Hidden Gum Risks in SFFF Foams
Hidden Polymer Risks in Modern SFFF Foams: Fomtec Highlights the “Hidden Gum” Challenge
Natural polymers have played an important role in firefighting foam technology for decades, helping improve foam stability, blanket performance, and resistance to heat. As the fire protection industry continues its transition away from PFAS-containing foams, these naturally derived polymers are once again becoming central to the development of Synthetic Fluorine Free Foams (SFFF).
However, according to Fomtec, not all polymer strategies deliver the same long-term reliability. The company is highlighting what it describes as the “hidden gum” problem, where partially hydrated polymers may create performance risks that only become apparent after a foam concentrate has been installed and stored over time.
The Role of Natural Polymers in Firefighting Foam
Natural polymers are large molecules formed from repeating monomers and are commonly found in materials such as proteins, starch, cellulose, and natural rubber. Because many of these materials are biodegradable, they are increasingly viewed as a more environmentally responsible option in the post-PFAS era.
Their application in firefighting foam dates back to the 1970s with the introduction of alcohol-resistant (AR) foams. Traditional hydrocarbon foams—including FP, AFFF, and FFFP—performed poorly on water-miscible fuels such as acetone and IPA because the fuel rapidly destroyed the foam blanket.
The introduction of natural polymers solved this challenge by creating a protective polymer layer between the foam blanket and the fuel surface. Beyond alcohol resistance, this also improved blanket durability, slowed foam drainage, strengthened bubble structure, and increased heat resistance.
These advantages eventually made AR foams the preferred solution for many high-hazard industrial applications where long-lasting foam blankets and burnback resistance are critical.
The Stability Challenge
Throughout the following decades, manufacturers experimented with different polymer types and concentrations.
Polysaccharides such as Xanthan Gum and Guar Gum became the most widely used natural polymers. While these materials improve foam performance, they also create two persistent engineering challenges:
- Increased concentrate viscosity
- Long-term stability during storage
Higher viscosity can usually be managed through appropriate equipment design, provided engineers understand the product’s rheological behaviour.
Stability, however, presents a much greater operational concern.
According to Fomtec, stability failures have occurred across the industry due to factors including raw material variation, manufacturing inconsistencies, storage conditions, and environmental exposure.
When instability develops, operational consequences may include concentrate separation, polymer settling, dehydration, and in severe cases, near-solidification of the concentrate.
These failures directly affect pumpability, proportioning accuracy, and overall foam discharge performance.
Why Natural Polymers Have Returned
With fluorine-free SFFF formulations, blanket integrity now plays a much greater role in extinguishment performance because fluorosurfactant film formation is no longer available.
Natural polymers help compensate by producing slower-draining foams, stronger bubble structures, and improved resistance to heat.
Generally, increasing polymer content improves fire performance, particularly for burnback resistance and maintaining a stable foam blanket on hot surfaces or in saltwater conditions.
However, increasing polymer content also increases viscosity.
For facilities using existing proportioning equipment originally designed for other foam technologies, viscosity has become a critical compatibility issue.
The “Hidden Gum” Approach
To overcome viscosity concerns, some manufacturers have adopted partially hydrated polymers.
Fomtec refers to this strategy as “hidden gum.”
Initially, partially hydrated polymers can provide attractive viscosity characteristics while still delivering good fire test performance.
The concern, according to Fomtec, is that these polymers may continue hydrating after installation when exposed to humidity, temperature cycling, shear forces, or small amounts of water contamination.
This means the concentrate’s viscosity may continue changing throughout its service life.
For emergency response systems, a foam concentrate that behaves differently over time introduces uncertainty into system reliability.
Water Exposure and Delayed Hydration
Foam concentrates inevitably encounter moisture during their operational life.
Storage tanks, humid environments, and routine handling can all introduce small quantities of water.
If partially hydrated polymers are present, additional water may trigger continued hydration, causing the concentrate to swell and thicken.
Fomtec developed an internal testing method to evaluate viscosity changes after water contamination.
Testing of three Fomtec SFFF products showed viscosity decreasing by approximately 20% after 15% water addition.
However, when four competitor AR-SFFF products were evaluated using the same procedure, all demonstrated viscosity increases exceeding three times their original value after water additions between 15% and 40%.
According to Fomtec, such dramatic viscosity changes could potentially affect:
- Pumpability
- Pressure losses
- Proportioner accuracy
- Strainer blockage
- Nozzle performance
- Overall system reliability during emergency operation
A Metastability Concern
Fomtec argues that the primary issue is not simply higher viscosity but unpredictability.
A foam concentrate may satisfy viscosity specifications during manufacture while still remaining chemically capable of significant thickening later in service.
The company describes this condition as metastability.
Once installed, this delayed change may create operational issues that appear to be mechanical failures but actually originate from changing concentrate chemistry.
For this reason, Fomtec believes manufacturers should clearly disclose whether their formulations rely on partially hydrated polymers.
Its own Enviro SFFF range is manufactured using fully hydrated natural polymers, as the company considers the risks associated with partial hydration unacceptable for high-hazard applications.
Although Fomtec acknowledges that it has not yet established a direct statistical relationship between viscosity increases and actual system failures, it argues that viscosity increases exceeding 300% justify caution.
The Drive Toward 1×3 Foam Solutions
Commercial pressures have also encouraged manufacturers to develop broader “1×3” foam solutions capable of protecting multiple fire risks with fewer product variants.
While this simplifies procurement and inventory, Fomtec suggests that broader performance requirements often demand higher polymer loading.
Higher polymer content may encourage greater use of partially hydrated polymers to maintain acceptable storage viscosity.
According to Fomtec, this combination could increase the potential for hidden gum instability across a wider range of operating conditions.
Performance Without Compromise
Fomtec states that after more than three years of research, it chose not to adopt partially hydrated polymer technology.
Instead, the company introduced ENVIRO 3×3 NEO in January 2026 using fully hydrated polymers while targeting high-performance standards including EN 1568:2018, UL 162, IMO, LASTFIRE, and ICAO Level B.
The company believes this demonstrates that high firefighting performance can be achieved without relying on polymer strategies that may compromise long-term stability.
Looking Ahead
As fluorine-free firefighting foams become the global standard, Fomtec argues that polymer hydration should no longer be viewed as a minor formulation detail.
Instead, it should be recognised as a critical factor influencing long-term operational reliability.
Beyond successful extinguishment tests, foam concentrates should also be evaluated for long-term storage stability, resistance to water ingress, rheological consistency, and dependable system performance under real emergency conditions.
For Fomtec, true firefighting foam performance is measured not only by laboratory testing, but by how reliably the product performs years later when a fire protection system is called upon to operate exactly as intended.
For more information please visit Fomtec website.
