High Gravity Brewing and the Steel's Masher

Usually when brewers make very high gravity beers, they use some combination of added sugars (anything from table sugar to malt extract), long boils (which concentrate by evaporation) or iterated mashes (by brewing up a batch of sweet wort then using that wort instead of water to mash in a second brew).

 However, in the 19th Century, Scottish brewers made exceptionally strong beers, probably the strongest in the world at the time (with gravities documented as high as 1.159 which, if fully-fermented, would be 26% alcohol) and didn't use these techniques to achieve these exceptionally high octane results.

So how did they do this? The answer lies in mash thickness. In other words, the amount of water added for a given amount of grain. The less water, the more concentrated the mash, the higher the gravity one can reach.

To understand this, let us consider the history of moistening grain with water.


Sticking one’s oar in

The simplest way, technologically speaking, of mixing malted barley and water is with a paddle or an oar of some kind. Hot water (or 'liquor' as it's known in brewing) is added to the mash tun and crushed grain is steadily added while stirring until well-mixed. 

This technique works but can lead to uneven mixing and is, obviously, very laborious. It's also not really possible to make concentrated mashes this way because the mixture simply becomes too stiff to stir. This makes high gravity brewing more difficult.

Mash rakes

In 1807, an English brewer, Matterface (a name of surpassing excellence, in my view), invented mechanical mash rakes, as depicted below.

These metal rakes are powered by a steam engine and therefore remove a lot of manual labour. They also allow for much stiffer, more concentrated mashes since we're no longer dependent on human arm muscles for mixing.

However the system is still very time consuming and is prone to uneven mixing among other problems.

Steel's Masher

A quantum leap in mash technology arrived in 1853 with the parenting of the Steel's Masher.

Both mash rakes and the oar-based technology are known as internal methods of grist hydration because the mixing of grain and water happens inside the mash tun. The Steel's Masher is the first successful external grist hydrator.

It was invented by Scottish brewer, James Steel and patented by his brother in 1853. The design is depicted below. Grain is dropped in the top, hot liquor pumped in beside and mechanical mixing arms combine the two and project the mixture into the mash tun. The grain therefore arrives hydrated into the mash tun.

This machine is an improvement in every way. It retains the ability of the mash rakes to make stiff mashes but does so much more evenly. It also works incredibly quickly. Mixing large amounts of grain would previously take a long time but large Steels Mashers are documented in the 1800's as mashing over 30 tonnes of malt in 20 minutes. This is fast.

They also create beautifully effective mashes. Full of enzymes, bouyant and with an open structure which allows liquid to flow freely, giving joyously easy work days to the brewer. One can imagine a brewer post-1853 weeping with joy at the astonishing effectiveness of this machine.

The Steel's Masher quickly became the standard technique in the UK and spread worldwide very quickly. It was described in Steel's obituary as having "revolutionised the process of brewing" and this seems not to have been an exaggeration. It remains, in my view, the best method of grist hydration 170 years later, which is rather incredible.

The Self-Acting Masher

Another method of grist hydration emerged, just over 10 years later, in 1864, invented by another Scottish brewer, Charles Maitland of Alloa.

This was known as a 'self-acting' or 'automatic' hydrator because it was not mechanical. It used the kinetic energy of the water itself, sprayed towards the grain, to mix the two, forgoing the mixing arms of the Steel's Masher.

Since they lacked any mechanism, these were cheaper to make and maintain. However, in the UK, they were regarded as an inferior, budget version of the Steel's Masher, being slower, less flexible, producing less good mashes and working in a narrower range of hydration rates.

They were favoured in mainland Europe where variations on the Scottish design were developed and patented in the subsequent years.

Whilst Steels Mashers were the standard method in the UK until at least the 1980's, the self-acting method came to be particularly associated with German brewing. For example, the 1981 2nd Edition of Malting and Brewing Science by Briggs et al (an important UK brewing textbook) describes Steels Mashers as being the norm for everything but 'decoction brewing' where the self-acting method was preferred.

The growing tendency to view German brewing as the gold standard for modern brewing technique appears to have led to the domination of self-acting mashers for most modern breweries, even those focussing on UK-style ales. However, the advantages of the Steel's Masher for certain UK-styles have not gone away.


Let's put some numbers to this. Liquor to grist ratio is typically measured in litres per kilo (or, in the US, pounds per pound, which yields the same numbers). The lower the number, the more concentrated the mash.

If you're mashing with a mash paddle or oar, you'd like to be around 3L/Kg. This is a nice, loose mash. Easily stirred and mixed relatively evenly. You could go crazy and push it up to 4L/Kg but there is little point.

On the lower end, you could get down to 2.5L/Kg but this will rather tiring on the arms. It will become hard to mix and prone to dry lumps. You may need to lie down afterwards. Going significantly below 2.5L/Kg is not possible unless you're The Incredible Hulk.

If one is using a self-acting hydrator, things are a little more flexible. These are designed to operate efficiently down to about 2.4L/Kg. This makes higher gravity beer with less labour. You can also push the device below the recommended rate and still get it to work. Some parts of your equipment may work less well (for example, if your mash requires pumping, that might be a challenge for thick mashes), but if you're willing to battle through heroically, you might get down to 2L/Kg. It will probably be a bad day but will yield high gravity wort. 2L/Kg is a very, very dry mash in contemporary terms.

What of Steel's Mashers? If we look back historically, these were recommended to operate between 1.5-2 barrels/quarter. This is approximately 1.6-2.1L/Kg, by my calculations. Sykes describes 1.6L/Kg as a very stiff mash (something of an understatement in contemporary brewing) and says 2.1L/Kg is a loose mash, which is an astonishing assertion to the modern ear.

Just as a self-acting hydrator can be pushed beyond its recommended limitations, so too can a Steel's Masher. One can go below 1.6L/Kg. In so doing, one can create a mash which, despite being ludicrously dry, is evenly hydrated but also buoyant, well-structured and easy to draw liquid from.


Discussing a possible collaboration with our colleagues at Newbarns Brewery in Edinburgh, it emerged that their brew kit (a splendid old beast from Burton-on-Trent) came with a rather large Steel’s Masher. We simply had to make a very large Scotch ale.

We resolved to target 1.4L/Kg and started the day early in acknowledgement of the possibility that we might end up trying to get liquid out of the thing for 7 hours before giving up and going to the pub.

The most amazing thing about the brew day was how easily and effectively the Steel’s Masher handled this. It worked very rapidly, hydrated the grain evenly and created a classic Steel’s Masher mash which, in Gordon of Newbarns’ words should look like one could walk across it.

Our wort left the mash tun at a pleasingly rich 1.126 (if you fermented all this sugar, it would be 16.5% ABV) and was then (sort of accidentally) boiled extremely vigorously for 3 hours. Whilst this is a relatively short boil in high gravity brewing terms, it concentrated the wort a great deal…

Since this was basically jam, we had to liquor it back (brewer speak for adding some water) to workable levels, but the intense boil had created a deep colour and rich caramel flavours. The beer is extremely delicious and, at the time of writing, available on this very web shop.

As a proof of the versatility of the Steel’s Masher, the beer was a revelation, turning high gravity brewing from a chore to an easy and efficient brew day. It’s also a revealing demonstration that 19th Century brewers were very smart. If you have access to a Steel’s Masher, I’d highly recommend trying this out. Epochal is currently saving its pennies to acquire one.