BLEEDING THROUGH a tampon or pad never makes for a good time. The risk of leaks is annoying and stressful for all women who bleed, and especially for the 20% to 30% whose menstrual flow is so heavy that they sometimes must change their tampons or pads every hour. Some dread leaving their homes for fear of getting caught out.

A new discovery could one day ease that anxiety. Writing in Matter on July 10th, scientists from Virginia Tech described an easy way to turn blood into a thick, semi-solid gel, which could limit leaks and spills from period products. It would be a rare step forward in menstrual care. This is “one of those quality-of-life issues”, says Bryan Hsu, the microbiologist who led the work, regarding which there has not been any progress “in a century”.

The team began by looking for a material that could make blood more solid. They did so by mixing various polymers—molecules whose structure consists of long chains—with pig’s blood and measuring how quickly the resulting concoction flowed down a test tube. After discarding those that produced too runny a gel, they settled on a powder based on alginate, a polymer found in algae. The team’s tests suggested that the positively charged calcium ions in the blood would attract the alginate’s negatively charged molecular chains, creating a tangled web capable of trapping the blood in a firm gel.