An assumption that harder intumescent coatings are better than pliable ones stops construction teams from optimizing material selection to save time and money.

The assumption stems from the 20th century emergence of Shore D durometer testing to assess epoxy protective coatings' level of cure.

The truth about hardness

Some stakeholders view hardness as the best marker of a coating's damage resistance. It's a good one, but not always the best, and should never be the only one.

For example, in colder conditions, high hardness is more a liability than a strength. Harder materials are more brittle, and impact damage to brittle materials spreads farther vs. the more localized damage that would occur in flexible coatings.

Prioritizing hardness over all other properties also prevents teams from optimizing material selection for fast-track projects.

If construction speed is the prevailing concern, then a combination of typical hard epoxy coatings as well as more weather-resistant solvent-based or hybrid materials give teams the best chance at rapid delivery under a wider range of conditions. But if specs are too rigid, that's not possible.

Hardness in the context of fireproofing performance

Hardness just doesn't matter.

Marketing fire-resistive materials is strictly regulated with many certifications and approvals required before products can be legally sold.

None of those certifications or approvals mentions hardness.

Learn even more about intumescent coating hardness in this article and this podcast episode.