A weighed sample is ignited at a set temperature, commonly 525 degrees C, and the inorganic residue is weighed. At 900 degrees C calcium carbonate breaks down to calcium oxide, so testing at both temperatures separates carbonate from other minerals. Ash is the quickest check that filler retention and coat weight are where the furnish sheet says they should be.
Ash is running 19 on the reel sample, two under target, so retention is off again.
Also heard as
- ash
- ash level
Related terms
Filler
Fine mineral powder added to papermaking stock to raise opacity, brightness and smoothness and to cut cost.
PCC
Precipitated calcium carbonate: a synthetic filler, often made beside the mill, that raises brightness and opacity.
Coat weight
Mass of dry coating applied to paper per unit area, usually stated per side in grams per square meter.
Furnish
The recipe of pulps, fillers, dyes and chemicals that make up a paper grade's stock.