We asked two leading bartenders to reveal their methods for making crystal clear block ice.
Jack McGarry is formerly of The Merchant Hotel in Belfast, where he gained a name for the quality of his ice as well as his cocktails; he has also worked at Milk & Honey in London and is currently working for London cocktail supremos Nick Strangeway and Henry Besant.
Erik Lorincz is head bartender at The Savoy Hotel in London, outgoing Diageo World Class Global Champion 2010 - and renowned for transporting block ice around the world for competitions.
Boston's "Ice King" Frederic Tudor is widely credited for being the man responsible for the first business involving the commercial distribution of harvested ice from lakes in New England. He began the long and arduous process on the 10th February 1806 and his development and refinement of the harvesting process enabled shipments to the most of America, the Caribbean, Europe and as far away as India.
By the 1840s Tudor's ice was all over the world. The accessibility and quality of ice initiated a massive transformation in drinking trends across the world. Ice become integral to any bar operator and the importance of ice led to another major change in the type, quality and availability of ice: the ice machine. Ice machines began to be developed during the 1850s, when men such as John Gorrie and Alexander Twining created and patented their own equipment.
The development of ice machines was crucial in spreading the culture of cold drinks. Today, although there remain a plethora of poor quality ice machines that turn out fast-melting, wet 'bullet'-style ice, there are some good machines on the market and it is quite possible to produce denser, drier ice cubes relatively cheaply.
Cube or block?
However, amid the climate of constant premiumisation and the need for the best bars to differentiate all levels of their service, the quality of ice that bars serve has become just as important as the quality of their spirits, juices or mixers, and has a bearing on the presentation of finished drinks equal to the choice of glassware. Cubed ice just doesn't cut it these days at the top level.
In most cases cubed ice is brittle, and contains impurities which are reflected in the cloudiness of the cubes. Cubed ice generally also has a high surface area which the liquid has to interact with, resulting in a high heat exchange and excessive dilution. In my opinion, it results in insipid and 'flat' drinks.
The result? Something of a return to the days of the Ice King himself, with block ice enjoying a massive resurgence. It is firm and rigid, free of most impurities, crystal clear and, most importantly, has a low surface area. Low surface areas decrease the area of which the liquid has to interact with and as a result lowers the heat exchange, lessening dilution. This results in drinks having longevity and fullness. I once recall Audrey Saunders calling ice "the soul of the drink". I couldn't agree more with that sentiment: block ice in my opinion completes a drink.
The perfect block ice
Of course, you can buy block ice from commercial suppliers readily nowadays, but during my time at The Merchant Hotel we became captivated by ice and how to make it perfectly ourselves. This led to many painful moments and it took us nearly five years to get it to the standard we wanted. We experimented with different types of water, freezer and freezing containers; with twice-frozen methods and methods to manipulate the air bubbles and impurities. Here are our conclusions.
Type of water- When we originally started out we employed the use of Fijian water which was said to have a low mineral content and to be very pure. We also then began to try distilled water which again was said to have very low mineral content and was very neutral. We even used twice boiled water - but realised in the end that regular tap water worked just as well.
Type of freezer- The best freezer to use when making ice is a chest freezer. The reason why is due to the fact the freezing element of the chest freezer is located at the bottom of the freezer which enables it to have a steady temperature even when the door is left open. Household freezers on the other hand have this element located at the back of the freezer and every time this is left open the cold air quickly escapes. These inconsistencies have dramatic results of the ice. Constant temperatures provide the optimum conditions for good structure which give you that "firm and rigid" ice.
Types of freezing containers- To put it simply: 'the bigger the better'. We used to use shallow containers which resulted in horrible cloudy ice, but then discovered that half-filling a much larger container gives water the best chance to make great ice. Ice freezes in layers and not all at once, so if you use a shallow ice container you aren't giving the mineral content any chance to escape, however with a much larger container the minerals are forced upwards. The minerals are the last part to freeze. When stacking containers on top of one another in a chest freezer it is also essential to leave room for air between each stacked container, or the water in the underlying containers will not freeze.
Other methods- We also tried to use air circulation systems - such as an electric fish tank pump - to develop the previous method and try to get the mineral content of the ice to freeze last, which we would be able to simply saw off. However we found this method needed constant supervision: the main issue was the adjustment of the pipe which constantly needed to be moved upwards to move the minerals to the next freezing level. In a busy bar this is simply not workable. We also tried using the Stanislav Vardnra method which was to line the inside of the freezer with insulating foam, which in turn slows down the freezing process and gives the ice a more relaxed and calm environment to develop. This creates great ice but it took almost four days to make, which again didn't meet our demands as it had to be more efficient.
In reality many of these variables work in conjunction with one another to produce great ice: good water, a chest freezer, large freezing containers and the appropriate amount of time to freeze, which was generally two days at -27 degrees. After two days freezing at this temperature all the potentially cloudy elements were still in water trapped in the middle of the block. We simply drained this water and then started the process of shaping our ice to our liking. The secret was simply to catch the particles before the block had fully frozen and scoop them out.
Many people have tried other methods to produce clear ice, including playing Jay Z 's "99 Problems" beside the ice (yeah, me neither) and I've even heard someone suggest placing vibrators inside the chest freezer. In my opinion, if you follow the way we did it at The Merchant you won't be disappointed.
The first time I came across bartenders creating and using crystal clear ice for mixing and serving cocktails was in Japan. It looked stunning and was a really dramatic addition to bartending - another example that proved my Japanese hosts were really thinking about every aspect of their craft. When I returned to the UK I wanted to recreate a similar started experimenting intending to create the purest ice possible, but it was harder than I thought and the final effect just wasn't right.
My first steps were using boiled water and mineral water, freezing them in small food containers. The final effect just wasn't right with either - the ice was cloudy and full of air bubbles, which made the ice very soft and easy to crack - not what you want if you want to shape ice for a particular glass or to create intricate shapes or spheres.
I also tried collecting the melted water from the crystal clear ice blocks that are often supplied to bars, attempting to refreeze it, but again, the ice just became cloudy. It was then that I realised that the magic lay in the method of freezing rather than the water source you start with.
I came across the solution by chance. One day I was hosting a large party at home and knew that the food containers I had been experimenting with wouldn't produce enough ice. So I decided to clear a whole draw in my freezer of food, filled it up with tap water to the top and put it back in the freezer - though not before covering with cling film to avoid the water turning to vapour or becoming snow inside my freezer. After three days about 60 percent of the ice block I created crystal clear and very solid, perfect for cocktails.
I wanted to improve on this though, as my method was not exactly rocket science. The next step was to perfect a slow-freezing process. I figured that if the water is frozen more slowly, air bubbles would travel to the more liquid parts of the water before they froze, rather than trapping them in the ice because the whole thing freezes too fast. To encourage the bubbles to the bottom, I insulated the contained around the sides and bottom, meaning that the surface would freeze first and then the ice would form from the top to the bottom. Using this method I came up with mostly crystal clear, very solid ice.
Transporting ice across the globe
Another advantage of creating crystal clear ice is that it melts more slowly precisely because it does not have as much air in it. In fact, it stays frozen for so long that I have taken to travelling long distances with my own ice block - including to last year's World Class finals in Athens, and even to Kentucky for a cocktail competition - long haul flights aren't really a problem as the temperature is obviously very low in the hold at 36,000 feet. What I do is wrap a 2kg ice block in bubble wrap, aluminium foil and cling film, and transport it in an insulated food bag. Ice stored in this condition can last more than a day without turning into water - though you will probably need to clear out your hotel mini bar when you arrive to make space for it.