I thought I’d have to dig through a bunch of old texts to find out when the inclusion of air rests in steeps started. The only mention of it in any old text that I had read so far was in Henry Stopes Malts and Malting An Historical, Scientific and Practical Treatise 1885. On page 332 he describes the newly adopted practice in Bohemia of Steeping for 24 hours followed by a 24 air rest and then a shorter steep of 8-10 hours (the date on the citation for this is 1874) He also describes the use of spray steeping on the continent.
As it turns out I didn’t have to look much further than this article by D.E. Briggs: Accelerating Malting: A Review of Some Lessons of the Past from the United Kingdom. 1986. In this paper Briggs describes the many methods used in the past and present to accelerate germination rates. Listed are methods such as abrasion to light crushing, low moisture squeezing as well as warm steeping and using additives like hydrogen peroxide and giberellic acid.
Any summary I could write about this article wouldn’t do it justice so I won’t try, but here are just a few interesting points in a very, very brief summary form.
Briggs does confirm that air rests were adopted by maltsters in Germany in 1875 but also mentions the traditional Norwegian practice of steeping barley in sacks submerged in streams and taking them out at intervals to drain and rest. Check out this old footage of traditional brewers in Norway from this awesome blog Larsblog shared by my friends at Spowtmalt.com I’m not sure what they’re saying but it’s fascinating to watch.
Interestingly Briggs notes that the practice of air resting fell out of use in the U.K. in the early 1900’s but was re-introduced in the 1950’s when it was recognized that an air rest after the grain had reached a water content of 35-37% overcame water-sensitivity and the grain could then be steeped again to a final moisture content between 41-46%
There is also a great description of how early chitting in the grain, which occurs with spray steeping and to a certain extent with air rests can affect the water uptake due to the more rapid absorption of water from the embryo over the starchy endosperm once the grain chitts. This can leave the inside of the endosperm dry even while the overall target moisture content is reached which can be detrimental to modification.
Briggs concludes by stating that despite all the new techniques and methods utilized in modern malting that each new batch of barley brings it’s own problems in production. He suggests that malt could be made more rapidly if there were a better understanding of various aspects of immaturity and vigor or dormancy. Also that further studies need to be done to improve methods that characterize the degree of maturity in grains. As well it would be advantageous to find methods other than prolonged storage to hasten grain maturation.
This article is well worth reading and sheds a lot of light on the recent history of the steeping process.