Digitalfire Ceramics Technical Articles
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An overview of the technical challenges a technician in the tile industry faces in making good tiles from the least expensive materials and process possible.
A complete discussion of how ceramic pigments and stains are manufactured and used in the tile industry. It includes theory, types, colors, opacification, processing, particles size, testing information.
Theory and description of various ceramic ink and inkjet printing technologies for ceramic tile, the issues technicians and factories face, inket printer product overview.
A history, technical description of the process and body and glaze materials overview of the monoporosa single fire glazed wall tile process from the man who invented it.
A detailed look at what materials contain organics, what its effects are in firing (e.g. black core), what to do to deal with the problem and how to measure the amount of organics in a clay material.
A technical overview of the bodies, firing, processes and types of porcelain tiles against the backdrop of the historical development of the process since the 1970s.
There are a wide range of soluble materials that can be in clay, this article enumerates them, provides procedures on identifying and measuring them and outlines what to do about the problem.
A detailed discussion of the oxides and their purposes, crystallization, phase separation, thermal expansion, solubility, opacity, matteness, batching, melting.
Understanding the functions of each of the major materials in a high temperature porcelain gives you the ability to tune their amounts and choose brand names to make the porcelain you want.
The classic white ball clay talc casting and modelling recipe has been used for many years. It is a dream to use as long as you are aware of the problems and risks.
Some starting recipes for stoneware and porcelain with information on how to adjust and adapt them
This article helps you understand a good recipe for a red casting body so that you will have control and adjustability.
An overview of the major types of organic and inorganic binders used in various different ceramic industries.
A detailed look and what deflocculation is, what the most common types of deflocculants are (there are many) and how they compare in function
A company using a rubbery casting slip and depending on outside technical support discovers how simple it is to fix a slip that is drastically wrong using simple testing.
A small tile decorating company diagnoses problems with commercial bisque tiles and seeks help to find the type of tiles available in the past.
How can you be sure that the porosity of your fired ceramic ware is low enough to prevent freeze-thaw breakdown in the winter?
A little background information about the origin and an explanation of what paper clay is
How can two potters have completely different opinions about the plasticity and workability characteristics of the same clay body
Guidelines for collecting, testing, reprocessing scrap clay in a multi-person ceramic studio.
Anything can be dried if it is done slowly and evenly enough. To dry faster optimize the body recipe, ware cross section, drying process and develop a good test to rate drying performance.
Jonathan Kaplan overviews clay bodies, body materials and body types, how they are formulated and tested, how to protect yourself when buying prepared bodies, how to take responsibility.
Why should potters who make wide platters or plates throw on plaster bats rather than wood or plastic? To avoid drying cracks.
Being able to make good consistent test bars and fire them in a consistent and proper way is a basic requirement of getting valid results for shrinkage and porosity measurement.
Learn to test your clay bodies and recording the results in an organized way and understanding the purpose of each test and how to relate its results to changes that need to be made in process and recipe.
Understanding the magic of deflocculation and how to measure specific gravity and viscosity, and how to interpret the results of these tests to adjust the slip, these are the key to controlling a casting process.
There is a big gap between industrial and studio gas kiln technology. Even the basic theory behind how to construct and file are different. Can potters learn?
Electric hobby kilns are certainly not up to the quality and capability of small industrial electric kilns, but if you are aware of the limitations and take precautions they are workable.
By understanding what sorts of change art taking place in the ware at each stage of a firing you can tune the curve and atmosphere to produce the best possible ware.
Interpreting how high a kiln fired based on the look of the cones can be a much more complicated matter than it might first appear.
In this NCECA 97 Presentation Nils Lou overviews his personal experiences using RFCs over a period of 25 years.
Ceramic industry can fire much faster and deal with much heavier objects than potters can, how do they do it. The answer is they pay more attention to the basics, it is all common sense and good equipment.
A list of ceramic industry and art magazines from around the world
Ceramic art and technical book sources from around the world
Potters often run operations that are on the edge of control and they tolerate production and ware problems that industry would not. However ethics an honesty with yourself will soon or later demand a better knowledge of process and materials.
If you are a potter and have gotten away with pushing the limits in your process for many years there will eventually be a day of reconing. It is better to understand why you do things the way you do and be ready to adjust.
Make your own plaster table. One person can pour a 350 lb plaster table in two hours.
If you are a potter you already know much of what is needed to manufacture tile. However there are some things you need to unlearn to make tile well.
This device to measure glaze melt fluidity helps you better understand your glazes and materials and solve all sorts of problems.
Moving a cone 10 high temperature glaze down to cone 5-6 can require major surgery on the recipe or the transplantation of the color and surface mechanisms into a similar cone 6 base glaze.
Someone is having a problem with a cone 6 glaze going glossy and crystallizing, this article rationalizes the problem in terms of chemistry
This is a base transparent glaze recipe developed for cone 6. It is known as the 20x5 or 20 by 5 recipe. It is a simple 5 material at 20% each mix and it makes a good home base from which to rationalize adjustments.
