Softening temperature determination using Seger (pyrometric) cones: which furnace atmosphere is appropriate during the test?

Introduction / Context:
Pyrometric (Seger) cones are standardized compositions that bend at characteristic equivalent temperatures, allowing comparison of softening behavior. The atmosphere during testing can influence surface reactions and readings if improperly chosen.

Given Data / Assumptions:

• Goal is to assess softening behavior without unintended chemical reduction.
• Oxidising or neutral atmospheres are typical for lab furnaces.
• Reducing atmospheres can alter chemistry of cones.

Concept / Approach:
Either oxidising or neutral atmospheres are acceptable, as both avoid undesired reduction of cone constituents. Strongly reducing atmospheres may change the cone composition or surface, corrupting the effective cone equivalent temperature. Hence, laboratories generally use air (oxidising) or neutral gas conditions for reliable, comparable results.

Step-by-Step Solution:
Identify atmospheres that preserve composition: oxidising/neutral.Exclude reducing: may alter cone chemistry.Conclude that either oxidising or neutral is suitable.

Verification / Alternative check:
Test standards and kiln practice notes endorse air or neutral atmospheres for cone work unless a special study requires otherwise.

Why Other Options Are Wrong:
Reducing only: not standard and can distort results.Neither: impractical; a furnace atmosphere must be one or the other.

Common Pitfalls:
Running tests in mixed or fluctuating atmospheres that cause variability in results.

Final Answer:
Either (a) or (b)