No, I’m not talking about Haribo gummy bears—though those are yummy—nor am I referring to the more psychoactive “gummy” favorite of Colorado…
The Edge Grinding Rubber, or “gummy stone,” is one of my most utilized and thought-about pieces of tuning equipment. A gummy stone can be used to remove rust. (But if you use it on your base edge, do so sparingly). Base edges are easily affected and shouldn’t be meddled with). A gummy can also be used to take the spiky-ness off of a particularly bad burr (but a file and diamond stones will do the actual fixing).
The most essential function of a gummy stone, though, is de-tuning: dulling an edge in a controlled manner that is harmless to the metal. My technician and I use it every single day.
Let’s start at the beginning. When a pair of skis is brand new, the edge is sharp from tip to tail. The first task is to remove any sharpness from the first and last inch. I spend some serious time rubbing a gummy in these spots to remove any semblance of sharpness. It might be a little more than an inch.
The point is that you are targeting the portion of the edge that does not touch the snow, even when the ski is carving at a high angle. The only time this part does touch the snow is in a haphazard position before, during, or after a crash. A dull first and last inch provides leeway for recoveries in weird scenarios. Most World Cup ski technicians I have spoken to prepare their skis this way. I know one technician who will even take a file horizontally back and forth across the edge to dull the tip and tail instead of a gummy stone.
The fun stuff
Now for the fun stuff. This is the part where you get to figure out the minutiae of sharpness. I spent an entire year tinkering and honing to find a method for my Rossignols—and then I switched to Nordica, which skis slightly differently—and I’ve had to develop a somewhat new method. I not only de-tune my skis differently based on snow type but also based on the ski model.
The way my technician and I use a gummy is not dissimilar to the way most racers use it, which is a good starting point for anyone. Personally, I use the gummy extremely lightly for slippery ice, just around the tip. Also, I will occasionally de-tune a few inches along the tail for grippier ice, salted snow, or hard, unaggressive snow. However, I like to leave the tip sharp to help me initiate the turn, but I want to keep the tail duller, allowing me to release the ski at the bottom of the turn). For that Styrofoam Colorado snow, I often run the gummy along the edge for 30-40cm from the tip and 20-30cm from the tail.
When testing your preferred gummy-ing method, remember that a little goes a long way—extremely light pressure will still remove sharpness—and it’s always easier to take more off than re-tune. It would be best to rarely take the gummy to the underfoot section of your skis; this part of the ski should always have solid grip. Testing your gummy method is part scientific and part feeling. Take extensive notes on snow type, course type, number of runs taken, length of gummy strokes and pressure applied. At the end of the day, when your edge allows you to be agile on the snow but does not lose grip during a well-built apex, that is the edge you are looking for.
Keep track of your tools
Lastly, try not to lose your gummy stone (there are a lot of Jimmy-owned gummy stones randomly lying around at this point). I suggest breaking your stone in two and keeping one half on your tuning bench and the other half on the mountain with you.
I wish you all the best in mastering the art of the gummy stone!