Related Experiment Video
Updated: Sep 23, 2026

Standard Test Method ASTM D 7998-19 for the Cohesive Strength Development of Wood Adhesives
Published on: May 17, 2020
Effect of burnout temperature on strength of gypsum-bonded investments
1Dental Technology, Faculty of Dentistry, Prince Philip Dental Hospital, The University of Hong Kong, 34 Hospital Road, Hong Kong, People's Republic of China.
Objective:
To investigate the variation of the strength of gypsum-bonded dental investments with burnout temperature.
Methods:
The disc-rupture test was employed at burnout temperatures ranging from 450 to 800 degrees C for four products (Beauty Cast, Cristobalite, Novocast (all WhipMix) and Deguvest California (Degussa)). In this test, an investment disc is created inside an investment mold such that it forms a diaphragm across the mold space, being an integral part of the mold. Copper was cast into molds of this type, and whether the disc had ruptured or not was determined by inspection when cold. The amount of copper cast in successive tests was varied in staircase fashion up and down depending on whether the disc survived or failed. The strength of the investment was represented by the 50% point of the transition from survival to rupture.
Results:
The strength of gypsum-bonded investment is temperature sensitive, there being marked differences between the products tested. Overall, the strength ranking (temperature range average/MPa) was: Cristobalite (10.1)>Beauty Cast (7.8)>Novocast (5.1)>Deguvest California (3.4). The strength ranking at high temperatures differs from that known for the room temperature values.
Significance:
The use by manufacturers of room-temperature strength data conveys no information about high temperature behavior. Investment properties should be optimized by reference to behavior under casting conditions.
Related Concept Videos
Strength and Heat of Hydration
The heat of hydration for each cement compound is significant; for instance, tricalcium aluminate (C3A) and...
Strength of Cement
For compressive strength tests, ASTM C 109-05 standards prescribe a cement-sand mix ratio of 1:2.75 and a water/cement ratio of 0.485 for making 2-inch cubes. These cubes are mixed, cast, and cured in saturated lime water at 23°C until testing. Flexural strength testing, outlined in ASTM C...
Masonry in Cold and Hot Weather Conditions
Other key practices include keeping masonry units and sand dry and...
Hot Weather Concreting
Mitigating the heat increase in concrete can be economically achieved by shading aggregate stockpiles to prevent heating from solar radiation,...
Mortar Properties
Design Example: Managing Concrete Workability
To address...
