Meet Henry and Jack Grover, the California twins who tested 9 hydrogels and found one that delayed charcoal reignition from 3 to 27 minutes |

Representative Image of hydrogels, charcoal briquettes, and the Thermo Fisher Scientific Junior Innovators Challenge logo in a collage (AI Generated Image)

Twin eighth-graders from Riverside, California, have tested nine hydrogels in a project exploring whether a sprayable gel could help stop burned areas from reigniting after a wildfire. Brothers Henry and Jack Grover, students at Riverside STEM Academy, are among the 30 finalists in the 2026 Thermo Fisher Scientific Junior Innovators Challenge. Their project, “Sprayable Hydrogels for Preventing the Rekindling of Wildfires,” compared different hydrogels for drying, adhesion and hydration before testing the leading material on hot charcoal briquettes. Society for Science reports that sodium polyacrylate, their top-performing hydrogel, fully hydrated in 15 minutes. When the twins applied it to hot charcoal, the material-treated briquettes took 27 minutes to reignite, compared with three minutes for briquettes sprayed with water. The brothers also designed a 3D-printed sprayer that could project the gel 18.3 metres.

Henry and Jack Grover reach the Thermo Fisher Junior Innovators Challenge top 30

The Thermo Fisher Scientific Junior Innovators Challenge is Society for Science’s national STEM research competition for middle school students. The 30 finalists were selected from the Top 300 Junior Innovators, who were chosen from 1,997 entrants. The finalists represent 17 US states and Puerto Rico, with Environmental & Earth Sciences the most prevalent project category. Nearly two-thirds of the finalists attend public schools.The finalists will take part in Finals Week in Washington, DC, from October 23 to 28 and compete for more than $100,000 in awards, including the $25,000 Thermo Fisher Scientific ASCEND Award. Society for Science says judges will evaluate the students’ research as well as their communication, creativity and collaboration skills during team challenges. The brothers had already worked with hydrogels in an earlier science fair project. Society for Science says they nearly lost their home in a wildfire. Henry has restored an older robot, collects old cameras and works on 3D animation, while Jack enjoys robotics, old cameras, antiques and amateur archaeology.

Why the twins tested sprayable hydrogels after wildfires

The project profile refers to the 2025 Palisades Fire and says the twins learned that it followed the rekindling of the earlier Lachman Fire. Federal prosecutors have also alleged that the January 1, 2025, Lachman Fire later became the Palisades Fire after reigniting six days later. That account remains disputed in the federal arson case against Jonathan Rinderknecht. Rinderknecht’s first trial ended in a mistrial in June 2026 after the jury deadlocked 10-2 in favour of acquittal. The defence disputed the prosecution’s account connecting the two fires. Prosecutors have continued to pursue the case. Judge Anne Hwang initially set a retrial for October 19, but after prosecutors filed a superseding indictment and Rinderknecht pleaded not guilty to the revised charges in August, the judge moved the retrial to November 2, 2026. The US Department of Justice currently lists November 2 as the scheduled jury trial date.Society for Science says Henry and Jack learned that firefighters struggled to put enough water on burned areas to keep them from reigniting. Their finalist profile says hydrogels appealed to them because they can absorb hundreds of times their weight in water and release it over a short period. Jack’s profile also says the brothers wanted to develop a more environmentally friendly fire-retardant material. A 2024 study published in Environmental Science & Technology Letters examined metals in wildfire suppressants and estimated that about 380,000 kilograms, or nearly 840,000 pounds, of the metals examined were released through aerial fire suppression between 2009 and 2021. The calculation assumed that all fire retardant applied during that period was Phos-Chek LC-95W. The manufacturer of Phos-Chek has disputed the relevance of that assumption to aerial firefighting, while the US Forest Service has said it has used LC-95W aerially, although rarely. The dispute concerns which retardant formulations were actually used in aerial applications during the period covered by the study.

How the Grover twins tested 9 hydrogels

The brothers compared nine candidate hydrogels through several tests before choosing the material for their charcoal experiment. They monitored changes in the samples as they were dried in an oven, tested how well the gels remained attached to vertically positioned leaves and then compared how quickly their two strongest candidates absorbed water. Sodium polyacrylate emerged as the top-performing material, reaching full hydration in 15 minutes.The twins then tested the selected hydrogel on hot charcoal briquettes. They compared it with water and measured how long the briquettes took to reignite. The water-treated charcoal reignited after three minutes, while the charcoal treated with the hydrogel took 27 minutes to reignite. The project profile does not give the number of repetitions for the charcoal test or report environmental testing of the gel. The experiment also used charcoal briquettes rather than a burned forest landscape, so the result does not establish that the material could prevent an actual wildfire from rekindling.

A 3D-printed sprayer could project the hydrogel 18.3 metres

The twins also tested how their material could be delivered. They designed a sprayer using a 3D printer, and Society for Science says the device could project the hydrogel 18.3 metres and worked with a garden hose.Research into hydrogel-based fire suppression extends beyond the twins’ experiment. A 2024 review published in Nanomaterials titled “Hydrogel Extinguishants” examines hydrogels for fire extinguishing and prevention, including their water storage, adhesion and heat-insulation properties. The review discusses natural and synthetic polymeric materials used in hydrogel extinguishants and lists sodium polyacrylate among the gelling agents reported for these materials. It also identifies the development of cost-effective, degradable and easy-to-use hydrogel extinguishants as an ongoing challenge. The review specifically describes natural polymer hydrogels as having properties including degradability and environmental friendliness. Sodium polyacrylate is a synthetic polymer, so those properties cannot simply be attributed to the material tested by Henry and Jack. The twins’ project profile does not report environmental testing of their sodium polyacrylate formulation.

From a wildfire concern to the national stage

Henry and Jack’s project began with the question of whether a water-absorbing material could help keep hot, burned material from reigniting. Their tests identified sodium polyacrylate as their fastest-hydrating candidate and found that charcoal treated with the hydrogel took longer to reignite than charcoal sprayed with water. Their 3D-printed sprayer then demonstrated one possible way of delivering the material. The brothers are now among the 30 finalists in the 2026 Thermo Fisher Scientific Junior Innovators Challenge. They will join other middle school researchers in Washington, DC, for Finals Week from October 23 to 28, with the competition offering more than $100,000 in awards.