For decades, many intumescent coating specifications have ruled out the use of materials that measure less than 70 in Shore D durometer testing.
Hardness is useful to know, but it has no influence at all on an intumescent coating's performance in the event of a fire.
What's it for, then?
It came from offshore oil and gas coating application best practices established in the 20th century.
The industry adopted durometer testing to judge if curing was complete. That mattered because most coating occurred onshore in shops prior to offshore installation. Loading, transportation, and unloading of platform components can be abusive and an incomplete cure was a recipe for damage that was very costly to repair.
Many other methods are available to test hardness, but Shore D durometer testing was most common because it was a good fit for the properties of typical hard epoxy coatings.
Copy-pasting for commercial intumescent specs
Language related to Shore D durometer testing entered intumescent coating specifications beginning in the 1990s.
The leading commercial intumescent materials of that era were based on epoxy resin technology, so there was no reason to reinvent the wheel in terms of assessing cure completion.
But while intumescent coatings today comprise a much wider range of technologies and properties, many specifications overlook this because they're holdovers from a prior generation.
Why that's a problem
Antique specifications exclude good materials to the detriment of construction project schedule and cost. Consider:
- 1. Some projects' schedules accelerate when non-epoxy intumescent coatings are selected, translating to substantial cost savings
- 2. Other hardness testing scales (for instance, Shore A) are better for assessing the cure of more pliable solvent-based, water-based, or hybrid intumescent coatings
- 3. Specs focusing too rigidly on Shore D hardness ignore the application and handling benefits that accompany other technologies
Cost and schedule savings are left on the table.
What should change?
Shore D durometer testing should be better contextualized in intumescent coating specifications.
It also shouldn't be the only testing method mentioned.
Specifications listing an array of suitable methods ensure the door stays open to all viable technologies. This maximizes opportunities to save during construction while achieving required fire ratings.
For more detail on this topic, read this article or listen to this episode of The Red Bucket podcast.
