Model SP-1000 for the Littleton Softening Point Temperature


The softening point of a glass is the most widely used production control parameter. Changes in the softening point temperature are indications of chemistry changes. According to ASTM C-338 the softening point temperature is the temperature at which a uniform fiber of glass (0.65 mm in diameter by 23.5 cm long) elongates under its own weight at a rate of 1.0 millimeters per minute when the upper 10 cm of its length is heated in a special furnace at the rate of 5°C per minute. This test is performed in a laser optic extensometer system that is manufactured by Orton. The Orton Model SP-1000 Series has been designed to automatically monitor the elongation of the sample fiber and calculate the Littleton softening point according to the ASTM C-338 method.

(Note: If forming a fiber is not desired, is impractical, or impossible, the softening point temperature RANGE can still be determined by the Parallel Plate Viscometer method, ASTM C-1351M.)


Automatic Softening Point Determination

 It takes 5 minutes to measure the Littleton Softening Point of a glass fiber. It’s simple. After the test fiber is pulled to meet the ASTM C-338 specified dimensions, the operator places the fiber into the preheated furnace, aligns the fiber in the laser path, clicks the start button in the software screen display, and walks away. The system does the rest. The operator is free to perform other tasks. Five minutes later, the operator returns and reads the Littleton Softening Point Temperature on the computer monitor. It's that easy. Model SP-1000 automatically calculates the rate of elongation and displays the softening point temperature which eliminates operator differences, operator judgments, operator biases, and errors. Model SP-1000 is a FAST, EASY, ACCURATE, RELIABLE, and REPRODUCIBLE instrument for R&D and for QC checks on batch chemistry changes.

EASY: The operator requires little training. After the test fiber is pulled to meet the ASTM specified dimensions, the operator simply places the fiber into the furnace, aligns the laser, clicks the START button on the computer monitor, and walks away. The operator is free to perform other tasks.

FAST: In less than five minutes the Littleton Softening Point Temperature is displayed on the computer monitor. It is possible for one operator to test 50 fibers during a single 8-hour shift.

ACCURATE, RELIABLE,and REPRODUCIBLE: The laser system automatically monitors the elongation, the computer calculates the rate of elongation, and the computer determines the softening point temperature. Operator differences, errors, and biases are eliminated. With good fibers, ±1°C is routine.

FLEXIBLE: The user can select the ASTM C-338 procedure, or modify the thermal cycle for individual testing requirements, such as high volume QC testing.

POWERFUL: The data acquisition software displays the test and conditions while the test is underway. The data review software shows the test results, and generates a report that automatically calculates the average temperature for a series of fibers.



Model SP-1000 Series

Photo of Model SP-1000 System Concept Drawing of Model SP-1000 System

Model SP-1000 Series
(required computer system not shown)

Concept Drawing of Model SP-1000


The Model SP-1000 Series was designed to provide the user with the choice to operate according to the ASTM C-338 procedure, or to operate the system according to a user-modified version of the ASTM C-338 test. Through the special Orton software loaded into the user supplied computer, the user selects the mode of operation, inputs the appropriate information, and the Orton software does the rest. The Orton software controls the thermal cycle, acquires the data, and analyzes the data according to the mode selected by the user.

The Model SP-1000 system is comprised of a special furnace to heat the fiber; a control system to heat and cool the furnace, a thermocouple to monitor the fiber temperature, a laser system to monitor the elongation of the test fiber, a software system to determine the softening point, and a software system to determine the softening point, and a software system for generating comprehensive or summary reports.


The furnace is initially heated to an equilibrium soak temperature and waits for the next test. After the fiber is inserted and aligned, the test is begun. The controller heats the furnace at a predetermined heating rate, normally 5ºC per minute. As the temperature increases and the fiber elongates, the laser system follows the tip of the elongating fiber and continuously sends its signal to a computer. The software calculates the elongation rate as a function of time, and concludes the test once the elongation rate exceeds a predetermined rate. The software determines the temperature at which the elongation rate is 1.00 millimeters per minute (or a user definable target rate), and displays that softening point temperature. The furnace cools to the next beginning temperature, and the system waits for the next test.

Descriptions and specifications contained in this page are for general discussion purposes, and are subject to change without notice. Please consult Orton for clarifications and specific details.

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