole journey, not the peak — which is why two potters firing "to cone 6" can be firing to places 58 °C apart. Their published equivalents: the same cone 6 bends at 1185 °C fired slowly and 1243 °C fired fast. And their own example — a kiln set to reach 2232 °F in one hour leaves porcelain grossly underfired, needing roughly nineteen further hours to mature. Same peak temperature, entirely different pot. And the advice everybody gives that is wrong Crawling — glaze pulled into islands with bare clay between them — is almost universally blamed on dust or oil on the bisque. The source says dust almost never causes it, adding, pointedly, that "glaze is a mix of dust and water!" Crawling is a drying failure. The glaze layer shrinks too much as it dries and cracks, and those cracks become the points the melt pulls back from in the fire. If you cleaned your bisque carefully and it crawled anyway, you were never looking at the right variable. What is in the 42 pages 10 full-page plates, because a glaze fault is diagnosed by eye and no diagram shows the difference between a rolled crawl edge and a sharp shiver flake. A 14-fault finder, arranged by what you can see rather than by what is wrong — find the row, read the chapter. Crazing against shivering, as one measurement with the sign flipped, and which oxides move the dial in which direction. Glaze crack or body crack? Six ways to tell them apart, including the ring test — because if it is a body crack, nothing about the glaze applies. Crawling, pinholes and blisters, each separated by appearance and traced to the stage of firing it came from. Heatwork: the published cone equivalents at all three heating rates, why your controller disagrees with your cone, and why the cone wins. The bisque firing, which decides faults that only appear in the glaze firing: gas release continues to 950 °C, so 700–950 is the window to fire slowly through. The fixes in the order the source gives them — finer silica, then more silica, then flux substitution, then boron, then frit — with what each one costs you in colour and surface. A firing and test-tile log, because the schedule is half the result and almost nobody writes it down. Safety, and one number this book will not print Crazing is not cosmetic: a newly fired crazed piece loses a large multiple of its strength, the cracks over a porous body produce what the source calls a bacteria zoo, and crazed glaze is inherently more leachable. Shivering is the more urgent — the flakes are described as razor sharp. The book quotes Council Directive 84/500/EEC directly for the legal migration limits, and the test that establishes them: 4% acetic acid at 22 °C for 24 hours. Cold vinegar standing overnight, not boiling. The US figures are deliberately absent. FDA CPG Sec. 545.450 exists and is named, but its action-level table was not readable at the publisher. Secondary sources quote it and agree with each other; agreement between secondaries is not a reading. The book says so in that chapter rather than quietly filling the gap. What it does not do No glaze recipes — recipes are the one thing this subject is not short of, and a recipe you cannot diagnose is a recipe you cannot adjust. No brand of clay, frit, glaze or kiln named anywhere. And no claim that a particular pot is safe for food, because that is a laboratory measurement rather than a reading exercise. What you get PDF — 42 pages, US Letter, prints cleanly at home. There is deliberately no EPUB: the value is full-page plates and a fault-finder table, and a reflowable format destroys both. 10 plates, 5 figures drawn from the published numbers, 14 faults, 3 printable worksheets and 7 numbered sources with a note at the foot of every page that uses one. Instant download. Nothing ships.