The process we used to improve the 20x5 base cone 6 glaze recipe
This glaze was developed using the 1214W glossy as a starting point. This article overviews the types of matte glazes and rationalizes the method used to make this one.
This is a frit based boron base glaze that is easily adjustable in thermal expansion, a good base for color and a starting point to go on to more specialized glazes.
These starting recipes use no frits and work in oxidation/reduction and are inexpensive to make. They can be used as bases for the whole range of typical cone 10 pottery glazes (celadon, tenmoku, oatmeal, white matte, brown crystal).
INSIGHT enables you to enter material analyses as recipes as a first step to inserting them into the materials database. Imposing an LOI and understanding how to set unity and its connection for formula weight are important concepts.
Glaze chemistries for each type of glaze have a typical look to them that enables us to spot ones that are non-typical. Limit and target formulas are useful to us if we keep in perspective their proper use.
Fired glazes are composed of oxide building blocks. Each of the oxides contributes different properties to the fired glaze and interacts with others in different ways. Understanding these gives you control.
Bob Kavanagh explains ceramic glaze calculation as a potter for other potters. He deals with theory and show practical examples.
An overview of the meaning of this unit for measuring quantities of molecules by Joseph Herbert and Tom Buck.
Understanding the advantages of disadvantages of stains vs. oxide colors is the key to choosing the best approach
In ceramics color is often a matter of chemistry, that is, the host glaze must be compatible and have a sympathetic chemistry for the stain being added. Chrome-tin stains are a classic example.
There are many things to know about to make the best use of stains, but one often ignored aspect is the relationship between glaze color and chemistry. If you want to control color you need to know about stains and chemistry.
Many potters do not think about leaching, but times are changing. What is the chemistry of stability? There are simple ways to check for leaching, and fix crazing.
Max Richens outlines the various mechanisms by which acids and bases can dissolve glass and glazes. He provides some information on stabilizing glazes against attack.
A post to a discussion on the clayart group by Gavin Stairs regarding the food safety of crazed ware.
A step-by-step process to put a liner glaze in a mug that meets in a perfect line with the outside glaze at the rim.
Glazed ware can be a safety hazard to end users because it may leach metals into food and drink, it could harbor bacteria and it could flake of in knife-edged pieces.
An example of how we can use INSIGHT software to determine of a glaze is likely to leach
Glazes must be completely melted to be functional, hard and strong. Many are not. This compares two glazes to make the difference clear.
Alberta Slip makes a great base for glazes because not only is it almost a complete glaze by itself but it has low thermal expansion, it works well with frits and slurry properties can be adjusted.
Is it better to do trial and error line and matrix blending of materials to formulate your glazes or is it better to use ceramic chemistry?
How to take a stockroom full of unused materials and turn them into a good glase. This article helps you appreciate that the glaze formula is the important thing, you can use any number of materials to supply the oxides.
How to have a volcanic ash analysed and them use ceramic chemistry to create a glaze that contains the maximum possible amount of the ash for the desired effect
This is an overview of the various mechanisms you can employ to make glazes dance with color, crystals, highlights, speckles, rivulets, etc.
Every industry ball mills their glazes as standard practice, no one ever questions the need. Yet few potters do. Maybe it is time you should think about it.
Many of the best frits do have a published chemistry, or the chemistry is approximate. Can we still use them in ceramic chemistry? Yes.
Todd Barson of Ferro Corp. overviews the glaze formulations being using in various ceramics industry sectors. He discusses fast fire, glaze materials, development and trouble shooting.
A discussion by Jonathan Kaplan on dealing the with fickle nature of this glaze
A study of the mechanism behind the color in color red glazes by Karl Platt.
Fara Shimbo's book on crystal glazes is the most understandable and practical we have seen. The book is full of color pictures and test tiles.
Inspite of the fact it is very fickle, the floating blue cone 6 glaze is a good example of a recipe that displays many different kinds of variegation. Gerstley borate is one of the main reasons for its properties.
There is more to glazes than their visual character, they have other physical properties like hardness, thermal expansion, leachability, chemistry and they exhibit many defects. Here are some simple tests.
Pictures of a ball mill rack that you can make yourself
A standard shape and size of glaze test is important to be able to compare one test with another, especially over time (so that old tests look the same as new ones)
Potters who are used to dipping and spraying glazes might be surprised to learn how well glazes can paint on if they have enough gum in the recipe.
Vince Pitelka describes his method of preparing a Terra Sigillata slip.
If you are the only technically oriented person in your company, school or pottery club you will get a charge out of this report from a right-brained potter always fighting to drag others into understanding glazes.
Tony Hansen's opinion of two good technical books for people who want to understand how glazes work.
It is possible to have a glaze slurry that is a joy to use, but only if you understand the physics of the materials in the glaze recipe.
