All Glossary

LOI-Adjust

LOI adjustment of the weight of a material is done to compensate for the weight loss when it is calcined. And to correct a chemical analysis (by weight) of a material.

Key phrases linking here: loi-adjusted, loi-adjust - Learn more

Details

LOI adjustment is needed in the following cases:

Where a calcined version of a clay is being used in place of a percentage of the same raw clay in a glaze recipe. Since the calcined version delivers more moles to the UMF, less of the powdered form is needed. Calcined kaolin is the most typical material. If the kaolin has an LOI of 12%, then 12% less of the powder, by weight, is included in the recipe.

An analysis lacks an LOI figure for a material that is known to have an LOI. Or, the accuracy of the analysis delivered by a lab is suspect. In either case, weigh, fire, and weigh again to derive the actual LOI and compensate the analysis. The following is the mathematical method of applying a 5% measured LOI to an existing analysis that had no specified LOI.

LOI-Adjusting an Analysis
100 - 95 = 5 / 100 = 0.95
--------------------------
K2O    7.3% x 0.95 =  6.9%
CaO    9.4% x 0.95 =  8.9%
MgO    1.0% x 0.95 =  1.0%
ZnO    1.0% x 0.95 =  1.0%
Al2O3 11.8% x 0.95 = 11.2%
SiO2  69.5% x 0.95 = 66.0%
LOI                   5.0%
--------------------------
     100.0%         100.0%

If the original already specified a 2% LOI, for example, then the formula to calculate the multiplier would be:

98 - 95 = 3 / 100 = 0.97

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