A frozen puck is a good puck.  A new innovation will help the NHL ensure that only frozen pucks are used at the 2019 Winter Classic.

Winter Classic pucks will feature a thermochromic coating developed by PPG.  The printing on frozen pucks will be purple, changing to clear when the puck’s temperature goes above freezing.

Officials will check puck color before each faceoff to ensure only frozen pucks are in play.

“Hockey pucks are made of vulcanized rubber and glide smoother and faster when frozen,” said Dan Craig, NHL Vice President of Facilities Operations. “Freezing a puck eliminates bouncing, and game officials closely monitor the puck for temperature changes that affect performance while in play. A coating that changes color when the puck is above freezing will more accurately alert the officials that it is time for a replacement.”

Pucks are typically stored at around 14 degrees Fahrenheit in a small freezer within the penalty box area.  Typically, 15-20 are used in a game.  Between whistles the linesman may head over to the penalty box for a replacement puck from the freezer.

From Rule 13:

The home team shall be responsible for providing an adequate supply of official pucks which shall be kept in a frozen condition. This supply of pucks shall be kept at the penalty bench under the control of one of the regular off-ice officials or a special attendant.

Checking the color is the simplest way to confirm that the pucks are within the optimal temperature range.



Studies have been done on the elastomeric properties of hockey pucks, comparing performance to the puck’s temperature.

“Freezing conditions can affect impact toughness and performance of the puck, along with other mechanical properties,” wrote Worcester Poytechnic Insititute’s Steven Deane-Shinbrot and Jonathan Rapp. “Controlling these puck properties will allow for improved puck performance during game play.”

The league will continue to test the color-changing pucks, considering a wider deployment in the future.

Technological improvements have been on the NHL’s radar for the past few years. One area the league has been working on is puck tracking, something that will certainly help determine the puck’s location for goals scored and offside plays.

The newly-announced color-changing enhancement will have a more direct impact to the game on the ice – particularly in outdoor games where the elements are out of arena operations team’s control.

“We’ve been able to offer a smart and elegant solution to a problem that can significantly impact game play,” said PPG’s Alicia Cafardi.

A very cool – or perhaps, cold – innovation indeed.