Before first ice: my thickness rules and the kit by the door

01My numbers

These are my minimums, measured with a tape through a drilled hole, and they are for clear, hard ice that has frozen from open water in steady cold. They are not generous, and I do not apologise for that. Ice varies across one lake by more than the difference between any two of these figures, and a small city lake with springs, a storm drain or two and reed beds all round varies more than most.

White ice is what forms when snow, slush or water lying on top of the sheet freezes. It looks solid and is full of air, and I treat it as having half the strength of the same thickness of clear ice. Many sheets are layered, a few centimetres of black ice underneath and white on top, and it is the black part that I measure and count. If I cannot tell where one layer stops and the next begins, I count none of it as black.

• Under 10 cm of clear ice: I stay on the shore.
• 10 cm: one person on foot, spud in hand, testing every step or two.
• 15 cm and more: a few of us, still spread well apart.
• White ice, snow ice or layered ice: I want twice the figure.
• Anything with an engine: never, on any of these waters.

02Testing from the shore outwards

New ice gets tested from the bank, before a boot goes on it. The spud, a heavy steel chisel on a long handle, is driven down hard a step or two ahead of me. Good ice rings and chips. Thin ice thuds, and if the spud goes through in one or two blows I turn round. Every twenty or thirty metres I drill a hole with the auger and measure with a tape hooked under the bottom of the ice, and each figure goes into the log with the time.

The small waters freeze first. Ginkūnai pond, sheltered and shallow, usually carries a person a week or so before Talša does, and Rėkyva, big and open to the wind, often last of all. Snow is the complication. A fall of snow on young ice insulates it and slows its growth, hides the thin places, and adds weight that can push water up through cracks into slush. After heavy snow I start testing again from nothing, however thick the ice was the day before.

03Where the ice is thinnest

Some places are thin on every lake, every winter, and I simply do not walk there. Around the reeds the ice is weaker and often hollow underneath. Where a ditch or stream comes in, or where water leaves the lake, the current keeps the ice thin. Springs leave soft round patches that look no different from above. Piers, posts and the stumps of old jetties all carry warmth into the ice around them. Pressure ridges, where two sheets have pushed against each other, can hide open water underneath.

Old holes are another trap on busy ice. A hole drilled a few days earlier and frozen over looks like the rest of the sheet under a dusting of snow, but it may be two centimetres thick. On Talša, where the same good spots get drilled by everyone, I walk around circles of older holes rather than across them, and I never step onto a patch of snow that sits lower than the ice around it, because that is often exactly what an old hole looks like.

04The kit by the door

The safety kit lives in its own bag by the door from December to March and goes onto the sled before any rod or tackle box. The ice claws hang round my neck on a cord from the moment I leave the shore, not in a pocket, because a pocket is the last place you can reach with cold wet hands. The throw rope is fifteen metres of floating line in a bag with a loop on the end. The phone rides in a sealed pouch in an inside pocket, next to a whistle.

There is also a dry bag with a full change of clothes, a small towel and a foil blanket. And there is the least visible piece of kit: a message to my wife with the lake, the bay and the time I will be back, and a promise to message again when I am off the ice. In early season I do not go without a second person. Most years that is the rule I find hardest to keep, and the one I am most glad of afterwards.

05If someone else goes through

The rope on the sled is for someone else, and the hardest part of using it is not running towards them. A second person in the water helps nobody. Call 112 first, or shout for someone to call, then talk to the person in the water in a calm voice: breathe, turn back the way you came, get your arms onto the ice. Stay on ice you know is holding, lie down if you must move closer, and reach with the spud handle or throw the rope past them so that it lands across their arms.

Once they have hold of the rope, they kick while you pull, low and steady, and they slide out on their stomach rather than trying to climb. Then both of you crawl or roll away from the hole before standing up. After that the job is warmth: wet clothes off, the dry change from the bag on, the foil blanket round them, and straight to a warm car or house even if they insist they are fine. People who have been in cold water can collapse later, and the paramedics would much rather see them early.