By Dave Thomas
The kiln operator of a large western malthouse noticed that friability was always lower from Kiln #3 of the six steam-heated kilns in the malthouse. She told this to the malt chemist in the lab, who replied “That’s weird! It’s the same barley, growing area, and crop year malted in exactly the same way! How could Friability be lower?”
The malt chemist started taking samples from all kilns, cutting them open and looking at them through a microscope. He found a layer of hardened caramel sugars immediately under the husk only in Kiln #3 samples. It was determined that the steam radiators on kiln #3 were leaking steam which resulted in a slight crystallization of the outer layer of these fully-modified malts in this kiln only.
The phenomenon was named “case-hardened malt”, a paper published in the Journal of the Institute of Brewing. The steam leaks were repaired and afterward malt friability levels returned to normal.