Making Outdoor Ice
By Jeff Schulz, Parks Foreman
The first thing I look for is the weather.
In order for good solid ice to happen we need temperatures during the day to be below 0c, ideally between -5c and -10c. Without sun because the sun gives us that beautiful Radiant heat from the UV rays, but also heats up the ground (concrete for spray pad and asphalt for the hockey rink) past the point of freezing. The air may be cold but the ground slab may be warmer than 3c. Last but not least is the wind, a calm wind or no wind is best as it will create unwanted waves. This will result in an un-even surface that will take more surfacing with the Zamboni.
At night I like to see the temperatures fall below -10c, this ensures that without the sun, and the cold temperatures that the slab will freeze.
At indoor facilities they have an “Ice Plant” were pressurized industrial coolants are pumped through kilometers of piping buried into the concrete that the ice slab will sit on.
Then I need the temperatures to stay in that -5c(day) and -10c(Night) range for several days so I can insure that the slab will be frozen and the first layer of water will adhere to the slab surface. This step is important, if we start putting water down and the slab isn’t frozen we can develop a “Floating Slab”, which is a layer of water under the ice but resting on the slab that won’t freeze. Think of a flat ice burg floating on water. This means we would have to break up all that ice to get rid of the water and re-flood entire surface.
Cold and Dark is best, and for hard outdoor ice you want to flood in the early morning (I start at 3am) this ensures that I am taking advantage of the coldest part of the day and avoid any problems with the sun for at least the early part of the day.
It takes a few days to get quality outdoor ice. The process of building an outdoor skating surface itself creates a hard surface as it’s done in layers. The more layers and more thin layers the better. This step requires cold temperatures and the dark. At this stage the sun can do a lot of damage to the surface, by heating up the trapped air pockets inside the ice, creating holes and craters that will then need to be filled in COMPLETELY or air pockets will result making a poor skating surface. This base layer takes one session to complete and it needs to be frozen to continue. This might take multiple sessions to complete based on weather conditions.
After the initial layers have been flooded and have “stuck” to the ground surface, we can then go and start building the layers that will become what you skate on top of. This seals the edges of the ice where it touches any vertical surface (Curb line or boards) and puts a sealing layer on top of the base surface.
The total volume of this first base layer should be half the final height of your slab, this provides impact resistance and a layer that can move with the ground in an effort to mitigate cracking or separation.
Every subsequent layer after this should be as thin as possible. This builds strength into the ice, fills any low spots, identifies the high spots and seals the layer below. Water must freeze to ice. Air or water pockets will prevent water from freezing and will create soft spots, which of course will reduce the over-all quality. This step will build the next 1/4 of your overall height. This can take many sessions or can take one session, again dependent on weather.
After many many many many layers (Hundreds) have been sprayed on the ice in a uniform fashion with consistent thickness, and is flat(ish) then we can begin with the Zamboni.
This first few passes with the Zamboni (Harriet) is to shave the ice as flat as we can get it. Taking off no more than 1/16 of an inch at a time until no further ice is being shaved at that height.
Now we can go either one of two ways, if doing lines and creases now is the time as we should be 3/4 of our total height and can bury then into the ice with layers laid down with the Zamboni. The other is to build up the layers using the Zamboni by making pass after pass on the surfaces lightly flooding with each pass building the slab to our final height.
Once your final height is achieved then we do a few passes (Dry Scrape) to set the final height of the skating surface and to polish the ice. Finally, ONE pass made by Zamboni (Wet Scrape) to put that beautiful sheet of ice on top to skate on.
5 – 10 minutes needed for ice to set up before skating can happen. Just think the NHL teams don’t skate on the ice seconds after is laid down, refrain from skating on fresh ice before this time please.
Remember that its ICE, frozen water, this cannot happen if the temperatures are higher than -1c, if its warmer than -1c at any time of the day we CANNOT make ice.
Nature does not hurry until everything is accomplished. Be patient, ICE is coming and we are excited for a great skating season at CGRA.
If you have any questions or suggestions please email me at firstname.lastname@example.org