By understanding how glazes melt and materials and chemistry interplay to determine behavior and temperature of melting and testing degree of melt you control the melting temperature of your glazes.
The trade is glaze recipes has spawned generations of potters going up blind alleys trying recipes that don't work and living with ones that are much more trouble than they are worth. It is time to leave this behind and take control.
Part of changing your viewpoint of glazes, from a collection of materials to a collection of oxides, is learning what a formula and analysis are, how conversion between the two is done and how unity and LOI impact this.
A big secret to getting control of glazes is to begin looking at them as formulas of oxides rather than recipes of materials.
It is better to understand and have control of one good base glaze than be at the mercy of dozens of imported recipes that do not work. There is a lot more to being a good glaze than fired appearance.
At Digitalfire we promote the idea of understanding and formulating your own glazes so you have control rather than relying on suppliers or the trade in glaze recipes.
The only way you will ever get the glaze you really need is to formulate your own. The longer you stay on the glaze recipe treadmill the more time you waste.
Identifying the mechanism of glazes from the recipe or visual inspection (what produces the color, opacity and variegation) is the key to moving adjusting it, moving it, reverse engineering it, even avoiding it!
By knowing which level to view a glaze from you are much better equipped to understand and control it. The levels are process, recipe, material, oxide.
A prayer for potters who wish to continue down the road of text book glaze recipes, never really getting what they want, never getting control.
At Digitalfire we use a Dragon to personify the kinds of thinking that prevent potters, educators and technicians from understanding and therefore controlling their glazes.
The perfect universal glaze recipe does not exist, the only way you will get the glazes you really need is formulate or adapt them yourself. Start with base recipes, learn to understand them from a material level, then learn the mechanisms, and chemistry.
Tom Buck discusses the change in color over time that can happen with some raku glazes
Understanding the advantages and disadvantages of low fire ware and the chemistry of physics of the glazes and bodies used is a key factor to exploiting this type of ceramics
It can be difficult to find an engobe that is drying and firing compatible with your body. It is better to understand, formulate and tune your own slip to your own body, glaze and process.
This page demonstrates how you might use INSIGHT software to do calculations that will help you increase the thermal expansion of a glaze while having minimal impact on other properties.
MgO is the secret weapon of craze control. If your application can tolerate it you can create a cone 6 base glaze of very low thermal expansion that is very resistant to crazing.
Band-aid solutions to crazing are often recommended by authors, but these do not get at the root cause of the problem, a thermal expansion mismatch between glaze and body.
Glaze and body can both be adjusted to solve crazing and shivering problems. This describes a simple project to create body glaze combinations guaranteed to craze and shiver to demonstrate the principles involved.
The fit between body and glaze is like a marriage, if is is strong the marriage can survive problems. Likewise ceramic ware with well fitting glaze is much stronger than you think it might be, and vice versa.
Understanding thermal expansion is the key to dealing with crazing or shivering. There is a rich mans and poor mans way to fit glazes, the latter might be better.
Before adding new materials to the Insight MDT, consider whether you really need to do this. You can build a custom MDT in your account at digitalfire.com.
One can look at a ceramic material from a mineral, physical or chemical standpoint. Each viewpoint is appropriate depending on the context, understanding this is a key to exploiting materials properly.
How Alberta Slip was created by analysing and duplicating the physical and chemical properties of Albany Slip
Few people actually understood what AP Green fireclay really was (it is no longer available). By carefully ascertaining its physical properties we were able to formulate a substitute material mix.
Michael Banks and Stuart Altmann talk about chemical analyses methods and their advantages and disadvantages. Also information on testing labs you can use.
The story of how Ravenscrag Slip was discovered and developed might help you to recognize the potential in clays that you have access to.
How to create a blend of materials to chemically substitute for another (Cornwall Stone is used as an example).
Mike Bailey and David Hewitt provide detailed information on how to identify materials from the properties of their powders
Ceramic materials are not just powders, they have a physical presence that make each unique and amazing. We cannot adequately describe the properties using just numbers, thinking in terms of generic materials is a key.
Joseph Herbert overviews the technical and practical aspects of this interesting group of materials
Having Your Glaze Tested for Metal Release
Health & Safety Information Sources
The materials you use present two hazards you need to think about, are they poisoning your while working with them and are they destabilizing your glazes so they dissolve into food and drink?
Toxicity concerns about the use of firebrick or alumina brick to make ovens used for baking bread
Understanding the theory behind sieve selection, how to properly sample a powder and how to carry out a particle size distribution test can give you valuable information about a material.
Some of the key tests needed to really understand what a clay is and what it can be used for can be done with inexpensive equipment and simple procedures. These practical tests can give you a better picture than a data sheet full of numbers.
XML is the future of ceramic material and testing information. This is a standard electronic medium of exchange in the science and financial world.
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INSIGHT is ceramic chemistry