Ask A Geochemist: Why Is It Hard To Rinse Off Soap In Iceland?

When washing your hands, you might have realised that here in Iceland, the soap doesn’t seem to rinse off easily. It’s a phenomenon that has puzzled us at the Grapevine for a long time—so we decided to find out what’s that all about.

According to Ingvi Gunnarsson, a geochemist at Orkuveita Reykjavíkur, the chemical composition of water affects how easily it rinses off soap. Water can be classified as hard or soft, and Icelandic groundwater is generally categorised as soft. Rinsing soap with soft water takes longer than with hard water, Ingvi explains.

But why is it easier to get the soap off with cold water?

Ingvi was intrigued by the follow-up question: “Never have I heard before that cold water rinses the soap off better than hot water,” he admits, but proceeds to contemplate the possible reasons.

“Low temperature geothermal waters—at least here in Reykjavík—are softer than fresh groundwater and therefore not as effective as cold water in terms of rinsing soap off your hands,” he says, adding that although there is a difference between the water compositions, it is not that big.

However, this might not be the only reason behind the phenomena. Ingvi says that another possible explanation is that hot water in Iceland comes directly from low temperature geothermal fields and is mildly alkaline. “Alkaline waters can be a little slippery to touch compared to neutral water, and therefore one feels that the soap does not come off one’s hands when washing them,” he explains. In reality, the soap has been rinsed off, but the alkaline water makes you feel like you still have some soap residue on your hands.