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Words beginning with D
Decal
A method of printing designs using ceramic inks onto specially prepared paper (a glue, then a base coat of clear material is applied followed by the inks). The design on the clear material is then transferred to glass or ceramic. To apply the decal you put it in water for a minute or so to loosen the glue enough to slide the clear decal onto the ceramic surface (slightly porous paper is used so that water can soak through it).
Decal ware must be fired to precise temperatures to develop and mature the color properly. The are many mistakes to be made in application and firing that will compromise the quality of the final product.Deflocculate, deflocculation
The process of making a clay slurry that would otherwise be very thick and gooey into a thin pourable slurry. Deflocculants (or electrolytes) are liquids or powders added in small amounts and they work their magic by imparting electrical charges to clay particles making them repel each other. It is the opposite of flocculation.
To deflocculate a slurry properly it is very important to be able to measure its specific gravity and viscosity accurately. Yet it is very common for slip casters to be tied to a recipes and have little understanding of how to control their slip. Many will work for years with substandard slip without knowing it, others will throw away all scrap rather than reprocessing it simply because they do not understand slip rheology.
It is common for potters to mix slips using clays intended for modeling or sculpture. Far better casting mixes can be made using mixes of materials that emphasize permeability instead of plasticity. Once you have used a slip properly formulated and deflocculated for casting you will never go back to using an inadequate slip.
Sometimes glazes are deflocculated to reduce their water content, this is most likely where glaze is being applied to once-fire ware.
Common deflocculants are sodium silicate, Darvan, Calgon.Devitrification
The crystallization of a ceramic melt during cooling. Devitrification is desirable in achieving certain visual effects (e.g. matteness) and undesirable when a transparent or glossy transparent glaze is desired.Dimpled glaze
'Dimpled' glaze surfaces are those that have tiny holes that do not go down to the ceramic underneath (a pinhole). These holes look as if they were produced by a pin-point being pressed into the surface of the glaze when its melt is very stiff. Dimples are considered a glaze imperfection and are usually caused by firing too quickly.Dunting
Cracking that occurs in ceramic ware that is cooled too quickly. Dunting can exhibit itself as simple hairline cracks or ware can fracture into pieces. Ware of uneven cross section, ware with glaze that fits poorly, or large pieces (i.e. large flat plates) are often subject to dunting. Ware with high amounts of cristobalite or quartz undergoes sudden volume changes when heated or cooled through the inversion temperatures of quartz.
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