{"time":1758643031657,"blocks":[{"id":"h2vm_OP1b1","type":"paragraph","data":{"text":"At this point, all competitive curlers in Canada should be familiar with the World Curling announcement from last June about the withdrawal of specific foams\nin a small selection of brushes from World Curling’s approved equipment list\nfor competitive play for the new 2025–2026 season. "}},{"id":"_UFVOi5OnB","type":"paragraph","data":{"text":"World Curling came to their decision based on the\noutcome of brush testing in Morris, Manitoba during the Victoria Day weekend,\nalong with feedback from the researchers on World Curling’s equipment advisory\ngroup, of which I am a member. "}},{"id":"0edTR4hFYQ","type":"paragraph","data":{"text":"To a significant extent, World Curling really didn’t have a choice but to try\nand address the concerns first brought to their attention with a players’\nmanifesto that was put together just prior to last January’s Grand Slam Masters\nevent in Guelph. The players who signed onto the manifesto were concerned that\nthe brushes approved for competitive play this past season were too good:\neither they permitted additional carry above reasonable expectations, or they\nimpacted the trajectory of a curling stone to a greater extent than they\nbelieved was in the spirit of the game.\n \n"}},{"id":"k7Deo_wLbw","type":"paragraph","data":{"text":"The on-ice testing performed in Morris confirmed that some of the brushes that\nhad previously been approved for competitive play were outside the scope of\ndesired effectiveness as judged by the players. Consequently, with the\nagreement of the manufacturers involved, these foams were struck from World\nCurling’s approved list of competitive equipment for the new season, and the\nannouncement was made public on June 20. "}},{"id":"S9igMPN1Vw","type":"paragraph","data":{"text":"Then my phone exploded.\n"}},{"id":"UU5TWFbe-Y","type":"paragraph","data":{"text":"\nSo how did we get here?\n"}},{"id":"OdcnONy3NX","type":"image","data":{"caption":"Remember Kemptville? • NRC-Dan Gamache","withBorder":false,"withBackground":false,"size":"full","alignment":"center","linkUrl":"","file":{"url":"https://deweb-519a7.b-cdn.net/post-images/6d194721-98cc-413b-9eac-1d4c05c4ea2d.jpeg","width":2674,"height":1612}}},{"id":"vovmgLkaV5","type":"paragraph","data":{"text":"\nAs a result of the original “Broomgate” in 2015, World Curling instituted three\nsignificant changes to brushing in competitive curling. They were:\n\n1) All brush heads approved for competitive play must utilize Oxford 55 420\ndenier mustard yellow nylon as the brush head fabric, as it was this fabric\nthat was tested in Kemptville, Ontario and was found to have the most desirable\ntrade-off of minimal impact on the trajectory of a stone, versus reasonable\nimprovement to the carry of a stone."}},{"id":"OOaHxrjr2u","type":"paragraph","data":{"text":"2) The existing rule that prohibited brushing a\nstone from any direction other than completely across the face of the stone was\ndropped, because the testing in Kemptville found that the brushing angle of\nattack made little difference in the trajectory of a stone. This meant that\n“corner sweeping” was no longer banned."}},{"id":"A0Cd0PoT2O","type":"paragraph","data":{"text":"3) World Curling, based on the study results from\nthe National Research Council in Ottawa, created a specification for the\ntesting of foam used in brush pads. That specification contained a minimum and\nmaximum amount of compression that a compliant brush head could have. That is,\nto be approved the foam could not be:\n"}},{"id":"LQ1hv7QVVZ","type":"paragraph","data":{"text":"\n• so pliant that it would be easy for an athlete to fully compress the pad,\nresulting with the brush head itself being in contact with the ice, nor"}},{"id":"Qtaw0-sf1V","type":"paragraph","data":{"text":"• so stiff that the brush only contacted the very\ntop of the pebble while sweeping.\n"}},{"id":"aezMPPtMg3","type":"paragraph","data":{"text":"\nThe foam specification was chosen based on an underlying assumption that the\nbrush head assembly would distribute the force produced by the athlete down the\nhandle evenly across the full contact area of the brush pad. That assumption\nappears as one of the specific points in the specification document.