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This is Rockology 101, Part I - the striking band

Editor: Chris Daffern
Date: 2014-02-08

“Rock me, give me that kick now … Rock me, show me that trick now … Roll me, you can do magic Baby, and I can’t get enough of it …” - Bjoern  Ulvaeus & Benny Andersson

Got your attention?  Not pop music.  This is Rockology 101, Part I – the striking band; the basics of curling stones, their TLC and control for players.

Why? Because curling stones are a curling club’s biggest asset.  To replace the OCC’s eight sheets of rocks, the current retail price for a new set is in excess of $83,200.  So while it’s important for clubs to have a long-term plan for the health of their stones, it is equally important for players to care for our rocks.  After all, we, the Members of the Oshawa Curling Club, are ultimately the owners, collectively, of our curling stones.

With time, unthinking, negligent and unconscionable on ice behaviour can dramatically undermine the performance of your rocks and ultimately cost the Club, i.e. us, the Members, a lot of money.  On the other hand, if we look after our rocks, before, during and after the season, on and off the ice, we can prolong their life expectancy to 40 or 50 years.

First, the fundamentals of a curling stone.

The typical curling stone will weigh around 40 to 44 lbs.

An acceptable curling stone must be able to resist abrasion and be tough, dense, resilient, uniform in colour and non-absorbent. This latter quality is highly important because moisture penetrating a stone and then freezing will cause chipping or pitting of the surface of the stone. Granite from the British Isles, particularly the Trefor quarry in Northern Wales, satisfies the requirements better than any other so far discovered, and is used almost exclusively.

A dull grey band around the greatest circumference of the stone is the striking surface of and is designed the stone, to absorb the shock when one stone strikes another.

So what can go wrong with granite?  The striking bands can be damaged from long term contact and become flat.

Each stone has a section called the striking band at its outermost point. This is the part of the stone that makes contact with other stones, as well as the boards.  When a rock is new, the striking band is actually convex, curving away from the rounded surface of the rock.  You shouldn’t be able to stand a rock on its end – the convex striking band should make it fall over.  This doesn’t last forever though.  Over time, the constant pounding of rock against rock and rock against board wears out the striking band to the point where it loses its convex nature and becomes flat.

When two stones make contact, the area that actually touches is about ¼ to ½ inch, but as the rocks are bashed around and the convex area flattens out, the contact area can increase to 1½ inches.  When the striking band goes flat, rock performance is compromised; you may experience “dead” rocks.  When the striking band does flatten out, it causes the rocks to react differently when they meet.  Two flat stones making contact absorb more of the energy and may not roll as far as a newer rock with a convex striking band.

The striking band is the key in determining the life of a curling stone.  Some granite is more prone to chipping throughout the middle of the striking band.  Reprofiling may be able to restore a rock by grinding down the surface of the rock to restore the convex striking band.  The cost?  $800 per sheet of 16 stones or $6,400 for the OCC.

In severe cases, some stones cannot be re-profiled as too much material needs to be removed to get below the chip – affecting the weight and dimensions of the stone.

What can we ALL do to protect our rocks from being damaged?  Stop them before they collide with out of play rocks, with backboards and hacks and with sideboards!

There are (usually) four players on each team.  That means there are usually three players for the shooting team (the skip or vice and two brushers) and one or two players from the non-delivering team (typically the skip and maybe the vice) at the scoring end of the ice each time a rock is delivered.  Collectively, you have a responsibility to stop rocks from crashing into the hacks or crashing into stationary stones that are out of play at the backboards.  This inattention or blatant disregard can damage the hacks and the ice but also, most critically, the rocks.  Sure, mistakes and distractions happen but anything less than that (most of the time) is simply negligence.

Secondly, brushers must be watchful and attentive to the path of rocks near the sidelines and the trajectory of any displaced stationary stones.  Just because you may not be required to sweep or brush a running stone does not mean your job is done.  Stop rocks that touch a sideline – immediately.  Prevent them from interfering with play on an adjacent sheet of ice; including stopping your stones from displacing a rock on another sheet.

Third point.  In the Oshawa Curling Club there are painted boards along the walls of ices 1 and 8 and between ices 2/3 and 6/7.  As rocks collide with these boards, the striking band profile will be affected and will flatten out over time.  Striking these boards may contribute to premature pitting of the band.  Paint may flake off the boards into the ice.  The striking bands become stained with the colour of the boards.  It doesn’t have to be.  As brushers, if a rock is clearly going to crash into the boards without contacting any other stones, you can stop the running stone.  Just be judicious when you do that.  The rock must clearly be going out of play.  If the rock is slowly moving towards the boards, it may be wise to let it run its course.  Who knows, the rock may stop or spin back and be that perfect corner guard you (or worse, your opposition) were looking for.  Gentle contact with the boards is not what we are concerned with.

That’s all for striking bands.  Stay tuned for Rockology 101 – Part II, the running surface of the stones.

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