|Monthly Tech-Tip |
This test is intended to record observations about the general quality of an extruded clay body that is going to be packaged and sold for use in pottery and industry. This test recognizes the fact that bodies that are going to be stored can change over time (stiffness, tendency to laminate, migration to the surface of solubles, cracking of the slug). These observations provide a benchmark for what it was like immediately after pugging.
Rate the clay according to what it normally should be by feel or penetrometer.H20 - Value (V)
Provide water content of sample on this date.HCHU - Value (V)
Hardchunks occur in the clay due to pugmill problems and are an indication of the manufacturers control of the pugging operation. Note their presence.STRE - Value (V)
Streaks of another color of clay occur in a manufactured slug when the
manufacturer switches clay types and does not clean out the pugmill well
Laminations are evident when a slice of the clay is bent to reveal splits running concentric to the center of extrusion. This can occur because of poor powder mix, excessive sand or grog, lack of plastic materials, fast pugging, poor deairing.DEAI - Value (V)
Deairing is essential to producing the maximum plasticity for a given mix of plastic ingredients. Improper deairing is evident by air bubbles or pockets, laminations in the slug, inability to hold together.DATE - Value (V)
Stiffness observations need to be connected with a date because clay can change as it ages.
Tests conducted on bodies made from materials, as opposed to the materials themselves.
|By Tony Hansen|
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