1. Moisture in Cotton by Oven Drying
J. G. Montalvo and T. M. Von Hoven
Southern Regional Research Center, ARS, USDA
New Orleans, Louisiana

2. OBJECTIVES
Brief review of standard test methods for moisture in lint cotton in USA & China
Present preliminary modeling studies of bias
“Review of Standard Methods for Moisture in Lint Cotton”, J. Montalvo and T. Von Hoven, JCS
Financial support by The Cotton Foundation and Cotton Incorporated is greatly appreciated.

3. STANDARD OVEN DRYING METHODS IN USA
Condition prior to drying
Std. testing atmos.
Oven temp (0C)
Accuracy
ASTM D 2495 N Y
__a
ASTM D 1348
optional
(dry air) __
ASTM D 2654
USDA Handbook 422
AATCC 20A
a Not stated in method

4. ADMITTED BIASES IN STANDARD METHODS
Known bias*
ASTM D 2495
b1, b2
ASTM D 1348 b2
ASTM D 2654
b1, b2 to none
USDA Handbook 422
AATCC 20A
* b1 is the mass of moisture that remains in sample after oven-drying
b2 is the mass of other volatiles loss during oven-drying

5. CHINESE STANDARD METHOD (GB/T6102.1) - 2006
Official definition
“The water and the other volatile substances loss during the drying test on raw cotton.”
Purpose
To determine moisture regain in raw cotton delivered to the laboratory.
Accuracy
No accuracy statement (biases b1 & b2).

6. PRELIMINARY MODELING STUDIES
Other sources of bias in weighings:
bc = bab + ben + (b1 + b2)
↓ ↓
PC PC2
Where the biases (b) are:
bc is combined; bab is analytical balance;
ben is environmental.
PC1 & PC2 are bias process controls.

7. MATERIALS AND METHODS Bias process controls
Balance (re-tare not allowed) - closed empty weighing bottle (PC1)
Environment - 1 g bleached and scoured cotton in an open weighing bottle (PC2)
Both PC1 and PC2 are weighed prior to processing the unknown cottons: weigh empty, filled and cooled sample bottles.

8. BIAS PROCESS CONTROL (PC1) WITH CLOSED EMPTY BOTLE
(10 mg)

9. BIAS PROCESS CONTROL (PC2) WITH BLEACHED COTTON IN OPEN BOTTLE
(10 mg)

10. ACTUAL COTTON RESULTS: MATERIALS AND METHODS
6 cottons (AMS) for oven drying tests
Empty weighing bottles weighed, added 1 gram conditioned cotton, reweighed
Samples heated in oC oven for 24 hours
Samples cooled in a desiccator for 1 hour and then weighed in conditioned lab

11. PERCENT MOISTURE OF SIX COTTONS

12. CONCLUSIONS
Reviewed standard methods in USA (all voluntary) and China (national std.)
Lack of accuracy information
Simple bias process controls demonstrated
Moisture content measured over a wide range of micronaire by oven drying & Karl Fischer
Need for accurate standard method(s) to determine the true moisture content