What alternative can be used instead of a wire mesh basket for testing?

Using panels with enclosed sides as an alternative to a wire mesh basket for testing is appropriate due to their ability to contain materials effectively while still allowing for airflow and the necessary observation during the testing phase. These panels provide a stable structure, preventing the test materials from spilling or falling out, which is crucial for maintaining the integrity of the test.

Panels with enclosed sides also offer more durability compared to other materials, ensuring they will withstand the conditions of various tests without deforming or breaking down. This makes them suitable for refractory testing where heat and other physical stresses can be a factor.

While other options, like plastic containers, metal trays, and cardboard boxes, might be considered for different applications, they do not have the same combination of containment, stability, and ability to withstand the conditions typically present during refractory testing. This is why panels with enclosed sides are a preferred alternative in such scenarios.