\n"}},{"id":"zJtsSiyMB5","type":"paragraph","data":{"text":"\nBroomgate 2.0 aka Foamgate\n"}},{"id":"6_LWyVY13h","type":"paragraph","data":{"text":"\nSince 2016, manufacturers of brushing equipment have developed numerous new\ndesigns to create brushes that are more effective, and weigh less, while still\nsatisfying the requirements of the World Curling specification. But what this\npast season’s experience demonstrated was three main points:\n"}},{"id":"peCPsuzuBf","type":"paragraph","data":{"text":"\n• the existing World Curling specification for foam, by itself, is only\ntangentially related to the behaviour of a brush when used on the ice surface;"}},{"id":"otB9pPFALw","type":"paragraph","data":{"text":"• differences in behaviour were independent of\nthe brush head fabric, as all testing conducted by both World Curling and at\nthe University of Saskatchewan used brush heads with the standardized Oxford 55\n420 denier mustard yellow nylon fabric; and"}},{"id":"nIRkSQ7HL_","type":"paragraph","data":{"text":"• as a whole, new brushing products are made\navailable in the marketplace without sufficient on-ice testing to demonstrate\ntheir suitability in actual brushing situations by competitive athletes.\n"}},{"id":"7tsP5KvFQr","type":"image","data":{"caption":"Ben Hebert, a Brier blur • Anil Mungal-The Curling News","withBorder":false,"withBackground":false,"size":"full","alignment":"center","linkUrl":"","file":{"url":"https://deweb-519a7.b-cdn.net/post-images/46f63c26-d515-41ef-9a7c-fc9ec86421a5.jpeg","width":2888,"height":1200}}},{"id":"GAirNAi0Uh","type":"paragraph","data":{"text":"\nLatest research\n"}},{"id":"YHodjJbXNR","type":"paragraph","data":{"text":"\nIn addition to the recent on-ice testing done at Morris by World Curling, two\nresearch projects continue to look at elements of brushing and understanding\nthe underlying physics of the sport. One of these projects concerns the study\nof brush heads and their construction, and the resulting pressure distribution\nwhen under load, which I’ve written about previously. "}},{"id":"cnc9E2Y1aA","type":"paragraph","data":{"text":"This work involves myself along with professors\nJohn Newhook, Michel Ladouceur, and Ryan Frayne of Dalhousie University. We\nintend to continue this work through this coming year in order to test the\nequipment that World Curling approved for this season, with the goal of\nproviding some insight into what a new, improved brush specification might look\nlike.\n"}},{"id":"mhg673zHrA","type":"paragraph","data":{"text":"\nThe second project, which I mentioned in a prior article, concerns an in-depth\nstudy of the physics of curling, including the characteristics of ice, stones,\nand brushing. This work is being performed at the College of Engineering at the\nUniversity of Saskatchewan by Sean Maw and his research team of staff and\ngraduate students; I am absolutely delighted to act as a consultant to this\nproject.\n"}},{"id":"01RZ4CXyTp","type":"paragraph","data":{"text":"\nSean delivered the project’s initial findings to World Curling in August.\nSean’s work is truly exciting in that his results, and the technology used to\nproduce them, are groundbreaking, involving the use of high-magnification macro\nphotography along with high-resolution infrared imaging that is able to discern\ntemperature changes with individual pebbles. "}},{"id":"Gm5O55JMK8","type":"paragraph","data":{"text":"The results are planned for future publication so I can’t go into\ndetails regarding the results, but I can say that Sean’s work, and that of his\ngraduate students, give us an entirely new understanding of the physics of the\nsport, and particularly of the differences between ordinary brushing and\n“knifing”. I would like to offer my sincere congratulations to Sean, Grant\nHarris, Corin Acton, and Derek Elvin for making an outstanding contribution to\nour knowledge behind the physics of curling.\n"}},{"id":"bmVh3H5Z6K","type":"paragraph","data":{"text":"\nWatch for my next column in The Curling News; I’ve got some thoughts on what’s\nto come."}}],"version":"2.31.0"}

Glenn Paulley

Competition Development Coach

Curling’s Foamgate: Current and Forthcoming Research